Fuel Cell Systems and Hydrogen Production
Fuel Cell Type < 5kW 5-250kW < 100W 250kW 250kW - MW 2kW - MW
Electrochemical Reactions 11
Efficiency
Efficiency Source: Hazem Tawfik, Sept 2003
Pressure Effects Hydrogen pressure Oxygen pressure Source: Hazem Tawfik, Sept 2003
Temperature Effect Source: Hazem Tawfik, Sept 2003
Humidity effect at Room Temperature Source: Hazem Tawfik, Sept 2003
Parametric Effects: Temperature has most effect Source: Hazem Tawfik, Sept 2003
Air Vs O 2 Source: Hazem Tawfik, Sept 2003
PEMFC Emissions PC25 Fuel cell: 200 kw Fuel: Natural gas Source: Hazem Tawfik, Sept 2003
Fuel Cell System Fuel Cell Stack Control System Fuel Delivery Air Delivery Thermal Management Water Management Power Conditioning
Critical Materials and Costs Example: Polymer Electrolyte Fuel Cell Stack (1 kw) -Polymer membrane - Catalyst (precious metals) - Bipolar plate Source: Material development for cost reduction of PEFC by J. Garche, L. Jorissen & K.A. Friedrich, Center for Solar energy and hydrogen research, Baden-Wuerttemberg (ZSW), Germany
PEMFC Challenges MEA tolerance for CO in reformed H 2 High temperature operation (~120 o C) MEA Durability - 40,000 hrs with < 10% degradation, 1% cross over, area resistance <0.1 ohm.cm 2 Cost - $1500/kW, $10/kW for MEA Efficiency - 30 ~ 50% Fixed cost of Graphite bipolar plate: $130/kW Running cost of hydrogen per kwh : $0.405 Source: Hazem Tawfik, Sept 2003
Fuel Cell Types Alkaline (AFC) Solid Polymer (SPFC, PEM or PEFC) Direct Methanol (DMFC) Phosphoric Acid (PAFC) Molten Carbonate (MCFC) Solid Oxide (SOFC)
Fuels Type Hydrogen Methanol Natural Gas Gasoline Diesel Jet Fuels Application Transport, stationary & Portable Transport & Portable Stationary Transport Transport Military
Fuel Reforming Hydrogen is produced from fuel reforming system such as methane and steam. CH 4 + H 2 O 3H 2 + CO CO + H 2 O H 2 + CO 2 water gas shift reaction Carbon monoxide has a tendency 11 to occupy platinum catalyst sites, hence must be removed. Other fuels: C 8 H 18 + 8H 2 O 17H 2 + 8CO
Fuel Reformer Steam reforming: It is mature technology, practiced industrially on a large scale for hydrogen production. The basic reforming reactions for methane and a generic hydrocarbon C n H m are CH 4 + H 2 O CO + 3H 2 ;ΔH = 206kJ /mol C n H m + nh 2 O nco + m 2 + n H 2 CO + H 2 O CO 2 + H 2 ;ΔH = 41kJ /mol 1
DMFC System
Liquid-Feed DMFC Reactions 1 10 2 6 3 5 7 4 9 1 11
Direct Methanol Fuel Cell Operating at ambient conditions
Micro-scale Methanol Fuel Processor
Hydrogen Production Source:
Hydrogen Production Source:
Hydrogen From Water There is enough water to sustain hydrogen!
Electrolysis
Electrolysis
Photoelectrolysis
Hydrogen Production
Photoelectrochemical Conversion System
Electrolysis Efficiency Systems that can be 85 %
Photoelectrolysis
Photoelectrolysis
Photoelectrolysis
Artificial Photosynthesis
Thermochemical Production
Thermochemical Production Thermal-to-hydrogen energy efficiency Solar-thermal heat source is a logical choice
Thermochemical Production Solar-thermal heat source
Thermochemical Cycle Efficiency Process Temperature ( o C) Heat-to-Hydrogen Efficiency (%) Electrolysis 20-25 Sulfur-iodine thermochemical cycle 850 45-49 Calcium-bromine thermochemical cycle 760 36-40 Copper-chlorine thermochemical cycle 550 41* * Energy efficiency calculated based on thermodynamics
Solar Thermal Hydrogen Production A concept for integrating solar thermal energy and methane gas to produce a range of solar-enriched fuels and synthesis gas (CO and H 2 ) that can be used as a power generation fuel gas, as a metallurgical reducing gas or as chemical feed stock e.g. in methanol production. http://www.energy.csiro.au/