September 9, 2003 Lee Jay Fingersh National Renewable Energy Laboratory Overview of Wind-H 2 Configuration & Control Model (WindSTORM)

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?

Wind-hydrogen interface optimization Generator Interface DC BusGrid Interface ElectrolyzerFuel Cell or Combustion Device Battery Multi-Pole Switch or Switches Wind turbine power converter

Classical wind-hydrogen storage system Power Grid Variable -speed drive Rectifier Electrolyzer Compressor Storage Fuel-cell Inverter Wind turbine Storage system efficiency: 25% to 35% Fuel e-e- e-e- e-e- e-e- e-e- e-e- H2H2 H2H2 H2H2 e-e- H2H2

Storage system with shared power converter Power Grid Variable -speed drive Electrolyzer Compressor Storage Fuel-cell Wind turbine Storage system efficiency: 30% to 40% Fuel e-e- e-e- e-e- e-e- e-e- e-e- H2H2 H2H2 H2H2 e-e- H2H2

“H 2 only” system Power Grid Variable -speed drive Electrolyzer In-tower low- pressure Storage Fuel-cell Wind turbine Storage system efficiency: 30% to 40% Fuel e-e- e-e- e-e- e-e- e-e- e-e- H2H2 H2H2 H2H2 e-e- H2H2

“Battery and H 2 ” system Power Grid Variable -speed drive Electrolyzer In-tower low- pressure Storage Fuel-cell Wind turbine Nickel- hydrogen battery Storage system efficiency: 80% to 85% Fuel e-e- e-e- e-e- e-e- e-e- e-e- H2H2 H2H2 H2H2 e-e- e-e- H2H2

“Battery only” system Power Grid Variable -speed drive In-tower low- pressure Storage Wind turbine Nickel- hydrogen battery Storage system efficiency: 85% to 90% e-e- e-e- e-e- e-e- e-e- H2H2

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

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

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%

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 H 2 storage (in-tower): $3/kWh ($100/kg)  FCR: 11.58%  O&M: fixed at $0.008/kWh

Example of system performance

Effect of forecasting

“Battery and H 2 ” and “H 2 only” systems

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

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

System designed for hydrogen production

Analysis of hydrogen production scenarios  Battery and H 2 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 H 2 production: $0.072/kWh ($2.40/kg) –Cost of H 2 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  H 2 only system – no electricity –Cost of H 2 production: $0.081/kWh ($2.70/kg) –Cost of H 2 production is higher because of lower electrolyzer capacity factor (38%)

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