Wood gas - for more than just a boiler

[Ugly]

I've been going over some of the build threads for some time concerning wood gas boilers that various members here have put together for themselves. Absolutely fascinating stuff and some excellent workmanship to boot so compliments and true admiration to all the builders.

What led me down the path of wanting to build my own is that wood gassifcation is more flexible than just as a method for heating up water. Has anyone here experimented with drawing off the wood gas from their self manufactured units prior to combustion for other uses? For example, I've stuck together gassifiers and filtered the wood gas to run internal combsution engines (small scale stuff - 8HP - in order to experiement with 12V electricity generation) - it's easy as pie and there's so much literature on it now that it's like following a "For Dummies" yellow book.

I'd like to build a fairly large wood gas unit where I can draw off the wood gas when I'm not using it to heat my water storage system and instead use the gas in a modified genset to co-produce (in grid tie fashion) electricity and offset my major utility expense. I own several rental houses that are on lots adjacent my own and in my utopian wood gas world I'd like to start supplying wood gas based heat and grid tie electricity to each of them. I've decided to start with my own and the one rental physically closest to me.

I've seen the first stabs at some attempts of commercialization of wood gas co generation on a small scale but none of it has made it's way into the mainstream despite various announcements.

I've done grid tie systems from other sources before (solar, wind) and I've had no problems passing my work before the ESA (electrical standards authority here in Ontario) for approval so I'm not the least bit worried about that aspect. Where I lack know how is on the boiler side and there seems to be a ton of that here.

Has anyone envisioned something multi purpose like this ? I'm thinking I could build a wood gas boiler based on some of the member approaches I've seen here with a modified approach to the combustion chamber that lets me (whenever I chose) to suck off the wood gas and use it elewhere.

My primary purpose is heat and DHW in keeping with the forum with a secondary purpose of generating electricity.

I'd be interested in thoughts or imput, areas of concern, aborted approaches, discussion points... whatever.

Regards,
Ugly

 

[Eric Johnson]

In Europe they run cars on the stuff. Here's the "El Kamina" from Sweden.

 

[stee6043]

If ever there was a noble use for an El Camino.....that is just great.....

 

[Wade]

Thats going to be next project, converting an old chevy 1 ton crew to wood gas. Cant afford real gas for something like that. Im also going to try the electrical generating aspect, but i think i will try producing steam turning a turbine. Too much maintenance for a motor to run and the cost of oil changes!! What size of unit are you thinking?

 

[Piker]

there's a cool thing called a sterling engine. Look them up on youtube... they are an external combustion engine that run off a pressure differential between two pistons. They are supposed to be more efficient than an internal combustion engine and can be run by a candle or propane torch... or a wood fired gasifier. Interesting stuff... there are some solar sterling generators about to go into use pretty soon that generate a great deal more energy than any photovoltaic solar panel out there.

Cheers

 

[Fred61]

Stirling is an external combustion engine VS an internal combustion engine. I don't know what their requirements are for cleanliness of the flame but they may help eliminate the need for the filtration that is needed to burn wood gas in an internal combustion engine

(broken link removed to http://utterpower.com/gasification_plant.htm).

 

[Kemer]

I have been thinking about this for awhile now and will be following this closley

 

[peakbagger]

If you search around on the web, there is a US forest Service sponsored study where they built a portable wood gasifer that generated power with a modified capstone microturbine. The intent was to drive it around to small wood working companies and process their waste wood. Dont think it went anywhere.

On the commercial side heres a website to check out. It may come up in German, but there is an option for english

http://www.pyrogas.de/

I talked to them about US sales, but currently they are focused on the EU due to the very hihg power incentives for green power.

Their US rep donated an old prototype to a local technical college. It was barebones but had a 20 KW output and fit on a car trailer.

 

[Ugly]

Thats going to be next project, converting an old chevy 1 ton crew to wood gas. Cant afford real gas for something like that. Im also going to try the electrical generating aspect, but i think i will try producing steam turning a turbine. Too much maintenance for a motor to run and the cost of oil changes!! What size of unit are you thinking?

