SOLAR ENERGY AS A NATIONAL ENERGY RESOURCE °:; · 2013-08-31 · charged with assessing the...

SOLAR ENERGY AS A NATIONALENERGY RESOURCE

NSF/NASA SOLAR ENERGY R\NEL

°":;:

pared undertional Science Foundation Grant GI-32488search Applied to National Needs (RANN) Program NSF/RA/N-73-001

https://ntrs.nasa.gov/search.jsp?R=19730018091 2018-07-27T19:08:31+00:00Z

AN ASSESSMENT OF SOLAR ENERGY

AS A NATIONAL ENERGY RESOURCE

PREPARED BY THE

NSF/NASA SOLAR ENERGY PANEL

Dr. Paul Donovan, Co-Chairman

Mr. William Woodward, Co-Chairman

Mr. William R. Cherry, Executive Secretary

Dr. Frederick H. Morse, Technical Coordinator

Dr. Lloyd O. Herwig, Executive Committee

December 1972

Panel supported by a Grant from the

Research Applications Directorate of the National Science Foundationto the

Department of Mechanical Engineering

University of MarylandCollege Park, Maryland

Any opinions, findings, conclusions or recommendationsexpressed herein are those of the authors and do not neces-sarily reflect the views of the United States government orthe agencies represented on this Panel.

11

PRECEDING PAGE BLANK NOT FILMED

NSF/NASA SOLAR ENERGY PANEL

CO-CHAIRMEN

Dr. Paul Donovan - NSF

Mr. William Woodward - NASA

EXECUTIVE COMMITTEE

Mr. William R. Cherry — NASA, Executive Secretary

Dr. Frederick H. Morse — University of Maryland, Technical Coordinator

Dr. Lloyd O. Herwig - NSF

SUBPANEL CHAIRMEN

Bioconversion — Prof. Martin D. Kamen, University of California

Thermal Space Conditioning — Dr. Jerome Weingart, California Institute of Technology

Photovoltaics - Prof. Martin Wolf, University of Pennsylvania

Unique Systems - Prof. Robert L. Bailey, University of Florida

Central Electric Power - Dr. Friedolf M. Smits, Bell Telephone Laboratories

EXECUTIVE COMMITTEE CONSULTANTS

Economist: Mr. Milton Searl — Resources for the Future, Inc.

Environmentalist: Dr. James McKenzie — National Audubon Society, Massachusetts

Psychologist: Prof. Raymond Bauer - Harvard Business School

Sociologist: Prof. Samuel Klausner - University of Pennsylvania

Industrialist: Mr. Paul Rappaport - RCA Research Center

Page Intentionally Left Blank


CONTENTS

Page

Introduction 1

Conclusions and Recommendations 5

Summary 7

Applications 13

Thermal Energy for Buildings 13

Renewable Clean Fuel Sources 22

Photosynthetic Production of Organic Materialsand Hydrogen 22

Conversion of Organic Materials to Fuels or toHeat Energy 29

Electric Power Generation 46

Solar Thermal Conversion 48

Photovoltaic Solar Energy Conversion Systems 52

Wind Energy Conversion 65

Power from Ocean Thermal Differences 68

References 75

Appendix A. Proposed R&D Funding 79

Appendix B. Membership of Solar Energy Panel 83

INTRODUCTION

The Solar Energy Panel was organized jointlyby the NSF and NASA in January 1972, andcomprised of nearly 40 scientists and engineerspossessing expertise in solid state physics, chem-istry, microbiology, power engineering, architec-ture, photovoltaics, and the thermal sciences aswell as several economists, environmentalists,and sociologists (see Appendix B). The Panel wascharged with assessing the potential of solarenergy as a national energy resource and thestate of the technology in the various solarenergy application areas, and with recommend-ing necessary research and developmentprograms to develop the potential in thoseareas considered important. The scope of thePanel's activities was defined to include allapplications of direct solar energy, as well aspower from wind, ocean thermal differences,and useful energy from replenishable organicmaterials. This report presents the findings ofthe Panel.

Current projections [ 1 ] of the total U.S.energy demand, see Figure 1, show a growthfrom approximately 64 X 101S BTU in 1969 tonearly 300 X 10!S BTU in the year 2020. Asignificant portion of this increase is projectedto be derived from nuclear energy, with the restbeing supplied by fossil fuels some of which arebeing rapidly depleted. In view of the Nation'sand the world's growing concern with environ-mental and health/safety factors as well as ouranticipated increasing dependence on importedpetroleum and gaseous fuels, it is important toevaluate the potential impact of solar energyutilization, since it is an inexhaustible source ofenormous amounts of clean energy [2].

The average yearly incidence of solar energyin space and on the ground in the continentalU.S. is:

In near-earth space 130 thermal watts/ft.2

On the ground (average) 17 thermal watts/ft.2

The 17 thermal watts/ft.2 results in an averagedaily (24 hour) energy supply of 410 thermalwatt-hours/ft.2. This value is approximatelytwice the amount needed to heat and cool anaverage house. Converting the 17 thermal watts/ft.2 into electricity at a 10% conversion effi-ciency would result in an average daily electricoutput of approximately 1,140,000 kilowatt-hours per square mile. In 1969, the PotomacElectric Power Company sold a daily average of30,000,000 kilowatt-hours to 425,000 cus-tomers in an area encompassing 643 squaremiles. Within 27 square miles or about 4% of theabove PEPCO serviced area devoted to a solarelectric generation system, PEPCO could inprinciple provide the necessary electric power.Under the same assumption of a 10% conversionefficiency and U.S. average solar incidence, in1969 the total electric energy consumed in theU.S. could have been supplied by the solarenergy incident on 0.14% of the U.S. land area.

There has been little Federal support of solarenergy utilization other than for powering artifi-cial satellites. Commercial and philanthropicsupport of solar power generation has beenalmost negligible. Programs in Australia, theUSSR, France, and Israel have all substantiallyexceeded U.S. effort. In principle, solar energycan be used for any energy need now being metby conventional fuels [3]. Three broad applica-tions have been identified by the panel as mostpromising from technical, economic, and energyquantity standpoints. These are: ( l ) t h e heatingand cooling of residential and commercial build-ings, (2) the chemical and biological conversionof organic materials to liquid, solid, and gaseousfuels, and (3) the generation of electricity. TheApplications chapter of the report is organizedinto three primary sections corresponding tothese broad application areas. Within eachsection, one or more methods or processes for

l

300 r 300

250 -

200 -

DOin"o

13CCLU

X800

150 -X 6

100 -

88e§ccLL

UJ00

ITO

CC

X 3

1

0 I

1970 1980

fr | ir : | H I - - - - ' — i • • • • • '

I

1990

GAS

I I I

2000 2010 20

YEAR

FIGURE 1. PROJECTED U.S. ENERGY DEMAND BY SOURCE [1 ]

converting solar energy to the desired form arepresented in the following format:

• Description of Concepts• Status• Limiting Factors and Recommended

Approaches• Goals and Projected Impacts• Short Range (3 year) R&D Program Rec-

ommendation• Long Range (10-15 year) R&D Program

Recommendation• Phased Program PlanThe Panel is confident that solar energy can

be developed to meet sizable portions of theNation's future energy needs. This report is

intended to document this confidence. It mustbe recognized, however, that severe time limita-tions prevented a thorough and critical formu-lation and review of the technology, economics,relative prospects, and development tasks ineach concept. Closer study is expected toeliminate certain areas from further attention,while some new and promising approaches maybe added. A more detailed, in-depth examina-tion of these and other methods for convertingsolar energy to useful forms is high on theagenda of our recommended research and devel-opment program. An introduction to the poten-tial and uses of solar energy may be found inreferences [4] & [5].


CONCLUSIONS AND RECOMMENDATIONS

CONCLUSIONS

• Solar energy is received in sufficientquantity to make a major contribution to thefuture U.S. heat and power requirements.

• There are numerous conversion methods bywhich solar energy can be utilized for heat andpower, e.g., thermal, photosynthesis, biocon-version, photovoltaics, winds, and ocean tem-perature differences.

• There are no technical barriers to wideapplication of solar energy to meet U.S. needs.

• The technology of terrestrial solar energyconversion has been developed to its presentlimited extent through very modest governmentsupport and some private funding.

• For most applications, the cost of convert-ing solar energy to useful forms of energy is nowhigher than conventional sources, but due toincreasing prices of conventional fuels and in-creasing constraints on their use, it will becomecompetitive in the near future.

• A substantial development program canachieve the necessary technical and economicobjectives by the year 2020. Then solar energycould economically provide up to (1) 35% of thetotal building heating and cooling load; (2) 30%of the Nation's gaseous fuel; (3) 10% of theliquid fuel; and (4) 20% of the electric energyrequirements.

• If solar development programs are success-ful, building heating could reach public usewithin 5 years, building cooling in 6 to 10 years,synthetic fuels from organic materials in 5 to 8years, and electricity production in 10 to 15years.

• The large scale use of solar energy as anational resource would have a minimal effecton the environment.

RECOMMENDATIONS

It is recommended that:• The Federal government take a lead role in

developing a research and development programfor the practical application of solar energy tothe heat and power needs of the U.S.

• The solar energy R&D program provide forsimultaneous effort on three main objectives:(1) economical systems for heating and coolingof buildings, (2) economical systems for pro-ducing and converting organic materials toliquid, solid, and gaseous fuels or to energydirectly, (3) economical systems for generatingelectricity.

• Research and development proceed onvarious methods for accomplishing the aboveobjectives and that programs with phased deci-sion points be established for concept appraisaland choice of options at the appropriate times.

• For those developments which show good.technical and economic promise, the Federalgovernment and industry continue development,pilot plant, and demonstration programs.

• Environmental, social, and political conse-quences of solar energy utilization be con-tinually appraised and the results employed indevelopment program planning.


SUMMARY

The following information is tabulated tofacilitate an overview of the Solar Energy Panel'sfindings:

Table 1. Status of Solar Utilization Tech-niques.

Table 2. Summary of Major Technical Prob-lems.

Table 3. Impact of Solar Energy Applicationson the Reference Energy System.

Table 4. Summary of Overall Program Fund-ing.

Comments From the Solar Energy Panel'sConsultants

TABLET. PRESENT STATUS OF SOLARUTILIZATION TECHNIQUES

The checkmarks in this table indicate theapproximate state of development for the vari-ous utilization techniques. The extreme righthand check indicates the progress as of 1972 butsome work may still be required in the otherareas. For example, water heaters are commer-cially available but combined water heating,heating and cooling systems are still in a state ofdevelopment.

TABLE 2. SUMMARY OF MAJORTECHNICAL PROBLEMS

This table identifies the major technical prob-lems to be overcome. As an example, before anyof the photovoltaic systems can become appli-cable on a large scale, solar arrays costing aboutSI .00 per square foot will have to be developed.Before the space power station can be feasible,major advances are required in the deploymentof huge lightweight structures in space, and lowcost synchronous orbit transportation. In all

applications substantialimportant problems.

cost reductions are

TABLE 3. IMPACT OF SOLAR ENERGYAPPLICATIONS ON THE REFERENCEENERGY SYSTEM

This table shows the expected impact thatsolar energy could have if developed to commer-cial utilization. The impact is compared with theReference Energy System's annual consumptionfigures for the particular application, an estimatein percent of the expected market, the annualsavings in fossil fuels based on $1 per millionBTU and an estimate of the significance of theimpact based on the specific application and thetotal U.S. energy needs. A minor impact isconsidered to range from 0 to 5%, a modestimpact from 5 to 10%, and a major impact isequal to or greater than 10%. For example, if by2020, 30% of the Nation's methane needs aremet by the bioconversion of organic wastes,then this would represent a major impact on thegas consumption market and a minor impact onthe total U.S. energy consumption (4.2%). At$1.00 per million BTU, assumed for natural gascosts, the value of the product is $12 billion peryear.

TABLE 4. SUMMARY OF OVERALLPROGRAM FUNDING

The funding recommended by the Panel forthe total 15 year program is shown in this Table.Since some systems will terminate at phaseddecision points in the R&D program, the itemshave not been totaled. Specific decisions justi-fied by the progress made in a preceding phaseare required before progressing to the nextphase. In general, the transitions will progress

Table 1. Present Status of Solar Utilization Techniques

Application

Thermal energy for buildings

Water heating

Building heating

Building cooling

Combined system

Renewable clean fuel sources

Combustion of organic matter

Bioconversion of organic materials to methane

Pyrolysis of organic materials to gas, liquid, and solid fuels

Chemical reduction of organic materials to oil

Electric power generation

Thermal conversion

Photovoltaic

Residential/commercial

Ground central station

Space central station

Wind energy conversion

Ocean thermal difference

Status

JCoCO

§QC

X

X

X

X

X

X

X

X

X

X

X

X

X

X

•*-<c0)

Q.-2

iQ

X

X

X

X

X

X

X

X

X

X

0>4-t

trt

CDffi

V)

X

X

X

X

X

X

X

X

c.0

c |"5. co E

— Q)Q- -0

X

X

X

X

4-1c."5.0)Q.

O

soL

X

X

CO

E cE '-58 2

X

X indicates effort is underway but not necessarily complete.

from feasibility studies, to component develop-ment, to prototype or pilot plant, to demon-stration models or plants. It is assumed thatsome of the funds designated for demonstrationplants will be cost shared by the industry andthus reduce the government investment.

COMMENTS FROM THE SOLAR ENERGYPANEL'S CONSULTANTS

To include the concerns from the variousother disciplines which would interface with the

development of any new energy source, theSolar Energy Panel had representatives from theeconomic, environmental, psychological, socio-logical and industrial interests. A summary oftheir comments follows:

Economic

On close examination, the possibilities for theeconomic use of solar power, given reasonableR&D support, appear much better than gener-ally realized. In regard to the level of R&D, ifthe nation is to obtain the maximum benefits

Table 2. Summary of Major Technical Problems

Application Major technical problems to be solved


Renewable clean fuel sourcesCombustion of organic materials

Bioconversion of organic materialsto methane

Pyrolysis of organic materials to gas, liquidand solid fuels

Chemical reduction of organic materialsto oil

Electric power generationThermal conversion

PhotovoltaicSystems on buildingsGround stationSpace station



Development of solar air-conditioning and integrationof heating and cooling.

Development of efficient growth, harvesting, chipping,drying and transportation systems.Development of efficient conversion processes andeconomical sources of organic materials.Optimization of fuel production for different feedmaterials.Optimization of organic feed system and oil separationprocess.

Development of collector, heat transfer and storagesubsystems.Development of low-cost long-life solar arrays.High temperature operation and energy storage.Energy storage.Development of light-weight, long-life, low-cost solararray; transportation, construction, operation andmaintenance; development and deployment of ex-tremely large and light-weight structures.Integration of large wind conversion system withsuitable energy storage and delivery systems.Large low pressure turbines, large heat exchangers,and long, deep-water intake pipe.

for its energy R&D expenditures, then R&Dexpenditures on various sources of energy andprocesses should be carried to the point of equalmarginal productivity of the incrementalresearch dollar for each source and process. Onthe basis of this, as well as other, criteria, itappears that an objective allocation of R&Dfunds would call for substantially increasedR&D support for a number of solar energyopportunities. There are also international bene-fits in making a viable solar technology availableto the world as well as balance of payments andnational security benefits in limiting our almostinevitable dependence on foreign energy sources.

Environmental

Solar energy utilization on a large scale could

have a minimal impact on the environment ifproperly planned. It is important, therefore, thata policy of research and review for environ-mental effects be made an integral part of theR&D process. Continuous feedback into thedevelopment program is critically important toprevent the undue expenditure of funds forprocesses that could ultimately prove unaccept-able from a public point of view. One of themajor obstacles to public acceptance of newtechnologies is the fear that there are unknownside effects that have not been adequatelyinvestigated or disclosed.

^The most environmentally tienign solar energy

systems might be those of small scale that wouldfit into space already occupied by buildings.When considering large land based systems, great

Table 3. Impact of Solar Energy Applications on the Reference Energy System'1'

System


Conversion of organic materials to

fuels or energy

Combustion of organic matter

Bioconversion to methane

Pyrolysis to liquid fuels

Chemical reduction to liquid fuels

Electric power generation

Thermal conversion

Photovoltaic

Systems on buildings

Ground stations

Space stations



Year

1985

2000

2020

1985

2000

2020

1985

2000

2020

1985

2000

2020

1985

2000

2020

1985

2000

2020

1985

2000

2020

1985

2000

2020

1985

2000

2020

1985

2000

2020

1985

2000

2020

Annual

consumption'2'

(1015BTU)

(3),7(3>21

(3>30

3776

160

(4)27

<4>31(4)41

<S>50

'5>80

<6I50

(5'80

37

76160

(3)g

<3>15<3>21

3776

160

3776

160

3776

160

37

76160

Percent of

total energyconsumption

in USA

151210

324353

231814

443627

433627

324352

996

324352

324352

324352

324352

Estimated

percent of

market

captured

1035

110

1

1030

1

10

110

15

550

110

110

1

10

110

$106 Annual

savings in

fossil fuel

@$1.00/

106 8TU

2,10010,500

76016,000

2703,100

12,300

6308,000

6308,000

7608,000

75010.500

16.000

76016,000

76016,000

76016,000

Significance'61

of impact on

reference energy

system by 2020

Major on building industry

Minor on total energyconsumption

Major on electric utility

Modest on total energyconsumption

Major on gas consumption


Major on oil consumption


Major on oil consumption

Minor on total energy

consumption

Modest on electric utility

industry


Major on building industry



industry



industry



industry



industry


Notes: (1) Each of the above impact estimates assumes the successful development of practical economically competitive systems. However

in each case a judgement has been made resulting in estimates that are less than the maximum possible. The estimates arc not

necessarily additive since not all systems will be carried to commercial readiness.

