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Turning wood into electricity for 2 months of the winter  RSS feed

 
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I'm kind of dreaming ahead a bit here.  I keep wanting to change our conventional house over to off grid solar.  I currently get grid power that supposedly comes from windmills.  I also pay an annoyingly large connection fee.  If I went grid tied solar the connection fee would only drop our bill by 50% (at best).

The problem is that I live in an area that is pretty cloudy in the early winter (mid Nov to mid Jan).  My greenhouse also could use some heating help during those same two months.  Hmm, could I kill two birds with one stone...

My thought would be to use a wood fired electrical generation method during those two months whenever the batteries get low.  Is there such a thing for residential scale applications?  Some options I've thought of are:

Wood Gas:  Make wood gas and burn it in a generator.

Heat Engine:  Burn wood to produce heat for the hot side of a Stirling engine.  Use a water loop in the soil of the greenhouse as the cold side.

TEG (Thermal Electric Generator):  Burn wood to produce heat for the hot side of a TEG.  Use water loop in the soil of the greenhouse as the cold side.

Steam Engine:  Burn wood to produce steam.  Use steam engine to turn a generator.  

I think I've discarded the wood gas option unless there's something off-the-shelf that could do the job.  I don't want to be dinking around with a complicated system all the time.  Low maintenance is a plus that this option doesn't have (in my opinion).

I don't know if you can buy a Stirling engine for this size application.  Same goes for the steam engine.  I think there are plenty of TEGs out there that could work.

For that reason I'm leaning towards a TEG system as the best option.  I don't know how much cold they need (GPM and temp) and what kind of wood burner would be optimal.  I also don't know if I'd need to run a fire for 18 hours a day to keep up with our electrical usage.

If a TEG system is the most likely to work, I'll probably start another thread or join in on an existing TEG conversation.

Bottom line...  Are there other ways of generating electricity for two months of the year, ideally with wood, that are sized for residential use?  Am I misunderstanding the pros and cons of the above options?

Thanks Permies!

 
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Honestly...and I am really not trying to be negative here, but it seems like a lot of those are non-viable. There are Sterling Engines available for yachts, but I think the price is around $27,000 for a 3 KW unit or some stupid thing. I might be off on the numbers, but it is an insane amount of money for very little power.

Steam is just unsafe and illegal at best, unless your have a boilers operators license.

Wood gas is complicated as you said...

I thought about biogas to run a small gemnerator, but it depends what you have for a feed source. I have sheep, but again it depends. Biogas is my only thoughts right now on this...

 
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I have made wood gas an I have burnt it in an engine via charcoal.  

If you desire to go this way, Wayne Keith's board,  is the place to learn how to get it done.

http://www.driveonwood.com

I recommend looking on youtube for "Simplefire" carcoal gasifier and also on Wayne's board.    it is very simple way to get started.

Wayne has driven hundred of thousands of miles on wood, and his forum is very elite for getting the job done.

 
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out of my price range but i was looking at these:
http://vulcangasifier.wixsite.com/vulcangasifier/evolution-series
 
Mike Jay
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I'm not sure if this company is still in business but they have a small scale Stirling engine that can do 1KW and it's $1800.  Sefton Motors of Detroit

Thanks for the added bit about legality Travis!  I wouldn't've thought of that.  But the explosion bit was on my mind...

Thanks for the link Mart!  I can see how you can drive a vehicle with wood gas but I think going from that to electricity adds one more variable.  I'll have to poke through there to see if they have that nut cracked already though.  Oh, looks like S. found it  Pricey but it goes from wood to electricity in one go.  My hunch is that it runs on pellets.

TEGs seem simpler than all this but I'm just starting to learn about the options.

We need more off-the-shelf solutions!!!  

 
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 Since there are dual fuel generators out there that can run on propane, it seems like a reasonable experiment to run wood gas through it. Im probably over simplifying it, but thats the path i would go.
 
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Mike,

I wholly applaud your desire to be as off-grid as possible.  I don't mean to just throw credentials around, but I have a master's degree with much of my work being done of the history of energy, so I feel pretty qualified to comment here.  I have two questions regarding your motivations:

1)  Is it your desire to produce energy (I am assuming this actually means electrical energy) more cheaply than can be acquired through the grid?

OR

2)  Are you trying to produce energy that is cleaner than that provided by the grid?

Beyond power backup, I find these two reasons to be the most common for people desiring to go off-grid.