I admire and love steam equipment, but I do it from a distance. I'm not willing to tackle it personally, I'm way too chicken of having it on the residential property. Maybe in the big commerical buildings at some future date but it's not on my own plate.

The average (over 24hrs) KW/h draw of the two houses combined with electrically heated water (I'll do DHW from the boiler as well so further savings that are not included in this calculation) is about 2 .... so a daily need of 48KW/h , if I generate 8KW for 6 hours a day equals a total offset of the electricity billa. This is a grid tie system, not replacement generation. Effectively, the grid is the storage medium for electrical production. The magic number to stay under for ease of a grid tie hook up is 10KW... anything over that requires licensing and special meters in this locale (additional costs).

Assuming a horsepower reduction on woodgas of 50% and a need of 2 HP per KW of generator I'd need to run an engine rated at ~35 HP for six hours a day (2190hrs per year). That's the equivelant of driving 300 miles a day at 50mph on an engine (more really, an engine isn't under constant load when driving). That's 110K miles a year equivelant(rounding up). No big deal. A minor rebuild of a small engine once a year is about six hours for me. At the price point we're talking about I'd have a spare on hand. Oil changes can literally be automated in stationary applications and we've allways consumed our waste oil in our diesel equipment (not our trucks however). There are various engines rated for 2500-5000 hours between maintenance cycles.

The thing I keep coming back to is how to balance out the needs of a boiler with storage that has a high BTU/hr need vs a small genset with a low BTU/hr need all in one device.... for thinking purposes, my engine needs 2545 BTU/hr per HP so sixteen HP = ~41,000 BTU/hr.... far less than two homes and DHW on those minus fourty days...

I just think I can build something that does both.... maybe I'm wrong .

 

[Ugly]

Stirling is an external combustion engine VS an internal combustion engine. I don't know what their requirements are for cleanliness of the flame but they may help eliminate the need for the filtration that is needed to burn wood gas in an internal combustion engine

(broken link removed to http://utterpower.com/gasification_plant.htm).

I've extensively reseached stirlings, microturbines and other heat to mechanical transfer systems. The problems are high costs and limited availability. The same with steam. Buying a 12 HP steam engine sounds great.... until you go write the check and realize I can rebuild a Kholer gas engine once a year for a century for the same money. Ultimately where all these systems shine is cogeneration in the greater than 50KW space. I'm working in the less than 10KW space.... a huge differnce. To boot I don't require paperwork nor inspections to run a gas engine. I'm all about KISS (keep it simple stupid) because I realize how many stupid things I've personally done over the years in an attempt to make life easier.

As an IT Exec I've often stared at my business counterparts and pointed out that the million dollars worth of software changes they want can be solved by equipping each emplyee with a notepad and pencil. I even offered to buy the erasers out of my own budget....

 

[Duetech]

I have seen a you tube segment where the priority was electrical and the by product was hot water from a diesel engine that worked on used veggie oil. I think a small gasifier supplemented with a motorized wood gas generator could be an "off the grid" reality. With the right battery/inverter/banking set up the motor could supplement the water heating and build the banks to run the home and gasifier until the next generation is needed.
Stirlings are nice but currently are cost prohibitive but the bigger units would work well vie the heat output of a gasifier.

