RESIDENTIAL EARTH-COUPLED AND GROUNDWATER HEAT PUMPDEMONSTRATIONS AND FOLLOW UP TECHNOLOGY TRANSFER

Gary De AllhusenNew York State Energy Research and Development Authority

ABSTRACT

A field demonstration of state-of-the-art residential earth-coupled heatpump systems was conducted in Upstate New York0 The monitored data indicatesthat properly sized, installed and maintained packaged liquid-to-airearth­coupled heat pump units with any water heating option will achieve a seasonalperformance factor (SPF) range of 205 to 3~O$ Horizontal and vertical earthloops were found to perform almost identically when horizontal systems aresized at 450 trench ftjton and vertical systems are sized at 180 verticalftlton, where tonnage refers to the nominal capacity of the heat pump~ It wasfound that properly sized earth-coupled heat pumps run continuously on winterpeak days at a demand of approximately 101 kWjtonll Although some backupelectric resistance cycles in as needed at night and in the early morning,only 1,,1 kWjton occurs the typical 7 p~m~ system peak of Niagara MohawkPower Corporation~

Concurrent wi the earth-coupled demonstration, fifteen groundwater heatpumps, installed in single-family residences throughout New York State, weremonitored from the 11 of 1982 to spring of 1984~ Two forms of SPF werecalculated from the data collected ring the heating season: unit SPF andsystem SPFe The energy suppli the house was the same for bothcalcul ons, but the unit SPF did not account for well pump energy whereas

system SPF did@ Unit SPF's ranged from 201 to 3@3$ Including well pumpA~'~~~B\I in calculation, system SPF's ranged from 1~9 to 3~00 A system SPF

can expected for a properly installed maintained groundwaterIn the cooling mode, energy savings were achieved by adding an

exchanger and bypass i ng compressor for di rect coo1i ng @

was sacrifi d in is rnode.. Utilizing the compresser forIS 5~1 O~

camp1 on pump projects, a techno logy transfer\lIas underta to disseminate the results of the denlonstrationse CIA

ical Gui to Ground ....Source Heat Pumps" was published summarizing theresul of the demonstrationse The audience for the technical guide was New

IS heating, ventilating and air conditioning industry0 As a followthe technical guide, a ground .... source heat pump seminar was produced~

seminar package consisted of research presentations made by each of theincipal investigators in the demonstration projects combined with

ptions of a number of field applications presented by ground-source heatindustry representati ves ~ A brochure was a1so pub1i shed whi ch provides adescription of the ground-source heat pump technology~

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RESIDENTIAL EARTH-COUPLED AND GROUNDWATER HEAT PUMPDEMONSTRATIONS AND FOLLOW UP TECHNOLOGY TRANSFER

Gary Do AllhusenNew York State Energy Research and Development Authority

INTRODUCTION

The ground-source heat pump program at the New York State Energy Researchand Deve1opment Authori ty (Energy Author; ty) is focused on adapt; ngstate-of-the-art water-source heat pump technology for application in New YorkState~ Two demonstration projects, cofunded in part by the Energy Authorityunder the ground-source heat pump program, were completed in late 1984~ Oneproject entitled "Residential Earth-Coupled Heat Pump Demonstration U monitoreda total of nine closed-loop heat pump systems, located throughout upstate NewYork, for space heating, cooling and domestic water heating performancevalues$ A second project entitled "Ground Water Heat Pump Evaluation ll

monitored fifteen open .... loop heat purnp systems located throughout the entireState for space heating and cooling performance values& In light of thesuccessful completion of the two demonstration projects, a major technologytransfer effort was undertaken to di ssemi nate the resul ts of thedemonstrations and aid in developing an infrastructure of high volume, lowcost earth loop installers within New York State" The following presents adescription of both the earth-coupled and groundwater heat pump demonstrationprojects as well as an overview of the Energy Authorityls technology transferefforts to date$

ENERGY SOURCES

There are two energy sources used in ground-source heat pump installations:groundwater aquifers and earth-coupled loops$