Regarding question #1
Unfortunately, the numbers don't work well in either case  (there is a reason that going off-grid is really only for the true believers).  In terms of cost, it is very unlikely that you can produce electricity as cheaply as the grid does.  As you have already found out (and I found this out painfully as well), solar is not going to work for you in January and February.  You just don't get that much sunlight.  For all of the options you have listed, I hate to be the one who bears bad news, but I think the most practical it using wood-gas to drive an internal combustion engine driven generator.  There have been a small number of Sterling engines adapted to generate electricity, and if you can find one that might be affordable, then by all means, it would fulfill question #1 (I will get to question #2 in a minute).  As has been pointed out, steam is probably not even legal (and actually has some major thermodynamic limitations--You have to get a bunch of water to boil before anything can possibly happen, and that boiling by itself requires a LOT of energy).  Sadly, the TEG, though the modules don't look terribly expensive, have very high heat requirements.

Regarding question #2
Sadly, any energy you are going to make along these four paths are going to require a LOT of wood.  Do you have access to a virtually inexhaustible supply of wood?  If not, how are you going to get it?  Don't get me wrong, a part of me absolutely LOVES the idea if generating energy from wood I personally cut from my own land in a sustainable manner and replanted with fast growing trees.  And this still might work if we are only talking about generating HEAT.  I still think a RMH is a great idea.  But you want electricity.  And the numbers work against you again.  Once again, wood gas running a IC engine is likely has the best thermodynamic efficiency as the internal combustion engine is a proven, reliable machine for generating power.  It is also plenty noisy and you already stated you don't like this route.  The Sterling engine, if you can find one, might be able to supply you with a small amount of electricity. In the 50s, there was a small Sterling engine that was developed for use in 3rd world countries that had no access to electricity.  The plan flopped due to high prices, but at least there was a modestly respectable thermodynamic efficiency.  We have already talked about steam.  And unfortunately the numbers get even worse for TEGs.  TEGs work on the principle that as certain materials heat (metals mostly), the electrons are boosted to higher orbitals, and when they come back to the original orbital, that energy release can be utilized to make the electrons flow through a wire.  Sadly, the thermodynamic efficiency of TEGs is actually the very worst of the options you have listed.  You would have to run a roaring fire to produce a minimal amount of electricity, some of which is going to have to run a liquid coolant pump to cool one side of the TEG.  TEGs are intriguing, fascinating little devices, and in certain circumstances, can produce some usable electricity, but again, there is a reason that power plants don't use TEGs to produce electricity--they use highly advanced steam engines!

In the end, sadly, I am afraid that of the 4 methods you mentioned for generating electricity, I am afraid that none of them can compete with the grid from a carbon emission standpoint.  I don't like this fact and wish it were wrong, but it is true.  Try this little thought experiment, it does not have a specific right or wrong answer, but tries to simply capture the problem of carbon emissions.  Which is better (at minimizing carbon emissions), cutting down a tree that converts CO2 into oxygen so that you can turn its mass back into CO2 (and not have the tree for CO2 fixation), or burning a liquid fossil fuel whose emissions are both CO2 and H2O, the CO2 of which can be at least partially captured by the tree you did not cut down?  The answer is not an easy one and I am not trying to definitively say that one side or the other is better.  I am only trying capture the argument as concisely as possible


Sorry if I am major downer or bearer of bad news.  And please understand that I am NOT saying that renewable energy is a bad thing.  It IS at present difficult for us to PRODUCE electricity that is both cleaner and cheaper and more efficient than the grid already does.  After all, the grid (meaning for the moment, coal power stations) wants to get as much electricity as they possibly can from their fuel (coal) to sell to consumers and the power company wants to buy as little coal as possible to generate the electrical demand.  They have a lot more money to throw at these issues than you or I do.

The BEST option that we have as individuals though is to conserve the electricity that we use.  That is the one real tool at our disposal that can both save money (quite a lot actually) and reduce CO2 emissions.

Once again, I have rambled on to the point where most people stopped reading long age and if you got this far, congratulations.  In all seriousness though, If you were to have any other questions or just like talking about energy, please know I am only a post away.  Other than that, I am sorry if I ruined your evening.

Eric
 
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Mike Jay wrote:

My thought would be to use a wood fired electrical generation method during those two months whenever the batteries get low.  Is there such a thing for residential scale applications?  



Mike, is there another place where you've indicated your major power draws in the winter time?  It may help to approach the question simultaneously from a production and use view that would reveal points for nipping and tucking on the power equation.

One thought that comes to mind is to use some sort of RMH in the greenhouse for keeping that warm....maybe you are already doing that.  I'm not sure about the next part, but depending on the size and discharge status of the battery bank in mid-winter, could you use one of those small, inverter-generators to re-charge the batteries during low-draw periods such as during the night or when you are away for a while?  I realize it may seem unwise to leave a generator unattended, but I'm wondering if you could get to a point where you know how long the gennie will run on X gallons of fuel, and fill it just enough to run out of gas/diesel when the battery bank is recharged.  The quiet operation of such a generator would (hopefully) not be obnoxious and the fuel consumption also possibly at a minimum.  Just musing here.....
 