The EKO 60's and 80's have twin nozzles in their secondary combustion chamber and theoretically one nozzle could be converted and diverted to function with out any secondary air so all the gas from that nozzle would be accessible for other uses and it wouldn't hurt to look at one of them for concept input. It would be nice to have selectivity in nozzle usage, turn it on turn it off..secondary air for heat no secondary air for electrical generation, but nozzle isolation would be a must though it doesn't seem it would be much of an obstacle. It might be harder to tap the wood gas if you were also trying to use it for heat generation but a deeper nozzle with a diverter in it might work. Coordinating one nozzle to do one function then switched to the other shouldn't be that difficult it would just revolve around secondary air control. Sounds like a fun challenge

 

[Ugly]

I have seen a you tube segment where the priority was electrical and the by product was hot water from a diesel engine that worked on used veggie oil. I think a small gasifier supplemented with a motorized wood gas generator could be an "off the grid" reality. With the right battery/inverter/banking set up the motor could supplement the water heating and build the banks to run the home and gasifier until the next generation is needed.
Stirlings are nice but currently are cost prohibitive but the bigger units would work well vie the heat output of a gasifier.

The EKO 60's and 80's have twin nozzles in their secondary combustion chamber and theoretically one nozzle could be converted and diverted to function with out any secondary air so all the gas from that nozzle would be accessible for other uses and it wouldn't hurt to look at one of them for concept input. It would be nice to have selectivity in nozzle usage, turn it on turn it off..secondary air for heat no secondary air for electrical generation, but nozzle isolation would be a must though it doesn't seem it would be much of an obstacle. It might be harder to tap the wood gas if you were also trying to use it for heat generation but a deeper nozzle with a diverter in it might work. Coordinating one nozzle to do one function then switched to the other shouldn't be that difficult it would just revolve around secondary air control. Sounds like a fun challenge

I thought of that approach as well... A stationary diesel on woodgas (works, seen it in person) in the 200HP range would put out about 80,000 BTU of recoverable heat without getting fancy custom made exhaust manifold water jackets. But in this approach, electricity is the goal and heat the by product. It would be big enough to drive the 50KW gen heads even on wood gas, slightly more with gear reduction. But then I decided that even on these lots (smallest is two acres) I'd have a heck of a time keeping that sucker quiet. vibration and exhaust muffling a small engine is pretty easy, but I've never once seen a stationary diesel that size that didn't sound like two skeletons having carnal relations on a tin roof.

What you're saying about the EKO's makes a lot of sense. In fact, it's really tweaked my thoughts and was the kind of random hit I was looking for. What if I designed a simple internal nozzle/valve assembly capable of diverting a third of the gas production elswhere, the gas wouldn't go anywhere dangerous until there was a vacuum drawing on the diverted flow.... Probably a workable idea imo... good thought and well worth working out the math on. I could always close off all secondary air if I didn't want heat but just generation....I think you just decided my first trial approach. Thanks. My only thought is I'd have tar and resin build up in those areas since the gas would rapidly cool on the way out to the first filter.. but that's not insumountable with a little backyard engineering.

I'm not wood crazy per se, but I figure I should use what I have in the biomass sense. If I was gowing oilseed, I'd buy an oil press and burn it raw wihout even bothering transitioning it to bio diesel. But I have wood. A lot of wood. Yeah I could use the cellulose and make methanol... but why process the heck out of any bio mass for a stationary application? wood gas works fine...

 

[Fred61]

The EKO 60's and 80's have twin nozzles in their secondary combustion chamber and theoretically one nozzle could be converted and diverted to function with out any secondary air so all the gas from that nozzle would be accessible for other uses and it wouldn't hurt to look at one of them for concept input. It would be nice to have selectivity in nozzle usage, turn it on turn it off..secondary air for heat no secondary air for electrical generation, but nozzle isolation would be a must though it doesn't seem it would be much of an obstacle. It might be harder to tap the wood gas if you were also trying to use it for heat generation but a deeper nozzle with a diverter in it might work. Coordinating one nozzle to do one function then switched to the other shouldn't be that difficult it would just revolve around secondary air control. Sounds like a fun challenge

Yea but isn't what's coming out of the nozzle not gas but burning gas. I would think that you need to capture it before that point. I don't believe the secondary air is what ignites ths gas, it just changes the air/fuel ratio. The Wood Gun had no secondary air and burned well. When it shut down it was so tight that the top chamber was like one big gas tank. Before opening the door the chamber needed to be purged by a switch that operated the fan which was on the output side. That unburned gas in the upper chamber is the stuff you want.