Groundwater heat pump systems use well water as the low-temperature heatsource~ The water is removed front the aquifer, passes through a liquid­to-refrigerant heat exchanger in the heat pump, and t n is returned to theaqui scharged into a stream or pond, or used for other purposes $ A

pump system is also called an open-loop system0

Earth-coupled heat pump systems use earth loops, or pipes buried in theground$ There are two basic loop configurations: horizontal and vertical &In the zontal system, an antifreeze solution circulates through a groundcoil buried in a 2$5 1 to 6 1 deep trench to absorb heat from the earth (trenchdepth depends on climate and operating characteristics of the heat pUlnp)0Horizontal loops can also be laid on the bottom of a pond or lake, utilizingthe heat stored in the water~ After passing through the ground coil, theantifreeze enters a 1iquid-to-refrigerant heat exchanger in the heat pumpwhere it exchanges heat with the refrigerant~ The vertical earth loop systemis designed to accomplish the same result as the ground coil system, but can

installed in vertical holes, thus minimizing site area requirements 0 Anearth-coupled heat pump system is referred to as a closed-loop system0

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Groundwater Supply and Discharge

The groundwater heat pump incorporates an open-loop water system, usinggroundwater as the low-temperature heat source for heating operationsoTypically, a well is required, but spring water or water from a lake with anappropriate operating temperature range has also been usedo The source mustbe adequate enough to provide between 105 and 3 gallons of water per minuteper ton of heat pump capacity for operation~

Groundwater is usually supplied to the heat pump by means of a drilledwell with a submersible pump system0 The punlp must be submerged enough toremain 15.... 20 feet below the lowest well-water leve10 A filtering screenshould be placed in a section of the indoor piping before the heat pump inorder to 1imi t the number of parti cles that pass through the 1iqui d-to­refrigerant heat exchanger 0 Once the groundwater passes through the heatpump, an acceptable means of discharging the thermally altered water must beprovi ded ~ Nany areas have codes and regul at; ons regardi ng the scharge ofgroundwater and these guidelines must be followed0

Earth Loop Configurations

Earth loops can be laid horizontal into trenches or inserted verticallyinto drilled holes~ Since both have similar performance, the overridingconsideration is the installed cost~

The basic horizontal configuration uses one pipe per trench, and can beinstalled in series or in 11 0 To lower cost, several multiple

gurations that require less trench length are lable0

A second configuration uses two pipes per trench, and can also beins led in es or in paralle10 A third horizontal configuration usesfour pipes per trenche This configuration must be installed in parallel toavoid excessive pressure drop and the necessity for larger pipe diameters~

confirms that 400 trench feet per nominal ton ofis adequate for the basic 1 to 105 inch diameter one ....

on$ also indicates that thehorizontal system can be sized at 250 to 300 trench feet

per ton0 Vertical parallel systems can be sized at 125 to 175 feet ofvertical bore per ton~

The best configuration is the one that can be installed for the leastcost a pa cular sitee When sized properly, all configurations shouldresult in a similar system performance~

ING PERFORMANCE

A meaningful indicator of system performance is the seasonal performancefactor (SPF)~ The SPF is a defined as the ratio between all energy suppliedto the house during a heating season and all energy consumed by the heat pumpsystem during the season~ The SPF includes all real inefficiencies of a heat

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pump system, such as cycling of the heat pump as well as pumping power andpower consumed by the electric resistance heaters. In the earth-coupled heatpump demonstration, SPF values ranged from a high of 3.0 to a low of lo5~ Inthe groundwater heat pump evaluation, SPF values ranged from a high of 3eO toa low of 1.9. For comparison, SPF values for air-source heat pumps average1.6 in northern climates (Blake, 1980). Listed below are SPF values for theindividual sites monitored under each project.

Site

123456789

101112131415

No cooling data

Earth-Coupled SystemsSPF/SEER

2.9/11.72.9/10.5300/13.52.5/8.02.1/--­2.9/11.3205/7081.8/5021e5/6.1

Groundwater SystemsSPF/SEER

2.4/9.62.1/7072.5/14.02*.3/ --­300/13.3202/--­2&2/--­2.2/8.4204/--­2.3/8012.1/5.6201/7.62.6/--­204/8.91.9/---

gure 10 Heating and cooling performance data.