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I don't know if this will be of any help as I'm not directly answering your question about wood options.  If you do find a viable wood option I'd be happy to hear about it!

I do live in a similar region with the winter "gloom belt" that keeps things pretty cloudy for 3 to 4 weeks to either side of the winter solstice.  About 5 years ago I went completely off-grid for my electric power.  I too discarded the grid-tied option because of the cost of the monthly line charge.  For me it was about 4 times what the electricity I actually used cost!  The biggest thing I do to deal with this great reduction in electric generation during the winter is go hard core conservative of power use.  I find I have to get in tune with what nature is actually providing, meaning I will save higher power consumption activities for when the sun is shining.  I strive to keep constant drains on power to the lowest level I can.  At this point I think the heat tapes that keep (insulated) pipes out in the well house from freezing are the biggest consistent draw I haven't been able to get rid of.  My fridge would be the next thing.

Still even going ultra conservative in this time period I find it inevitable that the sun stays hidden for a full week or more at times.  My best solution so far to charge the battery bank is a low cost propane generator.  I went with propane because it is used so infrequently keeping gas on hand for it was practical.  The gas would be likely to go bad.  I also use a propane torch in my work so I already keep tanks of propane on hand.  The downside, from a strictly functional perspective, is that the generator pulls the propane out at a high enough rate to cause the whole tank to cool significantly.  Therefor in the winter, which is when I might need to use this, the tank can get so cold the propane inside stops going from a liquid to a gas thus choking off the fuel.  Having a larger or full tank helps.  I usually will swap out a tank when it gets too cold with another and let it warm up again.

With my system as the battery bank is getting older I find I need to use the generator about once a year.  
 
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As mentioned above check out www.driveonwood.com
I have run a tractor, atv and generator on woodgas. I use charcoal gasification as the unit is much simpler. You mentioned you have a greenhouse that can use the heat... Then charcoal gasification is for you. Stirlings, TEGS and steam engines efficiency is one quarter  to 1/3 of what a gasifier equipped Internal combustion engine generator will deliver using off the shelf engines with spare parts a phone call away. Just like all DIY energy solutions you need to be the tinkerer type. Also remember 1 gallon of gasoline is equivalent to about 20 lbs of wood or 14 lbs of charcoal so you need a good supply of wood and the willingness to process it or its a non starter.  for that one gallon of gasoline equivalent expect 6 to 8 kW Hr of electricity... Its a fun addictive hobby if you go for it...
Best of luck,  David Baillie
 
Eric Hanson
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David,

I love your answer!  You have actually gone off grid and have found that you really have to conserve.  In my mind, the only way we will truly cut down on unnecessary energy usage is if we pay a huge penalty for that usage--in your case it means you will run out.

Regarding the propane generator.

I have a gas generator and I have found that the gas actually lasts longer than some fear it would.  Nonetheless, I think that propane is tops for longevity.  Given that there are dual fuel generators, do you think/know if you could start you generator on propane and then switch to oldish gas once the generator worms up a bit.  I have found that when I use ether to start the generator, even very old gas will run in the generator.  I am not suggesting that a person should just let the gas set around for years, but occasionally one does get gasoline and then not use it for some time and it would be a terrible waste to not be able to use it (and really, if it goes bad, what are you going to do with it anyways?).

I would love to know your thoughts on this issue,

Eric
 
Mike Jay
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Hi Wayne, I'd agree that I think it makes sense to use a propane capable generator for wood gas (vs a gasoline generator).  It just seems that there is a fair bit of tinkering needed to get the wood gas to be clean enough for the generator to run well over the long haul.

Thanks Eric for the post, I did read all of it  My motivation is #3.  Becoming more self sufficient and stopping my support of the local power company.  My state regulators seem to want solar and renewables to be harder to implement so I would like to get out of their grip.  Solar is pretty straightforward for much of my needs.

I do wonder... How much wood would a power system use if a power system did use wood?  If it's a cord or two a month, I could handle that.  If it's 10 cords a month, never mind.

That's part of my conundrum.  I don't know what options are realistic and I don't know how much power you can get from a given amount of wood.  Not knowing that makes my assumptions and dreams possibly unrealistic.
 
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Mike Jay wrote: Wood Gas: Heat Engine: TEG (Thermal Electric Generator): Steam Engine:




This is my current project.  I am still in the research / design phase.  My "off" solar season is a Monsoon and lasts 6 months.  I've looked hard at all of the same technologies.  Here is my take on it.

Stirling engines look great on paper.  But are pretty damn hard to implement.  Especially in isolated / rudimentary environments like I am in.   The materials, skills, and technology are not easily available.

Steam.  By far the most efficient.  I've read of conversion rates exceeding 60 -> 70%.  My uncle had several restored steam tractors that would make excellent farm scale generators.  But ..... right or wrong ...... that home scale technology is no longer widely available.

