AN ENERGY revolution started last week that will see fridge-sized boxes in every building generate electricity on demand from natural gas or biogas. At least, that was the story told by the publicity and excitement around the celebrity-backed debut of Californian company .
The firm鈥檚 solid-oxide fuel cells (SOFCs), dubbed 鈥淏loom boxes鈥� by the media, are already being trialled by eBay, Google and Coca-Cola, and Bloom says they can shrink a building鈥檚 carbon footprint by half.
Bloom鈥檚 claims are plausible, despite few details being released. But the company isn鈥檛 the vanguard of a revolution in electricity supply; the revolution has already begun. Several more experienced firms already make fuel cells much like Bloom鈥檚, and some are cheap enough to be heading into homes already.
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The technology at the heart of the excitement looks unspectacular: a chunk of ceramic. But the right ceramic can be an electrolyte that allows the movement of ions needed to combine natural gas with oxygen from the air without burning, driving power around an external circuit in the process. No expensive catalyst is required 鈥� an advantage over hydrogen fuel cells, most of which need platinum to work.
An SOFC must be heated to reduce the ceramic鈥檚 resistance and start the reaction, which then generates its own heat. Despite that, Bloom claims its cell can power a building more efficiently than an electricity grid, which loses power in transmission and is fed by power plants that waste heat from combustion.
Bloom鈥檚 boxes are impressively compact, but so are most SOFCs. As far as innovation goes, the firm will say only that the chunk of ceramic inside is painted with 鈥渟ecret inks鈥� that act as anode and cathode.
That suggests its interior is held together by the ceramic, says Helge Holm-Larsen of in Lyngby, Denmark, requiring a relatively thick chunk of it that would need heating to at least 900 掳C to operate. That cuts efficiency, although a fuel cell serving a constant demand would not need to start from cold very often.
For more variable demands, like those of an office or home, cutting the start-up penalty is crucial. Topsoe uses an enlarged anode to support its own SOFC鈥檚 interior, allowing a smaller electrolyte that operates effectively at 750 掳C, says Holm-Larsen.
Fuel cells can be even cooler, though. Those from in Crawley, UK, operate below 600 掳C thanks to a custom electrolyte of lower resistance. The temperature is low enough for steel welds to hold the device together inside.
Domestic boilers powered by Ceres鈥檚 cells are cheap and advanced enough for 37,500 of them to be heading to homes in the UK this year, as part of a four-year programme for customers of energy supplier British Gas. Once installed, the cell will generate most of a home鈥檚 electricity, says Ceres.
