Wind-Diesel Power Systems

Experiences and Applications

Winterwind 2008

E. Ian Baring-GouldNational Renewable Energy Laboratory

With help of

Martina Dabo – Alaska Energy Authority

Brent Petrie – Alaska Village Electric Coop

Presentation Outline

• What are wind diesel power systems?

• Markets in Canada and the U.S.

• Examples of systems from around the world

• Problems associated with development in Arctic climates

• What next?

Wind-Diesel Power Systems

• Designed to reduce the consumption of diesel

– Pits cost of wind power against cost of diesel power

– Reduces diesel storage needs

– Reduced environmental impact; fuel transport & emissions

• Used for larger systems with demands over ~ 100 kW peak load up to many MW

• Based on an AC bus configurations using wind turbines and diesel engines

• Storage can be used to cover short lulls in wind power

• Obviously requires a good wind resource to be “economical”

Wind-Diesel Penetration

– Used to understand control requirements

– Reactive power needs, voltage and frequency regulation

– Generally calculated on monthly or annual basis

– Total energy savings

– Loading on the diesel engines

– Spinning reserve losses/efficiencies

(kW) Load ElectricalPrimary

(kW)Output Power WindnPenetratio ousInstantane

(kWh) DemandEnergy Primary

(kWh) ProducedEnergy Wind n Penetratio Average

One of the critical design factors is how much energy is

coming from the wind – called wind penetration – as this

helps determine the level of system complexity

System Penetration

These are really three different systems which

should be considered differently

Note: People play loose with the definitions

Penetration

ClassOperating Characteristics

Penetration

Peak

Instantaneous

Annual

Average

Low

Diesel(s) run full-time

Wind power reduces net load on diesel

All wind energy goes to primary load

No supervisory control system

< 50% < 20%

Medium

Diesel(s) run full-time

At high wind power levels, secondary loads dispatched to

ensure sufficient diesel loading or wind generation is

curtailed

Requires relatively simple control system

50% – 100%20% –

50%

High

Diesel(s) may be shut down during high wind availability

Auxiliary components required to regulate voltage and

frequency

Requires sophisticated control system

100% -

400%

50% –

150%

Canadian Market Potential

Large communities and mines

• 10+ MW loads

• Large-scale turbines

• 40-190 MW of wind potential (low to high pen.)

• 25 mil – 120 mil l of diesel savings/yr.

Small communities

• 300 kW~2 MW loads

• 30-130 MW of potential (low to high pen.)

• 16 mil – 77 mil l of diesel savings/yr.

Study by Pinard and Weis for WEICan

Alaskan Market Potential

• 116 communities have a strong wind potential

• All rural communities have a potential between 90 & 240 MW of installed capacity

• New State Energy Plan to be released Dec of 08

• $150 M USD Renewable energy fund supporting RE projects

Study by Dabo of the Alaskan Energy Authority

Summit Station,

Greenland• National Science Foundation

remote research station on the Greenland Ice Sheet

• Diesel fuel flown in, ~$38.0/l (Works out to ~$1/kWh)

• Aggressive efficiency and fuel use reduction program

• 80 & 120kW diesel engines

• Testing 6kW turbine as the first step of a redesign

• Only ~2% annual energy comes from wind, up to 16% instantaneously

• Packed snow/ice foundation

• Very low air density

Main foundation plate

buried in the snow

Main house

with turbine in

backgroundP

hoto

Cre

dit: Ia

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arin

g-G

ould

Turbine after an ice fog

event

Photo Credit: Polar Services

Photo

Cre

dit: P

ola

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erv

ices

Kotzebue, Alaska• Large hub community in Northwestern Alaska with

a population of ~3,100

• Operated by Kotzebue Electric Association

• 11 MW installed diesel capacity

• 2 MW peak load with 700kW minimum load

• 915 kW wind farm comprised of 15, Entegrity e50, 50kW; 1 remanufactured V17 75kW; and 1 NW 100/19, 100kW wind turbine.

• Generated 1,064,242 kWh from wind in 2007, Capacity factor of 13.28 - ~5% of the load –saving over 71,500 gallons of diesel fuel

• Good turbine availability (92.8% 1/02 to 6/04) due to strong technical support

• Turbine curtailment used to control at times of high wind output

• PCE 07 – Capacity Factor 11.95 (4.42% of load)

• PCE 08 – Capacity Factor 9.13 (3.47% of load) – with clear evidence of missing data

Selawik, Alaska

• Coastal community in Northwestern Alaska with a population of ~840 permanent residents

• Operated by the Alaska Village Electric Cooperative

• Average load around 330 kW

• 4 Entegrity e15, 50 kW turbines with thermal load used to help support system control

• Turbines installed as part of a complete diesel plant retrofit project

• Initial reduced wind performance due to a number of issues – low wind resource, system integration issues, and turbine maintenance problems