Wood Gas.  Old, previously implemented, and stable technology.  Can be built from repurposed materials.  Fuel is ubiquitous.  Especially if you can do pelleting.  

Safety factors are inline with other technologies. Fabrication costs are achievable for the motivated.  Fuel produced can be blended with A.D. biogas.  Like A.D. fuel CANNOT be easily compressed.  So it is a "use it or lose it" scenario.

Significant waste heat is available for other uses.  In my case distilling water for battery banks.

MOST importantly the fuel produced can be fed into EXISTING petrol and diesel engines WITHOUT serious modification to the engine.  That means we can use our existing infrastructure while we work our butts off to develop an open-source, family-scale energy generating technology. (The guerrilla thumbs his nose at the oligarchs).


Here is the information necessary for an informed decision.


https://www.youtube.com/user/flash001USA/videos    ..... in my opinion this is the system to attempt.

https://www.youtube.com/user/MrTeslonian/videos
https://www.youtube.com/user/mazdalorean/videos
https://www.youtube.com/user/brentbobbaumer/videos
https://www.youtube.com/user/plasmacutter1/videos
https://www.youtube.com/user/CNCmachiningisfun/videos
https://www.youtube.com/channel/UC8_chLoN68OMEUXl4VlI7Gw/videos
https://www.youtube.com/user/joshuaburks/videos


The "Drive on Wood" forum is the best forum for interaction.  Very good thread on small engines.


Hope this helps.

 
David Baillie
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Eric, 5 years ago i decided to add a grid connection to the house to replace the propane generator. I now have a bizarre hybrid home. You are completely right though conservation is key. You cannot solve it with generation alone. So with that in mind for a generator the problem you will have is if the gas is too old it will not have the same energy density as fresh gas. Most generators work by turning the engine at a precise RPM to produce exactly 120 volts, 60 Hz. The governor allows you some flexibility in that regard. If the gas does not have the punch to deliver within the narrow range required your inverter will refuse the generator power or you might brown out your house. If you have old gas much better to use it up in a lawn mower, water pump or something less sensitive or refresh it by diluting it with fresh gas...
Cheers,  David
 
Eric Hanson
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Mark,

You really have me curious about the steam engine efficiency.  From what I have read, the maximum theoretical efficiency is just a bit over 68%.  However, in practical usage, a person is actually doing really, really well to get the overall efficiency up to 35-40%.  Obviously, steam works or we would not have every power plant on the plant (outside of hydroelectric) at some point running a steam turbine.  Coal, nuclear, concentrated solar all basically run a gas turbine, with the current working fluid of choice being steam.  I am just wondering how you got 70% as a possible figure.  Is this a theoretical number or an actual recorded rate?

Eric
 
Eric Hanson
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David,

Thank you for the very detailed answer.  Your experience off-grid actually sounds like a practical implementation of a phenomena called the Jevon's Paradox.  The Jevon's Paradox states that the more efficiently we use energy, the MORE energy (not less as one would think) we use.  The reason:  each individual unit of energy becomes easier to use.  It is actually the same reason Wal-Mart works.  Each item we buy is a little less pain on the wallet and therefore we make more purchases.  In your case, you bypass the Jevon's Paradox by drastically limiting your energy supply in the first place.  It is nice to see where the theoretical and the practical actually align.

Eric
 
Mark Cunningham
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Eric Hanson wrote:Is this a theoretical number or an actual recorded rate?



Mark Cunningham wrote: I've read of conversion rates exceeding 60 -> 70%.

 
Eric Hanson
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Mike,

Happy you can get meaningful information from my long posts.  When I start typing, it is hard to stop.

It REALLY bothers me to say this--as in I cry a little bit and choke back tears--but I have to ask "is the current electricity being generated on the grid the cheapest and most energy efficient out there?"  Sadly, there are some good numbers to support this conclusion (bear in mind, we are talking about Kw/h generated, not Kw/h consumed).  Certainly, we can train ourselves to use less, but generating electricity on the home scale just does not have the same forces supporting us that the grid does for it.

Eric
 
Eric Hanson
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Thanks Mark, that helps.

