| Archive for Downsizer For an ethical approach to consumption |
| Hairyloon |
DIY CHPI'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? |
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| vegplot |
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 |
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| Hairyloon |
We'd never have got anywhere without experimenting.
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.
That is not too bad if you're getting engines for nowt, which is not hard.
Only if that is the only source of heat/power. It should not be hard if you are also plugged into the grid.
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. |
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| marigold |
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... 
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| Hairyloon |
Nowt wrong with ignorance, your wonderings are perfectly valid.
Same place as the exhaust from the central heating currently goes.
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. |
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| vegplot |
Sounds like it might be feasible if you can get the engines cheaply. | ||||||||||
| Treacodactyl |
What do you plan to run the engine on? | ||||||||||
| vegplot |
Gas |
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| Treacodactyl |
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? |
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| vegplot |
Converting an engine to run on gas is cheap and easy. No idea about legality. |
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| Mutton |
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.) |
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| Hairyloon |
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. |
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| Mr O |
do you have acesss to a supply of wood? | ||||||||||
| Hairyloon |
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. |
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| stumbling goat |
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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| Hairyloon |
No disrespect, but it is actually irrelevant what the current cost is. The fact is, it offends my sensibilities to burn fossil fuel just for heat when it is relatively easy to get waste heat for heat. |
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| RichardW |
You will be doing just the same. The elec is the by product not the heat. The amount of elec you make compared to the amount of heat is quite small. An engine roughly produces 1/3rd motive power 1/3rd wet heat 1/3 exhaust heat With an efficiency of less than 70% The alt will only be about 50% efficient at best & prob more like 30% so you will put fossil fuel in & get 11% of that energy out as elec & 23% as wet heat & 23% as exhaust heat (if you recover it). The elec production is a by-product of the heating not the other way round. |
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| stumbling goat |
REALLY? okay. sg |
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| Mr O |
I would be looking at how to use the wood that you can get hold of rather than using fossil fuels |
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| Treacodactyl |
That's what I would suggest. A couple years back I did have a dig to see if there's any development of a wood-fired CHP boiler. IIRC a company was developing one but I couldn't get much info at the time. |
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| vegplot |
As an experiment it might be worth a try just to satisfy your curiosity. However, I doubt you will be satisfied with the results. | ||||||||||
| RichardW |
Even with dedicated designed for the job equipment its still marginal. Thats why there still is no viable affordable system on the market yet.
Some people that run old listers do recover the heat but the primary use was the power & the heat was being lost. In an effort to reduce the cost of running the genny just for power they capture heat as well. They are still using fossil fuels and are using more fuel than taking that heat and elec from the grid. The issue is normally no grid so the large extra cost does nor factor in. Our genny produced elec costs about 50p per kwh & as its a dry engine we cant recover worth while heat from it (plus is not on often enough to make heat recovery worth while). Can it be done? Yes Is it cost effective? no Is it fuel effective? no |
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| vegplot |
The only times I've seen this work well is when they are running on waste oil (veg or mineral motor oil) and where they needed power over extended periods (10 hrs per day lighting chicken sheds is one example). |
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| Hairyloon |
The thing about dedicated designed for the job equipment is that it is expensive to make, and it still wears out. That would make it very difficult to make a marketable system.
What are you running it on? |
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| Lorrainelovesplants |
I think you have to look at why you are burning so much gas, what your house insulation is like, your state of dress as you walk round the house, and what alternatives you have.
Our LPG bill was £2500 per year, and that was for hot water and CH (we have no access to mains gas). We have reduced this now to £600 per year (same house). We still have the LPG (its for baths, really cold snaps and early morning heat only) We installed a new woodburner with back boiler and this does our Living room heat, radiators in the 3 beds and bathroom down the hall, and gives me hot water in the evening to do the dishes (3rd tap on sink). Our wood is nearly free.......we use 5 tons a year, this keps us toastie warm. We had cavity wall insulation in the whole house for les than £100 (grant aided), and have heavy curtains on the one draughty door, and wear jumpers and socks (as well as usual cothes)round the house. We'll recoup the cost of the new woodburner in less than 2 years. I'd rather spend the money on other things. |
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| vegplot |
As Richard W as said you're going to get a lot more heat energy than electrical output. Balancing one against the other and still maintaining some sort of economy is very difficult and is one of the reason household CHP devices have failed in the market place. | ||||||||||
| Behemoth |
British Gas are just about to introduce a domestic CHP boiler. What that means I don't know but they think there is a market there, for the boilers at least. | ||||||||||
| Hairyloon |
A valid thought, but no. Once I saw the speed the meter was spinning at I turned it off. 
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| RichardW |
Red. Read all 57 pages of THIS THREAD & you will understand why (plus you will learn lots about CHP) If fully loaded to its max out put its cheaper but most of the time you dont have the genny maxed out & the 50p per kwh is the average of all our consumption via the genny.
If I remember right thats the same one the 3 other large elec suppliers have been dabbling with for a few years with promises of it hitting the market some time soon. If so the quoted cost was (please sit down) over £20k. From what the off grid community is saying its just a way that the big suppliers can say they are trying to be greener by supporting this company but the pubic wont buy it. |
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| Hairyloon |
I'll have to come back to that later.
How much is red these days? From what I can find, diesel has an energy content of 38-40MJ/l. A kWh is 3.6MJ, so the equivalent gas energy to a litre of diesel would be about 40p. A bit cheaper I think, but not that much. What's your peak efficiency with the genny at max? |