Generating Heat and Power at Home

20 April 2008

Interview with 

Elaine Ball, Baxi group


Chris - So how else can we generate electricity at home? Well Elaine Ball is from Baxi Group - and they've developed a household boiler system called the Ecogen which, as well as heating the house and water, also generates electricity. And here's the really good news - the electricity effectively comes for free...

Hello Elaine, thank you for joining us on the Naked Scientists. It's good to have you with us. How does it work?

Baxi Ecogen - internal viewElaine - The Ecogen, as you said is a gas appliance that, when it burns and generates heat, we also get electricity as well. The basis of the product is a Sterling engine which works similar to an internal combustion engine except that the unit is sealed and has helium in it. We have the gas burner external to the unit. What we do is we burn the gas at the top of the engine and we cool the gas at the bottom of the engine. That with the displacer moves the hot and cold gas around and drives a piston.

Chris - Right. The piston is connected to some kind of generating system?

Elaine - The piston is actually free and it's got gas bearings round it which helps with minimising the losses. Around the piston when it moves we have magnets and wire coils that produce electricity directly at 50Hz which means it can be fed directly into the home or exported back to the grid.

Chris - This sounds like a bit of a no-brainer. It sounds fantastic. Why has no one done this before?

Elaine - In the past there were a lot of challenges with actually getting the technology to work in an affordable and reliable way. Also an application that was good for the technology because when you're trying to use it to drive a mechanical energy there are a lot of heat losses. Because we're using it for a heating appliance we're actually good to get those heat losses because we actually then use that heat to heat the home, the radiators and the hot water cylinder, for example.

Chris - How much heat could it put into the average home? Is it more an electricity generator? More a boiler or is it really genuinely fulfilling both roles?

Elaine - The great thing about the technology is that it's generating electricity whilst producing heat. We call it a heat-led technology. Generally when you look at people's electricity demand it's generally when you want heat at the same time. It's great, you have your demand for heat in your dwelling and then you produce electricity at the same time. We'll produce one kW of electricity and the Sterling engine itself produces about 6kW of thermal energy. Then we have a second heater to give up to another 18kW which is great because there's lots of different house types across the country, different heat demands. Because it all modulates down it will basically suit the heat demand to the house. It meets a lot of applications.

Animation%20of%20the%20action%20of%20a%20beta%20stirling%20engineChris - You've installed this for a number of people who were in your test run. How are they finding it?

Elaine - They're really pleased with the unit because they've already seen fuel savings, cuts in their energy bill and we've also got a number of utilities on board. When they're exporting energy back to the grid they're also getting paid for that energy as well.

Chris - What sort of fuel costs and electricity bill changes are the people who've tested this seeing? What are they getting out of it?

Elaine - Well, we've seen about a 40% reduction in fuel bills. If we take one fuel trial in Preston in four months the boiler generated nearly 800kwh for a demand that was needed in the home for about 1200kwh. Because Terry was getting a net benefit from selling back he was basically getting 2/3 of his electricity for free.

Chris - But have we not had a problem where some of the utility companies don't play ball? Dr Karl in Australia was saying you only get paid 1:1 for the amount of electricity you sell back. In Germany you get a better deal. In some cases in the UK the companies won't buy the electricity off of you. You end up giving it to them for free.

Elaine - No and that's where there's a lot of consultation going on at the moment because we're trying to get a standard and a sort of fair quota across all the utilities. At the moment it really is dependent on which utility you're with and what system they're going to use. There's a lot of debate at the moment about feed and tariffs and whether we should adopt that in the UK or provide capital investment upfront through the government's carbon emission reduction programmes.

Richard - What kind of benefit are you going to get in terms of reducing carbon dioxide emissions?

Elaine - When we look at typical average annual usage of a boiler we get between 2.5 to 3 thousand run hours a year. If we look at an existing condensing gas boiler today and compare this product then if we get 3000 run hours then the homeowners going to save probably 2-300GBP per year versus an existing boiler. In terms of carbon that's equivalent to about a tonne of carbon dioxide in a year for each appliance. If you think about the twenty two million homes in the UK and the number of gas boilers that are sold then it doesn't take a lot of maths to think a lot of boilers is a lot of carbon dioxide saved.

Chris - Running an engine in your garage sounds noisy. Are people complaining these things are noisy Elaine?

Elaine - Actually as well as having the very first units in garages we installed out second field trial just before Christmas and we've got a number of units in kitchens. Where the Sterling Engine benefits over the internal combustion engine is that you've got none of these internal explosions and it's a very quiet operation so the noise levels of the products we've installed are typical to a normal gas boiler. We've got, as I say, units in kitchens and no complaints so far.

Chris - Does it take some special infrastructure to plumb it in and lastly, what's the cost to install this in someone's house?

Elaine - Because it's based very much on traditional gas technology in temrms of the gas and heating side it's the same installation that a normal gas engineer plumber could do today. The additional complication is the requirement of a new meter to be able to export to the grid and therefore getting involved with your utility to make that meter connection. Typically, it shouldn't be much more of an onerous task than a gas boiler today.

Richard - When can I get one?

Elaine - Well, we're looking to bring them to market at the end of this year/beginning of next year.



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