The ranges of SPF values were dependent upon many factors. Installation,system design, operation all impacted heat pump perfornlanceo For example, thegroundwater system th a low SPF value of 1.9 was at a site which had a deepwell (over 600 feet deep) with only marginal yielde Well pump energy wasrelatively high and the unit was operated with a groundwater recirculationloop which lowered the system's inlet temperature~ These factors, plus lessthan optimal flow rate through the heat pump contributed to the low system SPF(Rackliffe, 1985)~

COOLING PERFORMANCE

The steady-state efficiency of a heat pump in the cooling mode ismeasured in terms of its energy efficiency ratio (EER). The EER is defined asthe ratio of the rate of energy removed from the house to the rate of energyconsumed by the heat pumpe The system EER integrated over an entire coolingseason is called the seasonal energy efficiency ratio (SEER)~ In the

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e,arth-coupled heat pump demonstration, SEER values ranged from 13.5 to 502.In the groundwater heat pump evaluation, SEER values ranged from 14.0 to 5&6.For comparison, SEER values for central air conditioners range from 9~O to6.08 Figure 1 also lists SEER values for the individual sites monitored undereach project~

Groundwater heat pumps can provide cooling in two ways& By reversing the heatpump cycle, the compressor can be used to extract heat from indoors and rejectit to the water loop. Compressor cooling requires significantly more energythan direct water-to-air coolinge With direct water-to-air cooling, anadditional water-to-air heat exchanger is installed into the water loop andthe heat pump is bypassed~ The relatively constant 50°F water temperature canprovide sufficient cooling all summer long~ One advantage of using the heatpump for cooling, however, is that it provides better dehumidifcation thandirect groundwater cool;ng~ Overall, the groundwater heat pumps that utilizedthe compressor for cooling operation had average SEERs between 7$6 and 8~9~

Units using direct water-to-air cooling showed significantly higher SEERS,ranging from a low of 9~6 to a high of 14~O~ rect water-to-air cooling withearth-coupled heat pumps was attempted but was unsuccessful due to high earthloop temperatures (Hughes, 1986)~

Domestic Hot Water Options

The earth-coupled heat pump projheating options:

demonstrated three types of domestic

10 Space heating and partial water heating2e Space heating and total water heating3~ Separate heat pump solely for water heating

The total and partial water-heating options are similar in that anitional refrigerant-to-liquid heat exchanger is added to the basic heat

pump ~ The heat exchanger is added between the compressor and the revers i ngvalve~ th the heat exchanger in this position, the highest temperature

gerant is always available to heat water0 With the total space heatingal water-heating option, can be produced whenever the heat

heating or cooling~ heating is a free byproducting operation0

A heat pump with the total water-heating option has the same basicconfigu ons as the partial water-heating option, but differs in two keyrespects* rst, due to modified controls, the heat pump can activatespec; cally for hot water production~ Second, the additional heat exchangeris larger so that it can handle the entire output of the heat pump when

ired0

The separate domestic hot water heat pump is much smaller and lesscomplex than the basic heat pump0 No reversing valve is required because theunit is never used for cooling, and no fan or refrigerant-to-air heatexchanger is required because the unit only heats water@

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SPF values for earth-coupled heat pumps with a partial water heatingoption averaged 2&40 Systems with total water heating averaged 2~5o Theseparate heat pump was inoperable at source temperatures below 36°F@

Earth-Loop Performance

Source and sink temperatures provided by earth loops are best understoodby viewing some data examplese Figures 2 and 3 are provided for that purposeoThese figures present data from Site 3 of the earth-coupled demonstration,which has a vertical earth loop~ However, the temperature characteristicsillustrated apply equally well to horizontal systemse

Fi gure 2 presents hi stograms compari ng ambi ent and source temperaturefrequencies during times when the compressor operated over an entire heatingseasone The evident characteristics of earth-coupling is that it provides afloor for heat pump source temperatureQ