• Average Capacity Factor of 8.6% with an estimated fuel savings of 20,400 gal from Jan 06 to Aug 07

• 07 PCE states a Capacity Factor of 10.5 while no data is given for 2008

Toksook Bay, Alaska• Y-K costal community on Etolin Strait with a population of ~560

• Intertie to the town of Nightmute (pop ~240) energized April 2008

• Power system operated by the Alaska Village Electric Cooperative

• Average load just under 370 kW (both Toksook and Nightmute)

• 3 NW100kW turbines and resistive community heating loads

• Installed in the fall and winter of Summer/fall of 2006

• 24.2% average wind penetration with much higher instantaneous penetration

• Almost 700MWh generated by wind last year , saving almost 46,000 gallons of fuel

• First year turbine availability of 92.4% - currently under warrantee

• Average Net Capacity Factor of 26.0% from Aug 07 to July 08

• PCE 07 – Capacity Factor of 19.6 (20.16% of load for 8 months of operation)

Kasigluk, Alaska• Y-K community with a population of ~540

• Power system operated by the Alaska Village Electric Cooperative

• Average load 240 kW

• 3 NW100kW turbines and resistive community heating loads

• Installed in the fall and winter of Summer/fall of 2006

• Just over 22.4% average wind penetration with much higher instantaneous penetration

• Over 40 MWh monthly average wind generation, saving ~3000 gal/month

• First year turbine availability of 94.0% -currently under warrantee

• Average Net Capacity Factor of 24.06% from Aug 07 to July 08

• PCE 07 – Capacity Factor 14.7 (14.76% of load for 8 months of operation)

St. Paul, Alaska• Owned and operated by the Tanadgusix

Corporation (TDX) Power

• Airport and industrial facility

• High penetration wind-diesel system where

all diesels are allowed to shut off

• 1 Vestas, 225 kW turbine installed in 1999 and

2, 150kW diesel engines with a synchronous

condenser and thermal energy storage

• Current average load ~70kW electrical, ~50kW

thermal

• Since 2003, net turbine capacity factor of

31.9 % and a wind penetration of 54.8%

• System availability 99.99% in 2007

• In March of 2008, wind supplied 68.5% of the

stations energy needs and the diesels only

ran 198 hours ~27% of the time.

• Estimated fuel savings since January 2005 (3.5

years is 140,203 gal (at $3.52/gal is almost

$500k)

Wales, Alaska• Bering Strait community with a population ~140

• Operated by Alaska Village Electric Cooperative with the

implementation assistance of Kotzebue Electric Association.

System design by NREL.

• 65kW average load

• 2 AOC 15/50 wind turbines, Short term battery

storage with rotary converter and resistive loads

used for heating and hot water

• Operation with all diesels turned off

• System has had many problems associated with

system complexity, maintenance and confidence

of the local population to operate with all diesel

engines off line

• FY07 and FY08 PCE reports show no wind

production which is not consistent with reported field

operation.

Mawson,

Antarctica

• Installed in 2002-2003

• 4 120 kW with heat capture

• 2 Enercon E30’s 300 kW turbine

• Electrical demand: 230 kW average

• Thermal demand: 300 kW average

• Total fuel consumption of 650,000 l per year

• Average penetration since 2002 is 34%

• Best monthly penetration is 60.5% in April of 2005

• Turbine availability 93%

• Average fuel savings is 29%

• Even though a flywheel is used to provide power conditioning, a diesel always remains on

• Power station operation web site: http://www.aad.gov.au/apps/operations/electrical.asp

McMurdo Station – Antarctica

Photo by Bill Henriksen

Huge energy apatite - 13,182,536 kWh electricity generated in 2007, 4.39 M liter fuel to

make electricity, heat & desalinate water and 1.97 M liter fuel for building heat

McMurdo Wind Project

• Annual wind speed of 7.9 m/s at 39m

• Implement a fly wheel energy storage device to allow

smooth out power fluctuations

• Engineering currently underway – installation planned

for 2009/2010 Antarctic Season

Installation of Three

Enercon E-33’s (330

kW) wind turbines

Interconnect the two

stations of McMurdo

(US) and Scott (NZ)

13 Ton pre-cast concrete blocks

that will be anchored to the

ground and then frozen in place

Simulation of the three wind turbines above Scott Base

Modeled potential savings

• 21% of electrical energy from wind

• 463,000 liters of fuel every year between the two bases – initially reducing fuel consumption by 11%.

Implemented by Meridian Energy (NZ) with

the assistance of PowerCorp (AU),

Raytheon Polar Service (US)

Funding from the New Zealand Antarctic

Program and National Science Foundation

Complications Regarding Wind Energy

Development in Alaska Arctic

In addition to snow, ice,

and cold temperatures,

poor infrastructure,

above ground utilities,

and seasonal access

hamper development

activitiesAccess for specialty equipment required to place foundations and

erect turbines is a challenge.

