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1 kg of firewood is said to have around 4-5 kWh of energy. Some wood stoves claim a burning efficiency up to 90%, and I understand this means how completely the wood is burned. Pipe loss is not accounted for by this number so there are more losses.

Losses and inefficiencies aside, are there any residential scale electricity generators that run on firewood? Or is this not viable? Apparently there are several technologies that can create electricity from wood, but some alternatives are unrealistic for residential use.

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NO, not when you add "efficient" to the question. Certainly it is possible ,however efficient is the catch and everyone will not have the same definition. I suggest look up wood gasification on "u-tube"; there are several examples, some include running an engine driven electric generator. I am impressed by the ingenuity, however they seem to require frequent attention.

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Oh yes, you can generate electricity from wood.

Wood has actually been used as fuel for cars. You need a wood gasifier.

Usually this is a DIY project, because cars that run on gas are very impractical, as the gasifier is heavy and takes lots of space. Similarly, you should be able to modify a gasoline powered generator to use a wood gasifier as its fuel source instead of running on gasoline.

The efficiency will be terrible, though, and it's a high maintenance work to maintain the composition of the gas suitable for continuously running the generator. I'd say this isn't something that's good for commercially selling. We won't see any wood-fired commercial generators.

On large scale, coal-fired power plants can actually be modified to run on wood. However, coal-fired power plants are dying for a good reason, they are dirty and their efficiency is poor, and the generation is very inflexible, good for mainly baseload. If you run it using wood, it's still dirty (although the carbon dioxide is from biological sources so it doesn't cause global warming but otherwise it's dirty, causing lots of pollution) and the efficiency is poor. It's also good for mainly baseload. Natural gas fired combined cycle plants have displaced coal plants for a good reason: they are flexible and efficient.

In theory, integrated gasifier combined cycle plants could have some of the benefits of natural gas plants, while still being able to run on wood. They are expensive, though, and not a large-scale solution to the electricity generation problem because we will run out of wood if they are used en masse.

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  • But what about the "residential-scale electrical generation" that was actually the question? Commented Jan 10, 2022 at 13:32
  • If you read my answer carefully, you will note wood gasifiers on modified generators are residential-scale.
    – juhist
    Commented Jan 11, 2022 at 17:18
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Nope there's no commercial Wood Gasifiers at all no no.

Except just these few manufacturers running a couple of 100 or so installations: https://volter.fi/ https://www.holz-kraft.com/en/

Efficency is around 90% with a CHP mix of 30% electric power and 60% heating, ambient heating from the plant is sometimes used for drying the feedstock(fuel).

For it to be worthwhile you ofc need that amount of heat for something like: local distric heating, wood drying, industrial premises or perhaps a spa with heated pools ...

EDIT:

TEG:s are horrible at efficency generally. For a 0 maintenance home system depending on your electricity usage a micro-stirling might do the trick but depends on your electricity usage, there are 1kWe and 2kWe models available but they put out alot of heat (8 kWth / 16 kWth) when ran at those energy output levels, probably suitable for a outdoor pool or as you suggested a greenhouse, and perhaps also to heat a house with ofc. Although I've realised there's some aversion to lp-radiators in the americas with airducted heating and/or steam installs beeing the norm. Underfloor heating is ofc also an option for heating a home not sure of the aversion there.

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  • I assume this is a long comment-answer that should have been as a comment to my answer, and refers to industrial-scale generation and not commercially sold wood generators that you can run at home. I didn't exclude the former, I excluded the latter. Volter's 40 kW isn't residential-scale. Holz-Kraft's 30 kW - 1 MW isn't residential-scale either.
    – juhist
    Commented Feb 15, 2022 at 17:56
  • Oh right sorry my bad the non-residential scale plant that heats 60 homes + 2 schools + 1 church isn't residential scale you mean somthing in the lines of ieabioenergy.com/wp-content/uploads/2018/02/… in denmark. But I do ofc agree with you about replacing EVERYTHING with wood gasification is a folly, it would at best be a piece in the larger energy puzzle to be layed.
    – friskens
    Commented Mar 7, 2022 at 13:43
  • @juhist yeah sorry some mixup in what was ment by residential scale, on this side of the pond what the topic maker is asking about is refered to as personal use or personal residence use, while residental would reference a apartment block or multi-family home or even homes. You got to read up on the output of running combustion engines on woodgas though much cleaner then what you stated above, check the IEA document above for some real numbers from their 500kWe generators.
    – friskens
    Commented Mar 7, 2022 at 14:29

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