1. Operation and sizing of energy storage for wind power plants in a market system Magnus Korpås Norwegian 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

2. Local energy storage can increase the penetration of wind power v local load external grid dump load (possible)energy storage transmission line time local load transmission line capacity power

3. Local energy storage can increase the penetration of wind power v local load external grid dump load (possible)energy storage transmission line time wind power power

4. Local energy storage can increase the penetration of wind power v local load external grid dump load (possible)energy storage transmission line time power exported power

5. Operation strategy in a market system 19:0024:0001:0002:0023:00 Measure storage level Read wind, load and price 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

6. The operation strategy is demonstrated in a simulation study v local load external grid dump loadenergy storage transmission line Transmission line capacity4.0 MW Mean local load2.6 MW Wind power capacity10.0 MW Average wind speed8.2 m/s RMSE of wind forecasting2.6 m/s Energy storage efficiency75% Power capacity of storage4 - 8 MW Energy capacity of storage50 - 150 MWh

7. 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

8. wind power forecasted wind power power export scheduled power export Demonstration of the daily operation storage level estimated storage level

9. The impact of storage sizing on yearly revenue

10. The system manages to follow the scheduling plan

11. System performance is sensitive to the wind forecasting error perfect forecastingpersistence method

12. System performance is sensitive to the wind forecasting error improved scheduling method

13. System performance is sensitive to the wind forecasting error scheduling at 23:00

14. Conclusions and further work With a properly sized energy storage, owners of wind power plants 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 sites will be carried out

15. Only a small amount of power is dumped due to overproduction

16. Cost comparison AlternativeTotal yearly income wind + storage1.1 Mill $ wind + new grid1.0 Mill $ wind + downregulation0.9 Mill $ Cost of Regenesys pilot plant  20 Mill.$ Power capacity10 MW Energy capacity120 MWh Efficiency70 %

17. Several promising fuel cell consepts exists for energy storage Hydrogen-Oxygen 2 H 2 + O 2  2 H 2 O efficiency  50-60 % Hydrogen-Bromine H 2 + 2 Br  2 HBr efficiency  70-80 % Hydrogen-Chlorine H 2 + Cl 2  2 HCl efficiency  70-80 % Redox flow cells Regenesys, Vanadium and more efficiency  70-80 %

18. 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.)

19. Demonstration of the daily operation wind power forecasted wind power power export scheduled power export storage level estimated storage level