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You would need to look at the SSSI/RAMSAR citation and check the list of 'Potentially Damaging Operations' as they are called. Depending on what structures you needed you may be able to make a case for a water wheel.It all comes down to why the area is a SSSI. RAMSAR is pricipally about (wetland) birds so your header pool could be habitat enhancement! If your site is NATURA 2000 as well there will be a further list to look at. However you might find that the use of sustainable energy generation may actually be viewed very favorably and the structures may well bebefit the stream ecology (they may not of course but what is the harm in asking).
I think what you're after is different from conventional Combined Heat and Power. Normally CHP is about using the waste heat from power generation. You are already burning wood for space (and possibly water) heating, and you just want to convert a small amount of this heat, maybe 5 - 10% tops to electricity. This means that inefficient cycles that might not be suitable for conventional CHP may be viable, (although if you start lighting the woodburner in summer to get power it starts to get a bit silly). One option is to use the new generation of thermoelectric modules that are being developed - see
for example. These will work at much higher tempereature differences and efficiencies than current thermoelectric modules and are compact, safe and have no moving parts. The cold side needs to be kept at about 65C or so - perfect for integrating with water heating. Haven't found any of these TE modules for sale yet, has anyone else?
I found similar stuff on the web, but only generating minute amounts of power.
The ratings given by Toshiba seem much more useful. The stove probably runs at a much lower temp than 800 c, but getting 1 watt /cm2 looks quite useful. 10x10cm plate =100watts!?.
As usual, we're 5 years too early as it looks to be at experimental stage, but let's keep our fingers well and truly crossed!
I got excited about CHP from stoves a while ago when I realised that our house used less than 1/2KW/Hour of electricity and came to the same conclusion as you about how we could turn some of the heat from the stove into electricity. I even found some small steam turbine gen sets on ebay. These units are relatively small, although they are horendiously in-efficient, but if you are using the waste heat anyway, this doesn't really matter. I think they used to use them on steam trains for running electric lighting, so they had a pretty good boiler available! I have an engineering company, so if I find that we are at loose end one day I may do some sums and further investigation. I would be interested to hear any more info you manage to gather.
I have thought for some time that a small low cost device to turn low grade heat into rotary power could have all sorts of uses for eco power, such as solar steam power generation. The advantage being that it uses 200yr old technology, and if the heat source is £ free and co2 free the efficiency doesn't matter too much. I am concerned about £30K's worth of PV's clonking out after 15 years! Perhaps I should get serious about developing something. What do you guys think?
I think that the scale required (and the tinkering/fuel feeding needed with a low efficiency system) to get sensible amounts of energy is going to make it very hard to do.
The best existing thing, to provide a benchmark, I have seen is those big Canadian Stirling fans (http://www.gyroscope.com/d.asp?product=THERMALENGINE) as mentioned by somone earlier. This is a great product in that you just put in on the stove and walk away, similar to the ecofan, with maintenance amounting to a bit of oiling from time to time. The challenge is to produce a steam version to generate more energy than this at a similar price per KW (or fraction thereof) with a similar fit and forget approach.
At the end of the day much cheaper and simpler to get an old Lister engine and run it on chip shop fat (if you have the space) as ted said.
I love steam but getting it to be efficient at small scales is probably not possible - could be great fun & sort of 'practical' though if you went for the "hamster wheel mobile phone charger" type of approach.
If you've read all the comments, you'll see that the more knowledgeable chaps/chapesses say that it just won't work. I would be happy to see 100w/hour or even less coming out the back of my stove which is on 24/7 over winter period. I don't want a total solution to my electricity needs, but we've all seen tiny steam engines pulling 20+ adults along a track. Something 1/20th the size would surely be able to make some juice and be an interesting obsession for those that can.
There was a (profoundly eccentric) bloke in Kelso a while back offering a co-gen module for his apparently super-efficient open fires. I could never find out exactly how it was supposed to work and as he's now dead I doubt I ever will. Dean Warwick, company was (/is?) Ampliflare, I think. Whackiest brochures I ever saw.
