Going for the burn

Research into an innovative fuel cell concept that uses solid carbon is to be undertaken at the University of St Andrews.



According to the project’s leader, Prof John Irvine, there are considerable advantages to using carbon in fuel cells. ‘It has a much higher specific energy density than hydrogen,’ said Irvine. ‘This means that you have to carry a much smaller amount of fuel, which in turn means that much smaller fuel cells can be developed.’



Fuel cells are far more efficient than burning fossil fuels in power plants to drive boilers and dynamos. The theoretical efficiencies of hydrogen or methane fuel cells are 69 per cent and 90 per cent respectively, compared to 40 per cent for typical power plants. The carbon-oxygen reaction that drives a carbon conversion fuel cell is unique in that it is theoretically possible for it to be 100 per cent efficient, with all the potential combustion heat converted to power.



Methane and hydrogen fuel cells have other disadvantages. The fuels are continuously diluted by their own reaction products as they are consumed. The voltage drops to ever-lower values and as a result not all the fuel can be used. This problem does not arise with carbon as all the incoming fuel can be used to make electricity at about the same rate and voltage.



The idea of using carbon to directly produce electricity has been around since the late 19th century, since US inventors came up with prototype coal fuel batteries. However, it has only been recently that the concept has been revisited by researchers in both the UK and at the Lawrence Livermore National Laboratory in the US.



According to Irvine, one of the main problems with solid carbon fuel cells is the very low surface area of the solid compared to using hydrogen gas, for example. The new research will combine the methods used in molten carbonate and solid oxide fuel cells to maximise the cell’s efficiency in a way that has never been tried before.



‘We are looking at using a molten carbonated electrolyte between the carbon and the membrane, at a high enough temperature to allow it to conduct properly,’ said Irvine. He said he hoped that a working prototype could be ready within about a year.



The project is part of ongoing research at the university into innovative fuel cell technology, using a grant of around £100,000 from the economic development agency, Scottish Enterprise.



Sidebar


The US Army has been working with DARPA to create the Mobile Integrated Sustainable Energy Recovery program, which also uses sources of carbon as fuel. The concept will allow soldiers on the battlefield to use waste materials left behind such as plastic bags and teaspoons to convert into fuel to power Army systems.