(2) Nonrenewable fuel consumed to generate the electric power as projected in the energy reference systems and resource data

report, AET-8, Associated Universities, Inc., April 1972 |1].

(3) Nonrenewable fuel consumed to generate the projected electric power requirements for buildings, AET-8 (1 ].

(4) Methane consumed to meet projected energy needs, AET-8 (1) .

(5) Oil consumed to meet projected energy needs, AET-8 (11.

(6) Minor, 0-5%; Modest, 5-10%, Major, >10%.

10

Table 4. Summary of Overall Program Funding*

Applications


Renewable clean fuel sourcesPhotosynthetic production of organic

materials and hydrogenConversion of organic materials to

fuels or energy

Electric power generationSolar thermal conversionPhotovoltaic conversionWind energy conversionOcean thermal gradients

Long RangeR&D Program

(15 years)$ M

100

60

310

1130780610530

*See Appendix A for additional funding information.

care must be taken to find suitable areas thatwould not be of unique ecological or recrea-tional importance or cause serious alterations inlocal climate or weather.

One can indeed imagine designing "optimumsize" environmentally oriented communitieswhich would meet most of its energy needs fromdirect solar energy and the solar derived fuelsfrom the local waste treatment plant.

Industrial

Before solar energy becomes a major sourceof clean energy for our nation, it will require theinvolvement of industrial ingenuity and pro-ductive know-how to produce economic hard-ware and services. Some of the difficulties inachieving industry participation are: (l)mostcompanies are looking for short term projects

for their new enterprises with return on theirinvestments in 2 to 3 years; (2) long rangeprojects present great risk, and investmentcapital is very scarce unless there is a highprobability of return in a major line in theirbusiness; and (3) companies will undergo majorchange only under crisis (they will take chancesbut cannot take failure).

To overcome these problems several things areneeded. (l)The item needed must be definedvery carefully so that the direction is clear andfeasibility shown. (2) The Government mustmake a long range commitment to assure thatthe interest will not wane in a couple of years.(3) The incentives must be substantial so thatfuture profit is sufficiently assured over a periodof time that makes industrial investment payoff. Further, industries must feel that the systemis socially acceptable so that the public will lookupon it favorably. Solar energy utilization fitsinto this pattern extremely well.

Sociological

Research on the social conditions whichfoster solar energy technology protects againstthe truncating of a technological policy by thesocial responses it engenders. Analysis of socialproblems accompanying solar energy technologydevelopment requires a shift of focus from thephysical world to the world of social activity.There is a need for more social scientific work todefine the social (including economic, political,and cultural) problems presented by solar energyutilization. The establishment of National prior-ities for the use of solar among other energyforms should recognize the social impacts of theutilization of each energy form.

11


APPLICATIONS

THERMAL ENERGY FOR BUILDINGS

INTRODUCTION

Buildings may be heated and cooled withsolar energy by use of some type of solarreceiver or collector in which a fluid, such aswater or air is heated. The system includes aninsulated storage tank or rock bin and anauxiliary heat supply unit of some type tosupplement or substitute for the solar sourcewhen it is insufficient to meet the demand. Aheat-operated air conditioner provides coolingwhen supplied with solar or auxiliary energy,and various pumps, controls, and facilities areneeded for circulating air from the conditionedspace to either the heating or cooling unit.Figure 2 is a schematic diagram of one systememploying water as the heat collection fluid. Asseen, hot water for household use may also besupplied by a system of this type. Numerousalternate designs are possible.

The solar collector is one of the most impor-tant, and most expensive, element in the system.A sketch of one type is shown in Figure 3. Solarradiation is transmitted by the glass covers andabsorbed by the blackened metal sheet. Thiscauses the temperature of the metal sheet toincrease, so that water circulated through thetubes is heated. Water temperatures of 100 to200°F are commonly obtained, depending onconditions. Heat losses are minimized by therear insulation and overlying glass covers.

A practical location, and suitable area, for thesolar collector is the house roof. The collectorshould be south-facing for maximum efficiency,and it may be supported on the roof, on a framework above the roof in building walls partic-ularly in the high Northern latitudes. Storagemay be conveniently located in a house at

ground level or in a basement. In a temperate,sunny central U.S. location, a 1,500 square foothouse could be provided about three-fourths ofits heating and cooling needs with a 600 to 800square foot collector and 2,000 gallons of hotwater storage. Greater attention to energy con-servation in house design can significantly re-duce the heating and cooling requirements, bymore effective insulation, roof and wall orienta-tion, window arrangement, surface propertiesfor radiation control, solar transmission andshading.

STATUS OF RESIDENTIAL SOLARHEATING AND COOLING

The three residential solar applications, waterheating, space heating, and space cooling differsubstantially in status of development, so theyare discussed individually below. It is evident,however, that combinations of the three func-tions in integrated heating, cooling, and waterheating systems will have the best prospects foreconomical use. The status of the integratedsystem is outlined after the discussion of eachcomponent.

Water Heating

Solar water heaters are commercially manu-factured in Australia, Israel, Japan, USSR, andon a small scale in the U.S. The aggregatebusiness of these enterprises is probably severalmillion dollars per year. Solar water heaters arestandard items of equipment in households inparticular areas (e.g., northern Australia); areasof use are growing slowly. Application in the

GAS OR OIL FUEL(USED ONLY WHENSOLAR IS DEPLETED)

COOLWATER

TO HOUSEHOTWATERSYSTEM

WINTEROPERATION

I

SUMMEROPERATION

AUXILIARYHEATER

t t

V/V AUTOMATIC^^—

1

30

m>H

0c

H

<f

VALVE

HOTWATER

WARM AIR COOL AIR(WINTER) (SUMMER)

\ /

? /

>l

^ 1C 1<

> \

>/ N

HOUSE ROOMS

\ <

HOTWAT

»

>

\ <

1 £

1 £

1

V 4\ AIR RETURNS /

b*

/

'/s..^.^..RETURN BLOWER

f

»

WARWATRETl

FROM COLDWATER SUPPLY PUMP

FIGURE 2. RESIDENTIAL HEATING AND COOLING WITH SOLAR ENERGY:ONE ALTERNATIVE

SCHEMATIC DIAGRAM OF

U.S., once common in Florida but then dimin-ished by the availability of natural gas, is nowbeginning to increase. In addition to householdapplications, institutional installations are be-ginning to appear in Australia, for schools,hospitals, etc. [6].

The technology of solar water heaters is welldeveloped; further product engineering (partic-ularly of collectors) and larger scale manufactur-ing would result in cost reductions and increasedutilization.

Space Heating

Approximately 20 experimental solar heatedstructures have been designed, built, and oper-ated. Various combinations of collector types,heat storage techniques, heat transfer media, andauxiliary energy supplies have been used. Someof these buildings were laboratories, and somewere also designed as residences; only one fullyinstrumented and evaluated system has been incontinuous use, so long-term experience withsolar heating systems is limited.

14

TWO GLASSCOVER PLATES

BLACK METAL SHEET TO WHICH1/2" TO 1" TUBING IS BONDED

INSULATION (2" TO 4" THICKNESS)

ROOF SURFACE

'SHEET METAL TROUGH OR PAN

NOTES: ENDS OF TUBES MANIFOLDED TOGETHERONE TO THREE GLASS COVERS DEPENDINGON CONDITIONS

DIMENSIONS: THICKNESS (A DIRECTION) 3 INCHES TO 6 INCHESLENGTH (B DIRECTION) 4 FEET TO 20 FEETWIDTH (C DIRECTION) 10 FEET TO 50 FEET

SLOPE DEPENDENT ON LOCATION AND ONWINTER-SUMMER LOAD COMPARISON

FIGURE 3. SOLAR COLLECTOR FOR RESIDENTIAL HEATING AND COOLINGDIAGRAMATIC SKETCH OF ONE ALTERNATIVE

(elevation-section)

15

The performances of several of these heatingsystems were fully measured and evaluated, andthe results were published [6]. The capabilitiesof the various designs have thus been wellestablished. Subsequent economic studies haveshown that in a wide variety of U.S. climates,solar heating is less expensive than electricheating, and in a few locations, it is nearlycompetitive with gas or oil heating [7]. Table 5and Figure 4, based on one of these analyses,clearly demonstrates that solar heating, evenwithout supplemental savings from cooling, canbe a practical alternative to conventional heatsources.

Workable heating systems have evolved fromthese experiments. However, they are not fully

engineered, both from the point of view ofselecting the best systems or optimizing thedesign of those systems. Also, solar collectors,energy storage units and heat transfer systemsare in an early stage of component developmentand engineering. Though technical feasibility isassured, economic feasibility is being ap-proached for major regions of the U.S. FurtherR&D is needed to reduce costs and developbetter systems.

Air Conditioning

A few experiments have been conducted inthe U.S., Australia, and the USSR to study theoperation of absorption refrigeration systems

Table 5. Costs of Space Heating (1970 Prices) In Dollars Per Million BTU Useful Delivery [7].

Location

Santa Maria

Albuquerque

Phoenix

Omaha

Boston

Charleston

Seattle-Tacoma

Miami

Optimized solar heatingcost in 25,000 BTU/degree-day house, capital charges

@ 6%, 20 years

Collector©$2/ft.2

1.10

1.60

2.05

2.45

2.50

2.55

2.60

4.05

Collector @$4/ft.2

1.59

2.32

3.09

2.98

3.02

3.56

3.82

4.64

Electricheating,

usage30,000

kwh/year

4.281

4.63

5.07

3.25 3

5.25

4.22

2.292-3

4.87

Fuel heating,fuel cost

only

Gas

1.52

0.95

0.85

1.12

1.85

1.03

1.96

3.01

Oil

1.91

2.44

1.89

1.56

2.08

1.83

2.36

2.04

Notes: ' Electric power costs are for Santa Barbara, Electric power data for Santa Maria were not available.2 Electric power costs are for Seattle.3 Publicly owned utility.

Solar heat costs are from optimal design systems yielding least cost heat.

Electric power heat costs are from U.S. Federal Power Commission, All Electric Homes, Table 2 (1970). Conventional heatfuel costs are derived from prices per million BTU reported in P. Balestra, The Demand for Natural Gas in the United States, Tables 1.2and 1.3 (North Holland Publishing Co., 1967). The 1962 costs were updated to 1970 by use of national price indexes on gas (121.1 in1970 versus 112.8 in 1962) and on fuel oil (119.22 in 1970 versus 101.2 in 1962) as adjustment factors on each fuel price in eachstate. Bureau of Labor Statistics fuel prices indexes obtained from Gas Facts. Fuel prices were converted to fuel costs by dividing bythe following national average heat (combustion) efficiencies: gas, 75%; oil, 75%. Heat efficiencies are from American Society ofHeating, Refrigerating and Air Conditioning Engineers, Guide and Data Book 692-694 (1963 ed.).

All solar heat costs based on amortizing entire solar system capital costs in 20 years at 6 percent interest. Capital investmentbased on current prices of solar water heaters at $4 per sq. ft. plus current costs of other components, and on anticipated near-termsolar collector price of $2 per sq. ft.

16

ELECTRIC

5 r

$/106 BTU

SOLAR

GAS

OIL

ENERGY SOURCE

FIGURE 4. COSTS OF SPACE HEATING

using heat from solar collectors [6, 8]. Theseexperiments show that the concept is promising,and no major technical barriers to successfuldevelopment are seen. Other cooling methods,by use of dehumidifying agents with solarregeneration, jet compression with solar input,are also possibilities on which a very fewexperiments have been performed. It is evidentthat there are numerous technological options tobe explored; these include many types of cool-ing equipment [9] and cycles, alternative meth-ods of providing energy storage and auxiliaryenergy input, and combinations of these com-ponents in systems. Economic projections based

on the preliminary experiments done to dateand not reflecting major developments in com-ponents or systems are promising.

Combined Systems

Although no experiments have yet been per-formed, the same major components, solarcollectors and energy storage units, can be usedto supply hot water, space heating, and airconditioning. Most of the solar heated experi-mental houses have included means for heatingwater; only one has included air conditioningother than by nocturnal radiation or by use of

17

heat pumps. The economics of combined sys-tems, with their higher use factor on capitalintensive equipment, can be expected to bemuch better than that of either heating orcooling alone.

There remain, however, numerous design andoperating problems which require solution be-fore practical systems can be marketed and used.

There are the least uncertainties both in thetechnology and the economics of these domesticapplications. There is, moreover, a very highbenefit/cost ratio in that the total funds neededfor the development of a viable enterprise willbe only a small fraction of the annual value offuel savings, or of equipment sales, or of someother measure of benefits to the economy.

LIMITING FACTORS ANDRECOMMENDED APPROACHES

The principal factor limiting the adoption ofsolar heating in favorable sections of the U.S. isthe lack of well-engineered and economicallymanufactured and distributed solar heat collec-tors. The key problem is the development,optimization, production design, and manufac-ture of such units. The difference in the cost ofheat supplied by solar collectors relative toconventional sources is disappearing and nolonger appears to be a major problem. Marketingmay however, require innovative concepts forgeneral acceptance by builders and homeowners.

The key problems impeding wide utilizationof solar cooling and combined systems, inaddition to questions analogous to those forheating, are economical cooling subsystems,evaluation of alternatives, designs and productengineering, construction and operating exper-iences. These are technical development prob-lems whose solutions can be assured byreasonable effort. As with heating alone, highcapital investment may impede initial adoption,but full appraisal of costs shows that fuel savingswill more than offset first-cost disadvantagewhen systems become commercially available.

The approaches to wide utilization of com-bined systems are indicated by the character ofthe problems. Support is needed for engineeringdevelopment and design studies, testing andimproving well conceived systems, optimizationstudies, and production engineering design, fol-lowed finally by full demonstrations and trialpublic use.

There is no doubt that among all the possibleuses for solar energy, residential heating andcooling has the highest probability of success.

GOALS AND PROJECT IMPACTS

The goal of research on solar heating andcooling is fully developed and engineered sys-tems suitable for wide public use. Researchtoward this end must have the following aims:

• Efficient and economical solar collectordesigns.

• Heat storage materials and containers, lowin cost and dependable in performance.

• An air cooling unit efficiently operable byheat from the solar collector-storagesystem.

• Economical system designs for househeating, cooling, and water heating, sup-plied with optimum combinations of solarand auxiliary energy.

Achievement of the broad objectives listedabove, through various specific projects involv-ing research, engineering development, systemdesign, economic analysis, production engineer-ing, component and system testing, and fullscale demonstration, will place this applicationin trial public use well within a decade. Asuitable and achievable practical goal is a 10percent penetration of the market for newbuilding heating and cooling installations by1985.

The impact of successful solar heating andcooling development may be forcasted in severalways as indicated in Table 6. The maximumpotential use of solar heating and cooling wouldinvolve virtually all new houses and commercialbuildings. Assuming solar energy could supplyan average of 80 percent of the heating andcooling requirements in 90 percent of all newhouses and single-story commercial buildings,4.5 percent or 8.4 X 1015 BTU per year of theNation's year-2000 energy requirements may be

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saved. The corresponding figures for 2020 wouldbe 8 percent and 23 X 1015 BTU per year.

A more probable impact, considering the timerequired for a new development to achieve wideuse and the greater suitability and economy ofthe system when used in new rather than oldbuildings, is 10 percent of new buildings con-structed in 1985, 50 percent in 2000, and 85percent in 2020. As percentages of total build-ings, these figures become approximately 1percent, 12 percent, and 31 percent, respec-tively. Corresponding energy savings are 0.12,2.1, and 10.5 X 1015 BTU/year.

Equivalent annual values of probable fuelsavings at these three intervals are $180 million,$3,600 million, and $16,300 million. Gas and oilcosts are estimated at a present average price of$1.50 per million BTU delivered to residentialcustomers.

The probable sales of solar heating andcooling equipment should reach an annual grossvalue of $0.75 billion by 1985, $4.5 billion by2000, and $9 billion by 2020. This new billiondollar industry will involve heating and coolingequipment manufacturers, their material sup-pliers, and their customers. Heating and coolingcontractors, their employees, and other serviceswill participate.

Some of the intangible benefits of this devel-opment will be the alleviation of problemsrelated to inadequate gas supplies in some areasof the country, the reduction of excessive andexpensive electricity peak loads and associatedpower system failures during very hot weather,and the extension of oil and natural gas suppliesfurther into the future.

RECOMMENDATION FOR SHORTRANGE RESEARCH ANDDEVELOPMENT (YEARS 1-3)

The short range goal of R&D effort inresidental solar heating and cooling should be afully workable prototype system suitable fortest operation in favorably situated residences.This can be achieved within three years of thestart of a program so oriented. It cannot beexpected that the system will be the mosteconomical or most efficient or most convenient

that is possible, because more time and develop-ment will be required for such advantages to berealized.

Component design and system design studies,optimization studies, cost analyses, and proto-type construction and testing of componentsand the integrated system are the main require-ments of the three-year R&D program. Thestudies must involve solar collectors, heat stor-age units, heat exchangers, absorption refrigera-tion equipment, auxiliary heat supply facilities,control instruments, and various sub-assembliesand full assemblies of these components.

