Production of Hydrogen from Renewable Electricity: The Electrolysis Component

1. Production of Hydrogen from Renewable Electricity:The Electrolysis Component Workshop on Electrolysis Production of Hydrogen from Wind and Hydropower NREL DC Office, Sept 8,2003.

2. Renewable Electricity- Infrastructure Meets DOE Hydrogen Feed Stock Strategy: • Primary Indigenous Sources: Wind, “run of river” hydro, solar • No carbon-emissions in electricity-hydrogen generation • Mature technology, established cost progression But can we meet DOE cost target ? $2.00 per kg at plant gate

3. Wind-Electrolysis Integration Process Capabilities: • > 90% of energy consumed by cells (@ 20 bar) • generator following load • trade off between efficiency and cap $. Efficiency inversely proportional to cell surface area (cap$). • design to avg efficiency/wind resource: • Plant X = 53 kWh/kg • Plant 2X = 47.5 kWh/kg • “Current sink” characteristic • Voltage regulated by cells • Response like “leaky capacitor” • Value of by-products • Electricity on demand • Oxygen by-product @ $25 per tonne = .4 cent per kWh • D20 ?

4. Cost Target Implications • Simple Cost Model : • $/kg = Efficiency(price of electricity) + [Annual (CRF+O/M)]  (Capital Cost per kg/h)÷ [(capacity factor)  8760 h/y] • Implications • For Annual (CRF +O/M) =20% • Capacity Factor = .35 • Avg. Efficiency = 50 kWh/kg (=approx 80% wrt HHV)

5. Two Market Models: • Wind-Hydrogen Generation Model • Wind- Hydrogen&Electricity Generation Model

6. Capacity Factor Matching in Wind-Hydrogen Generation Model • Single tier market design: Large-Scale Hydrogen Production • Tech Implications • Power Conversion: Optimize DC-Wind conversion based on electrolysis cells • Optimize cell size to scale of production – cell cost key • Maintaining grid stability with high electrolysis penetration • Pressurized cell design amenable to distribution pipeline

7. Capacity Factor Matching in Wind Hydrogen-Electricity Generation Model • Two tier market design: • Primary Market : Electricity Secondary Market: Hydrogen • Deregulated electricity market design with environmental credits for emission avoidance • Capture distributed generation benefit • Closer to market • Higher value electricity market supports secondary hydrogen production (energy storage) • Technology Implications • Controls • System Cost Key

8. Cell Technology

9. Technical Challenges • Intermittent operation; long term electrode stability • Economic scale of cell; cost highly dependant on cells • Gas purity process dynamics: • Controlling gas/liquid separation • Reducing bypass cell currents • Cell pressurization • Power conversion & controls

10. Conclusions: • DOE cost targets are very challenging • Early pathways to develop infrastructure: • Replace SMR hydrogen under right market conditions (NG conservation/CO2 mitigation): • heavy oil upgrading • ammonia production • Distributed “hydrogen&electricity generation model” may play role in early infrastructure development – if value put on green electricity/green hydrogen.