Hmm... as any reader of Larry Niven's Ringworld books will know...

Heat as a byproduct of mass, localised energy production could cause its own problems. If my neighbours and I generate lots of our own electricity and heat up our neighbourhood, we will need to run our air conditioning units to keep temperatures inside cool enough for comfort. Which uses more electricity and doesn't actually get rid of the heat, it just moves it from inside the house to outside the house, increasing the temperature differential between the inside and the outside. The bigger the temperature differential, the more energy required to maintain that differential...

So... exactly how much heat energy, per KWh, does this unit generate? We could replace global warming via the greenhouse effect with global warming via just plain heat production.

Of course, production of heat in itself is useful, so perhaps a combination electricity generator and heat exchanger so that we can use that waste heat to warm our hot water tank, supply part of the heating for the house etc...

that it could generate the heat to heat the created water to either put in a normal central heating system or to power a shower or bath?

For home use where does the hydrogen come from? In liquid form dropped off by a BOC lorry? Created through electrolysis from solar power and water (collected from rain and supplemented by mains supply [water and electric]) ?

What is the carbon footprint of creating these fuel cells in the first instance though?

... but I'd probably want a bit more than 1KW out of my home power station.

Also, why generate 100-200V AC: just about everything I use could run on 5-12V DC:

If I bypassed the transformer, then PC, printers, monitors, TV, alarm clocks, hi-fi, central heating controller (gas-fired CH), oven controls (gas-fired oven too) etc. already use low-voltage DC internally.

More stuff uses batteries that can be charged at just about any voltage (phone, toothbrush, laptop, power tools)

For the other things: lighting can be done at low voltage (halogens, or LEDs); there's no reason why a fridge or freezer compressor can't use a 12V DC motor, same for a vacuum cleaner.

My shower can run from the combi-boiler: might even be able to wrap the fuel-cells in a heat-exchanger to pre-heat the water supply for the hot-water system.

The only thing left is kettle and toaster, but with the overhead of stepping-up the voltage it might be more efficient to use the hob and grill...

Distribution of low voltage at the high current level required will mean thicker wires (busbars?) around the house, but if the power unit is centrally-positioned then there shouldn't be too much problem. I could also supplement with PV panels on the roof, and a windmill/watermill. In fact, the fuel cell unit would provide a useful backup source for the cloudy, calm days when the stream has run dry...

All I need is a suitable supply of gas for my cooker and fuel cell - maybe a field full of cows (or a methane-hydrate reserve?)

Now all I need is the money (and a plot of land) to build my Grand Design!

I'm not sure they are 'PEFC' but Efoy has been selling fuel cells to the public for a number of years now - www.efoy.de.

-Matt

ITM Power are leagues ahead in both the electrolyser and fuel cell fields.

www.itm-power.com

Why?

Take a look at http://www.cfcl.com.au/, they're providing combined heat and power from the natural gas lines. They've just got a real production order from a european energy provider for 50,000 units.

> PEFCs you can buy are still some years away.

Well, why bother researching those?

These free ones are obviously superiour and already work...

They're not claiming to be the *first*, just the most efficient to date...

I like the idea, I really do. But I don't really like the idea of dragging a 200 amp capable cable behind a high-ish power vacuum cleaner. There is no reason to generate at 12v instead of 100-200v. It just makes no sense.

Everything you own already has the step down transformer in it, or in the power adaptor if it needs one. There's lots of problems with transferring low voltage / high current power, even over the comparatively short distance of a house. For one: voltage drop from one side of the house to another would probably be enough to make TTL based electronics become a little unpredictable. Not to mention the fact that having main cables in your walls carrying anything up to about 500 amps is hardly safe, and would be incredibly expensive and impractical to implement on any sort of scale.

There’s a reason leccy is carried across the country at 40Kv. Low voltage / high current is just plain inefficient.

Micro-generation is good because:

- the electricity is produced near the point where it is consumed, reducing transmission losses and ultimately the amount of transmission infrastructure needed;

- the waste heat from the generator (and it's a lot) can be used for space and water heating, rather than being dumped in the sea, rivers or air.

However, micro-generation in the UK centres around using natural gas from the mains (see "Whispergen"), rather than carting around hydrogen in lorries, which seems like a daft idea.