Eric
 
David Baillie
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the problem with steam is that magical 68 percent number is a theoretical limit using extreme high pressure dry steam operating a turbine at high speed continuously with drastic heat recycling... What you would produce at home would be closer to a wet steam medium pressure piston type engine operating at lower speeds... Your true efficiency would be closer to the single digits of energy value of the fuel transformed into shaft power... If you have a bottomless pit of heat required it does not matter but its a hell of a lot of wood. With woodgas you start with an off the shelf generator that has millions of hours of R and D built into it and is available at the hardware store for less then $1000. Your efficiency would be in the 20-30 percent range... All of those are loose numbers but not far removed from calculated ones. I am open to correction but I've put a fair bit of energy into figuring them out.
Cheers,, David
 
Eric Hanson
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David,

Thanks for that detailed answer.  Once again, those numbers sound a lot closer to the research I did when doing my masters degree.  I certainly appreciate the added detail and the end-numbers for the actual overall efficiency.  On a partially related note, because electricity is so darned flexible (it can power anything, right?), there is a temptation to convert all energy into electricity and then back into other forms of energy.  Each transformation of energy incurs a penalty (at times a quite large penalty) so the fewer changes in the form of energy, the better.  As you point out, the overall high amount of thermal energy for our hypothetical small wet steam engine eventually transforms into a relatively small amount of usable energy.  

Eric
 
David Baillie
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Agreed Eric. I was reading your first response and All I can disagree on is the lack of differentiation you seem to make about surface carbon versus Fossil carbon. Yes large Natural gas stations may be more efficient thermally but they are using a fossil carbon adding to the problem. Coal plants have far worse of a carbon profile still.  A surface carbon solution has the advantage of recycling similar quantities of CO2 from the active environment. Its a known element no different then a forest fire or a rotting tree.
 
Mike Jay
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So many replies!  I missed a few with my last post so I'll try to catch up here.  I also ran out of apples...  You guys rock!

John - My main winter power usage is somewhat normal stuff.  Fridge, freezer, lights, plug-in car, electronics.  The greenhouse will add some load for fans but hopefully not lights.  I don't really know what usage rate is good or bad.  I'm sure I think I'm good but I actually suck.  I think with solar under cloudy skies, I'd need 300 kW Hrs per month to satisfy my current (awesome/horrendous) usage.

I'm really hoping to heat the greenhouse with the thermal activity of a large compost pile.  It's not working just yet   So that has me noodling on a second way to heat it and also do power generation.  I'd consider wood backup heat for the greenhouse but I think I'd want a batch box or masonry heater so that I could load it up once and call it good.  Versus feeding a normal RMH periodically for a few hours.

David H - Your reason for getting off grid aligns very well with mine.  I do have to work further on conservation.  We were getting pretty good but just added a plug in Prius to the stable.

David B - If 20 lbs of wood = 6-8 kWH, that means I could get 300 kWH from 1000 lbs of wood.  That seems pretty reasonable.

Mark - Thanks for the list of YouTube videos!!!  That will keep me busy for quite a while!  I'm starting to think wood gas isn't as impossible as I did three hours ago

Eric - I'm sure the grid is much more efficient at making electricity.  I'm hoping that when I pay them extra for windmill power, that that's what I'm getting.  Or at least I'm paying to make sure some of their mix is wind.  I'm just trying to figure out if I can make my own power or if it's a fool's errand.

Ok, I'm going to shift my investigations more towards wood gas.  This helped a lot, thanks everyone!
 
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Mike Jay wrote:Mark - Thanks for the list of YouTube videos!!!  That will keep me busy for quite a while!  I'm starting to think wood gas isn't as impossible as I did three hours ago



You are most welcome.   Beyond building a gasifier ..... the most salient points that I have found are ....

1.)  There are lots of different reactor designs.  Some have inherent flaws.  Updraft and Stratified downdraft (FEMA) are notorious dirty gas producers.  The Imbert design, (Flash001usa, Mazdalorean, MrTeslonian), appear to produce a much cleaner fuel.    My fuels are all soft, punky, wet tropical woods.  They consider Pine a hardwood here.  So  I may have to do extra work to compensate for that.

2.)  I am attempting a wood versus a charcoal gasifier.  I have seen math that states that you lose half of your energy translating from wood to charcoal.  And you have the added smoke, tar, and wood vinegar to deal with.    But I may be forced into charcoal if I cannot work out the details.

3.)  Your hearth must match the vacuum of your load.  Too small or too large .... you don't crack all of the tars and gum up your engine.  That calculation is discussed ad-nauseum in the wood gas sub-culture and there is some wiggle room in those dimensions.   Short and skinny.  Know what you need to run then build for it.

4.)  Quality of fuel is important.  Size and moisture content.  Most of the serious folks have developed infrastructure to assist in standardizing their fuel.  But pretty much anything that burns can be used.  One fella used plastic trash and almost blew himself up it was so powerful!


Please keep me in your loop.  Maybe together we can work out bugs.
 
s. drone
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are you using wood chips?
i have seen a large pile steaming in the dead of winter
i am hoping to heat a greenhouse this way too
 
Mike Jay
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There's a whole world to come up to speed on.  Luckily I have time and about 4 other projects to do first...

On one hand I'd love to build one.  On the other hand, I'd be willing to buy a tested design that I know will work.  In the brief looking I've done so far, the Dobson Gasifier sounds pretty nifty.  I'm not sure if one's been built though...

