Wind-H2 Configuration & Control Model (WindSTORM)

1. Overview of Wind-H2 Configuration & Control Model (WindSTORM) September 9, 2003 Lee Jay Fingersh National Renewable Energy Laboratory

2. Introduction • Wind is intermittent • Hydrogen production, storage and fuel cells can be used to store electricity • Batteries can also store electricity • Hydrogen can also be produced from wind to be used as a fuel • What is the best approach to combine hydrogen systems with wind?

3. Wind-hydrogen interface optimization Wind turbine power converter Generator Interface DC Bus Grid Interface Multi-Pole Switch or Switches Electrolyzer Fuel Cell or Combustion Device Battery

4. Classical wind-hydrogen storage system Storage system efficiency: 25% to 35% e- Power Grid Variable-speed drive e- Wind turbine e- Rectifier e- Inverter e- e- e- Electrolyzer Fuel-cell H2 H2 H2 Fuel H2 Storage Compressor

5. Storage system with shared power converter Storage system efficiency: 30% to 40% e- Power Grid Variable-speed drive e- Wind turbine e- e- e- e- e- Electrolyzer Fuel-cell H2 H2 H2 Fuel H2 Storage Compressor

6. “H2 only” system Power Grid Variable-speed drive Wind turbine In-tower low-pressure Storage Electrolyzer Fuel-cell Storage system efficiency: 30% to 40% e- e- e- e- e- e- e- H2 H2 H2 Fuel H2

7. “Battery and H2” system Storage system efficiency: 80% to 85% e- Power Grid Variable-speed drive e- Wind turbine e- e- e- In-tower low-pressure Storage e- e- e- H2 Electrolyzer Nickel-hydrogen battery Fuel-cell H2 H2 Fuel H2

8. “Battery only” system Storage system efficiency: 85% to 90% e- Power Grid Variable-speed drive e- Wind turbine In-tower low-pressure Storage e- e- e- H2 Nickel-hydrogen battery

9. Battery technology discussion • Batteries for grid interconnect will be subjected to an enormous number of cycles in a 20 year lifetime • One of the only battery chemistries that can withstand repeated daily cycles for 20 years is Nickel-Hydrogen • Used in space applications for the same reason • Uses the same reaction as nickel-metal-hydride • Uses separate hydrogen storage rather than storing hydrogen in the electrode • Cycle life reported to be 10,000 to 500,000 cycles • 2 cycles per day for 20 years is 15,000 cycles

10. Analysis Approach (WindSTORM) • Analysis is needed to answer “What is the best approach to combine hydrogen systems with wind?” • Simulate calendar year 2002 • California ISO load data • Windfarm data from Lake Benton, MN • Requirement: Power must balance hourly • Seek to reduce necessary traditional generation capacity (windpower capacity credit) • Determine optimal control methodology • Calculate system size and cost

11. Analysis parameter assumptions • Wind has 50% capacity credit • 100 MW wind farm reduces peak requirements on traditional generation by 50 MW • Equivalent to 50 MW “firm” power from 100 MW windfarm • Wind has 12% energy penetration • Wind has 20% capacity penetration • No net hydrogen production • Battery charge efficiency 95% • Battery discharge efficiency 90% • Electrolyzer efficiency 75% • Fuel cell efficiency 50%

12. Cost assumptions • Cost of Wind: $1,000/kW • Cost of battery: $70/kWh • Cost of electrolyzer: $600/kW (2010) • Cost of fuel cell: $600/kW (2010) • Cost of H2 storage (in-tower): $3/kWh ($100/kg) • FCR: 11.58% • O&M: fixed at $0.008/kWh

13. Example of system performance

14. Effect of forecasting

15. “Battery and H2” and “H2 only” systems

16. Important notes • The battery hours of storage required and cost of energy can vary dramatically with changes in the system: • Windfarm location • Windfarm size • Control methodology • Forecasting method

17. Alternate approach – produce hydrogen • Utilize slightly larger electrolyzer and more aggressive control strategy to produce some net hydrogen • All other requirements remain in effect • Electricity price: $0.04/kWh • Hydrogen price: $0.10/kWh • Capacity credit: $18/kW/year

18. System designed for hydrogen production

19. Analysis of hydrogen production scenarios • Battery and H2 system with hydrogen production • 5% of windfarm output turned into hydrogen • Enough to support about 2,250 vehicles • 10.7% of windfarm revenue from hydrogen • 5.8% of windfarm revenue from capacity credit • Cost of H2 production: $0.072/kWh ($2.40/kg) • Cost of H2 production is low because electrolyzer capacity factor is greater than 58%. • Cost drops to $0.062/kWh ($2.06/kg) if electrolyzer cost drops to $300/kW • H2 only system – no electricity • Cost of H2 production: $0.081/kWh ($2.70/kg) • Cost of H2 production is higher because of lower electrolyzer capacity factor (38%)

20. Conclusions • It is possible to “firm up” wind power for a roughly 10% increase in COE. • Using batteries is cost effective • Using hydrogen systems alone is not cost effective because the closed-cycle efficiency is too low • Hydrogen production can be simultaneously accomplished and is cost effective • Hydrogen production alone Is less cost effective • Control strategy and proper system sizing are very important • With further investigation, it may be possible to do much better