 

[daleeper]

I'd have a heck of a time keeping that sucker quiet. vibration and exhaust muffling a small engine is pretty easy, but I've never once seen a stationary diesel that size that didn't sound like two skeletons having carnal relations on a tin roof.

I'm not wood crazy per se, but I figure I should use what I have in the biomass sense. If I was gowing oilseed, I'd buy an oil press and burn it raw wihout even bothering transitioning it to bio diesel. But I have wood. A lot of wood. Yeah I could use the cellulose and make methanol... but why process the heck out of any bio mass for a stationary application? wood gas works fine...

Ugly, I will never be able to hear a diesel generator run now without having an awful visual in my head.

I like your idea of utilizing what you have rather than trying to convert it to something else, but sometimes the market can be more efficient than physical conversion. I would think your heating needs could be met real easy with wood. Woodgas in and of itself looks more like wishful thinking by the time it is made and equipment adapted, although in the stationary application you are suggesting might just work where you can utilize the heat generated in the gasification process for dhw and space heat. It would look to me like you would keep the gasification process for electricity generation as the primary system, capturing the heat for dhw and space heat, and have a wood boiler system to make up the heat needs difference. This would allow you to develop the most efficient system for each purpose rather than a one size fits all system. Water heat storage will be key in this system.

Keep us posted on your thoughts.

 

[Kemer]

Hey Ugly

I found this site today and it might be interesting to you.(broken link removed to http://victorygasworks.ning.com/.Its) a online cumunity for gsaification.

 

[Duetech]

Hi Ugly,


My reference to the diesel generator was mostly for reference purposes as I was really interested in your wood gas approach and I don't like the smell of diesel. The hot water by-product they had was just a bonus and the idea was offered to allow consideration for perhaps building a smaller boiler supplemented by the engine hot water output. Smaller automobile gasoline engines converted to wood gas are probably a better choice, via availability, and many smaller gas engines are hitting 200,000+ miles and that equates to 3300+ hours of operation. Exhaust systems that are quiet are available via retail parts out lets. Diesels always seem to chug and clatter and I don't mind piece and quiet since I live in the country.
Opening the convertible gasifier from the side might be another approach. I.e. dual chambers, dual exhaust would complicate matters from an "end" enclosure opening. A solid steel separator insulated with refractory to divide the two chambers and yet allow ease of access to either secondary chamber. Possibly only one loading door. Both nozzles could be selective or one dedicated heat and the other selective on or off but with the on/off flexibility is also the flexibility in the percentage of aperture you want where you could tap 100% of the gas from one side but just not running that side at maximum capacity. Some of the owners of the twin nozzle EKO's have shut one nozzle off completely and still have the btu output they need but the fire/coals extend across both nozzles. To extend burn time on my EKO40 I have considered reducing (i.e. dividing) the length size of the nozzle by placing a block between the secondary air out lets to force a more virulent mix of the primary and secondary gasses so even a conventional single nozzle could be used for dual purposes if reasonably isolated. Keep us posted!

 

[mtnmizer]

The local Forest Service had a biomas seminar locally last month, and it
was reportedly well attended. There are a few school systems burning wood in this area.
Large scale gasifcation boilers.

Synthetic Liquid fuel can be made from wood using the
Fischer-Tropsch pyrolysis process. The energy
content of a ton of dry wood is around 17 million BTU’S.
I believe the wood is heated and the gases are catalysed with
natural gas to make the liquid.

The Swedes are said to be within 10 years of complete energy independence
with wood including synthetic liquid fuel...no carbon foot print to speak of..

I see mountains sides of brown dead trees from where I am sitting right
now...unbelievable amounts of fuel---- millions of acres of dead and dying
trees..it goes for miles in every direction.. Dan

 

[Ugly]

Ugly, I will never be able to hear a diesel generator run now without having an awful visual in my head. (snip)

(snip) This would allow you to develop the most efficient system for each purpose rather than a one size fits all system. Water heat storage will be key in this system.