My fuel source would likely be pine or poplar.  An awesome source (if it would work) is wood chips from the city.  They wouldn't be dry which I assume would be a problem?  

Hey S. Drone, I am using wood chips for the compost heater.  Here's my thread on issues with getting it to heat up Getting wood chip compost to heat up
 
David Huang
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Thanks to everyone for the information on this thread.  It does sound like I might want to look into wood gas if I want to pursue wood as a back up power source at some point.  Though I must admit given how little I use a back up power source I'm not likely to invest the time/money into that research anytime soon.

Eric Hanson wrote:
Regarding the propane generator.

I have a gas generator and I have found that the gas actually lasts longer than some fear it would.  Nonetheless, I think that propane is tops for longevity.  Given that there are dual fuel generators, do you think/know if you could start you generator on propane and then switch to oldish gas once the generator worms up a bit.  I have found that when I use ether to start the generator, even very old gas will run in the generator.  I am not suggesting that a person should just let the gas set around for years, but occasionally one does get gasoline and then not use it for some time and it would be a terrible waste to not be able to use it (and really, if it goes bad, what are you going to do with it anyways?).

I would love to know your thoughts on this issue,

Eric



In hindsight it probably wouldn't have been a bad idea to get a duel fuel generator.  I don't remember if I looked into them when I was shopping around for my propane one.  I went with propane for the longevity of the fuel and the fact that I already keep tanks of it on hand.  If I used a gas powered lawn mower or other such thing where I'd have gas on hand already I probably would have entertained duel fuel more.  I use a scythe though for "mowing" my lawn once or twice a year.    Downsides to duel fuel generators that I can imagine would be a higher cost due to increased complexity, and also do to increased complexity, more things to break down.  In general I try to keep my tools as simple as possible so there is less to break and they are easier to fix.  

While on the subject of the propane generator I can offer up one more tidbit from real world experience.  The cheap ones at least (mine was about $400) put out really "dirty" power!  This is doubly so if the propane tank starts getting too cold and choking off the gas supply.  To save my electronic devices when I'm "out" of solar power and recharging the battery bank from the generator I will flip the circuit breakers so the generator power is ONLY going to the battery bank.  This means I go the day without power in the house.  I'm sure a higher quality generator would provide cleaner power one could run the household appliances on.  Again, since mine is barely used I opted to not go that route and save some money.

Interesting connection to Jevon's Paradox too.  I hadn't really thought about my set-up in that fashion, but it certainly does apply... when it's cloudy and power is limited.  During those times I have hard limits due to being off-grid.  Related to this is something I realized only after I went off-grid.  For years before hand I was all about conserve conserve conserve so that my system didn't need to be real large.  I had gotten my monthly power usage down to 100 KWH or less.  I no longer know what I use on an average monthly basis since I don't have a meter to tell me, but I know that during much of the year I am often using way more.  The paradox for me was realizing that during the sunnier times of the year my panels would produce tons more power than I can use.  I had to have more panels in order to get through the winter months.  So when it's not winter I'm looking for productive ways to use that extra power.  In spring and fall, when I need some heat in the home, if it's a sunny day I actually heat with electric space heaters!  I never would have guessed this before I had the system.  In fact I gave away a couple electric space heaters thinking there was no way I'd ever use them when I was off-grid.  I've since also gotten and electric wood chipper, and electric chainsaw.  As the saying goes, "make hay while the sun is shining".
 
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I second the request for some idea of your energy usage!


Here I have a similar problem with lack of winter sun. I've got a pretty substantial battery bank en route, and enough panels to charge it fully in one sunny day. It should last me a week. I still can't absolutely count on that one sunny day.

My usage is pretty low, the killer is refrigeration... but there are options..

Here it is not consistently cold enough to just use a cabinet vented to the outdoors in the winter; some days it will be a freezer, some a fridge, and some it will be 15c and stinky. But *most* of the time outside air would be cold enough... so in theory one could be automating the process of using this cold air to chill a thermal mass. At the fanciest point an ice-battery fridge could be built relying purely on ice frozen by outside air, in a cold enough climate..

Another option is an ice-battery fridge with the freezing powered by a compressor. This seems pretty optimal... 'just' a matter of designing and.building.. in theory it looks quite possible to have several days of energy in ice form, added to the electric energy storage.

I think an ice battery fridge that utilized ground source cooling for the chiller could be very interesting.


In the medium term I am planning on a TEG system to backup my solar. Importantly it will tie into my primary wood-burning heat source. No extra fire. I'm a lot more familiar with this stuff than refrigeration, and cost will be lower... but my goal is very modest. If I can get 50w average output, that would run my fridge, lights, and phone generating 12 hours a day..