Figure 3 presents a trend plot of hourly source and ambient temperaturesover a week of cold weathere The evident characteristics of earth-coupling isthe relative stability of source temperature@ Groundwater heat pumps exhibitsimilar characteristics except the source temperature generally falls aroundthe 50°F line in Figure 3~

Groundwater System Performance

The groundwater system design and operation have an impact on theperformance of the GWHP & The we 11 pump size is one of the nlore importantfactors@ The well pump power consumption rate for heating ranged from 0&41 kWto 2@12 kw for the houses in the project@ The range of well pump powerexpressed in watts per gallon/rninute was 47 to 247W/gpm~ The flow ratescorresponding to these values ranged from 4Ql gpm to 11~1 gpm~ This range ofwell pump power differed from the American Refrigeration Institute standard of63 W/gpm used by some GWHP manufacturers for system performance calculations$

Since increases in the well pump power will reduce the SPF, particularattention should be given to the pump size@ Well pump power consumption isgenerally not lineral1y related to flow rate0 Therefore, the operation of theGWHP at an off....design ow rate below the recorrunended flow may be moreeconomical because reduced capacity is more than offset by well pump energysavings§ Conversely, if the well pump is oversized, the flow rate may beincreased without a significant increase in well pump resulting in an increasein SPF@ The best approach is to properly size the well pump so that theoptimum flow rate for the well pump matches the optimum flow rate of the GWHP~

At 1ess than opt imum condi tions, flow rate adjustments may improve systemperformance@ The well pump energy consumption is particularly important atinstallations th direct water-to-air cooling~ For example, at one directwater-to-air cooling installation, the well pump used more energy than theblower$

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IMPACT OF GROUNDWATER AND EARTH-COUPLED HEAT PUMPS ON ELECTRIC UTILITIES

The components of a each system all require electricity for operation~

Consequently, widespread installation and operation of these heat pumps withinan electric utility's service area could have some impact upon the utility~

The two main factors to consider are: 1) the effect of on the demandcurve and 2) the effect on tota1 revenues a& The overa11 effect wi 11 dependupon the percentage of the demand comprised by residential heating and if theelectric utility·s peak demand occurs during the summer or the winter~

The majority of the impact on electric utilities is likely to be relatedto the heating season~ Unless the utility is a summer peaking utility and anyadditional summer peak load created by new heat pump air conditioning is amajor concern, the impact of these heat pumps will be related to their heatingoperation$

gure 4 shows the demand profile for a New York State electric utilityon the day when its 1983-84 wi nter peak occurred 0 Fi gure 5 shows a demandprofile for House 1 in the groundwater heat pump project on the coldestweekday of the 1983.... 84 winter& Earth .... coupled heat pumps exhibit a similardemand profile to that shown in Figure 5~

Compari son of these fi gures shows that the tota1 house peak demandsncided with the utility peak demands 0 Although the heat pump systems did

not significantly alter the shape of house electric demand curves, they didprovide a uniform base load~ If less efficient electric heating systems hadbeen used the house demand curves would have been shifted upward, resulting inhigher peak demands~

ECONOMICS

The performance of groundwater and earth-coupled heat pumps is verysimilar so, for the purpose of presenting the economics, they will be treatedtogether& The major energy savings from these systems is for space heating,

though heat; also provides a significant savings potential 0 Anve owni a 9 rce heat pump is that air

itioning is included0 performance of ground-source heat pump airconditioning is at least comparable to, and in many cases better than, theperformance of a conventional air conditioner~

There are two factors to consider when evaluating the econornics ofground-source heat pumps: (1) the annual operating cost savings and (2) thefi cost of the system~

The operating cost savings are governed by the following factors:

o Cost of electricityoo Performance of alternative heating systemseo Cost of alternative fuels0o Relative maintenance COStS0

