Combined Heat and Power (CHP) - wood gassification??

[joholondon]

You fellows may have heard of this technology - it allows you to use the heat (usually wasted) from generating electricity in one system. 1 kW of electricity produces 3 (I think) kW of heat. It's like an engine and heat exchanger. See http://www.cogenco.co.uk/sn_combined.php for good diagram.
Ken Livingstone and Greenpeace both recommended CHP as the way forward for London. They called it "decentralised energy" and it's an efficient, proven technology ( http://www.greenpeace.org.uk/climate/solution/index.cfm ). *However* so far, it's only used on a bigish scale - hospitals or small communities.
I want to have such a unit in my house, but at the moment
a) the scale is too large and
b) I'd have to use natural gas or some kind of piped gas to run the system.
I want CHP that can run off grid, ideally using biomass, with gas as back up. I'd also like the electricity that runs the system to be off grid.
I've just been speaking to a guy from Cogneco who says that they are trying to develop this kind of combined system and that it may be ready in about a year. He said the wood would be gassified, rather than burned.

Does anyone know anything about gassification? Or is it all just hot air?!javascript:emoticon(':lol:')
Laughing And why is gassification better than getting the electricity using some kind of steam engine?

Actually, even better would be if the system allowed you to cook too - like with an Aga. So you'd get hot water, cooked food and electricity all off one system and all off-grid.

And maybe it could make me a cuppa too?!

[Moonwaves]

This guy http://the-goodlife.blogspot.com/ has been doing some experimenting with wood gassification. I can't seem to make any sense out of it but I'm not terribly technically minded - you might find it interesting though.

[joholondon]

Thanks moonwaves. It looks like his might be just for heat, but am not sure. I've had a look at Wikipedia ('biomass gasification' and 'gasification') and it's pretty involved. I suppose what I really want to know is if what I want, this super-efficient offgrid CHP unit, is ever going to be available.

[JayBee]

I just noticed that my blog received a mention.

Here is where I am up to on gasification.

So far I have built a wood gasification stove, which as mentioned above is for heating space and water. It is of the type "Inverted Downdraught Gasifier".

For a CHP unit you will need to research "Downdraught Gasifier", which is indeed more involved. You could build an "Updraught Gasifier" but you will have to do a lot more work scrubbing the wood gas so that it doesn't make a mess of your power unit.

The idea is to produce wood gas (containing carbon monoxide and hydrogen) with no tars or creosotes. Only then can you drive an engine to run a generator. The waste heat being used in a heat exchanger to warm water for radiators and/or cylinder.

I recommend the following reading material...

http://www.fao.org/docrep/t0512e/t0512e00.htm

A PDF document is available top right of the front page.

I also recommend that you join the Wood Gas group on Yahoo Groups. There are lots of files, photos and documents to browse. There are lots of people running engines and vehicles on wood gas.

[Jack]

Gidday

I haven't had enough time to look at all this yet but will as soon as I get the time.

However, is what yoiubare talking about like the old gas producers that were used back in the War. Rommel drove tanks accross the desert using any old waste carbon or organic matter. I also remember an old truck house beinhg driven round New Zealand burning anything from coal to wood chips to sheepsh!t. They were downdraft burners that also burnt water and produced and very clean hydrogen gas and carbon dioxide.

[paddy]

Is this where you you shove the unburnt gasses from a fire ( smoke ) into a gas type burner and burn them or into an engine and do same?????

Anyway as some one mention somewhere else....."you cant get more out than what you put in"

So if a ton of wood as x amount of Btu's then no matter what you do with it will produce no more than it's total Btu's.

Thing you should do is burn it efficiently to begin with and then you wont have to bother with a second process.

Also one other major rule you should never forget in these things.......Carbon Monoxide is simply unburnt fuel, so if you are producing Carbon Monoxide your original burning process is quite simply....no good.

[Muddypause]

They were downdraft burners that also burnt water and produced and very clean hydrogen gas and carbon dioxide.

I fear you may be venturing into mythical territory there, Jack.

But you are right that no end of inventiveness was pressed into service during the war to counter the shortage of oil. Some of it actually worked, to a degree.

What an interesting thread this is. JayBee, I've just watched the video on YouTube - is that wood gas burning at the top of the stove there? Not just flames from the wood itself? I'm just wondering about the economics of this idea - you burn wood to produce wood gas, which you then burn to produce heat. Is the net result more heat per tree? Or is it simply that wood gas is a convenient thing to run an ICE on?

Interesting blog, BTW. I'll have to spend more time with it sometime.

[JayBee]

Gidday

I haven't had enough time to look at all this yet but will as soon as I get the time.

However, is what yoiubare talking about like the old gas producers that were used back in the War. Rommel drove tanks accross the desert using any old waste carbon or organic matter. I also remember an old truck house beinhg driven round New Zealand burning anything from coal to wood chips to sheepsh!t. They were downdraft burners that also burnt water and produced and very clean hydrogen gas and carbon dioxide.