A microhydro system would be better, but I'm not willing to do it without permits in a salmon-bearing creek, and those are unlikely to be forthcoming.


Edit: now that I see a rough idea of the target, TEGs don't seem very practical unless you were wanting to cut back pretty hard on *continuous* usage; my baseline is well below 1kwh/day, but only because the major draws can wait for sun..
 
David Huang
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Mike,

Your posts make me think you are thinking that you'd have to supply all your power from some other source during the months it's cloudy around you.  The reality I've found is that you can still generate a fair amount with solar panels.  You may want to look up solar insolation tables for your region.  These can give you an idea of the average equivalent hours of full sun you'd get.  You'll want a table that breaks it down to averages for each month so you can see what Nov - Jan provides.  Then if you get enough panels to supply enough power for the average daylight in those months you won't need as much back-up power, though you will have loads of extra power potentially going to waste in the other months.  People often ask me why I don't sell the extra back to the power company.  I suspect you already know what the answer to that is.  Because due to the monthly line charges to be hooked up to the grid the end result would be me PAYING hundreds of dollars a year to give them power.  I do hear that I have one of the worst power companies in my region as far as solar goes.  They really don't want it.  Situations might be different with a different company.
 
David Baillie
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Mike Jay wrote:There's a whole world to come up to speed on.  Luckily I have time and about 4 other projects to do first...

On one hand I'd love to build one.  On the other hand, I'd be willing to buy a tested design that I know will work.  In the brief looking I've done so far, the Dobson Gasifier sounds pretty nifty.  I'm not sure if one's been built though...

My fuel source would likely be pine or poplar.  An awesome source (if it would work) is wood chips from the city.  They wouldn't be dry which I assume would be a problem?  

Hey S. Drone, I am using wood chips for the compost heater.  Here's my thread on issues with getting it to heat up Getting wood chip compost to heat up

pine and poplar have both been used successfully in raw wood gasifiers. Chunks tend to be the norm; chips tend to be a problem on more homemade units. Consistency of fuel can also be a problem with chips. for electricity you want clean consistent gas  and that starts with clean consistent dry fuel. The smaller the gasifier the less tolerant of fuel variations it becomes. In your case an imbert design or wayne keiths design would probably be in order. The dobson looks interesting but I have not heard of a successful homebuilt. Lots of complexity there.  For charcoal designs you gain ease of construction at the cost of preparing the fuel. I make my charcoal in a wood stove so there is no wasted heat or gasses.
Cheers,  David
 
Mike Jay
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David H, I am expecting that I'd get some output from panels in cloudy winter weather.  Maybe I'm being pessimistic about the volume of energy I'd get.  I'm handy enough that I'd happily make adjustable mounts to optimize the angle.  

I know a solar installer in my area who is off grid.  I'll have to get a proper quote from him to see how bad it would be.  

We're both reading off the same song sheet when it comes to our utilities :)   I'm sure they'd take my extra energy.  But they'd pay me a couple pennies a KWH and the fancy meter to measure it would probably run $40 a month.
 
Mike Jay
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Thanks David B!  So wood chips wouldn't likely work.  Unless I make a screening device to eliminate the dust and the big stringy pieces.  And then dried them out.

I make some charcoal already in my wood stove.  I'm guessing it would take a literal ton to do gasification with it though.  Is the charcoal gasifying process simpler and less likely to make dirty/poor gas as well or is it just the construction that gets easier with charcoal?
 
David Baillie
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At your consumption level net metering is not worth it. In terms of solar production assume 1.5 hours of production as an average in the two worst months. As mentioned above come summer you have more then you know what to do with. I decided to put in a grid connection to make up the difference. It is the cheapest back up power you will have. Use it instead of the propane generator. The industry term for it is Grid Zero where you use the grid when you need it but don't sell back. You can simply rig it to turn on at night to top off batteries for much less complex of a system.
 
David Baillie
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yup you got it. Think of wood as many different compounds all producing a slightly different quality of gas heart wood, bark, resinous wood versus hardwoods porous like pine or dense like oak. Each gasifies differently. On a big unit there is lots of room for variation because it balances out. On a smaller unit... nope. There are some people who do small raw wood well but they are not common. I'd suggest extreme caution on Mr teslonian's units... Enough said. Charcoal is very consistent by contrast. For volumes assume 8 to 10 gallons of charcoal per gallon of gasoline equivalent. A video... one of mine:  https://youtu.be/LKZPTBA-boU
 
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David Baillie wrote: A video... one of mine



Nice.  Simple is robust.  Here is a neat charcoal system I've had my eye on.

