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
n B
arin
g-G
ould
Turbine after an ice fog
event
Photo Credit: Polar Services
Photo
Cre
dit: P
ola
r S
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
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