Here's a report about a micro CHP system tested in Canada that used a gas fired boiler together with a Stirling engine to provide about 750W electrical output together with 6.5kW of heat.
these are made in NZ by whisper gen, unfortunately for the UK one of our main power suppliers bought the rights (power gen I think) apparently if you go to ireland you can buy them ! tom
I looked at the Whispergen CHP stuff, it seems a nice unit, but, just like a wood burning stove, the summer months present a problem if you just want electricity. However, if the Stirling engine produces juice from a gas boiler, surely one could be bolted on to a wood burning stove?
dickster, they certainly could, prior to steam engines being build they were 'the' motive force, whole factories were run. with modern equipment/materials/technologies a small Stirling generator could be easily produced. Philips electrical did in the fiftys/sixtys it used any liquid fuel, but any heat source would do in a fixed installation. see http://www.starspin.com/stirlings/ph1p.html I built one in the seventy's that used solid meths blocks as fuel it would run well for 1/2 hour, after that the whole unit became too hot to have enough heat differential to run, the hot end could have been placed into the stove and the cold end(cooler the better) could have been jacketed and maybe even preheat the incoming house hot water supply. You would have a constant clankety clank noise and regular oiling/maintenance to contend with, whereas the whispergen is a hermetically sealed magnetic piston oscillating directly through a coil, maintenance free. tom
Not sure you have your history right however - I think there was one factory and early stirling work was at the same time as the development of steam. The problem remains one of scale.
So let's get this straight. This page has developed to the point where it might be possible to have a whispergen (quiet) type sterling engine pre-heating my hot water and producing electricity. How good is that!!!!
I read this morning that there's a £1m prize for new green ideas.
Anyone know how the Whispergen Sterling bit bolts onto the hot bit?
Anyone know where to get one?
Let's share the money! (and invest it in educating us all in greener ways)
dickster, the problem is one of scale. You need a reasonably large engine to get a decent return. The Whispergen units claim to produce around 1 tenth the input heat power as electricity (ie. as Paul states, a 6.5kW heater produces 750W electricity). However, if you scale it down, it gets more and more inefficient. So a 1kW stove is unlikely to produce more than 25W electricity. Unless you use it immediately, you have to store it, so you loose more - the end result is that, even with your stove running at full power and constantly, you're unlikely to generate enough to run one light bulb for a couple of hours each day.
Given that whisper gen units are pretty expensive bits of kit, the return on your investment is rather poor. The embodied energy is probably more than it would ever generate from a small stove anyway.
tuna, Can you get a 1kw stove ? or are we talking camping stoves, our wood burner is rated at 12kw. Any idea how much a whispergen costs ? I can't seam to find out. They do replace your boiler as well as generating electric for the price
Sorry, yes of course you're right that stoves are rated as much higher, however I don't think that many actually put out that much heat. A 3kW electric heater will cook a medium sized room (say 12' x 20') in no time. If you ran your stove at 12kW for any length of time, you'd be burning through a few tons of wood each month.
Fron an article in Home building and rennovating the payback on a whispergen is quite good. Around 5 years compared to installed a new gas condensing boiler. This assumes you were selling electricity at half the rate you are buying it. Sticking on ein just becuase you can wouldn't be a good idea. They are only suited to 3 bed older houses or better insualted new houses as the heating part of the boiler isn't that highly rated.
One thing to consider with any mods to a wood burner is that lowering the combustion temperature by adding back boilers or possibly a stiring engine would reduce the efficiency of the burn. This is something I've found out from living in a smoke control area. You can get all these new highly efficient wood burners but not many a suitable for smoke control areas. The ones that are, can't have the back boiler option as it stops the clean burn. So it's better put next to a large soap stone or masonry wall to absorb the heat on a max burn, to then be re-radiated out slowly and get a 75% efficiency on the initial burn (wood-> useable heat). If you start adding boilers and the like that initial 75% will drop (to what I don't know) and you'll create more carcinogenic and particualte pollutants.