 
Eric Hanson
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David B,

I hope you don’t misunderstand my earlier post.  Very true, surface carbon can be recycled.  My only concern would be that if does get recycled and that a person takes the added effort to deliberately recycle that carbon by replacing trees that were removed.  Atmospheric carbon can be recycled through plants, and it does not matter if that CO2 came from coal, natural gas or wood.  What does matter is that people take individual responsibility to actively recycle that carbon by planting (ideally) fast growing trees of some type.

Again, I hope you don’t misunderstand my post (and from the sound of your other posts, I think you get the thrust of my point),  I am merely pointing out that it is incumbent upon us to go out of our way to turn atmospheric carbon Back into wood.  For example,  I would not support clear cutting forests to produce electricity.  This is a pretty drastic example, but I make it just to be clear that done uncontrollably, even burning wood can have a detrimental effect if we don’t actually recycle that wood.

Thanks for all the detailed information.

Eric
 
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Mike Jay wrote:David B - If 20 lbs of wood = 6-8 kWH, that means I could get 300 kWH from 1000 lbs of wood.  That seems pretty reasonable.



That does sound good, but almost too good. With the average home using 900 KW of electricity per month, and a cord of hardwood being 5200 pounds, you could get 5 weeks of power from a cord of wood. That would be almost all of the height of winter from 2 cords of wood.

That does not seem right to me. If I kept a stove burning for ten weeks straight, I am pretty sure it would consume far more then two cords of wood. That figures out to about (3) arm loads of wood per day.
 
Mike Jay
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Hi Travis!  Based on the videos I've been watching, I think these systems burn through wood a bit slower than a wood stove.  And I think you only operate them for a part of a day.  So if you took two cords of wood and built a fire for 3 hours a day, maybe it would last 10 weeks.  

From GEK Gasifier:  
Relating Gasoline/Diesel to Woodgas to HP to KWe in your vehicle or genset

1 gal of gasoline or diesel will make about 15HP of shaft power for one hour.  If driving a genset, this will produce about 10 kWh of electricity.

1 gal of gasoline or diesel is equivalent to about 20lbs of biomass through a gasifier.

1 ton of biomass to power through a gasifier-engine system is equal to about 100 gal of liquid fuel in a genset, or 1 MWh of electricity.

Thus, the main rule of thumb (equivalencies) to remember:
1 kg of biomass ≅ 2 lbs biomass ≅ 2 m3 woodgas ≅ 1 HP-hour ≅ 0.75 kWh electrical

 
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One good thing about a grid tied system is that you have the ability to transition to extreme efficiency and just might be able to use the same system with storage off grid.

I also like grid zero as a strategy where appropriate.

The desire to produce power independently has its own economics. For some the economics, which would otherwise be considered 'poor', are fine as long as we do it ourselves for our various reasons.

Your electricity usage is very high to start with teg units.... 1-2 kwh/ day as an adjunct to wood heating is a practical device.

You could size your generator as a heat plant and use its waste electricity when there is solar shortfall.

That narrows or possibly leaps the gap in percieved and current economics, but does improve offgrid practical effectiveness and lowers cost of operation. If you recover heat from the fueling facility and generator and use all or most of the heat recovered, and use low impact biomass sources, the economics and reduction of overall environmental impact could be met.

I dislike oil changes as a requirement of operation and noise and vibration are also a nuisance. My economics are different than conventional consumer economics, it "costs" too much.

If you are looking to wood, you likely have a source and as long as you need heat anyway, co-generation is good tact. Solar to reduce fuel consumption, wood for heating and backup offset, grid for storage insertion of excess generation and diversity if desired or a divorce from the grid for the ready to move on adventurer or idealist.

When you are the independent power provider, there is work and you see the cost. When you are the corporate utility, the cost and work is heavily subsidized and cannot be seen as clearly.

Here is a good example. What is the environmental cost of spraying exotic herbacides down all the power line work and keeping the trees off it. For those who do not wish to fund this activity, economics will shift to account in some way for it.

Cities, industrial power, power, energy exchange and support. The grid does some great things and the most streamlined approach is an all electric or mostly electric home with a net zero renewable energy system which would include biofuel, possibly waste products of all kinds as a makup source if you want independence.
 
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1000lbs of wood produces 300kw of heat energy
To converts from heat to mechanical energy = 25% to 50% efficiency, so you will need 2 to 4 times as much wood. so 4,000lbs for 300kw of mechanical energy.
To convert from mechanical energy to electrical energy there is yet again some energy losses, but I am not even going to go into that.
Pretty much you will be going through 1000lbs of wood per week. I hope you will not have to chop any of that wood

It seems that you go thru 10kwhr per day so a 2kw+ generator with 5hrs of run time and the grid as storage will cover your electrical energy production needs.
You will also have 30kwhr of 'waste heat' to heatup your greenhouse, aquaponic system, radiant floor heating and hot water.
But getting 1000lbs of wood delivered every single week is being connected to the grid. But it might be more environmentally friendly?
 
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