Direct Carbon Fuel Cells (DCFC) : the ultimate biomass conversion technology ?

Did you say converting carbon directly into electricity without "burning" it ???

Yes ! this is now possible

Moreover :

• the process presents an overall efficiency of 70% which is a very good performance compared to traditional burning+heat plants (35% maximum according the Carnot theoretical thermodynamics limitation)
• environment friendly as it is CO2 capture-ready, and reduces emission by 50% prior to sequestration (the total quantity of CO2 emission is half for the same quantity of energy produced,  the sequestration process is easier, is more secure and is also cheaper to achieve)
• no water required all along the process (no steam, no cleaning, etc.)

Operations began in 2006 at Stanford University. Tests are continuing on various grades of coal, wheat and rice straw, corn stover and wood.

diagram of the fuel cell process

Made of a core of ceramic tubes, the system operates at 900°C and emit only a pure stream of CO2, ready to be captured without the capital and energy cost of separation from nitrogen. Ash, sulfur, lead, mercury and other solids would not be released to the atmosphere but would be carried to landfills or re-cycled.

In the production of distributed base-load electricity, coal or biomass is fed into the base of the system. The carbon in the coal or biomass is gasified without water into carbon monoxide by the re-circulating carbon dioxide. That is: C+CO2= 2(CO). The CO then moves up the inside of the ceramic tubes. At a temperature of 900 degrees Centigrade the oxygen in the air on the outside of the cell walls is under pressure to cross the barrier and oxidize the CO on the other side. It cannot cross as an oxygen molecule but only as an oxygen ion. So the O2 picks up four electrons from the utility grid, crosses the barrier, bonds with the CO and sheds the electrons, creating the electric current. That reaction is 2(CO)+O2ion= 2(CO2)+4e.

That's simpler and twice as efficient as a 20th century coal power plant.

The system is compact and modular, groups of directcarbon Fuel Cell systems, each with the footprint of a forty-foot cargo container, can be grouped for generation of electricity in the megawatt range.

Source : directcarbon

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, Yttria-stabilized zirconia or potassium carbonate at a temperature of 600 to 850°C. The overall cell reaction is carbon and oxygen (from ambient air) forming carbon dioxide and electricity

The reaction yields can reach 80% of the carbon–oxygen combustion energy as electricity, yet no burning of the carbon takes place. DCFCs for stationary applications provide up to 1 kilowatt of power per square meter of cell surface area — a rate sufficiently high for practical applications. Some developers are designing DCFCs for mobile applications that can deliver energy densities in the range of 1,000–2,000 Wh/kg, far higher than any advanced battery.

Source : Mongabay


Conclusion : this is a very promising technology !