Keep us posted on your thoughts.

I'm really sorry about that visual, I should think things through a little before I click post....

I agree in some sense that two specialized units may beat an all in one type of approach. I've had very good results with a simple gasifier running internal combustion engines. I consciously decided to at least explore this path with the hot water for heat and DHW as the central purpose and any other wood gas use as secondary since I believe the ability to make things real on a broader scale is to simplify as much as possible in order to gain adoption. If my wife can stick a few sticks of wood in what she perceives as an outdoor boiler no matter what else it runs on the side, I may consider that I've achieved my goal. If I can divert wood gas from/to other purposes sucessfully after achieving my main goal of heat of and hot water, I'm heading down that path. Once you have quality wood gas, you have heat, hot water, mechanical interfaces and refrigeration all in one point. I've built all these things at one time or another, now I'm just hoping to tie them together into one neat bundle. I may end up reverting to a clean wood gas (filtered) boiler type system based on low pressure nozzles (like methane burners that already exist). I have two months to consider and then I'm building something. By that I mean I'm putting down the pad and putting up the building while I also start on building the design I settle on.

Like I said I lack wood gas boiler knowledge and the folks here are doling it out in bucket fulls.... for example, I already changed the building size and doubled the water storage potential inside the shed. Because while mathematically I might have been able to get by with what I was planning, the experience that people here have shared shows me I didn't always take enough factors into consideration. I don't need to be hit on the head twice to understand how limited a single brain can be.

Hey Ugly

I found this site today and it might be interesting to you.(broken link removed to http://victorygasworks.ning.com/.Its) a online cumunity for gsaification.

Thanks Kemer, I like reading that site.

(snip)smaller gas engines are hitting 200,000 (snip)

(snip)Opening the convertible gasifier from the side might be another approach. I.e. dual chambers, dual exhaust would complicate matters from an “end” enclosure opening. A solid steel separator insulated with refractory to divide the two chambers and yet allow ease of access to either secondary chamber (snip)

Thanks Cave for the input once more. I decided a standard air cooled twin cylinder gas engine is what I'm using because of my low HP needs and the fact we use them for other things around here. I've literally rebuilt a dozen of them and they fairly easily run dual fuel (wood gas, gasoline) modes without me programming engine management computers. My (older) jeep for example will run any mix of gas and ethanol, but it was hell to program and I had to custom modify several sensors. (Now of course you can buy a car or truck that runs these fuels in any ratio direct from the factory.) Something about the simplicity of flipping a butterfly valve that switches to wood gas and advances the timing make me think my great grandfather would approve.

I started drawing out different chamber designs based on photos posted by members here from their builds and all the while considering the fact I want to draw off a fraction of the gas from pyrolysis before combustion takes place. When I think I have something reasonably rational I'll post it for a critique. Keep the thoughts coming.

(snip) Synthetic Liquid fuel can be made from wood using the
Fischer-Tropsch pyrolysis process.

(snip)I see mountains sides of brown dead trees (snip)

Yeah that processing is fascinating stuff, I've been keeping an eye on published research in this field. My genuine concern however is that while ~technically~ the carbon footprint is low, the calcium shock to the lakes is starting to take hold because of the removal of wood from the forests without letting it decompose. Basically we're over cutting and simply planting another tree wont replace that calcium loss. In terms of biomass use, managed grass crops may be the most sustainable method out there. A minor ecological advantage of an approach like a boiler attached to your managed private forest is that you do have the option of mixing the mineral residue post combustion back to the location you got it from and carefully managing your "take" from the forest. It's all a balancing act, I'm not going to pretend I know the answers but so far solar and wind are having the lowest environmental impact. Neither are decent small scale options (imo) where I live, low wind speeds, lousy winter sun.