Yes, downdraught gasifiers were used during the war instead of petrol to drive various vehicles. Petrol engines were originally run on gas, which is why Americans still cling to the term "gas engine" and gasoline is just a petrol replacement for gas.

Adding a small amount of steam to a gasifier will produce more hydrogen. The hot charcoal breaks the H20 apart to create H2 and CO (Carbon Monoxide and not Carbon Dioxide which is not flammable).

Is this where you you shove the unburnt gasses from a fire ( smoke ) into a gas type burner and burn them or into an engine and do same?????

Anyway as some one mention somewhere else....."you cant get more out than what you put in"

So if a ton of wood as x amount of Btu's then no matter what you do with it will produce no more than it's total Btu's.

Thing you should do is burn it efficiently to begin with and then you wont have to bother with a second process.

Also one other major rule you should never forget in these things.......Carbon Monoxide is simply unburnt fuel, so if you are producing Carbon Monoxide your original burning process is quite simply....no good.

You are not burning the smoke, which is soot and won't ignite. You are burning flammable gases such as carbon monoxide, hydrogen and various alkanes. In engine applications you have to filter out soot, tar and creosote so that the engine does not seize up.

Yes, gasification does not create extra energy from nowhere. However, it does release the energy in wood more efficiently. Capture of heat and unburnt gases, which can either be burnt immediately for heat or filtered for engines.

Carbon monoxide (and hydrogen) is indeed unburnt fuel and is liberated in a gasifier (as in old town gas applications) for use elsewhere. Either ported to a gas hob (as town gas was) or to an engine for CHP/vehicular applications.

[JayBee]

What an interesting thread this is. JayBee, I've just watched the video on YouTube - is that wood gas burning at the top of the stove there? Not just flames from the wood itself? I'm just wondering about the economics of this idea - you burn wood to produce wood gas, which you then burn to produce heat. Is the net result more heat per tree? Or is it simply that wood gas is a convenient thing to run an ICE on?

Interesting blog, BTW. I'll have to spend more time with it sometime.

The flames at the top of the stove are produced when hot gases meet the air coming through the ring of secondary air holes at the top of the inner can.

There are some initial flames on top of the wood chips but they cease after a layer of char forms on top. From then on its gas being driven off and burning at the top.

I have built long flues with secondary air holes half up the flues where the gas ignites a foot or more above the wood chips. It is quite an art and some people experiment to a level where they can get an almost pure blue flame (ie almost pure CO and H2 gas). I am at a 50/50 blue/yellow stage but won't take the stove further as I wish to move on to automotive gasification.

In a wood gas stove (inverted downdraught gasifier) the idea is to burn the wood more efficiently. I am getting approximately 1% ash and very little soot.

Gas was the first fuel for IC engines. Today they can be run on LPG or methane from a digester. The idea of using free wood appeals during these times of high oil prices. Also the idea of an off-grid power generator with heat capture for hot water appeals too.

There are a variety of gasifiers depending on the application.

Inverted Downdraught gasifiers for stoves - boiling water in kettles and space heating

Updraught gasifiers - former method for "producer gas" and requires a lot of gas scrubbing to produce a clean gas for engines. Can also be piped to a burn somewhere else for hob type applications where filtering is not required.

Downdraught gasifiers - modern gasification centres on this as the resultant gas is cleaner and needs less scrubbing for engine use.

[Jack]

Gidday

The old world war gas producers produce hydrogen gas which does not need scrubbing. The only thing going into the engine is hydrogen and carbon dioxide with the normal air intake, so it is extremely clean burning. And yes, I have seen one running on sheep sh!t.

It is not mythical cos O have seen a vehicle truning on it.

I have also seen pottery kilns run on waste oil and water and when the water is added the temperature can reach over 2000C and even melt fire bricks. They are exrtremely easy to set up but must be kept at more than 800C or else the water won't crack into it's two separate gasses.

[Muddypause]

Sorry Jack, I misunderstood you. I thought you were suggesting that old chestnut of running a car on water.

[Jack]

Gidday

Well why not?

They drive that bloody space shuttle up into space on it don't they?

[Jack]

Gidday

I threw a googly and got this:-
http://highforest.tripod.com/woodgas/woodfired.html

[paddy]

I'm out of here

[Muddypause]

They drive that bloody space shuttle up into space on it don't they?

Hydrogen, Jack, hydrogen. It is fudging things to call that water. You can certainly run a vehicle on hydrogen (even a space shuttle), and, under certain conditions, water can be use to enhance the combustion process of another fuel. But you cannot use water alone as a fuel even though, temptingly, it consists of hydrogen and oxygen.

The problem comes down to the same old one of energy economy - it uses up more energy to separate these two elements than you get back when you recombine them. What you can do is separate the oxygen and hydrogen away from the vehicle, using a form of energy that you have in abundance to divide the molecules, and then store the resultant hydrogen for use as a fuel. But this is just a matter of convenience - water can be turned into fuel only by using another form of energy to do it. Because of this, nearly all stored hydrogen is derived from fossil fuel, not water at all.

There are no end of perpetual motion machines that claim to be able to run on water alone in one way or another. They are all fakes.