Maybe you should put your energy [;-)] into getting that stream making a continous trickle of electric , and have a pumped storage system.
I see 2 alternatives that would be eaiser. Use Gasified Wood chips to power a small gas turbine (or modified diesel generator) alternatively run a generator from Biodiesel.
If there was a good auger fed Woodchip boiler that could provide CHP for the home then somebody would corner the market.
Efficiency is great, however there will always be a more efficient way of doing everything. Are there any less efficient ways of doing this? Is there an enclosed waterwheel generator that could be hooked up to a garden hose? Something like that I would think could be used in an application such as a wood burning stove an old car radiator and a one way pressure check valve. You might not get 400W of power from it but I would think any charge you could put toward the batteries would benefit.
Sorry to disappoint but scale is everything when it comes to CHP. If you want to see how to do a woodchip installation go to Markland Grange nursery near Doncaster and have a word with Tom Nuttal. He uses wood waste turned into woodchip fed into a conventional steam boiler to produce sufficient steam to run a 250kw turbine and a 150kw compound engine as well as various engines in his steam museum. The waste heat he uses to heat his glasshouses. Museum steaming days are wednesdays and saturdays. I will hopefully be doing the same shortly with two 300kw Bellis and Morcom steam engines. The technology can easily be scaled down but the thing you have to remember is that for every 1kw of electrical energy you will probably have 4kw of waste heat. Minimum size would probably be in the region of 6kw electric and 24kw of waste heat.
Why can't we scale down to much smaller, as in my original question?, (Apologies to previous commentators). I just read that 1Kg of log = approx 4KWh, 1kg of log = 1KWh of leccy using your 25% rule of thumb. If I'm considering spending oodles on alternative generating methods and only using 4.5 Kwh per day, could a stove with boiler do the job?
"The technology can easily be scaled down but the thing you have to remember is that for every 1kw of electrical energy you will probably have 4kw of waste heat. Minimum size would probably be in the region of 6kw electric and 24kw of waste heat."
I got a feeling you may be off the mark there renewablenjohn although I am happy, as always, to be corrected. I understood that the thermal efficiency of the best of the steam locomotives was around 10-11 percent and a 'decent' reciprocating engine around 12. Compound and then Triple expansion engines can get you up to 25% efficient but you then have to run a generator to produce the leccy. 20% seems little high.
As you scale down engine losses become greater and thermal efficiency decreases.
You misunderstand the 6kw and 24kw is the total heat you can recover for your CHP unit and does not include the unrecoverable losses in conversion and up the chimney which could be the same amount again ie CHP efficiency 50%
Minimum size 60kw fire (heat energy in) converts to 6kw electric (10%), 24kw usable/tranferable heat (40%), rest losses due to conversion and waste heat.
Sounds better!
So if 1kg log = 1kwh it will = 0.1kwh electricity (if you are lucky), I would be inclined to cut this in half due to scale losses (given our target production id 4.5 kwh). So we are looking at a very rough minimum (calculated by means which has probably got some of the more physically minded pulling their hair out) of about 100kg of very dry wood and a lot of heat looking for something to do.
You can see why CHP only starts to work at a community level.
Dickster have you thought about a trail run?
Buy the biggest ready made steam engine the research and development committee will allow. There are the stuarts we talked about earlier or ANTON ( or many more). Then get a boiler made up to suit
You could probably get a cross tube boiler made that sat in the flue outlet on your fire. Same bore as your flue with a number of 10mm tubes criss crossing the flue space. A good model boiler maker should be able to help. This one is very well thought off:
This chap used to make the boilers for the puffin (which Stuart now sell) when it was made by cheddar valley steam). You could of course just get one of them and base your research on it:
There are others in the ads in the back of model engineering etc.
You will need to manualy or automatically feed it with water for the time your fire is running (boiler feed pumps can be had on ebay or many model steam people do them) as you must not let it run dry.
All you then need to do is hook it up to a model boat motor (in reverse) to see how much power you get.
If you call the model engine maker of your choice they should be able to tell you what the power output of the model is & how much gas it uses for a run.
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