RECOMMENDATIONS FORDEVELOPMENT IN 4TH TO10TH YEARS

After initial performance testing of a func-tional unit, the residential solar heating andcooling system should be subjected to a rigorousprogram of improvement and optimization.Three interrelated objectives are increased: effi-ciency, reduced cost, and greater simplicity andpracticability of application to general use. Mostof the effort should be placed on conceptspreviously investigated, but there should besome work on promising alternatives, especiallythose involving cooling methods.

The types of projects requiring support in thisphase of development are the same as thoselisted for the initial program, plus engineeringdesign and testing to increase effectiveness ofcomponents and complete systems, productiondesign and engineering study (ideally in coopera-tion with manufacturers) to reduce equipmentcost, and architectural and construction analysesto achieve practical applicability to residentialuse. Prototype testing and demonstration opera-tion of complete systems will be a substantialportion of the total effort during this period. Apublic information and education programshould be included in the demonstration phaseof development. Commercial production andsale of residential and commercial solar heatingand cooling systems should commence beforethe end of this ten-year period.

20

PROGRAM PLAN FOR THERMALENERGY FOR BUILDINGS

Table 7 contains a recommended program ofdevelopment to achieve practical use of solarenergy in the heating and cooling of buildings.Tasks previously discussed are indicated here inabbreviated form. Sub-division of tasks to theextent herein is necessarily subject to modifica-tions as work proceeds and results are obtained.Some tasks may require more effort than indi-cated, others less. The program must thereforehave sufficient flexibility for modification asneeded.

There should be continuous objective evalua-tion of the results of the program in order thatplanning of subsequent work or programtermination can be timely and effective. Inaddition to this continuous decision process,there should be certain planned milestones ordecision points. The first of these is set at 3years from program commencement. At that

time, technical and economic data, some ofwhich will be provided by prototype systemoperation, will provide a firm basis for planningthe next development steps or for discontinuingthe development. Abandonment is not antic-ipated, but many factors, some not even relatedto solar energy, may alter the present favorableprospects of this application.

Another decision point is indicated at the endof the fifth year, prior to starting a substantialdemonstration program. Information available atthat time will permit confident appraisal of themarket for solar heating and cooling, the impactof this application, and the requirements andorientation of a demonstration program.

The funding level estimated for the entire 10year program is $100 million. If the totalprogram is carried through approximately asoutlined, it is fully expected that at its con-clusion, residential heating and cooling withsolar energy will be in general public use.

Table 7. R&D Summary and Milestones for Solar Heating and Cooling of Buildings

Task

Year

10

Collector

Storage

Cooling

System design

System construction and testing

Production engineering

Architectural

Demonstration' 1> (including public information)

£££££

. Notes: (1) In cooperation with commercial builders and developers.A Technical and economic viability decision.A Demonstration decision.

21

RENEWABLE CLEAN FUEL SOURCES

The natural conversion of solar energy intoplant materials by photosynthesis and the fur-ther conversion of this stored energy into moreconcentrated forms such as natural gas, petro-leum and coal is the basis of the world's fossilfuel supply.

Because these fossil fuel reserves are beingdepleted rapidly, it is essential that considera-tion be given to means for providing largeadditional supplies of high quality, concentratedfuels by using forces similar to those whichproduced our fossil fuels. The managed produc-tion of plant tissue (e.g., trees, grasses, waterplants, fresh water and marine algae) with moreefficient use of solar energy and required nutri-ents carried out on suitable land and water areascould provide starting organic materials.

The plant materials which constitute theproduct of photosynthesis have a comparativelylow heat content per unit weight. The conver-sion of this plant material into higher heatcontent fuels (gases, oils, solids) similar to thosemaking up the fossil fuel reserves is thereforeessential for effective storage and efficient use asclean, contemporary fuels.

This section considers methods for produc-tion of various forms of stored energy viaphotosynthesis and also considers a number ofpromising methods for conversion of organicmaterials produced by photosynthesis into com-monly used fuels. Figure 5 presents a summaryof typical processes and products.

PHOTOSYNTHETIC PRODUCTION OFORGANIC MATERIALS AND HYDROGEN

Introduction

As indicated in Figure 6, the successfulutilization of a moderate portion of the area(land and water) under the control of the UnitedStates for conversion of solar energy into storedchemical energy via photosynthesis could pro-vide the entire electrical energy needs of thecountry.

The large scale photosynthetic production of

plant material at solar energy conversion effi-ciencies, e.g., 3-5%, greater than usually ob-served in ordinary agricultural operations, 0.1%,would supply materials that could serve directlyas fuels for production of part of man's energyneeds or that could be subsequently convertedinto other forms of higher quality fuels. Con-cepts to be considered here are directed towardproduction of large amounts of land-grownproducts, e.g., trees or grasses, and also largeamounts of water-grown products, e.g., algae orwater plants. Because the ultimate purpose ofgrowing the plant material is to provide a sourceof material that can be converted to heat energyby combustion or to enriched fuels by applica-tion of appropriate conversion processes, otheravailable organic materials that can be convertedin the above ways will also be examined. Theselatter materials comprise the large amounts ofsolid wastes—agricultural, animal, industrial, andurban-which are presently creating grave en-vironmental problems and which actually repre-sent a rich energy resource.

LAND PL ANTS

In natural ecosystems, land plants such astrees and grasses show a net productivity rangingfrom about 4 to 26 tons of dry plant materialper acre per year. Under intense cultivation theyields of certain crops have been reported to beabout 40 tons of dry material per acre per year.Assuming an average yearly insolation of about2 .4X10 1 0 BTU per acre per year and anaverage heat of combustion of the dried plantmaterials of 16 X 106 BTU/ton, the efficiencyof solar energy conversion ranges between about0.3% and 3.0%.

If, through advanced management practicesincluding exploitation of modern developmentsin plant genetics, plantations were operated toproduce continuous crops at greater than 3%solar energy conversion, less than 3% of the landarea of the U.S. would produce stored solarenergy equivalent to the anticipated U.S. electricenergy requirements for 1985.

22

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FIGURE 6. AVAILABILITY OF SOLAR ENERGY VS. LAND AREA

24

WATER PLANTS

The fixation of solar energy in the form ofplant tissue grown in, or on the surface of,bodies of water can supply large amounts oforganic material. Algae may be grown in shallowponds and with management and some additionof nutrients to the water can produce largequantities of organic materials. Floating plantscan be cultivated in a similar fashion.

If high levels of nutrients in the form ofanimal wastes are added to ponds containingappropriate bacterial populations, algae andfloating water plants can produce heavy yieldsof plant tissue. In the process of growth, theplants remove soluble nutrients from the water.Removal of the plants by harvesting thereforerequires continued addition of waste materialsto the ponds.

Status

PRODUCTS OF PHOTOSYNTHESIS

Tree Farming

All aspects of tree farming in the sense ofplanting, cultivating, and harvesting trees on alarge scale and as a continuing crop, are pres-ently practiced for such industries as lumber andpaper. Therefore, no new technology is neededto demonstrate the technical feasibility of thatpart of the concept. Tree farming for energymay be somewhat different because it will betotal plant farming. The objectives will be tomaximize the total pounds per acre produced,including trunk, limbs, and roots [10].

Grasses

The intensive farming of grasses, which havebeen reported to produce in the range of 13-15tons per acre per year, would be expected to besimilar in all respects to the cultivation andharvesting of hay.

Algae Culture

Extensive studies have been carried out overmany years relating to the culture of specificalgae strains as a potential high protein foodsource. The growth of algae for the purpose ofremoving nutrients in sewage oxidation ponds is

a common procedure. Recent reports [ 11,12]have indicated continuing yields of 20-30 tonsof dry material per acre per year with peakproduction at the rate of about 50 tons per acreper year.

The harvesting of this material is commonlycarried out using flocculation and centrifugationprocedures. Using these processes of harvesting,the reported costs of a dried product are about$.05/pound [13]. A small scale pilot plantsystem has been operated at the University ofCalifornia, Berkeley, since 1959. Larger systemsare operating in Asia.

Water Plants

Floating water plants, such as water hyacinth,presently are pest plants in many rivers and lakesin tropical and semitropical areas. The rate ofgrowth is rapid and in nutrient-rich ponds netproductivity of up to 85 tons of dry product peracre per year has been reported [14]. Presentmethods of harvesting these plants do notappear to be sophisticated but interest in theplants as a cattle feed is developing and improve-ments may be forthcoming.

ORGANIC WASTES

Agricultural Plant Wastes

The principal wastes in this category are thecrop residues left in the field at the time ofharvest. The main problem relating to utilizationof most crop residues is that of material collec-tion and transportation. Although it has beenestimated that the annual amount of wastedstraw is sufficient to satisfy all of the annualU.S. cellulose demand, it is not utilized foreconomic reasons.

Animal Wastes

On the basis of 118 X 106 head of cattle inthe U.S. [15,16] , the expected dry organicwaste would amount to about 13 X 107 tons peryear. Much of this waste is found on open rangeand is not recoverable. If it is assumed that10-20% of the cattle are maintained in restrictedarea feed lots, the total waste from which energyrecovery can be considered amounts to13 X 106 to 2 6 X 1 0 6 tons of dry organic

25

material per year. Lesser amounts of wastes arealso available from other types of animals raisedin confined areas. It is therefore estimated thatabout 2 X 107 tons of dry waste per year wouldbe available for use. Since local concentrationsof these wastes may be very large, the cost as araw material could be the cost of transportationto a processing site less some credit for acceptingthe waste.

Urban Solid Wastes

Urban waste generation may be assumed toapproximate 5 pounds per person per day [17].Of this approximately one-half is dry organicmaterial obtained from waste paper, kitchenwastes, and garden or lawn wastes. Although thisamounts to about 108 tons of dry organics peryear over the entire population, the portiongenerated in cities where severe disposal prob-lems exist approximates 2 to 4 X 107 tons peryear. As with the animal wastes the cost of thismaterial as an energy source could be thetransportation charges to the conversion site lessa credit for accepting the waste.

Summary

It is considered that the total animal andurban solid wastes available under conditionsnot involving potentially prohibitive collectioncosts may amount to 4 to 6 X 107 tons of dryorganic material per year. The average heatcontent of this material may be 16 X 106 BTUper ton. Therefore, an annual energy supplyamounting to 0.6 to 1.0 X 101 s BTU is avail-able. This represents approximately 6% of pres-ent energy requirements for electrical generatingplants.

Limiting Factors and Recommended Approaches

PRODUCTS OF PHOTOSYNTHESIS

Tree Farming

Considering a tree crop as a source of rawmaterial for conversion to energy or to anupgraded fuel, the technical problems fallprimarily in the area of cost reduction. At thepresent time, the cost of wood chips producedfrom lumbering wastes is reported to be about$20 a ton at a production site. Assuming a

similar cost at the "forest plantation" site, anadditional cost for transportation of the chips tothe point of use must be considered.

If utilization of the tree crop is envisioned asfuel for a 1,000 MW power plant, the requiredfuel supply is assumed to be obtained from anarea of 400-500 square miles and would requiretransportation over distances of 10 to 15 miles.Handling of the fuel during drying operationsincurs additional costs. These processing chargessuggest fuel costs at the power plant in the rangeof $1.50 to $2.00/106 BTU.

There appear to be no significant socialproblems associated with this concept. Environ-mental problems would involve particulate emis-sions and low-level sulphur dioxide emissions.These would be handled by adequate controlson the combustion unit.

In this concept, the main problems are to findcheap land, increase the solar conversion effi-ciency, and develop low cost methods of har-vesting, processing, and transporting the ma-terial. Specifically the cost of dried wood fueldelivered to the power plant site must becompetitive with alternate fuels at the time theplant goes on line. To accomplish this goalinnovative procedures for harvesting, size reduc-tion, drying, and transporting of the fuel may berequired to develop commercial feasibility.

Similar costs of the wood chips would beassociated with their conversion to fuels withhigher energy content. The resulting fuel wouldobviously have a still higher cost.

Grasses

Reduction of costs attached to cultivation,harvesting and transportation appear to be theprimary problem areas. There may also besignificant problems connected with plant pests.No estimates of costs for this crop are immedi-ately available but costs for hay should provide aguide.

Algae Culture

Some technical problems which have beenrecognized include development of unwantedalgae predators and pathogens in algae cultures,accumulation of non-algae turbidity, and algaeseparation. Some problems of an economic

26

nature are large land use and associated costs,cost of pond construction and maintenance, andharvesting costs. Estimates using present tech-nologies indicate costs of $0.05 a pound for dryalgae mass. New harvesting techniques areneeded to bring about large decreases in costs.

Water Plants

Technical problems associated with growthand harvesting of floating water plants includethose of predation by animals; elimination ofnuisance insects; and development of innovativeharvesting procedures to minimize expenditureof energy for harvesting and transporting them.

Studies are required which will lead to im-provements in the efficiency of conversion ofsolar energy to stored chemical energy in planttissue for each of the several classes of plantsconsidered suitable for use as fuels or as sourcesof new supplies of high quality fuels.

System studies are required to establish firmlythe step or steps in the plant growth andharvesting which make the largest contributionsto the total cost. Harvesting presently appears tobe the highest cost item and primary effortshould be directed towards innovative develop-ments in this area.

Studies of optimum transportation methodsfor candidate plant materials should be carriedout.

ORGANIC WASTES

Technical problems related to use of organicwaste materials as energy sources are largely dueto the variable composition and tendencytowards degradation of the wastes. These prop-erties make themselves apparent during storageand transport.

Goals and Projected Impacts

The goals and R&D requirements for proc-esses involving the production of organic mate-rials by photosynthesis to serve as energysources or as raw materials for enriched fuelsproduction are described in Table 8. The poten-tial impact of these materials on the energysupply system is presented in Table 9.

Recommendations for R&D

Continued improvements are needed in solarenergy conversion to plant material and inharvesting and transportation processes. Aphased program plan for new fuel and energysources is shown in Table 10.

Emphasis should be directed toward possiblelarge scale utilization of marine areas for photo-synthesis of new plant material and for conver-sion of plant material to high quality fuels. Thefunding level estimated for the entire 10 yearprogram is $30 million.

ADVANCED CONCEPT-BIOPHOTOLYSIS OFWATER TO PRODUCE HYDROGEN GAS

Concept Description

The direct formation of hydrogen gas usingthe photosynthetic apparatus of green plants orblue-green algae has been proposed. Under thestimulation of light, the photosynthetic appa-ratus in chlorophyll and other accessory pig-ments can raise the oxidation-reduction poten-tial of the electrons released from water to alevel as much as 0.3 volt more negative than thehydrogen electrode. Thus it is thermodynami-cally possible to couple the reducing potential ofthese electrons with an enzyme (hydrogenase) tobring about the reduction of hydrogen ions toform hydrogen gas. The hydrogenases may existeither endogenously in algae or exogenously inbacterial sources. A particular problem is theneed to accomplish the reduction to hydrogengas in the normal presence of oxygen. Severalpossibilities can be investigated for accomplish-ing the required coupling of photosyntheticallyreduced substances and appropriate hydrogenaseactivity. In effect, the normal processes ofphotosynthesizing cells in fixing carbon areinterrupted and diverted to provide hydrogengas as the reduced product. This process repre-sents essentially a photolysis of water.

The requirements for such an aqueous systemwould be (1) light, (2) a stabilized photosyn-thetic apparatus capable of generating re-ductants from water, (3) a suitable electron

27

Table 8. R&D Requirements for Development of New Fuel and Energy Sources

Steps to economic feasibility Major technical problems Time scale

1. Improve solar energy conversion in fresh wateralgae, marine algae, and floating plants bymaintaining required nutrients in ample supply.

2. Develop new harvesting procedures for algae.

3. Optimize algae-bacteria symbosis.

4. Develop new harvesting procedures for floatingwater plants.

5. Attempt improvement in solar energy conversionin land plants.

6. Decrease cost of harvesting of land plants.

7. System selection and system components develop-ment.

8. Pilot plant, 500 Ib./day.

9. Demonstration plant, 25 ton/day.

10. Commercial plant, 1,000 ton/day.

1. Improvement in crop yield.

2. Cost of harvesting.

3. Cost of transportation.

Steps 1-6Research1973-1976

Steps 7-9Development1977-1988

Step 10Commercialafter 1988

carrier such as ferredoxin, and (4) a ferredoxin-coupled hydrogenase under conditions to con-vert hydrogen ions to molecular hydrogen.

This concept is being pointed out in spite ofits relatively speculative nature because of recentdevelopments that suggest its accomplishmentand the extremely important ramifications ofproducing hydrogen directly. The use of hydro-gen obtained in this process to produce electricpower via the H2 -O2 fuel cell offers the possi-bility of providing very clean and very efficientpower sources dependent largely on solarenergy.

Status

The thermodynamic feasibility of this processfor producing hydrogen gas has been established.An efficiency as high as 10% has been observedfor the photosynthetic portion of the process.The combination of the process components to

produce a working system has not beendemonstrated.

Limiting Factors and RecommendedApproaches

TECHNICAL

Besides the large amount of multidisciplinarybasic research and development work necessaryto demonstrate the ability to actually producehydrogen by biophotolysis of water using solarenergy, engineering studies will need to beconducted to determine the technical feasibilityof capturing the solar energy in the photosyn-thetic apparatus in a closed system in a mannerpermitting recovery of the hydrogen formed.

ECONOMIC

If the economics of the technical process forhydrogen production referred to above arefavorable, other costs, such as raw materials, will

28

Table 9. Impact of New Energy and Fuel Sources.