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The initial cost will include the following components:

o Any retrofit duct system modification costS$o Local excavating and exterior piping costS$o Any well-drilling costs beyond those used for domestic purposes~

a Accommodations to groundwater discharge codes and ordinances9o Cost of the heat pump and installations relative to the cost of

alternative heating and cooling systemso

Space Heating Savings

The operating cost savings available depend on what fuel is currentlybeing used on how much that fuel costs~ Figures 6 and 7 graphicallydemonstrate the cost savings that can be achieved by using ground-source heatpumps versus oil and natural gas heating systemse For example, if youcurrently use oil at $1.20 per gallon, and electricity at 6.5¢/kWh, fromFigure 6 you can determine that approximately 50% of your oil bill can besaved, or $452 of a typical $900 annual oil heat cost$ Note that this figuredoes not account for the differential maintenance cost of different equipment,the expected useful life of the equipment, or the purchase costs of the equip­ment$ The maintenance requirements for a ground-source heat pump should notexceed the combined maintenance requirements of a fossil-fired heating systemand central air conditioner~ On the other hand, reduced maintenance costs canbe expected if the ground-source heat pump is replacing an air .... source heatpump~ The smaller range of source temperatures of the ground-source heat pumpis less severe on the mechanical system~

Water Heating Savings

The savings available depend on what fuel is currently being used, howmuch the fuel costs, and which water-heating option is being consideredGFigure 8 and 9 illustrate the savings that can be achieved with the variousheat pump water-heating options versus electric and gas hot water heaterseFor exarnple, at a current cost of 6$5¢/kWh, Figure 8 shows that a partialwater-heating option can reduce your electric water heating bill by about 23%or $86 of an annual $371 hot water bille

Payback

Payback is calculated by dividing annual energy savings into theincremental installation cost~ The best paybacks are available in newconstruction or where existing equipment requires replacemente Here theappropriate cost to use in the calculation of payback is only the differencein cost between a ground-source system and the conventional alternative~

example, a typical replacement market three-ton earth-coupled heatpurnp system with partial water heating and a two .... pipe-per-trench horizontalearth loop in a mature market might cost $5,400~ However, if the homeownerneeded to replace the oil furnace for $1,500 and planned to add centraltwo-ton air conditioning for $1,600 the incremental installation cost is only

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$2,300$ Using the above examples, your annual energy savings for spaceheating and water heating are $452 an $86, respectively~ or $538 total,resulting in a 4.3 year payback period.

Since ground-source heat pump systems provide both heating and cooling,their economic attractiveness is greatest when compared to an alternativesystem which includes air condit;oning~ Homeowners desiring both heating andcooling will certainly constitute the bulk of the market for this technology.If cooling is not desired, the first cost premium for this device is greatest,as will be the anticipated payback periode

To summarize, the important considerations are the savings that will berealized each year by installing a ground-source heat pump system versus theinitial cost of a ground-source systeme These considerations will varydepending upon local energy costs, the type of ground-source heat pumpinstallation, and the cost of the ground-source heat pump system versusalternative heating systems.

TECHNOLOGY TRANSFER

The principal objectives of Phase 3 of the Residential Earth-Coupled HeatPump Demonstration were: (1) to develop models to generalize site-specificresults into a computerized predictive technique for earth loop sizing andECHP system performance prediction in upstate New York, and (2) to documentacceptable practices for residential earth-coupled heat pump systeminstallation in upstate New York~

Model Developments or Adaptations of Existing Approaches

Two system model formulations were developed under this project~ Thefirst, hereafter referred to as the IIModel for Design and PerformancePrediction ll

, is built around monthly bin analysis~ This model meets thetechnical requirements set forth by the cosponsors, and serves as II rawmaterial U for equipment suppliers interested in incorporating it into theirmarket support software at their own expense0

system model, hereafter referred to as the uSimplified ModelPerformance Prediction ll

, is built around annual bin analysisG This modelis derived from results generated by the monthly bin analysis model, andserves as II raw material ll for utilities interested in incorporating it intotheir customer service software at their own expense~ This software meets

requirements which are appropriate for the "economic comparison ofcompeting systems ll application0

Two project deliverables, in addition to this report, are provided underseparate cover~ The Manual of Acceptable Practices is a IIhow to do it ll bookfor upstate New York directed at contractors $ The "Simpl ified Model forPerformance Prediction ll deliverable consists of a user1s manual and IBM PCdiskette for a computer program which analyzes earth-coupled heat pump systemsonlY0 This;s the uraw material ll which utilities can incorporate into their

