Build your own wood gas generator

[papaof2]

I've mentioned using a wood gas generator when gasoline wasn't available in several stories. Here are a couple of videos on relatively simple builds. The poster demonstrates them by running an AC generator with the wood gas produced. He uses wood pellets in one generator (as in pellet stoves - a source of very dry wood) but also mentions using dry wood and then filling the gaps in the cooker with wood pellets to have a tighter pack of the "fuel".

wood gas generator build
www.youtube.com/watch?v=AyTqo4mCUUY

wood gas generator build - no welding
www.youtube.com/watch?v=Bvl5XxVVjDM

The first one is noted as big enough for a 20-25HP engine. The second only needs drill, angle grinder and torch (for soldering) to build. Some parts are available on Craig's List and/or a junkyard (small helium tanks).

I haven't built one yet.

[cutter]

I don't know if they are still there, but at one time FEMA published plans for a gasifier on its website.

[papaof2]

I have several references that I downloaded from various sites (usually saved with some note about the site). I'm not certain, but what I saw on FEMA may have been a copy of a document written during WWII - wood was more readily available than gasoline then.

I thought the "no welding" version was possibly the most useful to the general population of DIYers.

I have a basic Harbor Freight wire welder (about $100 on sale and I've even done some small but useful work with it, including extending a shepherd's crook hanger for bird feeders to get them out of the squirrels' reach) but a lot of people don't have access to any type of welding equipment. That extended crook is still in place out back some 15 years later so I'll guess my welding is OK ;-)

[cutter]

I don't remember where I saw it, but I also saw a downdraft design that could be opened and refueled while in operation.

[papaof2]

There are basically two designs. One using a closed cooker to "boil off" the volatile parts and the other using oxygen-starved partial combustion with the fire being in the cooker itself. Not having the test equipment to determine which would be most efficient with a given type of wood, I chose the external heat version for the story because it will work with bigger wood pieces than the in-the-cooker fire which seems to be aimed at sawdust or woodchips as fuel. The second type can be refilled while in use, but the mixture would probably go lean at the engine with an unrestricted air supply at the cooker.

Just the opinion of a shade tree engineer ;-)

[cutter]

Yeah, as I remember the article, gassifiers were used heavily in WWII England. As I recall, those units were picky eaters. I think I read something about an entire industry springing up to manufacture wood fuel in specific sizes and shapes, so those units would function reliably.

[papaof2]

In the video links, the guy mentions using stove pellets because they are a well dried wood - they also can "fill" around other wood pieces for the best percantage fill. Much of the "smoke" in the wood gas generator output when it is running "open" appears to be water vapor, so a drier wood should produce more useful combustible gases in its output. Some water vapor is unavoidable as burning hydrogen + oxygen always produces water ;-)

I'm thinking it would be possible to make an "efficient" wood gas gen if you monitored the temperature inside the cooker and the temperature, CO and oxygen content (maybe also the water vapor %?) of the gas exiting the cooker - beginning to sound like the ECU on a modern car, isn't it? However, all those sensors are readily available and there's a wide range of microprocessors that could do the sensor reading and processing to control various valves related to keeping optimum temperature and air flow for producing wood gas.

Since a given wood gas gen would typically be fueling one specific engine, you could also include the engine RPM as part of the sensing and processing. Good software could detect the engine lugging and needing more fuel or overspeeding and needing less fuel and make appropriate changes in the valve(s) controlling the output of the wood gas gen.

Not the first efficient wood-fueled adaptation in my writings. See the "smart" thermostat in chapter 147 of "Jack's War, Part 2". Just don't get hooked on the rest of the story - it's 300K+ words.