Time Scale Plant growing Solid wastes

1%10%

Resource Effect

Fuels

Environmental Effects

Land use

Air

Water

Waste

Thermal

Economics (Projected)

Primary orSecondary EnergySource

20002020

Conserves fossil fuels.

Large areas required for landplant growth.

Beneficial-02 added, C02

removed.

Large areas required forwater plant growth.

None.

$1.50-$2.00/106 BTU(Assumes developmentof successful harvestingprocess).

1985-20002000-2020

Conserves fossil fuels.

Some storage area required.

Some storage required.

Beneficial, eliminateswaste disposal problem.

None.

1.00/10* BTU.

be negligible. Hydrogen as a fuel can be trans-ported economically and its use in H2-O2 fuelcells provides an efficient means for electricpower generation.

SOCIOLOGIC

The cycle of converting water to hydrogenfuel and of using this fuel in H2-O2 fuel cellsresulting in water as the combustion residue hasgreat attraction for preserving the environmentand for recycling of materials.

Although this is a speculative area of tech-nology, the benefits to be gained from develop-ment of an economic process for producing largequantities of hydrogen are very large. A modestlevel of support should be provided for thesetypes of concepts that can lead to important

breakthroughs. The estimated funding for a 15year program is $30 million.

CONVERSION OF ORGANIC MATERIALS TOFUELS OR TO HEAT ENERGY

Each of the organic materials described in thepreceding section can be converted directly intothermal energy by combustion or can be con-verted to more concentrated fuels by a numberof biological or chemical processes. The choiceof conversion method is frequently dictated bythe physical nature of the material. For ex-ample, certain freshly harvested plants having avery high water content would be most profit-ably converted to a concentrated storable fuelby a biological process that operates in an

29

Table 10. Phased Program Plan for New Fuel and Energy Sources.

ResearchYear

10 11

Yield improvement

Algae

Water plants

Marine algae

Land plants

Trees

Grasses

Harvesting

Algae

Water plants

Marine algae

Land plants

Trees

Grasses

System development

Components

Pilot plant

Demonstration plant

Commercial plant

Selection

Selection

Commit pilot plant

JA Commit demo

I —J

30

aqueous medium. In other cases where thematerial is relatively dry or is resistant tobiodegradation, direct combustion to heat en-ergy or conversion to concentrated fuels bypyrolysis would be indicated.

This chapter will consider the advantages anddisadvantages of direct combustion of the var-ious organic materials or their conversion toother fuels by fermentation, pyrolysis, or chem-ical reduction. These methods are compared inTable 11.

Combustion of Organic Materials

CONCEPT DESCRIPTION

The photosynthetically produced organicmatter described earlier can be burned to pro-duce steam in equipment similar to that usedwith coal. Since the plant material has a highpercentage of constituents other than carbonand hydrogen, the heat of combustion per unit

weight is significantly smaller than coal. Also theplant material, if freshly harvested, would con-tain water to the extent of about 47% in thecase of most trees and of about 95% for somewater-grown plants. In order to provide enoughheat for the combustion to be self-sustaining,the fuels are normally dried to about 10-15%water.

The organic solid wastes which constitute animportant additional source of stored energymay also be burned directly. They have watercontents ranging from about 85% for freshlycollected agricultural plant and animal wastes toabout 20% for many urban solid wastes, so againa drying step is usually required. The heats ofcombustion of these materials are in the samerange as those of the plants mentioned above.

Because of the varied form and size of organicmaterials, size reduction or briquetting may bepracticed. Particulates in the stack gases mayrequire additional pollution control equipment,

Table 11. Comparison of Methods for Conversion of Solid Wastes to Clean Fuel

Process requirements

Form of feed

Temperature

Pressure

Agitation

Other

Form of product

Yield (percent oforiginal material)

Heating value

Percent of original heatcontent recovered inproduct (assume 8,000BTU/lb. dry waste)

Chemical reduction

Aqueous slurry(15% sol ids)

320°-350°C

2,000-5,000 psi

Vigorous agitation

Uses CO

Oil

23%

15,000 BTU/lb.

37%(corrected for CO use)65% anticipated

Pyrolysis

Dried waste

500°-900°C

Atmospheric

None

None

Oil and Char

40% oil; 20% char

12,000 BTU/lb. oil*9,000 BTU/lb. char*

82%(60% if char not included)

Fermentation

Aqueous slurry(3-20% solids)

20°-50°C

Atmospheric

Slight

None

Gas

20%-26% (maximum)

23,800 BTU/lb.

60%(77% maximum)

*AII of gas and 1/3 of char used to supply heat.

31

and certain of the materials contain significantlevels of sulfur.

STATUS

Power production by combustion of urbansolid wastes is already practiced on a commercialscale [18], principally in Europe, and mosttechnical problems have been solved. There havebeen reports of corrosion problems and ofuneven boiler operation due to variable composi-tion but they are not considered serious.

Although not used for large scale powerproduction, wood in the form of chips orsawdust is used extensively for power produc-tion in lumbering and related industries.

Animal wastes are used regularly in India toprovide at least a part of the relatively small heatrequirements.

The technical feasibility of power productionfrom varied organic materials has been estab-lished, but the economic feasibility is uncertain.The efficiency with which power can be gener-ated and the costs associated with pollutioncontrol, corrosion, fuel collection, processingand transportation must be examined.

LIMITING FACTORS AND RECOMMENDEDAPPROACHES

Economic

The actual cost of the fuel at the power plantis probably the key factor in establishing theviability of this concept. In the cases of use ofurban solid wastes and concentrated animalwastes produced at large feed-lots there could bea credit paid for removal of the wastes.

Technical

The non-uniformity of the fuel and therelatively low heat content due to presence ofwater and inerts can lead to uneven operation ofsteam producing plants. The nature of the fuelsmay also result in problems inyolving pollutantsand particulates which must be removed fromstack gases [19].

GOALS AND PROJECTED IMPACTS

Although quite large quantities of urban,animal, and agricultural wastes are produced inthe U.S. every year, the amounts available in

restricted areas and in sufficiently high concen-trations to suggest probable economic utilizationis thought to be between 4 and 6 X 107 tons ofdry organic material. The average heat contentof this material is assumed to be about 15 X 106

BTU per ton.If all this material were burned to produce

steam and subsequently electric power, thepower generating capability would be in therange of 5,000-10,000 Mw(e). This is a relativelysmall percentage of the electrical power con-sumption in the U.S. in recent years, however apotential supply of this magnitude should not beneglected.

For the above reasons it becomes importantto consider the impact of the combustion ofplant materials grown specifically for thepurpose of providing a continuing large volumesupply of stored chemical energy.

For example, selected tree crops can be grownon a large farm and harvested on a continuingbasis. The product can be reduced in size, dried,and transported to an electric power plant site(1,000 Mw) and used for fuel. The ash resultingfrom the combustion can be returned as afertilizer component to the farm. The tree-firedelectric plant would be centered in a forestedarea where the land could not be used profitablyfor other crops. This land would be harvestedand replanted to provide a continual regener-ating fuel supply. Because this process wouldresult in the mining of a lesser amount of coal,benefits which can be foreseen include a reduc-tion in strip mining and of the acid wasteproblems accompanying such mining, and areduction in the emissions of sulfur dioxideresulting from the combustion of high sulfurcoals.

The R&D requirements for further develop-ment of the process of direct combustion oforganic material is described in Table 12. Thepotential impact of the process on the energysupply system is described in Table 13.

RECOMMEND A TfONS FOR R&D

Studies of solid waste collection, drying, andtransportation should be carried out to developlower cost, more effective procedures for obtain-ing benefit from large amounts of potential

32

Table 12. R&D Requirements for Combustion of Organic Matter.

Steps to economic feasibility

Plants/trees

1. Feasibility study.

2. Develop new harvesting methods.

3. Develop new techniques for size reduction.drying and storage of the prepared fuel.

4. Improve total crop yields.

5. Develop sulphur removal techniques.

6. Component development.

7. Pilot plant- 1 MW.

8. Demonstration plant— 50 MW.

9. Commercial plant-500- 1,000 MW.

Organic solid wastes

1. Feasibility study.

2. Develop combustors for agricultural waste.

3. Develop collection, drying, and transportation tech-niques.

4. Laboratory experiments.

5. Pilot plant- 1 MW.

6. Demonstration plant-50 MW.

7. Commercial plant-500- 1,000 MW.

Major technical problems

1. Large energy expenditure inchipping operation.

2. Efficient drying.

3. Transportation of fuel toplant site.

4. Efficient removal of sul-phur oxides and particu-lates from stack gases.

1, Combustion of wastes ofvariable composition andenergy content.

2. Reduction of moisturecontent of wastes.

3. Efficient removal of sul-phur oxides and particu-lates from stack gases.

Time scale



Step 9CommercialAfter 1988




energy. Studies of whole plant farming toincrease the solar conversion efficiency arerequired. Detailed systems analysis and eco-nomic arid optimization studies should be under-taken to evaluate system concepts for growingand preparing organic materials for direct com-bustion for electric power generation. Thesestudies should be primarily oriented to identify-ing process steps making the largest contribu-tions to the total cost, and to suggest proceduresfor improving the economics. The expectedfunding for the 15 year program is $140 million.

Bioconversion of Organic Materialsto Methane

CONCEPT DESCRIPTION

Most organic materials in the presence ofsome moisture and in the absence of oxygen aresubject to natural fermentation in which a largepercentage of the carbon content of the materialis converted into a mixture of methane andcarbon dioxide. Figure 7 is a schematic of a unitfor converting solid waste to methane byanaerobic fermentation. The conversion occurs

33

Table 13. Impact of Combustion of Organic Matter on Energy System

Time scale Plants/trees Solid organic wastes

Initial (1%)

Significant (10%)

Resource effect

Fuels

Materials

Environment

Land use

Air

Water

Visual

Waste

Thermal

Other

Economics

Fuel cost ($/MBTU)

2000

2020

Conserve fossil fuels.

Large areas required for dryingwood chips.

Some sulfur oxide and unburnedhydrocarbon emissions.

Same as for fossil fuel combustion.

Ash returned to soil.


Possible negative popular reactionto growing forests for burning.

$1.25-S2.00 (estimated).

2000 (possibly 1985)

2020 (possibly 2000)

Conserve fossil fuels.

Reduce waste disposal problems.

Some land areas required for dryingand waste storage.

Combustion produces air pollutants.


Ash returned to soil.


Decreases supply of soil conditioningorganics.

S1.00-S2.00 (estimated).1

Based on reasonable truck and rail haul distances and costs. No charge for wastes. No subsidy for agricultural wastes.

at or around normal atmospheric pressures andat temperatures ranging from about 15°C up toabout 50°C. The process operates with organicsolid concentrations as low as a few percent andas high as 60-70%.

The volatile products of the fermentation aremethane, carbon dioxide, trace amounts ofhydrogen sulfide, and nitrogen gas. The volatileproducts as produced contain from 50 to 70%methane with carbon dioxide representing al-most all of the residual. The heat of combustionof this crude product therefore ranges between500 to 700 BTU/cu. ft. of gas and the gas can beburned directly for electric energy production.The gases can also be treated readily to removecarbon dioxide and hydrogen sulfide; and, thepure methane remaining can be pressurized forintroduction into existing natural gas pipelines.

The heating value of this methane is about 1,000BTU/cu. ft.

In general between 4.5 to 6.5 cu. ft. (STP) ofmethane can be obtained from the conversion of1 pound of dry organic materials or from9 - 1 3 X 1 0 3 cu.ft./ton. This corresponds to aheating value of 9-13 X 106 BTU/ton andrepresents 60-80% of the heating value of theoriginal organic materials.

If the entire amount of solid wastes believedto be economically recoverable were subjectedto anaerobic fermentation to methane, a total ofbetween 3.6 and 7.8 X 101' cu. ft. of methanewould be expected. This would represent arecovery of 3.6 to 7.8 X 1014 BTU/year orapproximately 2-3% of the yearly consumptionof methane in the United States.

Under conditions where the starting organic

34

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material has a high water content the energyrequired for drying prior to combustion mayequal or exceed the heat content of the organicmaterial so a process such as fermentation,where drying is not required, becomes an effi-cient means for recovering the heat energy.

STATUS

The anaerobic fermentation process has beenin use for many years for reducing the volumeand weight of domestic sewage solids throughconversion to liquid and gaseous products. Ingeneral the amount or composition of gasproduced is of secondary interest since solidsreduction is of principal concern. Many of thelarger installations, processing up to 100 tons ofsewage sludge per day, have used the generatedgases for supplying their power requirements.

The use of anaerobic fermentation for theprimary purpose of fuel production throughconversion of organic materials such as urbanorganic wastes, agricultural wastes, animalwastes, and plant crops (including algae orfloating plants) specifically grown for thepurpose of such conversion is in its infancy.

Laboratory scale studies have been carried outat a number of locations using domestic solidwastes and animal wastes [20,21]. The studieshave progressed to the point where most of theground work leading to small pilot installationshave been completed. The small pilot installa-tions would accommodate solids up to 200Ib/day with expected gas production up to1,000 cu. ft. methane per day.

Studies have also been carried out in whichalgae grown in sewage ponds and floating waterplants (water hyacinth) grown on many tropicaland semitropical bodies of water have beenconverted to methane by the fermentationprocess [13,22]. Bacterial populations havebeen developed which permit the fermentationprocess to be conducted in a marineenvironment.

Economic evaluations of the fermentation ofsolid wastes to methane have been made. Be-cause a credit can be allowed for receiving thesolid wastes from municipalities, the methaneproduction costs using this raw material appear

to be competitive with imported liquified nat-ural gas. Preliminary estimates of methane costsproduced by fermentation of algae grown onsewage ponds suggest costs between SI.50 and$2.00/106 BTU.

Similar estimates of costs of produced meth-ane from all materials which are grown andharvested are to be expected and point up, inparticular, the need for substantial improve-ments in harvesting techniques.

In addition to the obvious mitigation of thesewage disposal difficulties, advantages of theuse of conversion of organics to methane byfermentation include the low energy require-ments of the system, i.e., atmospheric pressureand temperatures from 20°C to about 50°C;theproduction of a single hydrocarbon gas which iseasily purified; and, the relatively high recoveryof the heat content of the feed in the form ofmethane. Disadvantages include the large size ofinstallations and relatively slow rate of reaction,resulting from the necessary very mild operatingconditions.

The process equipment, although of large size,is not complicated and is not excessively costly.

LIMITING FACTORS AND RECOMMENDEDAPPROACH

The technical feasibility of the process hasbeen demonstrated. Full scale development canbe undertaken after pilot scale operations havedemonstrated optimum operating conditions formaximum conversion of organic material tomethane; and, after established viable methodsfor ensuring operation of a living biologicalsystem exposed to numerous challenges havebeen developed.

GOALS AND PROJECTED IMP A CT

The technical feasibility of biocbnversion oforganic material to methane has been establishedfor many years. The immediate goal should beto establish the economics of the process usingorganic materials resulting from photosynthesisand organic wastes. This requires fermentationprocess optimization and construction and oper-ation of pilot plants. The potential impact ofthis process is described in Table 14. The processhas the potential to supply all our gas needs.

36

Table 14. Impact on Energy System of Fuel Production by Bioconversion of Organic Materials to Methane

Time scaleMethane production by

fermentation of solid wastesMethane production by fermentation

of algae/floating plants

1% impact10% impact

Resource effect

Fuels

Materials

Environment

Land use

Air

Water

Thermal

Visual

Waste

Other

Economic

Fuel cost

19851995

Could ultimately supply 2-3% of US gas needs.

Insignificant—only construction materials required.

Approximately same as present waste disposal landuse.

Minimized air pollution from waste depositoriesand fossil fuel combustion.

Locally possible significant; nationally small.

No thermal discharges involved.

Significant improvement over garbage dump/burning facilities.

There is approximately 60+% weight reductionin solid wastes; Solids equivalent to about 40%of the initial waste weight appear as sludge. Pre-sently discarded.

A new multi-billion dollar protein food and methanefuel industry would be created if high protein cellsin digester sludge are recovered and excess fresh wateror marine algae are grown.

About same as imported LNG; could be less.

19851995

If methane is produced from algae/F.P.100% of US gas needs in 2020 could be suppliedusing 5% of the area of the U.S. (2% Solar EnergyConversion Efficiency).

5% of U.S. land area to produce 100% of year2020 U.S. gas needs.

Significant: surface areas of ponds and lakesmay be covered with algae or floating plants.

No thermal discharges involved; for proteinproduction from algae thermal pollution whichwould have accompanied farm energy produc-tion would be eliminated.

Low profile aesthetic appearance beautifieslandscapes with artificial lakes; lake surfaceswill be covered with vegetation.

Utilizes solid or liquid wastes on large scaleinstead of continuing present disposal problems.

Higher than for solid wastes. Must reflect costof producing algae or floating plants.

37

However, the amount of gas that will besupplied by this process will depend on the gascost and the availability of land and/or waterarea for growing the organic feed.

A first estimate of the cost [23] of usingwaste as the organic feed is shown in Table 15.The costs are based on a 1,000 ton organic perday plant and are cited for each system compo-nent in terms of cost per 103 cu. ft. methaneproduced.

