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Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Tue Oct 27, 09 2:39 pm Post subject: DIY CHP
I've just got gas central heating (it came with the house), and having noticed how fast the meter flies around when it is on, has given me big motivation to start pursuing my ideas about combined heat and power. My original idea was to get a convenient engine (whatever came to hand first), tie it to a genny, and plumb it all in. Anyone any experience or other thoughts on the subject?

vegplot

Joined: 19 Apr 2007
Posts: 21301
Location: Bethesda, Gwynedd

Posted: Tue Oct 27, 09 2:47 pm Post subject:
As an experiment it might be worth a try. I assume an engine will have a useful of around 2,500-3,500 hours. Assuming you use it 3 hrs per day that around 850 days life. Balancing heat and power requirements can be difficult though. I doubt you'd get anywhere near the cost of unit electricity you'd get from the mains and you're still using a fossil fuel

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Tue Oct 27, 09 2:59 pm Post subject:

vegplot wrote:

As an experiment it might be worth a try.

We'd never have got anywhere without experimenting.

Quote:

I assume an engine will have a useful of around 2,500-3,500 hours.

What is that based on?
180,000 miles at 60mph or something like?
A fair enough estimate, but I think there are a number of advantages in a stationary engine which should help extend its life.

Quote:

Assuming you use it 3 hrs per day that around 850 days life.

That is not too bad if you're getting engines for nowt, which is not hard.

Quote:

Balancing heat and power requirements can be difficult though.

Only if that is the only source of heat/power. It should not be hard if you are also plugged into the grid.

Quote:

I doubt you'd get anywhere near the cost of unit electricity you'd get from the mains and you're still using a fossil fuel

I don't know.
Electricity at 12.5p/kWh
Gas at 3.5p/kWh.
If I can make 30% efficiency I'm quids in, and that is ignoring the fact that the heating becomes free.

It would be better with a Stirling engine, but I can't simply pull one of those out of a handy scrap car.

marigold

Joined: 02 Sep 2005
Posts: 12458
Location: West Sussex

Posted: Tue Oct 27, 09 3:09 pm Post subject:
In my ignorance I wonder a) where the exhaust from the engine will go and b) whether your neighbours (assuming you have some) will be driven nuts by listening to it chugging away...

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Tue Oct 27, 09 3:25 pm Post subject:

marigold wrote:

In my ignorance I wonder

Nowt wrong with ignorance, your wonderings are perfectly valid.

Quote:

a) where the exhaust from the engine will go

Same place as the exhaust from the central heating currently goes.

Quote:

and b) whether your neighbours (assuming you have some) will be driven nuts by listening to it chugging away...

The neighbours have a selection of trials bikes and howling dogs, they can go stuff, but speaking of stuffing, there is plenty of room for sound deadening.

vegplot

Joined: 19 Apr 2007
Posts: 21301
Location: Bethesda, Gwynedd

Posted: Tue Oct 27, 09 5:04 pm Post subject:
Sounds like it might be feasible if you can get the engines cheaply.

Treacodactyl
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 25795
Location: Jumping on the bandwagon of opportunism

Posted: Tue Oct 27, 09 5:18 pm Post subject:
What do you plan to run the engine on?

vegplot

Joined: 19 Apr 2007
Posts: 21301
Location: Bethesda, Gwynedd

Posted: Tue Oct 27, 09 5:23 pm Post subject:

Treacodactyl wrote:

What do you plan to run the engine on?

Gas

Treacodactyl
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 25795
Location: Jumping on the bandwagon of opportunism

Posted: Tue Oct 27, 09 5:26 pm Post subject:

vegplot wrote:

Treacodactyl wrote:

What do you plan to run the engine on?

Gas

That's what I thought but, even if the engine is free, will it not cost a bit to convert from petrol to LPG? Could you legally connect one to mains gas?

vegplot

Joined: 19 Apr 2007
Posts: 21301
Location: Bethesda, Gwynedd

Posted: Tue Oct 27, 09 5:33 pm Post subject:

Treacodactyl wrote:

vegplot wrote:

Treacodactyl wrote:

What do you plan to run the engine on?

Gas

That's what I thought but, even if the engine is free, will it not cost a bit to convert from petrol to LPG? Could you legally connect one to mains gas?

Converting an engine to run on gas is cheap and easy. No idea about legality.

Mutton

Joined: 09 May 2009
Posts: 1508

Posted: Tue Oct 27, 09 6:09 pm Post subject:
Think it was on CHP Association website - there are trials underway of domestic CHP run on mains gas, supposed to be the size of a gas boiler. Seem to remember links leading to diagrams of internals. (In a rush, so not looking up the links for you.)

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Tue Oct 27, 09 7:58 pm Post subject:

vegplot wrote:

Treacodactyl wrote:

What do you plan to run the engine on?

Gas

Yes.
Phase two might be to build a biomass gassifier, but will probably keep mains gas as back up.

And for whoever was asking, the main parts of an LPG conversion for your car are the tank and the evaporator, both of which are needed on mains gas.

Mr O

Joined: 13 Feb 2005
Posts: 5512
Location: Nova Scotia, Canada

Posted: Tue Oct 27, 09 8:04 pm Post subject:
do you have acesss to a supply of wood?

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Tue Oct 27, 09 8:40 pm Post subject:

Mr O wrote:

do you have acesss to a supply of wood?

People are reasonably prone to paying me to take it away... they usually want it taken out of the top of their trees first though.

stumbling goat

Joined: 20 Jan 2009
Posts: 1990

Posted: Tue Oct 27, 09 9:18 pm Post subject:

i have just had a new vailant condensing boiler fitted in my loft. apparently they are 90% efficient.

my old baxi back boiler which had a gas fire in the lounge was only 60% efficient. i never used the fire as i could not see the point in using a flame to heat one room?

i like the idea of a wood burning fire in my lounge, there are ample woods nearby where i could collect wood to burn. and a more carbon neutral and economic means of heating the house and providing hot water would be great. but i think i am stuck in a 60's terrace which has limitations.

i would work out what your costs would be with your current boiler set up as is?

what could you reduce it to by searching for the best deal for combined elctric/gas supply?

what could you do with your boiler, or whatever it is that heats tour water and rads?

would a drain down and flush through improve the efficiency of the system?

is your area a hard water area? when my old pipes were removed a 28mm pipe was reduced to 15mm bore due to hard water calcification build up. amazing to see it and break it off in huge flakes.

hth.

sg

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