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Fuel Cells, Operates below 40°C, pH 7. Use any organic material…
Fuel Cells
Bio Fuels
Microbial
Mediated (humic acid, thionine)
Plants / Bacteria
Can also reverse process to generate hydrogen by applying voltage to bacteria. Complete reversal is microbial electrosynthesis where CO2 reduced by bacteria using external electric current.
Soil
Sediment microbial fuel cells (SMFCs) generate energy while decontaminating wastewater, mimic constructed wetlands. MIDES project desalinates seawater with 85% reduction in energy consumption (Aqualia with Leitat in Denia, Spain). Uses nano carbon cathodes, anodes and ion exchange membranes, thus less reagents required for desalination and energy, lowering operation costs.
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Ceramic Membrane (clays, mullite, fly ash)
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Liquid / Gas Fuels
Noble Metals
DMFC
Direct methanol and water fed to anode, 90-120°C, 40-50% eff.
PAFC
Phosphoric acid membrane, platinum catalyst, 150-200°C, <200KW, 40-80% eff.
AFC
Alkaline membrane, < 80°C, 40-60% eff., susceptible to CO2 poisoning
PEMFC
Proton exchange membrane (acidic), platinum catalyst, 50-80°C, 50-250KW, 40-50% eff.
Non-Noble Metals
MCFC
Molten carbonate salt electrolyte, nickel catalyst, ~650°C, 10KW-2MW, 60-80% eff., uses CO2 from fossil fuel plants
SOFC
Solid oxide ceramic electrolyte, perovskite catalyst, 800-1000°C, <100KW, 60% eff.
Solid Fuels
DCFC
Direct carbon, 80% eff., pure CO2 waste stream
Operates below 40°C, pH 7. Use any organic material (wastewater bacteria etc.) to feed cell. Graphite anode. High efficiency +/- 8 times hydrogen production, but low power output at tiny scale.
Reversible fuel cells produce electricity from a fuel and oxygen and generate heat and water as byproducts. They can also use do the opposite i.e. use excess electricity from renewable power to split water into oxygen and hydrogen (electrolysis).
This storage capability is a key enabler for intermittent renewable energy technologies. Example: Fully enzymatic hydrogen fuel cell (Armstrong Group), graphite anode to immobilise hydrogenase with graphite cathode modified with fungal laccase.
All mainly using hydrogen at the anode, and oxygen at the cathode.