One configuration of system components, asindicated by asterisks on the table, indicates acost of pure methane at pipeline pressure of$0.45/103 ft.3 CH4, or $0.45/106 BTU assum-ing 103 BTU/ft.3 methane. The costs weredeveloped using 1967-1969 dollars. The creditfor receiving the waste from the municipalitieswas taken as representative of the East Coast ofthe U.S. and amounted to $5.25/ton. There arenumerous arrangements of components whichcould lead to even lower methane productioncosts but their utilization depends on specificgeographic and other factors.

Table 15. Cost Estimate for Bioconversion ofOrganic Waste to Methane

(Based on a 1,000 ton/day plant).

* Acceptance of solid waste frommunicipality

* Transfer station* Size reduction* Salvage transportation

(alternatives)Rail haul 50 miles

* 100 milesTruck haul 50 miles

100 milesBarge 50 miles

100 milesPipeline (10% slurry) 50 miles

100 miles* Transfer station digestion

(107 ft.3)* Conventional

Low cost* Sludge disposal* Gas purification* Gas pressurization to pipeline

pressure

Cost per103 ft.3

methane

$0.184$0.317

$0.166$0.213$0.897$1 .460$0.133$0.146$0.352$0.600$0.146

$0.274$0.156$0.250$0.025$0.025

Credit per103 ft.3

methane

$0.880

$0.125

No firm estimates of costs have been obtainedfor the conversion of other organic materials tomethane. The use of animal manures and ofplant wastes as biodegradable materials has beensuccessful but process costs will depend stronglyon transportation and gathering costs. The sameuncertainties apply to the conversion of plantsgrown specifically for the purpose. The costs ofharvesting, drying, transportation, and otherprocesses using present techniques are too highto permit an economic process. Innovative lowcost cultivation and harvesting procedures areessential.

RECOMMENDA TIONS FOR R&D

The R&D recommendation for conversion oforganic wastes is presented in Table 16. TheR&D for the conversion of grown organicmaterials is much the same as that for organicwastes. Additional studies are required to estab-lish which grown organic matter is best and todevelop economic techniques for growing, har-vesting, and processing organic materials forbioconversion. The expected funding for a 15year program is $60 million.

Pyrolysis of Organic Materials to Gas,Liquid, and Solid Fuels

CONCEPT DESCRIPTION

Pyrolysis is a process of destructive distilla-tion, carried out in a closed vessel in anatmosphere devoid of oxygen. This process haslong been applied commercially to wood for therecovery of organic by-products such asmethanol, acetic acid and turpentine in additionto the residual charcoal. Any organic materialmay be subjected to this treatment with theexpectation that there would be obtained gas,liquid and solid products all of which couldserve as fuels. In addition, materials which aredifficult to dispose of, for example, plastic andtires, can be converted to fuel or other usefulproducts by this process. The gases are usually amixture of hydrogen, methane, carbon mon-oxide, carbon dioxide, and the lower hydro-carbons. The liquids are oil-like materials, andthe solids are similar to charcoal. Operating

38

Table 16. R&D Requirements for Bioconversion of Organic Wastes to Methane


1. Minimize cost of waste transport.

2. Maximize efficiency of conversion to gas.

3. Laboratory scale-1 Ib. organic waste/day yielding5-10 ft.3 methane/day.

4. Pilot plant—10 tons organic waste/day yielding100,000-200,000 ft.3 methane/day.

5. Demonstration plant—100 tons organic waste/dayyielding 1-2M ft.3 methane/day.

6. Commercial unit-1,000-10,000 tons organic waste/day yielding 10-100M ft.3 methane/day.

1. Find better waste trans-port means.

2. Minimize cost of methanefuel generated.

Steps 1-3Research1977

Steps 4-6Development1983


temperatures range from about 500°C to as highas 900°C or more.

STATUS

Extensive batch studies of pyrolysis oforganic wastes have been carried out in theUnited States, Europe, and Japan [24,25,26,27]. It has been established that pyrolysis istechnically feasible as a method of processingsolid municipal wastes. The efficiencies in thepast have been low and the net fuel productionwas small. Significant increases in efficiencyhave apparently been made, and it is nowreported that the combustible gases are suffi-cient to operate the plant and that about twobarrels of oil are obtained per ton of dry organicmaterial. A pilot plant handling four tons ofurban waste per day has been operated. Figure 8shows a schematic of the process. Laboratorytests show that at higher temperatures theprocess can also be used to make gas instead ofoil. The heating value of the gas was about 770BTU/ft.3, 80% of the dry organic matter beingconverted.


There do not appear to be any factors limitingprogress to the demonstration phase which

would be in the 50 ton per day size. Currentdesigns are for processing urban wastes whichare a non-uniform complicated mixture ofmaterials. If a grown organic of relatively uni-form properties were used, the efficiency mightbe improved and the operating costs reduced.The major uncertainty in the near term utiliza-tion of this process is the cost of the fuel.

GOALS AND PROJECTED IMP A CTS

The immediate goal should be a 50 ton perday demonstration plant. The next step shouldbe a 500 ton per day operation. The first use forsuch a plant would be for urban waste disposal.The 500 ton plant could handle the urbanwastes for a city of about 300,000 people. Theexperience gained in operating the plant onwaste organics would be directly applicable toone operating on grown organics.

If the total amount of solid wastes previouslyassumed (4-6 X 107 ton/year) were converted tooil, 1 30,000 to 230,000 barrels per day wouldbe produced which is about 1% of our dailyrequirement. When larger amounts of materialare available economically the impact willincrease.

A first estimate of the cost of producing fuelfrom organic wastes is presented below for a2,000 ton/day pyrolysis plant.

39

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Total Plant Capital(excludes land) Si 1.5 X 106

Working Capital . . $0.4 X 106

Annual Operating Costs (amorti-zation, 25 years @ 6% $3.313 X 106

Annual Net Profit FromSales $3.647 X 106

This indicates a total operating cost of about$.450/ton of as-received wastes. The net pro-jected revenue from sale of products, afterallowing for the disposal of unrecovered inorgan-ics, is about $5.00/ton (when based on 350operating day/year). These economics suggestthat a 2,000 ton/day processing plant could beoperated at no net cost to a municipality.

RECOMMENDATIONS FOR R&D

Research is not required for the pyrolysisprocess. Although temperatures between 500°Cand 900°C are used, the pressures are low andconventional structural materials can be used.The chemistry has been studied and demon-strated in both laboratory and pilot plantexperiments. Work can begin immediately on a50 ton per day production facility. Table 17 listssome major development projects. The expectedfunding for a 15 year program is $50 million.

Chemical Reduction of OrganicMaterials to Oil

CONCEPT DEFINITION

Organic materials, when subjected to elevatedtemperatures and pressures in the presence ofwater, carbon monoxide and catalyst, are par-tially converted into oil having a heating value ofabout 15,000 BTU/lb. The continuous process iscarried out at temperatures between 300°C and350°C. Pressures between 2,000 psi and4,000 psi are used with product yield increasingsomewhat with increasing pressure. The resi-dence time of organic material under reactionconditions is from 1 to 2 hours. During thereaction, oxygen is removed from the solids andappears as carbon dioxide in the product gas.Not all of the organic material is converted to oiland some residue is left for disposal. Figure 9schematically illustrates the process.

STATUS

Laboratory batch experiments have convertedorganic refuse into oil by treatment with CO andwater at elevated temperatures and pres-sures [28]. Simpler materials, such as sucroseand cellulose that typify the carbohydrate struc-ture of organic wastes, were also studied. Asmall continuous unit, capable of handling onepound of feed per hour has been operated intests of 5 to 20 hours duration. The product is a

Table 17. R&D Requirements for Pyrolysis of Organic Materials to Gas, Liquid, and Solid Fuels


1. Full scale conceptual design studies.

2. Economic, environmental and systems analysispilot plant studies.

3. Demonstration plant—50 b'bl. oil output/day.

4. Demonstration plant—500 b'bl. oil output/day.

5. Commercial units-10,000 b'bl. oil output/day

1. Optimize operating parametersto maximize fuel productionfor different feed materials.

Steps 1-3Research1976

Step 4Development1980

Step 5Commercialafter 1985

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liquid consisting of oil, water and unconvertedrefuse. The oil must then be separated from thisliquid. Oil yields amounting to 40 percent byweight of the dry feed have been obtained inbatch laboratory experiments.


The process has been demonstrated in alaboratory size plant. No technical problemshave been identified that would preclude fullscale operations. The recommended approach isto proceed to a one to ten ton per day pilotplant to establish technical and preliminaryeconomic feasibility. Successful performancewould indicate economic information. This op-eration could lead to a commercial plant of1,000 ton per day capacity. A one to ten ton perday plant would provide sufficient informationto permit this process to be compared withother fuel making processes.


The immediate goal is a pilot plant experi-ment of at least one ton per day. The organicfeed systems and the oil separation system aresensitive to size. Consequently, the pilot plantsize should be selected so that the importantcharacteristics of these components are tested.The pilot plant would be used to qualify theprocess for the small scale demonstration plantphase (100 ton/day) leading to a 1,000 ton/daycommercial operation. Information reported forthis process suggests 100% recovery of the heatcontent of the feed in the form of an oil andcarbon.

Using the solid waste quantity considered tobe readily accessible, namely 4-6 X 107 tons dryorganic material/year and assuming a 40% yieldof a product having the stated heat of combus-tion of 30.4 X 105 BTU/ton, between 4.8 and7.2 X 1014 BTU/year becomes available for use.This represents 67% of the heat value of thesolid waste.

A first cost estimate for a 900 and a 10,000ton/day oil production facility indicates:

Preliminary Cost Estimates:Part A: Key Economic Factors1. Process gas is CO, costing $.01/lb.2. CO consumption is 0.5 Ib./lb. refuse.3. System pressure is 4,000 psig.4. Process yield is 2 b'bl. oil/ton of dry refuse

(anticipated).5. Income of S4/b'bl. oil.6. Income of $5/ton of dry refuse, disposal

charge.

Part B: Cost FiguresPlant size 900 ton/day 10,000 ton/dayPlant cost S20X106 $200 X 106

Direct operating cost $2.1 X 106/year $15X 106/yearNet operating profit 0 $11 X 106/year

The smaller plant was considered to havemore than enough capacity to handle the solidwastes from a population of 300,000 people orfrom a cattle feedlot serving 200,000 head.

The larger plant was considered to handle thesolid wastes from a population of 3.33 X 106

people or from a cattle feedlot serving 2.2 X 106

head.

RECOMMENDATIONS FOR R&D

Construct and operate a one ton per day pilotplant to pinpoint unforeseen technical problemsand to establish the economics of the process.At least two years would be required to com-plete this task. At this time decision could bemade relative to design, construction and opera-tion of a 100 ton/day demonstration plant.

A total of seven years (2 years design andconstruction and 5 years operation) shouldallow development of good process cost infor-mation and, if economic, permit a commercialsize plant to be built and operated. The esti-mated cost of this 15 year overall program is$60 million.

Comparative costs of various fuels from dif-ferent sources is shown in Figure 10.

Enzymatic Reduction of Organic Substances

CONCEPT DESCRIPTION

Closely related to the conversion of organicmaterials to gaseous fuel by means of a fermen-tation process is the conversion of suitable

43

CD

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SOLARSOLIDFUEL

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UNDER-GROUND

1971AVERAGE

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SYN.CRUDEFROMCOAL

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CRUDE

FUEL TYPES

FIGURE 10. COSTS OF FOSSIL & SOLAR RENEWABLE FUELS

44

organic materials to valuable pure products,chemical raw materials or clean fuels by specificenzyme attack.

Enzymes are organic substances, produced byliving cells, that are capable of catalyzing rel-atively specific synthesis or degradation reac-tions.

It is anticipated that the action of selectedenzymes on components of organic solid wastescould lead to the production of salable products.For example, cellulases are able to convertcellulose (waste paper) to simple sugars; otherenzymes are capable of converting these sugarsto alcohol. In a similar sense proteases and

peptidases are able to hydrolyze the —CO—NH—links in proteins and peptides to amino acids andother potentially useful foods.

STATUS, GOALS, AND IMPACTS

The recent developments which have resultedin the immobilization and stabilization ofenzymes by physical or chemical coupling withvarious solid substrates promises the eventuallow cost industrial scale conversion of organicsubstances to provide high yields of new com-pounds desirable as feed concentrates for man oranimal, raw materials for further chemicalsynthesis or as clean fuels.

45

ELECTRIC POWER GENERATION

Solar generation of electricity for use on earthholds the promise of an abundant clean sourceof power. Solar energy systems can be designedso that they have a minimal effect on the localheat balance.

Even though most of the present powergeneration plants cause a very significantamount of pollution, it is technologically possi-ble, but costly, to reduce air and water pollutionto acceptable levels. The question of utilizingsolar radiation for central power generation thusbecomes primarily a question of establishing itseconomy in comparison with conventionalpower systems considering future trends in fuelcost, energy conversion and the cost of environ-mental protection.

A variety of approaches have been suggestedfor the use of solar radiation in central powergeneration. Each approach involves clearly iden-tifiable steps in a chain leading from solarradiation to power delivered to the consumer asshown in Figure 11. Certain steps in differentconcepts correspond to the same generic func-tion even though the specific implementationsmay be different.

At the start, a distinction is made between"natural" collection and "technological" collec-tion of solar energy. Natural collection occurs inthe atmosphere, giving rise to wind and rain, andon the earth's surface, resulting in the growingof plants, and the creation of temperaturedifferences in the ocean.

In technological energy collection man-madestructures collect the incoming solar radiation.The solar radiation may then be convertedthrough the photovoltaic effect directly intoelectricity, or the heat generated by solar radia-tion, as one possibility, might be used directly to"fuel" a conventional power plant. In both casesthere is power only while the sun shines.

In an alternate approach, an energy storagefacility may be used from which heat is with-drawn at a constant rate, or on demand, for theoperation of a power plant or from whichelectrical energy can be directly withdrawn. In athird possibility, the energy might be used to

generate a chemical fuel such as hydrogen andoxygen.

Electric power which is only available whilethe sun shines could be used to generatechemical fuel, for example, hydrogen, by theelectrolysis of water. Chemical fuel could beshipped as such and could be converted toelectrical power deliverable to a consumer eitherthrough a conventional power plant or through afuel cell.

If one provides energy storage then electricpower can be available on demand from a powersource which delivers power only while the sunshines. After transmission, this power is deliver-able to the consumer.

Solar power plants are capital intensive, whilethe "fuel" is free. This implies that all electricitythat the power plant can generate should beused. Particularly if the power has to be trans-mitted over a considerable distance, the electri-cal output should be constant throughout a24-hour cycle to minimize transmission cost. Inorder to equalize the diurnal variation in solarenergy input, energy storage systems will berequired in most cases.

In terms of today's cost, a large central solarpowered plant with energy storage that iscapable of delivering electricity at a constantrate, or on demand, must compete with othersources of electricity costing about 9 mills perkWh. Smaller plants, located close to an end usermay compete with power worth up to threetimes the value indicated, due to savings indistribution cost and the higher fuel cost ofconventional "intermediate load" plants.

In special cases, solar power generation with-out storage might be used for "peaking" applica-tions. In general, however, such power if de-livered directly into a network requires conven-tional standby capacity of equal magnitude.Energy provided in this manner would be worththe cost of fuel saved in the conventional plant.

Typically its value would be a factor of twoor three lower than energy produced in a plantwith energy storage. Other possible uses of suchinterruptible power include delivery to other

46

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energy storage facilities, the production ofchemical fuel (another method of energy stor-age), or the use in certain manufacturing facili-ties such as aluminum plants. In all cases solarpower without storage must compete with"dump" power such as excess energy from aplant which normally is not fully utilized aroundthe clock.

Clearly if low cost methods of storing elec-tricity become available, the power generated byall types of power systems can be made availableon demand and will have the same nominalvalue. A potentially important energy storageand transmission system involves the use ofhydrogen which can be generated by electrolysisand can be converted back to electricity at thedemand point by use of fuel cell tech-nology [29]. This system can not only providestorage but also permits very low energy trans-mission costs over long distances.

SOLAR THERMAL CONVERSION

Concept Description

Thermal conversion systems consist of solarcollectors and thermal storage devices deliveringthermal energy to a turbine power plant.Through the use of high temperature selectivesolar absorber coatings recently developed forthe space program, temperature in the range ofstandard steam turbogenerators can be achievedwith relatively low solar concentration—on theorder of 10. This makes possible the use ofrelatively low precision optics for concentratingthe solar radiation.

One of the current concepts [30] consists offive major elements, as shown in Figure 12: (1) asolar concentrator to concentrate the sun'senergy; (2) a receiver to absorb the concentratedenergy; (3) means to transfer the heat to thethermal storage facility or to the turbo-generator; (4) a thermal storage element to storethermal energy for use at night and on cloudydays; and (5) a turbo-generator to produceelectrical energy.

Several variations of this basic approach havebeen proposed, and some are under active study.The most promising systems employ "linear"

heat absorbers, e.g., absorbers extending pri-marily in one dimension thus permitting heattransfer through a pipe and concentrators withcylindrical symmetry. Estimates of conversionefficiencies (direct solar insolation to electricalpower) in the range of 20 to 30% have beenmade. In the southwestern part of the U.S.approximately 10 square miles are needed for a1,000 megawatt power plant capable of oper-ating on the average at 70% of capacity.

Status

There are no technical limitations that wouldprevent a solar thermal power station from beingbuilt today. The question is whether it would beeconomically competitive with other methods ofpower generation. It is this question which hasto be answered to make the approach a practicalreality.

