operation and sizing of energy storage for wind power plants in a market system magnus korpås...
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Operation and sizing of energy storage for wind power plants in a market system
Magnus KorpåsNorwegian University of Science and Technology (NTNU)
Contents:• Why use energy storage for grid-connected wind farms?• Scheduling and operation of the energy storage• Results from a simulation study
Doctoral project financed by Statkraft SF and the Norwegian Research Councile
Local energy storage can increase thepenetration of wind power
v
local load
external grid
dump load (possible)energystorage
transmissionline
time
local load
transmission line capacity
powe
r
Local energy storage can increase thepenetration of wind power
v
local load
external grid
dump load (possible)energystorage
transmissionline
time
wind power
powe
r
Local energy storage can increase thepenetration of wind power
v
local load
external grid
dump load (possible)energystorage
transmissionline
time
powe
r
exported power
Operation strategy in a market system
19:00 24:00 01:00 02:00 23:00
Measure storage level
Read wind, load andprice forecasts
Determine the hourly trading of electricity which maximizes the expected profit over the scheduling period
Operate energy storage in order to follow the production
plan for each hour
The operation strategy is demonstrated in a simulation study
v
local load
external grid
dump loadenergystorage
transmissionline
Transmission line capacity 4.0 MWMean local load 2.6 MWWind power capacity 10.0 MWAverage wind speed 8.2 m/sRMSE of wind forecasting 2.6 m/sEnergy storage efficiency 75%Power capacity of storage 4 - 8 MWEnergy capacity of storage 50 - 150 MWh
Purchase price in the regulating power market.Purchase and sales price in the spot market.Sales price in the regulating power market.
Electricity price profile used in the simulation study
5 10 15 2010
20
30
40
50
time [hours]
elec
tric
ity
pric
e [$
/MW
h]
wind powerforecasted wind powerpower exportscheduled power export
Demonstration of the daily operation
storage levelestimated storage level
30 40 50 60 700
20
40
60
time [hours]
stor
age
leve
l [M
Wh]
30 40 50 60 700
5
10
pow
er [
MW
]
The impact of storage sizing on yearly revenue
150100
50
310
320
330
340
350
4
6
8
year
ly r
even
ue
[100
0 $]
Power
cap
acity
[MW
]
Energy capacity [MWh]
The system manages to follow the scheduling plan
50100
150
0
2
4
6
8
10
12
8
6
4
Dev
iati
on
fro
m p
rod
uct
ion
pla
n [
%]
Power
cap
acity
[MW
]
Energy capacity [MWh]
System performance is sensitive to the wind forecasting error
perfect forecasting persistence method
200
250
300
350
400
RMSE of wind velocity [m/s]
reve
nue
[100
0 $]
0 m/s 2.57 m/s
3.16 m/s
4.84 m/s
System performance is sensitive to the wind forecasting error
improved schedulingmethod
200
250
300
350
400
RMSE of wind velocity [m/s]
reve
nue
[100
0 $]
0 m/s 2.57 m/s
3.16 m/s
4.84 m/s
System performance is sensitive to the wind forecasting error
scheduling at 23:00
200
250
300
350
400
RMSE of wind velocity [m/s]
reve
nue
[100
0 $]
0 m/s 2.57 m/s
3.16 m/s
4.84 m/s
Conclusions and further work
With a properly sized energy storage, owners of wind powerplants can take advantage of electricity price variations
The operation strategy shows good performance,but is sensitive to the wind forecasting accuracy
The simulation method is suitable for any energy storage device and intermittent energy source
System simulation and economic analysis of relevant siteswill be carried out
Only a small amount of power is dumped due to overproduction
50100
150
0
1
2
3
4
5
4
6
8
Am
ou
nt
of
du
mp
ed w
ind
po
wer
[%
]
Power
cap
acity
[MW
]
Energy capacity [MWh]
Cost comparison
Alternative Total yearly income
wind + storage 1.1 Mill $
wind + new grid 1.0 Mill $
wind + downregulation 0.9 Mill $
Cost of Regenesys pilot plant 20 Mill.$Power capacity 10 MW Energy capacity 120 MWhEfficiency 70 %
Several promising fuel cell consepts exists for energy storage
Hydrogen-Oxygen
2 H2 + O2 2 H2O
efficiency 50-60 %
Hydrogen-Bromine
H2 + 2 Br 2 HBr
efficiency 70-80 %
Hydrogen-Chlorine
H2 + Cl2 2 HCl
efficiency 70-80 %
Redox flow cells
Regenesys, Vanadium and more
efficiency 70-80 %
Benefits of energy storage for a grid-connected wind farm
• increase the penetration of wind power
• utilize extisting grid capacity
• power smoothing
• sell electricity at peak hours, charge at off-peak hours
• voltage and frequency control
• improve reliability (line faults, generator outtakes etc.)
Demonstration of the daily operation
30 40 50 60 700
2
4
6
8
10
time [hours]
real
pow
er [
MW
]
wind powerforecasted wind powerpower exportscheduled power export
30 40 50 60 700
20
40
60
time [hours]
stor
age
leve
l [M
Wh]
storage levelestimated storage level