The long-heralded announcement of Bloom Energy's solid oxide fuel cell on 24 February generated huge amounts of excitement. Many compared the launch of the Bloom Box to the arrival of a new Apple product. Is it an innovative as the company claims? The technology may be good and the product reliable. The claims at the press conference were for a technology that will eventually revolutionize power production. Solid oxide fuel cells (SOFCs) are indeed an extremely interesting way of generating small quantities of electricity for homes and offices at attractive running costs and low carbon emissions. Other developers, such as Ceres Power in the UK and Ceramic Fuel Cells in Australia/Germany, have products close to market launch and – so far – it is completely unclear whether Bloom's product is better or likely to be more attractively priced or more long-lasting.

SOFCs take a hydrocarbon fuel and split it at very high temperature (perhaps 600 degrees C) into hydrogen and carbon. The carbon combines with oxygen to make CO2 and the hydrogen reacts with oxygen from air to make water. This later process causes electrons to flow through the ceramic electrolyte and generate a usable current. The crucial problem is making the cell robust, cheap, and durable at the high temperatures experienced in the cell.

Ceramic Fuel Cells has numerous partnerships with large utilities around the world interested in taking its products into local markets. Its product turns about 60% of the energy value of natural gas (largely methane in the UK and Europe) into electricity, making it more efficient than all but the best combined cycle power stations. The remaining energy – residual heat – can be used to provide domestic hot water or, in theory could be used to offer space heating or energy conversion to air conditioning in summer. The carbon dioxide savings are substantial, even if grid natural gas is used. Ceramic Fuel Cells, and probably Bloom, can also use synthesis gas ('syngas') from super-heating wood in the absence of air or can even split liquid ethanol made from agricultural wastes. In theory, a SOFC can use low or zero-carbon fuel and offer huge greenhouse gas savings on fossil fuel combustion. SOFCs can also be used for grid balancing. When demand is high, the grid operator will have the ability to increase power output of domestic fuel cells remotely and turn it down when the wind turbines on the hilltops are spinning fast. Ceramic Fuel Cells has successfully demonstrated this feature of its technology.

The problems with SOFCs, probably including the Bloom Box, are well known. The fuel cells burn out and have to be replaced by professional engineers. Ceramic Fuel Cells talks of the units needed to be switched every two years though the company hopes this will improve to once every four years. The cost of the units is high. Ceramic Fuel Cells has mentioned a figure of about £2,000 ($3,000+) for a machine that can continuously develop 2 kilowatts of electric power but I think this number is highly optimistic and the true figure is likely to be several times this level for some years to come.

In most circumstances, the Ceramic Fuel Cells device will also need to be supplemented by a conventional domestic heating boiler. These machines are so efficient that they do not generate enough heat to keep even a well-insulated house warm. The average UK house uses a running average of about 4 kilowatts of heat during the six-month heating season while the Ceramic box only provides about 0.5 kilowatts.

The UK government's new feed-in tariffs provide a substantial incentive for householders to install SOFCs in domestic homes. Ceramic Fuel Cells has made great play of the attractiveness of this new subsidy. Provided its power plants work at even approximately the price suggested Ceramic Fuel Cells will find a ready market in the UK. The Bloom Boxes, which appear to be aimed at office buildings and go up to 100 kilowatts, will not benefit from this subsidy.

Does the Bloom Box represent a substantial technical advance over Ceramic Fuel Cells? On the information provided so far, I could see no obvious technical innovation that puts Bloom ahead of the Ceramic Fuel Cells machines. But Ceramic Fuel Cells works from Melbourne, not Silicon Valley, and can't get the California Governor and Colin Powell to come to its product launches. We'll soon see whether the unflashy Australians have just lost their market to Bloom or whether Ceramic Fuel Cells' long and painful development has just been validated by Bloom's hyperbolic endorsement of the potential of the SOFC.

This article was also published on the Guardian Environment Network on Thursday 25 February 2010.