Early systems, remarkably similar to thelinear absorber system, were considered longago. The most notable was a steam driven waterpump built in Meadi, Egypt, in 1913-1914. Witha parabolic trough reflector with cylindricalsymmetry and a pipe receiver in its focal linesufficient steam was generated to operate a50 hp steam engine.

Major new developments in civilian and mili-tary aerospace and in nuclear technologies, whenapplied to the basic thermal conversion ap-proach, make the systems look far more attrac-tive. For example, long life and low costparabolic trough reflectors may result fromrecently developed durable reflective nickelcoatings on plastic substrates. A variety ofreflector coatings [31,32] were developed forthe space program as well as high precisionparabolic antennas made of fiberglass and rein-forced plastic. Fresnel lenses represent todayviable alternatives to reflectors.

The receiver located at the focus of theFresnel lens or parabolic reflector is to be coatedwith selective solar absorber coatings whichefficiently absorb solar energy and have lowemissivity at longer wavelengths. Such coatingshave been developed under government funding.With these coatings the design of efficient linear

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solar collectors with low precision optics oper-ating at temperatures up to 1,000°F can becontemplated.

Considerable heat transfer technology hasevolved as part of the reactor development andthe space effort. Vast data exist on liquid metalheat transfer. Heat pipes* which can operateefficiently at steam turbo-generator tempera-tures have been developed and some of theseheat pipes have been operated for over ten years.

Satisfactory schemes for storing thermalenergy have been proposed, ranging from heatstorage in large volumes of solids or liquids toheat of fusion of salts and salt mixtures. Liquidmetal and molten salts containment techniqueshave been developed and heat storage usingfused salts have been used in satellites. There ishowever a question of the applicability of thespecific techniques from an economic point ofview.

The present funding level of R&D directedspecifically at solar thermal systems is approxi-mately $500,000 per year.

Limiting Factors and Recommended Approach

The key problem in central electric powergeneration via solar thermal conversion is to findan engineering solution that is economicallyviable and that assures long-life operation with aminimum of maintenance. Specifically, the opti-cal components, e.g., concentrator and absorbersurfaces, have to maintain their performance formany years while exposed to the elements.

It is recommended that all promising alter-natives of component elements be studied undervarious environmental and simulated operatingconditions. Subassemblies should be preparedand tested for feasibility demonstrations.

All available data on direct (nondiffuse) solarinsolation for various parts of the countryshould be compiled. Measurements should bemade to supplement any missing data needed forsystem trade offs. Continued systems analysisshould be carried out in parallel with thecomponent studies to evaluate the potentialperformance and cost competitiveness of the

*A high efficiency, isothermal heat transfer device.

50

subsystems under investigation. In addition,methods for best interfacing the solar-generatedpower with the existing electrical power gridshould be studied.

When economic viability is indicated, a pilotplant of 10 to 25 megawatts should be con-structed and operated. Based on the data fromthe pilot plant a size optimization study shouldbe made and a full-scale demonstration plantshould be considered. The size of the demonstra-tion plant might be 100 to 1,000 MW asindicated by the optimization study.

A first attempt at estimating the cost of sucha facility has been made, based on mass pro-duced components. This pre-supposes a con-siderable amount of engineering and a successfulsolution to several unresolved problems. For thesolar collection part including energy storage, acost of $600/kw has been obtained. The turbinegenerator unit and other power plant peripheralsadd about S150/kw. Due to the summer-wintervariation in average solar insolation such a plantcan be expected to operate at a capacity factorof 70 percent. This gives an estimate of energycost of about 20 mills/kWh assuming 15.5% costof capital and 1 mill/kWh for operation andmaintenance.

Although this number has a considerableamount of uncertainty it is sufficiently close totoday's costs that a detailed evaluation leadingto commercial readiness is warranted, since it isquite probable that this approach will be a viablealternative to electric power generation as fuelcosts rise and environmental controls increasethe capital cost of power plants.

Goals and Projected Impact

GOALS

The first major goal of the solar thermalconversion program is to establish technicalfeasibility for a low cost design. This should beachieved within about five years. If the cost orcost trends indicate that the system may be costcompetitive in the future, a pilot plant followedby a full-scale demonstration plant should bebuilt and operated. The program should bedesigned to permit commercial availability by1990.

IMPACT

If at the date of commercial availability theapproach proves economical, maximum impacton our nation's electrical needs is expected to belimited to about 1/4 of the new power plantstarts after the year 2000 since the siting of suchplants is restricted to areas with high direct(nondiffuse) solar radiation. Therefore, at best,about 15-20% of the total U.S. generatingcapacity in the year 2020 can be solar thermal.A more realistic estimate might be that 10% ofthe new starts after the year 2000 will be solarplants leading to 5% of the Nation's generatingcapacity in the year 2020.

No adverse environmental impact is expectedexcept for the cooling problems similar to thoseof conventional power plants. Solar power

plants will be principally located in remote areaswhere the effects of appearance will be minimal.

Short-Range R&D

The recommended short-range research anddevelopment program (see Table 18) is geared tosatisfying the first program goal of establishingcost competitiveness within about five years.The expected total effort planned over a 7-yearperiod is estimated to cost $25 million. A keyfeature of the program is to continue environ-mental life tests of the exposed optical elementsand a system and heat storage analysis.

Long-Range R&D

The recommended long-range research anddevelopment program (see Table 19) consists of

Table 18. Solar Thermal Conversion Short-Range R&D Program(Feasibility Study and Component Development).

TaskYear

System analysis (concept definition, componentintegration, cost trade offs, power plant interfaceand environmental impact)

Establish environmental test procedures andpreliminary tests of components

Heat storage

Analysis and selection of approach

Verification tests

Concentrator development

Heat transfer

Analysis and selection of approach

Verification tests

Collector subassembly verification test

Improved solar absorber coating development

life test

I life test

I life test

51

a pilot plant and demonstration plant design,construction and operation. The estimated pro-gram costs for these plants are SI00 million andas much as SI,000 million, respectively. In-dustry may share the cost of the demonstrationplant. The overall R&D program is laid out tomeet the second program goal of making thesolar thermal conversion power plant commer-cially available by 1990.

Phased Program Plan

The long and short ranged R&D plans arephased into three phases as shown in Table 20.Milestones are indicated where information willbe available for making key decisions before thenext larger and most costly tasks are initiated.The estimated funding for the total 15 yearprogram is $1130 million.

PHOTOVOLTAIC SOLAR ENERGYCONVERSION SYSTEMS

Concept Description

Photovoltaic conversion systems are based onthe utilization of the photovoltaic effect in solidstate devices. In these devices, absorption oflight generates free electrical charges which canbe collected on contacts applied to the surfacesof the semiconductor. The theoretical limitefficiency for the conversion process is about25% for a single-semiconductor device operatingat room temperature [33,34,35]. Device opera-tion at lower temperatures results in increasedefficiency [36], but operation below ambienttemperature in the earth environment is energe-tically not advantageous.

The various proposals for photovoltaic sys-tems to supply large amounts of electrical powerfor terrestrial consumption can be classified intothree types:

1. Photovoltaic systems on buildings, withthe converters attached to or incorporatedinto the building structures, and supplyingenergy to activities connected with thebuildings;

2. Ground central systems [37], with large

contiguous or distributed, but connectedphotovoltaic collectors,' serving either adistribution system or single large con-sumers; and

3. Central systems in space, with powertransmission to central ground stations andsubsequent distribution.

Status

Photovoltaic devices made from silicon havesupplied essentially all of the power used by thespacecraft of all nations. Their performance andreliability in space is well established. In addi-tion, small quantities of solar cells have beenmade and applied utilizing other semiconductingmaterials, predominantly cadmium sulfide,cadmium telluride, and gallium orsenide.

For terrestial energy applications, solar cellsare in use in the U.S., Great Britain, Japan, andother countries in form of small "packagedpower" systems to energize transistor radios,various types of remote sensing devices, harborand buoy lights, microwave repeater stations,highway emergency call systems, etc. [38].Some of these systems have been in successfuloperation for over 9 years. However, largephotovoltaic systems for terrestrial applicationshave not been built, although the basic technicalcapability exists.

Present annual U.S. production of siliconsolar cells, manufactured nearly exclusively forthe space program, amounts to 50-70 kw elec-tric [39]. The average efficiency of presentproduction cells is near 11 percent for space, 13to 14 percent for terrestrial applications, with13 to 13.5 percent for space and 15.5 to 16percent terrestrial applications reported on re-cent laboratory cells [40]. To make extensiveapplication of silicon solar arrays for terrestrialconsumption economically feasible, their pricewill have to be reduced by a factor of at least100 from present levels [41]. A significant partof this is expected to be gained through therequired million-fold expansion of productionrates and attendant automation. However, it isfelt that new process approaches will have to beidentified to provide for a continuous flow of

52

Table 19. Solar Thermal Conversion Long-Range R&D Program(Pilot and Demonstration Plant)

TaskYear

10 11 12 13 14 15

Pilot plant

Design

Component fabrication

Plant construction

Plant operation

Demonstration plant

Design

Component production

Plant construction

Plant operation

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operations from the raw material to the com-pleted array, possibly in part similar to inte-grated circuit fabrication. A number of ideashave been advanced for individual process stepswhich could be important to the establishmentof such integrated processing. Foremost amongthese are methods for obtaining ribbons orsheets of single crystal or large crystal silicon by(1) edge-defined film growth [42], (2) dendriticgrowth [43], (3) rolling silicon [44], and(4) casting sheets with subsequent re crystalliza-tion through heated or molten zones [45]. Oncesuch single or large crystal sheets are available,integrated solar arrays could be formed from

.them by possibly as few as 7 operations, e.g.,vapor deposition, heating, and ion implantationin a continuous, flow through process. Opticalfilters with a comparable number of such opera-tions are now quoted at $0.40/ft.2. Anotherapproach consists of automated assembly of

small silicon spheres, produced by a modifiedshot tower method, into a large plastic encap-sulated assembly. All of these approaches re-quire experimental verification of technicalfeasibility. Several cost analyses have been pro-vided which show possibility of reaching theeconomic goal of generating cost-competitiveelectric power [42,46]. Silicon itself is thesecond most abundant element in the earth'scrust and is produced in the U.S. at the annualrate of 66,000 tons in metallurgical purity atS600/ton [46], which is a sufficiently low basicmaterial cost.

Thin film Cu2S—CdS solar cells have beenprepared in pilot line quantities (total 10 kw)for over 12 years, with efficiencies of 4 to 6percent for terrestrial applications, and over 8percent reported on development models [47].The processes used for their fabrication appearreadily amenable to low cost mass production

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methods. In the past, the thin film Cu2S-CdSsolar cells have been plagued by degradation andlow yields for long life [48].

Interest in the U.S. has been reawakened forterrestrial applications, and recently reportedprocess changes are hoped to result in long lifearrays [47,49]. A cost estimate for a systemusing Cu2 S—CdS solar cells and including powerconditioning, system protection, installation,and a 15% annual cost of capital, taxes, andmaintenance, has arrived at a cost of 2 to4^/kwh of generated electricity [50].

Other semiconductor materials have not beensufficiently developed to be of interest forextensive solar energy applications at this timebut research into new methods of solar energyconversion should be initiated [51 ].

Current R&D is primarily directed towardsincreasing size and decreasing weight of space-craft power systems, increasing resistance againstradiation in space, and increasing the efficiencyof silicon solar cells towards 20 percent in space.This work is supported by NASA and the U.S.Air Force at a combined annual level of approxi-mately $3 million.

NSF under the RANN program and NASAunder its Applications program have an interestin terrestrial applications, and are beginning tosupport R&D towards low cost photovoltaicapproaches. During the last year, one companyhas started to develop reduced cost photovoltaicsystems in an effort to expand the market in"packaged power" as a step towards large scaleterrestrial applications of photovoltaic systems.Also, a group of companies has pooledcapabilities to develop the concept of obtainingpower from space.

Photovoltaic Systems on Buildings

CONCEPT DESCRIPTION

The application of photovoltaic arrays onbuildings locates the generator at the place ofthe load, reducing the need for energy transmis-sion and distribution with the associated lossesand costs. The system thus matches the distri-buted nature of solar energy to the distributedpattern of energy consumption.

In this approach, photovoltaic arrays are

mounted on buildings or form part of theirstructures, the latter presenting economic andpossibly aesthetic advantages. The basic installa-tion does not differ from that of solar thermalcollectors. A particularly attractive approach isto combine the photovoltaic array with a flatplate thermal collector [52,53], since mostbuildings require both thermal energy (hot watersupply, space heating, absorption refrigeration,air conditioning, low temperature process heat,etc.) and electrical energy (lighting, motivepower, electronics, high temperature processheat, etc.). In this case which is illustrated inFigure 13 the absorber surface of the thermalcollector is formed by the solar array whichconverts a portion of the incoming solar energyinto electrical energy, and permits collection ofabout 50% of the remaining energy in the formof heat. Although some of the efficiency of thesolar array is traded off for thermal energycollection, this combination system providesadvantages:

• up to 60 percent of the available solarenergy can be utilized;

• the thermal collector uses the same landarea as occupied by the buildings; and

• the components fulfill several functions,yielding a more cost effective system.

As in all terrestrial solar energy utilizationsystems, energy storage is required. In general itis considered uneconomical to provide localstorage capacity for more than an average day'srequirement [6]. Thus, auxiliary energy will beneeded at times. The overall system conceptshown in Figure 14 includes several subsystems:solar array, electrical power conditioning, energystorage, auxiliary energy, and possibly powerline interfaces. Storage can be provided bybatteries, electrolysis cell-fuel cell systems,flywheels, etc. [54,55,56].

Benefits of the use of photovoltaic systems onbuildings are:

• Minimal effect on the ecology through useof land areas already being used for otherpurposes.

• About three times the present averagehousehold consumption of electric powercan be collected from average-size familyresidences, even in the northeastern U.S.

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Assuming the energy storage problemsolved, this energy surplus may make theelectric automobile feasible.

• Invulnerability to breakdowns in energydistribution or centralized generationsystems.

• The small size of the individual unit makesprototype testing and demonstration rela-tively inexpensive, and will help to attractconsumer oriented industries.

STATUS

Systems larger than the "Packaged Power"systems have not been built, although thetechnology and the components are available.Only preliminary feasibility studies have beenperformed on combination thermal/photovoltaicsystems.

LIMITA TIONS AND KEY PROBLEMS

The maximum installable array area approxi-mately equals the ground area covered bybuildings. Attention will have to be paid to theorientation, location and shading of buildings inthe same manner as for thermal collectors. Thiswill make most existing buildings unsuitable forretrofitting. The introduction will therefore gen-erally be limited to new construction. Further,only up to 90% of the new buildings will besuitable for solar energy collection. In addition,the highly fractionated nature of the construc-tion industry will result in slow market growth,taking 20 years or more to reach saturation.

Low cost ($0.50 to $3.50 per ft.2 forcombination systems, less for others based on$0.02/kWh credit for the energy supplied by thesystem) and long life of solar arrays (minimum:10 to 20; goal: 20 to 40 years) in the earthenvironment are the key problems to be solvedfor reaching commercial readiness. For Si solararrays, cost reduction is the primary task. ForCu2S—CdS solar arrays, the major tasks appearto be increases in both life and efficiency. It isestimated that the development goals can beattained with adequate effort within 10 years.

Development of energy storage devices ofsufficiently low cost and long life is the secondkey problem. Again, multiple approaches areunder investigation. The remaining subsystem

and system problems such as inexpensive DC toAC conversion equipment, require engineeringdevelopment.


The key problem areas, status and goals forphotovoltaic systems on buildings are outlinedin Table 21. An estimated schedule to demon-stration of commercial readiness is shown inFigure 15. Since confidence in reaching the keycomponent goals is high, and subsystem andprototype systems are relatively small and inex-pensive, it is recommended that subsystemdevelopment and system testing be undertakenin parallel with the component development.This approach will cut time to start of introduc-tion approximately in half. The projected im-pacts are shown in Table 22.

Ground Central Stations

CONCEPT, STATUS, IMPACTS

Significant areas in regions of adequate insola-tion would be covered with photovoltaic arraysto feed power into a distribution grid in themanner of a utility power plant [37]. Manyvariations have been proposed, including ar-rangement of the arrays for partial shading topermit agricultural activities beneath, or dis-tributed arrangement of the arrays intercon-nected to form a central station [50]. Sincesolar arrays without concentrators accept diffuseradiation, significant amounts of power can begenerated even on overcast days.

The basic technology required for photo-voltaic ground central stations does not differsignificantly from that of the systems on build-ings, except for scale and for site preparationand installation.

Because of the commonality in technology,and the smaller unit size of the systems onbuildings, the emphasis should initially be placedon technology development for the latter systemtype, with simultaneous feasibility studies andsubsequent systems definition for the groundcentral stations.

The projected impacts are shown in Table 22.

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TASK

KEY COMPONENTSDEVELOPMENTLIFE TESTPROCESS DEVELOPMENTMANUFACTURING

AUXILIARY COMPONENTSDEVELOPMENTLIFE TESTPROCESS DEVELOPMENTMANUFACTURING

SUBSYSTEMSDESIGNDEVELOPMENTLIFE TESTMANUFACTURING

SYSTEMPREDESIGNDESIGN-1ST ITERATIONDESIGN-2ND ITERATIONPROTOTYPE DEVELOPMENTPROTOTYPE TEST

PILOT LINE/TEST MARKETINGMANUFACTURING PLANT

EQUIPMENT DESIGNPLANT CONSTRUCTION

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Electric Power From Space

CONCEPT DESCRIPTION

A satellite in synchronous orbit around theearth's equator receives solar energy for 24hours a day, except for brief periods around theequinoxes. In this orbit, a satellite receives six toten times the amount of solar energy available insuitable terrestrial locations in the U.S. Asillustrated in Figure 16 the dc power generatedin space by such a satellite would be beamed viamicrowaves to the gound and there reconvertedto high voltage dc or ac power to meet base ordemand load needs. In addition such satellitescould serve as communications or observationbases.

