Direct Carbon Fuel Cells

The Direct Carbon Fuel Cell (DCFC) converts fuel to electricity directly rather than burning it to boil water to make steam to turn a turbine, to turn a generator, to produce electricity. The DCFC can convert solid fuels to electricity at 70% efficiency and reduce CO2 emissions by 50% without sequestration.

A Fuel Cell is an electrochemical device that efficiently converts a fuel’s chemical energy directly to electrical energy without burning the fuel. However, instead of using gaseous fuels, as is typically done, DCFCs use aggregates of extremely fine (10- to 1,000-nanometer-diameter) carbon particles distributed in a mixture of molten lithium, sodium, Yttrium-stabilized zirconium or potassium carbonate at a temperature of 600 to 850°C. The overall cell reaction is carbon and oxygen forming carbon dioxide and electricity.

The reaction yields 80 percent of the carbon–oxygen combustion energy as electricity, yet no burning of the carbon takes place. DCFCs provide up to 1 kilowatt of power per square meter of cell surface area — a rate sufficiently high for practical applications.

The overall process of producing electricity in a DCFC from biomass gains efficiency by its simplicity. It involves only two steps: (1) drying (and/or pyrolysis, or hydrothermal carbonization) to obtain char, and (2) feeding the resulting fuel directly to the DCFC.

If the carbon feedstock for the fuel cell were to be derived from biomass, and the CO2 captured and sequestered, super-efficient carbon-negative electricity would be generated. That is: electricity the use of which results in the active removal of CO2 from the atmosphere

DirectCarbon, a company spun out of Stanford University in 2006, are currently trying to commercialise this technology. Great progress has also been made at the Max Planck Institute in Germany and the University of Queensland in Australia.

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