Regards,
Ugly

 

[renewablejohn]

To get an understanding of the gasification system GEK do an excellent prototype kit which allows you to practically explore the different gasification techniques in a well put together package.


(broken link removed to http://www.instructables.com/id/Building_the_GEK_Gasifier_in_seven_parts/)

(broken link removed to http://www.allpowerlabs.org/gasification/gek/index.html)

 

[Ugly]

That's a great looking kit, I've already built a NEMA and then followed it up with a Imbert design with a monorator for higher moisture products... both worked . I'm fairly confident I can do a(another) straight gassifier anytime. I'm less confident I can do a boiler/gassifier all in one. There are a few good designs around for gassifiers on the small scale including at the site link someone above posted for victory gasworks...

In all likelyhood the day I finish this project, a dealer will open down the street selling exactly what I built in one easy to buy package that doesn't require me think and will have cool add on features like high velocity ceramic turbines....sigh...

 

[Duetech]

Ugly,
I really don't know how far separated the exit of the primary chamber and the actual entry of the secondary chamber can be and still get ignition but a simple nozzle located "slide out" scoop collector might work if you were to build the secondary air outlets in a downward flow design. That way you could tap the wood gas prior to exposure to the secondary air.??

 

[sweetheat]

seems I remember a few threads back people talking about listeriods , small diesel motors capable of running off of wood gas cogen electrical power at the same time. listeroid diesel motors , yuotube showed some different applications for wood gas. or try www.freewatt.com, its possible to do a diy cogen with woodgas. I beleive they call it product, sweehheat

 

[Mushroom Man]

Cogeneration is a terrific idea. Having a large back-up power source is attractive in case of an outage. Electricity via gasification does not seem at first blush to be overly complicated. It seems to be mostly about cooling and filtering the gas before it gets to the the intake manifold. Then keeping up a frequent maintenance schedule.

However there are some questions that come to mind; like:
1. How much pyrolized woodgas can one divert to electrical production without materially impacting the efficiency of heating. Perhaps by using really small diameter splits you could maximize gas production.
2. Where do you drill in to connect the gas outlet tube without breaching the water jacket? These gasifiers are expensive and you would not want to wreck one with ill-conceived experimentation. It would be good if we could back out of the experiment gracefully if it proved too cumbersome or it didn't work as expected.

 

[oldmilwaukee]

What an excellent thread - I was just pondering this last week as I was plumbing my Tarm 40 (after all, the "40" stands for 40 Kilowatts!) here in my off-grid house and the 48 volt lead acid batteries were down to 46 volts after a solid week of no sun. Couldn't I buy an extra door for the Tarm, and tap it to pull off wood gas for a small gas motor? All I need is about 1.5Kw - or two horsepower, so start with an 4 hp motor and hope for 50% system efficiency? I could even use a DC genny so long as it produces 48 volts or better, since my house is already setup for that. Ugly, based on your previous tinkering, do you _really_ think it would be feasible to draw combustible gas from an existing wood (gasification) boiler like the Tarm?

WTB: extra door for a Tarm Solo 40.

 

[Ugly]

Ugly,
I really don't know how far separated the exit of the primary chamber and the actual entry of the secondary chamber can be and still get ignition but a simple nozzle located "slide out" scoop collector might work if you were to build the secondary air outlets in a downward flow design. That way you could tap the wood gas prior to exposure to the secondary air.??