The use of microwaves at a frequency near3GHz for power transmission from the satelliteto earth provides minimum loss in the iono-sphere and troposphere. This loss has beenestimated to average 6 percent and to remainmoderate even in severe rainstorms. To obtainadequate beam definition- at this frequency, atransmitting antenna of approximately 1 kmdiameter is needed. The transmission efficiencyis expected to be in the 55 to 75 percent rangefrom dc in space to dc on earth [57].

The transmitting antenna diameter determinesthe economical system size, which ranges from4,000 to 15,000 MW power output on earth.The system as initially conceived utilizes 2 milthick silicon solar cells to form two solar

60

Table 22. Impact of Electric Power Generation by Conversion of Solar Energy

Impacts

Initial impact (1%)

Growth

Total

Significant impact (10%)

Growth

Total

Resources

Materials

Environmentaf(operation only)

Land use

Air

Water

Radioactivity

Noise

Visual

Safety

Waste

Thermal

Residential/commercial

1980 earliest1985 probable

1985 earl iest1995 probable



Non-critical if SiAdequate if CdS

None

None

None

None

None

Minimal, may require largerroof angle

None

None

None beyond conven-tional dark roofs

Large industrial& ground

central stations

1990

2000

2000

2020

x

Non-critical if SiAdequate if CdS

2002:3Xl02mi2

2020: 3Xl03mi2

None

None

None

None

Dark surfacesobservable

None

None

Possible developmentof heat islands

Space station

1990-2000

2000-2010

2020-2030

Undetermined

2000: 30 mi2

2020: 300 mi2

Rocket exhaust from launch

Undetermined

None

Restricted to launch

Undetermined

Low intensity microwaveradiation

None

10-20% above consumableenergy is added toterrestrial heating burden.

61

7-KMDIAMETERRECEIVINGANTENNA

SOLAR CELL PANELS

1-KMDIAMETERANTENNA

FIGURE 16. SPACE STATION CONCEPT TO PRODUCE 10,000 MW.

collectors capable of providing about 10,000Megawatts on earth. For economy, lightweightmirrors would reflect solar energy onto the solarcells to achieve a concentration ratio of approxi-mately 3. The 25,000 ton station would betransported in parts to low earth orbit by 300 to1,100 flights of a second generation spaceshuttle, and from there to synchronous orbit byion propulsion.

STATUS

Since 1963, over 50 satellites of the U.S. havebeen placed in synchronous orbit. They havebeen powered by silicon solar cells, with acombined capacity of approximately 7 kW, and

the power systems of some have functioned formore than 5 years. Through them, a consider-able amount of information on photovoltaicpower system performance and on attitudecontrol in synchronous orbit is available. TheAir Force has successfully flown a 1.5 kWrollout array of 22W/lb. [58], while designs of a100 kW capacity system for the NASA MannedSpace Station are being prepared. Present pricesfor space flight qualified solar arrays range from$1,000 to $8,000 per ft .2 .

A partially reusable space shuttle is underdevelopment, designed to provide transportationto low earth orbit for SI00 per pound. Solarpowered ion propulsion has been demonstrated

62

in space through the NASA SERT program.Both of these systems can form the technologybasis for the space power station transportationsystem.

Microwave generators with more than 5 kWoutput and 76 percent efficiency have beendemonstrated. Highly directional, self-steering(retro-directive) antenna arrays have been de-veloped by the Air Force for radar and com-munications purposes. For the receiving antennasystem, rectifier diodes with 75 percent effi-ciency are available.

For the space power station system which willbe 100,000 times larger than the Manned SpaceStation, only preliminary concept studies havebeen carried out.

LIMITATIONS AND KEY PROBLEMS

Demonstration of commercial readiness as-sumes availability of the presently planned spaceshuttle. Installation of the operational systemwould require a second generation shuttle, withan estimated development cost of $10 billion,which would be capable of providing transporta-tion to low earth orbit at a cost of S50/lb. At anannual average introduction rate of 3.5 stations,up to 11 shuttle starts per day may be required,excluding flights for servicing. With a 2 to 3 dayturn-around time, approximately 30 shuttles($100 million each) would be needed, withadequate service and launch facilities and noisebuffer zone.

Chemical pollution could be minimizedthrough use of hydrogen-oxygen fueled shuttles,but the influence of the additional water in theupper troposphere requires study. The micro-wave safety and radio frequency allocation/interference questions require answers, whichare expected to be found in a planned Office ofTelecommunications Policy Program.

At a projected cost for the commercial systemof $20 billion per station ($2,000/kW),including transportation and ground stationcosts, the cost of the generated electric powerwould be near 38 mills/kWh. With 52 percent ofthe projected station cost attributable to thesolar arrays, achievement of a solar array costreduction to $32/ft.2 or less assumes specialimportance. Special engineering problems to be

solved include the large weight reduction for thesolar arrays and their deployment in extremelylarge structures of low weight, combined withthe requirement for orientation and attitudecontrol. The interaction of large flexible systemswith the attitude control operation requiresspecial investigation. Methods for assembly oflarge, flexible systems, composed of many parts,by automated or man assisted methods in spacewould need to be developed, as well as low costtransportation to synchronous orbit. The micro-wave transmission system requires engineeringdevelopment based on existing technology. Thistask is expected to be eased through repetitiveuse of few component types in benign operatingmodes. Demonstration of commercial readinessof the system would require a major nationalcommitment, comparable to the "Peaceful Usesof Atomic Energy" and "Man on the Moon"programs. However, such a commitment is notrequired during the first 10 years of the project,during which technology development of generalusefulness would be carried out.

The development tasks, with status and goals,are outlined in Table 23. Development of thesystem depends on successful completion ofmost of these tasks. It would therefore bedifficult to assign, at this time, a successprobability higher than low to the entire system.Through component and subsystem technologydevelopment and systems studies in the firstphase of the proposed program, this uncertaintywould be stepwise decreased in the early yearsand should be essentially removed before adecision on commencing the second phase ismade, which includes the major nationalcommitment.

GOALS AND PROJECT IMPACTS

The impacts are listed in Table 22 and thephasing and milestone schedule is shown inTable 23. This schedule has been designed toallow for:

1. Sufficient systems/technology assessmentsto determine its true potential beforeproceeding to system development or dem-onstration.

63

.Table 23. R&D Summary and Milestones for Photovoltaic Electric Generation.

TaskYear

10 11 12 13 14 15

Feasibility studies, componentevaluation, data collection



Ground station

Technology development

Low cost solar array development

Low cost solar array pilot plant

Energy storage

Other subsystems

Microwave transmission

Spacecraft structures

Spacecraft solar arrays

Systems definition


Ground station

Prototype design and verification


Space central station"'

Ground station

Prototype construction and test


Space central station'21

Ground station

Basic research

4,4;

"AT"

4,,

Notes: H) Includes flight experiments for verification.(2) Initiated after 15 years.

Milestones: /1\ Technical and economic feasibility of system evaluated.

/2\ Technical feasibility and cost potential of process established.

/3\ Processes further improved.

/^\ Pilot plant constructed and operation initiated.

/5\ Process sufficiently refined and evaluated to justify construction of large scale production plant.

^3\ Feasibility of long-life, low-cost storage subsystems established.

/7\ Basic engineering development of other subsystems complete.

y^\ Technology adequately developed to permit systems development.

/§\ Results of systems definition indicate feasibility for prototype design.

^(X Prototype design and component/subsystem verification tests justify prototype construction.

fl K Prototypes successfully demonstrated, justify test marketing.

fl2\ Prototype tests successful, justify test marketing of small systems, demonstration plant for large systems.

64

2. Sequential reviews where major program-matic go-no go decisions/commitments canbe made.

3. Flexibility for the nation's decision makersto permit exercising this power systemoption, when and if needed.

Recommended Research Program for allPhotovoltaic Systems

The proposed research programs are designedto demonstrate technical and economic feasi-bility on the component and subsystem levelbefore entering into costly systems demonstra-tions. Systems feasibility studies should becarried out simultaneously to provide directionto the technology development work, and toprepare for ensuing decisions on systems devel-opment. These studies may have to provide thenecessary input for feasibility analysis and latersystem design.

The main development required is the produc-tion of very low cost arrays, regardless of whatultimate photovoltaic system is used. Therefore,work should be continued at an accelerated ratein materials, processes, and system design tomake low cost solar arrays available. Their use infuture space programs and specialized groundapplications is assured even if they could not beproduced economically enough for large scalesolar power stations. As soon as it becomesevident that a low cost solar array of adequatelife and performance is attainable, a pilot plantshould be designed, built and operated to provethe process.

During the first 3 program years, the emphasisshould be almost completely on component andsubsystem development and feasibility studies.As a possible exception, low cost prototypedevelopment could be started on photovoltaicsystems for buildings to facilitate earlyintroduction.

In the following 7 years, the photovoltaicsystems for buildings should proceed to proto-type evaluation, pilot line operation and testmarketing, assuming the technology develop-ment having progressed satisfactorily. The spacepower station would continue in technologydevelopment and in systems definition, which

should also commence for the ground centralstations. It may be noted that the low cost solararray process development is equally applicableto all three systems. The space power stationhowever, requires modification to achieve espe-cially low weight and radiation resistance.

In the time span beyond 10 years, the systemdesign and development of the space powerstation prototype and transportation systemcould take place, followed by system demonstra-tion. The photovoltaic systems for buildingsshould then be in commercial status, and designand test of the first ground central station couldproceed.

A detailed schedule and milestone chart hasbeen included for the pacing item, the Low CostSolar Array Research and Development task (seeFigure 17).

A number of approaches should be pursuedunder each schedule item. The milestones formdecision points for continuing or shifting efforts.

Table 23 presents a milestone plan, arrangedin program phases for each of the major systemtypes. The transition points from one phase tothe next form the major milestones which arethe key decision points in the individual pro-grams. The estimated funding for the overallphotovoltaic R&D program is $780 million.

WIND ENERGY CONVERSION

Concept Description

Solar energy sustains the winds [59]. It iscalculated that the power potential in the windsover the continental U.S., the Aleutian arc andthe Eastern seaboard is about 10' ' kilowattselectric. Winds are remarkably repeatable andpredictable. The momentum in moving air canbe ext rac ted by momentum-interchangemachines located in suitable places such asplains, valleys and along the continental coastalshelves [60].

A desirable windpower system incorporatesits own storage and its own peaking capability asshown in Figure 18. It is thus able to spanbetween variable wind to patterned electricityconsumer demand. This system could be nearlypollution-free. The electrical energy generated

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by the aeroturbines located off-shore is used toelectrolyze water. The hydrogen thus producedis transmitted by pipeline to shore or com-pressed and stored for use during calm periods.In such a manner hydrogen can be supplied on acontinuous basis to fuel cell or thermal electricgenerating stations. It should be emphasized thatthe offshore-hydrogen storage approach is onlyone of several worthy of exploration.

Status

There was a mature technology for wind-power sixty years ago. Steady improvement wasmade through the 1950's directed toward large-scale applications. In 1915, 100 Mw of elec-tricity were being generated by windpower inDenmark. Today electricity brought in by cablefrom Sweden's hydroelectric plant is less expen-sive. In the 1940's a 1.25 Mw machine was builtand operated at Grandpa's Knob, Ver-mont [61], but was shut down by a materialsfailure of the blade. A conceptual design usingaeroturbines to produce 160 billion kilowatthours of electricity per year has recently beencompleted for the offshore New England re-gion [62]. This preliminary study shows thatthe electrical power when used to producehydrogen which is then piped onshore forconsumption in power plants is cost competitivewith conventional methods of producing electri-cal power.

Limiting Factors and Recommended Approaches

The limiting factors in the large scale applica-tion of windpower are a combination of avail-able wind energy and weather modification. Theeffect of large numbers of closely spaced wind-mills has not been assessed. There are no knowntechnological limitations to the application ofwindpower.

The windpower program should start with aFederally financed research and developmentprogram which would include among its firsttasks: (1) examination of global and local limita-tions on the extraction of kinetic energy fromthe winds with emphasis on possible weathermodification, and (2) a study of legal constraintsagainst the large-scale use of windpower.

Goals and Project Impact

It is proposed that windpower be developedin the regions described in Table 24. Themaximum generating capacities are also shownin this table. The maximum total energy gener-ated by conversion of wind power is about 19%of the year 2000 annual electricity production.The annual capacity in each site was calculatedusing available wind velocity-duration data, atspecified heights, impinging that wind againsteither 200 ft. diameter (2 Mw) or 60 ft.diameter (lOOkW) wind turbines.

Short Range R&D Program

A 3-year program is set forth in Table 25. Alarge fuel cell development program is includedbecause some of the most attractive conceptsrequire efficient (>50%) and inexpensive(<S 115/kW) fuels cells. The same need for a fuelcell program can be found in many of the otherSolar Energy and Ocean Energy Programs, how-ever. Any energy scheme which produces hydro-gen, methane or an alcohol fuel should beequally interested in this major task.

Long Range (4th through 10th year)R&D Program

A recommended program phasing is presentedin Table 26. The estimated funding for this 10year program is S610 million.

POWER FROM OCEAN THERMALDIFFERENCES

Concept Description

Between the Tropics of Cancer and Capricornwhere the intensity of incoming solar energyreaches its peak, 90 percent of the earth'ssurface is water. That surface layer is in thermalequilibrium at a temperature that never dropsbelow 82° F. To the far North and South theintensified summer insolation melts down theprevious winter's accumulation of frozen pre-cipitation. That meltdown slides to the depthsof the oceans and slowly moves toward theequator, forming the cold water ways of the

68

Table 24. Maximum Electrical Energy Production From Wind Power

Site Annual power productionMaximum possible

by year

(1) Offshore, New England

(2) Offshore, New England

(3) Offshore, Eastern Seaboard,along the 100 meter contour,Ambrose shipping channelsouth to Charleston, S.C.

(4) Along the E-W Axis, LakeSuperior (320m)

(5) Along the N-S Axis, LakeMichigan (220 m)

(6) Along the N-S Axis, LakeHuron (160m)

(7) Along the W-E Axis, LakeErie (200 m)

(8) Along the W-E Axis, LakeOntario (160m)

(9) Through the Great Plainsfrom Dallas, Texas, Northin a path 300 miles wideW-E, and 1300 miles long,S to N. Wind Stations tobe clustered in groups of165, at least 60 milesbetween groups (sparsecoverage)

(10) Offshore the Texas GulfCoast, along a length of400 miles from the Mexicanborder, eastward, along the100 meter contour

(11) Along the Aleutian Chain,1260 miles, on transectseach 35 miles long, spacedat 60-mile intervals,between 100 meter contours.Hydrogen is to be liquefiedand transported to Cali-fornia by tanker.

159 X 109 kWh

318 X 109 kWh

283 X 109 kWh

35 X 109 kWh

29 X 109 kWh

23 X 109 kWh

23 X 109 kWh

23 X 109 kWh

210 X 109 kWh

190 X 109 kWh

402 X 109 kWh

1990

2000

2000

2000

2000

2000

2000

2000

2000

2000

2000

Estimated Total Production Possible: 1.536 X 101 2 kWh by year 2000

69

Table 25. Recommended Tasks, Short Range (3Year) R&D Program for Windpower Development

1. Conduct technology review and economic fea-sibility studies.

2. Investigate global and local implications oflarge scale extraction of kinetic energy fromthe atmosphere.

3. Study institutional constraints against largescale windpower schemes.

4. Review and advance pertinent aerodynamic,structural, mechanical, and electrical theoryand applicable design practice.

5. Assess environmental impact on marine, forestand plains ecology.

6. Study and advance marine architectural andpipeline theory.

7. Investigate and plan for least-cost large-scaleproduction of components and subsystems.

8. With NOAA, establish and carry out a programfor identification and quantification of "espe-cially windy sites." Give emphasis to GreatPlains and Rocky Mountains.

9. Design an appropriate set of demonstrationunits.

10. Start a large scale fuel-cell R&D program aimedat low-cost long-life hydrogen-oxygen andhydrogen-air mini-substation fuel cells.

oceans. It is thus possible under several hundredmillion square miles of ocean to find a nearlyinfinite heat sink at 35 to 38°F, at a level aslittle as 2,000 ft. directly beneath a nearlyinfinite surface heat reservoir at 82 to 85°F[63]. Both heat reservoir and heat sink are

replenished annually by solar energy. A heatengine operating across a 50°F temperaturedifference in an 85°F heat source would be able,theoretically, to convert to useful work, 9percent of the heat flowing across it.