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customer service software which compares commercially available residentialheating and cooling systems (Hughes, 1986)e

In addition to the Phase 3 effort, a separate technology transfer projectwas undertaken to disseminate the results of both the earth-coupled andgroundwater heat pump demonstrati on projects" Under thi s project aground-source heat pump technical guide was published describing earth-coupledand groundwater heat pump systems, installation practices, performancecharacteristics and system economics$ The guide was distributed toprospective New York State ground .... source heat pump dea1ers and i nsta 11 ersincluding HVAC contractors and dealers, well drillers, excavators, designengineers and architects~ In addition, a leaflet was produced providing ageneral description of ground-source heat pump systems and was targeted morefor the uninformed publice

A ground-source heat pump seminar was also produced to introduce thetechnology, demonstrate installation and maintenance procedures and discusseconomic benefits of ground-source heat pumps~ Topics for discussion duringthe seminar included the results from the recent earth-coupled and groundwaterheat pump demonstration projects, presented by the principals of the twoprojects, as well as practical field experiences as discussed by severalmanufacturers 0 The seminar will be offered throughout a number of upstateutilities' franchise territories in the coming Fall$

CONCLUSIONS

A primary advantage of ground-source heat pumps over other heatingsystems ;s their ability to efficiently produce hot water, as well as thermalcomfort, all year longe And, depending on the application, the homeowner canbenefit from substantial heating cost savings, significant water heating costsavings, and some cooling savings$ A payback period of 3 to 10 years islikely$ Add; onally, everyone benefits when utilities experience a moreuniform load~ Ground-source heat pump systems have proven to be a highlyeffective load management and conservation tool, demonstrating electricdemands of only one-third to one-half those of competing electric heatingsystems on winter peak days, while their electric consumption during the restof the ng season is more uniform~ They also show slightly lower electricdemand on summer peak dayse

FOOTNOTES

(1) Bla ,P~J~, eteal~, Heat Pump Monitoring, ESEERCO Research Report EP5-6,nal Report, October 19800

(2) Hughes, P0J~ Residential Earth-coupled Heat Pump Demonstration Phases 1and 2$ NYSERDA, January, 1986@

(3) Hughes, P~J0 Residential Earth-coupled Heat Pump Demonstration .... PhaselIle NYSERDA, 19860

(4) Rackli , G$B~ Ground Water Heat Pump Evaluation0 ESEERCO, April, 19850

t'QU'D SOURCE TEMPERATURE

UOIJRS I"· IHTERVAlo.no J0.00 I0.00 I0.110 r0.00 J0.00 J0.00 J0.00 I0.00 i0.00 I

90.00 I.1937.00 Ja •• Me ••• @.~.e.$d@mee~@@m~1086.00 lee~._e~e@me.ee~@e375.00 14h"~§Ill.e

0.00 I0.00 I0.00 I(J.CJO I0.00 I0.00 I0.00 E0.00 I0.00 I0.00 !

3118 .. 00

AMBIENT TEMPERATUREof

HiJEI\'V/U. fliDliiO unuRS iH JHJERVAL-85.00 0.00 f .-10.00 0.00-5.00 IS.OO Je0.00 20.00 is5.00 71.00 Jd9G.

10.0n 131.00 J•• d8.9

IS.OO 159.00 Id~ •••• @.20.00 210.00 r•••••• M••••

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# 60.00 39. no I • ~65.00 20.00 Ie70.00 1.00 .115.00 3.00 I80.00 0.00 I05.00 0.00 I90.00 0.00 IgS.OO 0.00 I

100.00 0.00 IlfilAl 3110.00

figure 2. Ambient Ys. source.tempera~ure histogram

50

46

49

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~ 3(;

i 26As

~ 20

IS

10

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t ...,$ $ ••• $.' ••••• ; ••• 'I,•••••••••••••••• ,.~~:~~~~ : ~~~~~~~~~:~~~:~~t~~~~~::::::::::..........." ., .,..1' 0 •• •