Photo Credits: Alaska

Village Electric

Cooperative

• They must not settle, tilt or be uplifted

• Pile foundations (six to eight piles) may extend 1/3 to 2/3 the height of the tower into the ground

Foundations in

permafrost are

a challenge

Wind towers on land in

most of the world are

built with a ‘point of

fixity’ at the base of the

tower where it typically

rests on a massive

concrete foundation.

Point of

Fixity

Reinforced

Concrete Pad

30 m

10 - 20 m

In order to be

properly secured in

permafrost, wind

turbines may require

pilings in the ground

which are 1/3 to 2/3 of

the height of the

tower.

The tower foundation is

elevated to allow cold

air to pass over the

ground to keep it frozen

and to avoid heaving of

the tower base.

0.5 to 5 m

Frozen ground at

surface in March

Frost line in

September/October

after seasonal thaw

One problem with Alaska

permafrost conditions is

that the point of fixity may

be below the ground

surface and may vary

throughout the year as the

frost line of the active

layer migrates.

0.5 to 5 m

No lateral support

when thawed

New ‘point of fixity’

When the active layer is

thawed, there is minimal to

no lateral support to the

piling near the base of the

tower.

Frozen/Solid Ground

In such conditions, the piles

act as an extension of the

tower.

The rotating turbine, and

strong wind forces can

create destructive

frequencies in the

‘extended’ tower.

Wind site

Overview – Toksook

Bay

2-5 meter of frozen silts lie over tilted bedrock at the site.

• Holes pre-drilled

• Piles driven to

refusal

• Piles later cut

Six piles for a single tower foundation

Rock bolts would be placed

into the rock and tensioned to

the pile cap.

Additional Mass was added by

placing a rebar cage and

concrete in the pile.

Drilling out center of

piles to 6 m below end

of pile

The steel foundation

cap contains I-Beams

to connect the piles

and a ring to make the

tower base.

Steel Foundation

Star (Typical of 3)

Concrete and rebar was incorporated into the tower base and piles to add 59,000 kg of dampening mass.

Rebar Cage to go into a pile.

Drain

Conduit

Bolts

Meter base and riser to

connect to overhead

distribution system

Forms were placed underneath the foundation star to hold the concrete in place until it cured.

Finished Product

• Design load 280 kN

• Tested up to 930 kN –

less than 50 mm

movement

• Thermal siphons

used to keep

permafrost frozen

• Temperature

measurements taken

regularly

Potential Methods to Further reduce

the use of diesel fuel

Currently wind in rural Alaskan communities is used primarily to supplant electric power generation – but a

good amount of energy in rural Alaska is used for heating and in the transportation sector.

• Electric or hybrid electric vehicles may help reduce fuel use in transportation – residential, municipal fleets or business sector.

• Electric heating through thermal loads will not replace the fuel heaters for space and hot water heating, but they can be used to limit fuel use and help support increased wind power penetrations.

Transportation SectorWill not replace all vehicles in rural communities – but can

certainly replace a large number of vehicles.

Snow Machines

• Not commercially available but the Univ. of Wisconsin Madison prototype electric snow machine has a range of 32 km and can go up to 50 kmh

• Uses about 0.33 kWh/mile for “fuel”.

• Currently being used at Summit Camp on the Greenland Icecap – with summer highs around 0, and people like it.

ATV’s

• Several commercial manufactures with rages up to 40 km on single charge and max speeds up to 56 kmh.

• Use about 0.15 kWh/mile

Trucks and Cars

• Large variety of light duty electric cars and trucks

Doran e-ATV

EVS e-force sport ATV

Bad Boy Buggy utility

electric ATV in Greenland

Univ. of Wisconsin

Madison modified Polaris

E-Ride electric truck –

being tested in

Antarctica in 08/09

Electric Heating• In many rural communities – around 90% of heating

uses fuel based sources

• From a technology standpoint – simple control of electric space or water heating in a rural community is very easy to do.

• Community level control is much less tested / verified

• Assuming 95% efficiency, this works out to about 39 kWh/gal (139,200 BTU/gal) of fuel used for heating

• At a cost of $4.00 / gal for heating fuel this equals ~$0.10/kWh which is currently less than wind in many rural communities, but not out of the question for use at times of excess wind energy.

• Several projects currently underway in Alaska

• Very limited data on energy use for heating (space and water)

Conclusions

• Strong defined market in the U.S. and Canada

• Other potential markets yet defined

• Many successful wind-diesel projects have been implemented, but every project is not successful

• Projects can be very difficult and expensive to implement

• All energy options should be considered in communities include advanced diesels and control, locally derived fuels & “other” community loads.

• Need to expand beyond standard energy markets

• Social sustainability issues dominate over technical ones

Renewable power systems, specifically wind-diesel, can be implemented successfully in artic areas