The Gulfstream carries 1,000 and 1,500 mil-lion cubic feet per second of near-tropical seawater through the Gulf of Florida [64]. Thestream can be said to flow in a path about 20miles wide. Within a 500 mile length of thatpath, the thermal difference between the surfaceand the depths range from 27.5°F to 39°F [65].That heat difference occurring at a surfacetemperature of 71.5°F, would permit a theoreti-cal maximum conversion of heat into usefulwork of 5%. An overall practical efficiency of2% can be expected. If one BTU from eachpound of the warm Gulf Stream flowing throughheat engines could be converted into usefulwork , an annual energy production of700 X 1 0 1 2 kWh would result. A collectionsystem of units moored on one mile spacingsalong the length and across the breadth of thatstream are thought capable of an annual energyproduction of 26 X 1012 kWh. In a suggesteddesign, each unit would resemble a vertical axisspar buoy of about 100 feet diameter with anoverall height of 220 feet. In one version, thehotside heat exchanger would project outwardto either side from a huge underwater kite. Thetotal wing span (beam) for such a 400 MW unitis on the order of 400 feet.

A method for converting sea thermal differ-ence into electrical power is shown in Figure 19,the Claude cycle [66]. One modification of theClaude cycle interposes an intermediate workingfluid (e.g., propane) between the heat sourceand the heat sink. The expansion turbine oper-ating on a hydrocarbon or flurocarbon fluidwould be a fraction of the size of the turbineusing vaporized sea water and the degassingejectors could be eliminated in that cycle.However, the hot-side heat exchanger might befar more expensive than the flash evaporatorwhich it replaces, so a trade-off will have to bemade. For economy of energy transport, theelectrical power can be conducted to electrolyticcells to make hydrogen fuel for use in fuel cells.

A preliminary estimate of the capital cost ofeach of these concepts is in the $200 to $400range per kW of capacity; further information isneeded for confident appraisal.

70

Table 26. Proposed Windpower R&D Program.

TaskYear

10 11 12

1. Execute the tasks proposed to confirmwindpower technical and economicfeasibility (Table 25).

2. Plan for large-scale component andsystem acquisition.

3. Provide continuing R&D support forwindpower development.

4. Design, build, install, and operatewindpower components and pilotplants.

5. Development of fuel cells for usewith aeroturbines.

6. .Construct, emplace, and operateseveral complete 100 Mw windsystems.

/1\ Decide if pilot plant should be started.

/2K Begin production of adequate prototype fuel cells and/or other storage devices for the 100 Mw wind system.

/3\ Start detailed design purchasing and fabrication of several 100 megawatt wind units complete with energy storage and deliverysystems.

(ij First demonstration units operable.

Status

In 1929 the Claude cycle was successfullydemonstrated in Cuba; 22 kW of useful powerwere produced in an engine whose actual overallefficiency was less than 1 percent. Two experi-mental units of 3,500 kW net output, eachworking in the Claude cycle were installed offthe Ivory Coast in 1956 by the French. Due tomechanical failure and other problems the plantswere abandoned after a short time. There is asmall continuing French R&D effort in this fieldat the time and the NSF has just funded afeasibility study in the U.S.

Limiting Factors: Recommended Approach

Large-scale use of the ocean thermal differ-ences process could be limited by a combinationof technical and economic problems.

The possible technical and economic prob-lems require analysis. At least three competitiveconcepts, three heat engine cycles, and twoenergy transmission systems should be analyzedin enough detail, separately and in variouscombination, until credible cost estimates can bemade.

1. The concepts to be investigated:

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a. Afloat units, well out in the movingwater of the Gulf Stream.

b. Afloat units, near shore in nearly stag-nant water in the Gulf Stream.

c. Afloat units, well out in the Gulf ofMexico at the shelf's edge, in essentiallystagnant water.

2. The cycles to be investigated:a. Rankine cycle, sea water working fluid.b. Rankine cycle, distilled water working

fluid.c. Rankine cycle, hydrocarbon or fluoro-

carbon working fluid.

3. The Energy Transmission Systems to beinvestigated:a. ac or dc electricity transmission via

cable.b. On-site electrolytic generation of

hydrogen, energy transmission via pipe-line gas.

The analyses would get down to a configura-tion for each subsystem and component, ade-quately described and specified as to permitcareful cost estimation. Verification of technicalfeasibility and determination of costs would gohand-in-hand.

There is no social limiting factor seen tolarge-scale ocean thermal differences use. Noneof these plants will be visible from the beach.

It is anticipated that the large-scale use of thisprocess would best meet socio-economic-political approval if it includes economicaldistribution of energy throughout the country.A new concentration of industry and populationnear the Gulf and southeast Atlantic Coastmight not be acceptable. Pipeline distribution ofenergy as hydrogen gas seems to be an answer.

There are no anticipated adverse environmen-tal effects associated with large-scale use of theocean thermal differences process, but possibleeffects on marine life and shipping would need

to be studied. There is potential for improve-ment of the marine environment by the equi-valent of natural upwelling of cold bottomwater, rich with nutrients, into the photic zone.

Once technical and economic feasibility havebeen established by analysis, the development ofcomponents, subsystems, and prototypes shouldbe undertaken.

Goals and Projected Impact

In the concept description it was estimatedthat 26 trillion kilowatt hours/year of energycould be recovered from the Gulf Stream off theU.S. southeast coast. If that energy is convertedand transported as hydrogen gas, subsequentlyreconverted to electricity in fuel cells, about halfto two-thirds of the energy would be recovered.If to that one adds a small portion of the energythat could come from the Gulf of Mexico, atshelf edge and beyond, the total annual produc-tion could exceed the year 2000 projected totalenergy demands.

A Recommended Short Range (3 year)R&D Program

A 3-year program of study oriented towardproblem definition, concept feasibility, prelim-inary design, and economic evaluation is firstrecommended. Distribution of effort by activityis indicated in Table 27. At the conclusion ofthis program, data for a decision on cont inuingthe development should be available. The meritsand prospects of this system should be com-pared with others under investigation and withconventional methods. Part of the study out-lined above has already been initiated with NSFsupport.

The Proposed 15 Year R&D Program

The 15 year R&D program, outlined in Table27 is estimated to cost S530 million.

73

Table 27. Electrical Power From Ocean Thermal Differences: 10 Year R&D Program.

TaskYear

10 11 12 13 14 15

1. Conduct technology and economicfeasibility studies.

2. Conduct oceanography review ofselected sites; establish and monitorecological base line.

3. Design, fabricate, and test keysubsystems and components.

4. Prepare contract design, specifications,and bid package for large-scale plantacquisition.

5. Design, build, install, and operatea 10 megawatt pilot plant.

6. Demonstration plant (400 Mw).

czu

Ac

A\ Determine if oceanography review and subsystem development should start.

/?v Make selection of best-suited components for demonstration plant.

/& Determine if 10 Mw pilot plant should be built.

ff\ Determine if 400 Mw demonstration plant should be built.

74

REFERENCES

1. Data for Use in the Assessment of Energy Technolo-gies, AET-8, April, 1972. A report submitted to theOffice of Science and Technology Executive Office ofthe President, Under Contract OST-30, Associated Uni-versities, Inc., Upton, New York.

2. Rau, H., "Solar Energy," The Macmillian Co., NewYork,N.Y., 1964.

3. Farber, E. A., "Solar Energy Conversion and Utiliza-tion," Paper No. 439, Engineering Progress at theUniversity of Florida, Vol. XXIII, No. 7, July 1969.

4. Abbott, C. G., "Solar Radiation as a Power Source,"Smithsonian Institution Report, 1943.

5. Daniels, P., "Direct Use of the Sun's Energy," YaleUniversity Press, 1964.

6. "Proceedings of the UN Conference on New Sourcesof Energy," Vol. 5, U.N., New York, 1964.

7. Tybout, R. A. and Lof, G. 0. G., "Solar HouseHeating," Natural Resources Journal, 10, (2), p.268-326, April 1970.

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20. Golueke, C. G., "Comprehensive Studies of SolidWaste Management: Third Annual Report," ResearchGrant EC-00260 to the University of California, U.S.Environmental Protection Agency, 1971.

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22. Blackett, P. M. S. et al., "Utilization of SolarEnergy," Research Applied in Industry (London), 5, P.527,1952.

23. Christopher, G. L. M., "Biological Production ofMethane from Organic Materials," United Aircraft Re-search Laboratories Report K910906-13, May 1971.

24. Kaiser, E. R. and Friedman, S. B., "The Pyrolysis ofRefuse Components," Presentation at 60th AnnualMeeting, American Institute of Chem. Engrs., Nov.26-30, 1967.

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26. Hoffman, D. A. and Fitz, R. A., "Batch Report

75

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29. Jones, L. W., "Liquid Hydrogen As A Fuel for theFuture," Science, 174, No. 4007, p. 367-370, October,1971.

30. Meinel, A. B. and M. P., "A Harvest of SolarEnergy"; A presentation made at the REERIO Con-ference on the Energy Crisis at LasCruces, New Mexico,May 4, 1972.

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33. Prince, M. B., J. Appl. Phys., 26, 534, 1955.

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37. Cherry, W. R., "The Generation of Pollution-FreeElectrical Power From Solar Energy," Transactions ofthe ASME, Journal of Engineering for Power, 94, SeriesA, No. 2, p. 78-82, April, 1972.

38. Ralph, E. L., "A Commercial Solar Cell ArrayDesign," Heliotek Division of Textron, Sylmar, Cali-fornia, Presentation to Solar Energy Society Conferenceat Greenbelt, Maryland, May 1971.

39. Wolf, M., "Historical Development of Solar Cells,"25th Power Sources Conference, Atlantic City, May23-25, 1972.

40. Lindmayer, J., Proceedings of the 9th IEEE Photo-voltaic Specialists Conference, Silver Spring, Md., May2-4, 1972.

41. Wolf, M., "Cost Goals for Silicon Solar Arrays forLarge Scale Terrestrial Applications," Proceedings of the9th IEEE Photovoltaic Specialists Conference, SilverSpring, Md., May 2-4, 1972.

42. Currin, C. G., Ling, K. S., Ralph, E. L., Smith, W.A., Stirn, R. J., Feasibility of Low Cost Silicon SolarCells," Proceedings of the 9th IEEE Photovoltaic Spe-cialists Conference, Silver Spring, Md., May 2-4, 1972.

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45. Tyco Laboratories, Final Report #AFCRL-66-134;1965.

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76

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APPENDIX A

PROPOSED R&D FUNDING

Table 1. Proposed Funding for Thermal Energyfor Buildings (SM)

Development*Demonstration

Total

7624

100

'Collectors, storage, coolers, system engineering, product engi-neering, and architecture.

Table 2. Proposed R&D Funding for Photosynthetic Production of Organic Materials and Hydrogen (SM)

Activity

Production of low cost fuelsImprove crop yields

Water plants (algae and floating plants)Investigation of plant harvesting

Land plantsWater plants (algae and floating plants)

Investigation of crop transportLand plants and solid wasteWater plants

Production of hydrogen

Total

Research

1

13

21

11

19

Development

1

12

11

17

23

Pilot plant

2

46

33-

1.8

Total

4

611

6

528

60

Table 3. Proposed R&D Funding for Conversion of Organic Materials to Energy ($M)

Activity

Combustion of organicsCombustion of solid wastes

Total

Feasibilitystudy

11

2

Componentdevelopment

1010

20

Pilotplant

3030

60

Demonstrationplant

2828

56

Total

6969

138

79

Table 4. Proposed R&D Funding for Conversion of Organic Materials to Fuels (SM)

Activity

Bioconversion to methanePyrolysisChemical reduction

Total

System orlaboratory

studies

923

14

Pilotplant

231218

53

Demonstrationplant

293541

105

Total

614962

172

Table 5. Proposed Funding for Solar ThermalElectric Generation (SM)

Feasibility studies andcomponent development*

Pilot plantsDemonstration plant**

Total

30100

1000

1130

"Collectors, storage, energy transfer, and system engineering.""Amounts represent total government and private funds on a

cost-share basis.

Table 6. Proposed Funding for Photovoltaic Electric Generation ($M)

Low cost solar array developmentLow cost solar array pilot plantGround/building subsystemsSpacecraft subsystemsSystems for buildingsGround stationsSpace central stations

Total

Feasibilitystudy

123

6

Technologydevelopment

401703070

310

Systemsdefinition

4

45

49

Phototypetesting

570

340

415

Total

401703070

676

388

780

80

Table 7. Proposed R&D Funding for Wind Energy and Ocean Thermal Gradient Conversion ($M)

Activity

Wind conversionOcean thermal gradient

Total

Feasibilitystudy

42

6

Componentdevelopment

9643

137

Pilotplant

2055

75

Demonstrationplant*

490430**

920

Total

610530

1140

'Amounts represent total government and private funds on a cost-share basis.**One 400 Mw ocean plant.

81

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APPENDIX B

MEMBERSHIP OF SOLAR ENERGY PANEL

EXECUTIVE COMMITTEE

Dr. Paul DonovanNational Science Foundation1800GSt.,N.W.Washington, D.C. 20550

Mr. William H. WoodwardNASA HeadquartersCode: RPWashington, D.C. 20546

Mr. William R. CherryCode 760NASA Goddard Space Flight CenterGreenbelt, Md. 20771

Dr. Frederick H. MorseDepartment of Mechanical EngineeringUniversity of MarylandCollege Park, Md. 20742

Dr. Lloyd 0. HerwigNSF-RANN1800GSt.,N.W.Washington, D.C. 20550

Prof. Raymond BauerHarvard Business SchoolBoston, Mass. 02163

Prof. Samuel Z. KlausnerUniversity of Pennsylvania4025 Chestnut StreetPhiladelphia, Pa. 19104

Dr. James J. McKenzieMass. & National Audubon Society36 Fabyan StreetArlington, Mass.

Mr. Paul RappaportDavid Sarnoff Research CenterPrinceton, N.J. 08540

Mr. Milton SearlResources for the Future, Inc.1755 Massachusetts Ave., N.W.Washington, D.C. 20036

BIOCONVERSION

Chairman

Dr. Martin D. KamenDepartment of ChemistryUniversity of CaliforniaLa Jolla, Calif. 92037

Members

Dr. George L. M. ChristopherUnited Aircraft Research Labs.East Hartford, Conn. 06108

Dr. Bessel KokRIAS Inc.7212Bello Ave.Baltimore, Md.

Prof. L. KrampitzDepartment of Microbiology .Case Western Reserve UniversityCleveland, Ohio

Prof.'William J. OswaldUniversity of CaliforniaDepartment of Sanitary Engineering

and Public HealthBerkeley, Calif.

83

PHOTOVOLTAIC SPACE CONDITIONING

Chairman

Prof. Martin Wolf113 Towne BuildingUniversity of PennsylvaniaPhiladelphia, Pa. 19104

Chairman

Dr. Jerome WeingartEnvironmental Quality Lab.California Institute of TechnologyPasadena, Calif. 91109

Members

Prof. Karl W. BoerEnergy Conversion ProgramUniversity of DelawareNewark, Delaware 19711

Dr. Peter GlaserArthur D. Little, Inc.20 Acorn ParkCambridge, Mass.

Mr. Paul GoldsmithTRW Systems, Inc.1 Space ParkRedondo Beach, Calif.

Members

Prof. John DuffieSolar Energy LaboratoryUniversity of WisconsinMadison, Wise. 53706

Dr. George LofColorado State UniversityFort Collins, Colo.

Lt. Robert Reines3415 Anderson SEAlbuquerque, N.M. 87106

Mr. P. Richard Rittlemann610 Me 11 on BankButler, Pa.

Mr. Peter A. liesCentralab Semiconductor Division4501 N. Arden DriveEl Monte, California

Dr. Sheldon E. IsakoffEngineering Physics Lab.DuPont Co.Wilmington, Delaware 19898

Prof. J.J. LoferskiDivision of EngineeringBrown UniversityProvidence, R.I. 02906

Dr. Remo PellinMonsanto Chemical Co.860 N. Lindberg Blvd.St. Louis, Mo. 63166

Dr. Nicholas F. YannoniAir Force Cambridge Research Lab.Bedford, Mass. 01730

Prof. Richard ShoenSchool of ArchitectureUCLALos Angeles, Calif.

CENTRAL ELECTRIC POWER

Chairman

Dr. F. M. SmitsBell Telephone Laboratories555 Union Blvd.Allentown, Pa. 18103

Members

Prof. E. R. G. EckertDept. of Mechanical EngineeringUniversity of MinnesotaMinneapolis, Minn. 55455

84

Prof. D. K. EdwardsEnergy & Kinetics DepartmentUCLALos Angeles, Calif. 90024

Prof, William GouseCarnegie Mellon UniversityPittsburgh, Pa. 15213

Dr. L. I.MaisselIBM CorporationBoardman RoadPoughkeepsie, N.Y. 12602

Dr. Aden B. MeinelOptical Sciences CenterUniversity of ArizonaTucson, Ariz. 85721

Dr. L. T. PapaySouthern California Edison Co.P. O. Box 8002244 Walnut Grove Ave.Rosemead, Calif. 91770

Prof. E. M. SparrowDept. of Mechanical EngineeringUniversity of MinnesotaMinneapolis, Minn. 55455

Mr. R. M. Van Vliet4057 Rushton DriveDay ton, Ohio 45431

UNIQUE SYSTEMS

Chairman

Prof. Robert L. BaileyDept. of Electrical EngineeringUniversity of FloridaGainesville, Fla. 32601

Members

Mr. J. Hilbert Anderson1615 Hillock La.York, Pa. 17403

Dr. Erich A. FarberSolar Energy LaboratoryDept. of Mechanical EngineeringUniversity of FloridaGainesville, Fla. 32601

Prof. William F. HeronemusDept. of Civil EngineeringUniversity of MassachusettsAmherst, Mass. 01002

Dr. George C. SzegoInterTechnology Corp.Warrenton,Va. 22186

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