Production of Hydrogen from Renewable Electricity: The Electrolysis Component

1
Production of Hydrogen from Renewable
ElectricityThe 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
• gt 90 of energy consumed by cells (_at_ 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 _at_ 25 per tonne .4 cent per
  kWh
• D20 ?

4
Cost Target Implications

• Simple Cost Model
• /kg Efficiency?(price of electricity)
• Annual (CRFO/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)

Cost of Wind Electricity 2.5 /kWh 3.0 /kWh
Cost of Electrolyser (_at_ Avg Efficiency) 12,000/kg/h 8,000/kg/h
5
Two Market Models

• Wind-Hydrogen Generation Model
• Wind- HydrogenElectricity 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
Product Name Stuart Cell EI-250 M-Platform IMET
Cell Technology Unipolar Gen II Unipolar Gen II DEP Bipolar
Production Capacity 5 Nm3/h to 1000 Nm3/h 1000 Nm3/h and greater 50 Nm3/h and greater 1 Nm3/h to 100 Nm3/h
Cell Pressure Atmospheric Atmospheric Atmospheric up to 25 bars
Typical Application Generator Cooling Hydrogen Peroxide Fiber Optics Bus filling station
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 hydrogenelectricity generation
  model may play role in early infrastructure
  development if value put on green
  electricity/green hydrogen.