$

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Figure 3$ Hourly temperature trendso

UTILITY AVERAGE HOURLY DEMAND VERSUS HOUR OF DAY6000

A5750V

~5500AG5250E

H5000oU4750Ri 4500

04250E~4000

~3750

3500

03250

3000o 2 4 6 8 10 12 14 16 18 20 22 24

HOUR OF DAY SOURCE-NIAGARA MOHAWK

Utility Average Hourly Demandversus Hour of Day

HOUSE 1 AVERAGE HOURLY DEMAND VERSUS HOUR OF DAY12

AllVE,0RA 'l>

G 9E

H 80U 7Rl 6y

D 5EM 4AN

:30

2KW

\\

\ .,#­.......

1\I ,TOTAL, \ HOUSE

I \I \

J \- J \

1\I

/ --\I \I \I \

i\ I \I \ J \I \ I \, \ J \

'$ \ •

I \I \,,

II,

oo 2 6 8 10 12 14 16 18 20 22 24

AY .

House 1 Average Hqurly Demandversus Hour of Day

ASSUMPTIONS ASSUMPTIONS

80 r-HEAT PUMP SPF ::: 2.9 80 GAS COST HEAT PUMP SPF = 2.9

...., 80Oil AFUE == 0.65 80 $1.20rrHERM GAS AFU E = 0.60FURNACE BLOWER kWh =: 0.75 x HP BLOWER kWh _______~URNACEBLOWER kWh = 0.75 x HP BLOWER kWh

70 70 70 --t 70Oil COST (/)

(J) CJG 60 SlAO/GAL 60 z 60 rtt QnITLJc:ol~ ~ ~ -i 60z :;5: Sl.30/GAL «« $1.20/GAL ~

en(J) 50 $1.l0/GAL 50 C) 50 I- ,

~ ~ -.J 50 j

" z ...z $l.00/GAL i=i= 40 «

40 ..- " "'- ~ ~ -I 40 .« 40 ww J:J: ww 30 30

u30

"'~ ~J:!u «of:( a.0.. en

$.401THER~(J)

20tL 20u.. 20 0

0 'if.;!.

10 10 10 10

0 03 4 5 6 7 8 9 10 11 12 13 14 15 4 5 6 7 8 9 10 11 12 13 14

ELECTRICITY COST (CENTS PER kWh) ELECTRICITY COST (CENTS PER kWh)

1-1Figure i.9 Space Heating Savings-Ground-Source Heat figurl 7 Space Heating Savings-Ground..Source Heat$

~ Pump \IS Oil Heating Pump \IS Natural Gas--..J

80 r- -, 80 80 r- -, 80'TOTAL

70 70 70 WATER HEATING --I 70 1en GAS COST (cents/therm)C) (J)

z TOTAL WATER HEATING SPF = 2.4<.'J

:> 60 60 z 60 --t 60« :>en «

SEPARATE HEAT PUMP SPF ::: 2.0 en

" 50 50 CJ 50 t- " --I 50z z ... "of\.

~ i=UJ 40 t 40 «

40 i-* "- '" -t 40J: wJ:

a: a:w ·ft- 30 30 UJ 30 r- ,

" "- --t 30.l-e( PARTIAL WATER HEATING SPF :: 1.3 «~ - ~I.L 20 20 u.. 20 I- , "- '" -i 200 0;!. I

~10 10 10 10

0 0 0 03 4 5 6 7 8 9 10 11 12 13 14 i5 3 4· 5 6 7 8 9 10 11 12 13 14 15

., ELECTRICITY COST (CENTS PER kWh) ELECTRICITY COST (CENTS PER kWh)L. . " .,_..... ;,:-' .. "'" . ... ,"""'- ..... ... .. J, "_ _ ~...~

Figure.8 . Water Heating Savings-Ground-Source Heat figurE' q . Water Heatings Savings-Ground-Source HeatPump \IS Electric Hot Water H~at~r Pumpvs Natural Gas Hot Water Heater

19