That's one of the places I was heading with my all-at-one time approach. Basically there's three ways to do this entire project in my mind. The first is a one-at-a-time approach where I'm using the entire entire supply of wood gas (AFTER I fire my storage system) by diverting it from the secondary chamber entirely when I want generation.
The second approach is the one I'd like to come to grips with if I can - ie get all the things I want running including the secondary burn chamber all-at-one-time by simply diverting a fraction of unburnt gas (what I'm angling at in this thread and you're being most helpful in thinking about).
The final approach is actually the easiest and may be the only real way I'll get this done this year and that is to build a single large gassifier off a modified Imbert and then direct the wood gas through filtration to a heater (burner), a motor and a heat exchanger for A/C respectively. Wouldn't it be great to just buy an EKO with a big valve on the side that says "Suck out wood gas here"

seems I remember a few threads back people talking about listeriods , small diesel motors capable of running off of wood gas cogen electrical power at the same time. listeroid diesel motors , yuotube showed some different applications for wood gas. or try http://www.freewatt.com, its possible to do a diy cogen with woodgas. I beleive they call it product, sweehheat

I've had and subsequently sold both an Indian made Listeroid and a Chinese Changfa stationary motor, I literally got so &*&^^%%$ off at parts and support I couldn't stand either. When I phone either a Kohler dealer or Kohler proper in the USA I get real support by real (is okay to say English speaking?) folks who actually care if my elevator motor works - some of those engines are super tough. We have one 18hp with ~12000 hrs on it and I've only changed the oil and plugs and it's still fine. Sorry to rant as I don't want to discourage anyone from checking them out because they are a lot of fun (I admit I had a blast with them and don't regret setting them up - biodiesel and straight veg oil in my case), I've just dismissed them as serious products for my needs.

Cogeneration is a terrific idea. Having a large back-up power source is attractive in case of an outage. Electricity via gasification does not seem at first blush to be overly complicated. It seems to be mostly about cooling and filtering the gas before it gets to the the intake manifold. Then keeping up a frequent maintenance schedule.

However there are some questions that come to mind; like:
1. How much pyrolized woodgas can one divert to electrical production without materially impacting the efficiency of heating. Perhaps by using really small diameter splits you could maximize gas production.
2. Where do you drill in to connect the gas outlet tube without breaching the water jacket? These gasifiers are expensive and you would not want to wreck one with ill-conceived experimentation. It would be good if we could back out of the experiment gracefully if it proved too cumbersome or it didn’t work as expected.

Mushroom, I'm planning on building from scratch, I appreciate the notes of caution. I checked out the designs of the current gassifiers that are sold and concluded that modifying an existing unit may be too problematic. Not because I'm afraid of running one "out of spec" or ruining it, just that I don't want to inherit any units existing flaws, I'd rather deal with my flaws of which I'm sure there will be plenty. Did I say plenty? I need to start on my own and build in the ability/flexibility to change it until I get what I want working. Off the shelf units are not really "mod friendly" as you've pointed out. I have the equipment required to deal with all metals including experience with stainless. My neighbour has a kiln so I'll cast my own refractory next door.

What an excellent thread - I was just pondering this last week as I was plumbing my Tarm 40 (after all, the “40” stands for 40 Kilowatts!) here in my off-grid house and the 48 volt lead acid batteries were down to 46 volts after a solid week of no sun. Couldn’t I buy an extra door for the Tarm, and tap it to pull off wood gas for a small gas motor? All I need is about 1.5Kw - or two horsepower, so start with an 4 hp motor and hope for 50% system efficiency? I could even use a DC genny so long as it produces 48 volts or better, since my house is already setup for that. Ugly, based on your previous tinkering, do you _really_ think it would be feasible to draw combustible gas from an existing wood (gasification) boiler like the Tarm?
WTB: extra door for a Tarm Solo 40

I'll be honest and tell you.... I don't know. All I've seen are drawings/pictures and rough schems for the Tarm. If I had a nice wood gas boiler like that with a warranty and support I wouldn't touch it. Well maybe the odd lingering stroke...lol... Seriously, I don't think any of the units I've reviewed lend themselves to modification as I said above, I think they work best doing what they do - heating water. For free, you can build a nice Imbert gassifer from designs all over the net with whatever scrap you can find to put together and drive an almost free to get lawnmower engine using charcoal/woodchips/dry sticks etc... Because you already owna nd operate a wood gas unit, your learning curve is low low low....

Regards,
Ugly