Backyard Wood Powered Generator

Free electricity? Free heat? Yep, you can have both with a wood powered generator.

| July/August 1981

Sometimes it's difficult to decide just which is a bigger financial burden: the expense of operating a motor vehicle or that of providing a household with power and heat. So, in an effort to ease the strain in both cases, the folks out at MOTHER EARTH NEWS' research center have spent the past several months designing and testing various systems that use inexpensive—or sometimes even free —wood scraps as a replacement for costly fossil fuels.

In "Wood Gas Truck: Road Power From Wood Gasification," we detailed how to make a wood gasifier small enough to power a car or pickup for about $125 in parts and materials. In that report, we also mentioned that we were in the process of adapting the technology to a stationary generating system. Well, just days before the deadline for this issue, our research crew put the finishing touches on that wood powered generator. And—although we haven't yet had a chance to devote enough working hours to the unit to convince us that the design is as good as we can make it—our initial testing seems to indicate that it'll perform as well as any conventionally fueled standby generator of similar output in addition to providing a sufficient amount of hot water to actually heat a home!

From the outset of this project, we not only wanted to build a working demonstration piece that would allow visitors to our Eco-Village to see—and, in some instances, later duplicate—what we had done, but also wished to set up an honest-to-goodness functional AC power source that would fully supply our maintenance shop, thereby reducing our dependence on the local utility's services.

As it turned out, we were able to accomplish our goals ... and to do so using inexpensive scrap or junkyard parts, which we mated to the 10-kilowatt, 120/ 240-volt alternator originally purchased for a hydroelectric installation. (See "Mother's Hydroelectric Plant." Since the head and flow at our water-power site offer a potential of little more than 2 KW, we decided to replace the oversized AC generator there with a more suitable 2.5-KW alternator, thus making the larger unit available for use with the wood-gas plant.)

Gasifiers, Condensers, and Filters

The electricity-from-scrap system is surprisingly straightforward. To start with, rather than using just one gasifier, we chose to utilize two—plumbed independently of each other—to permit the engine to operate without interruption. (As an added benefit, this setup also allows us to clean or service one chamber while the other keeps the plant running.) And because, in a stationary mode, the wood-filled tanks aren't subject to the vibration and movement they would encounter if mounted on a vehicle, we've gone ahead and installed an electromechanical grate shaker (made from an automobile wiper motor) in each firebox, to insure that fuel residue doesn't accumulate and stop the flow of the combustible "smoke" fuel produced by the gasifiers.

When the vapor leaves the "in use" unit, it goes directly into a ten-foot-long, slightly inclined horizontal condenser which [1] removes a good deal of unburnable water vapor and some residue, and [2] cools and thus densifies the fuel charge, making it more potent. This "chilling chamber" is nothing more than a series of tubes, enclosed—all but their ends—in a conduit "jacket" that's filled with water and plumbed into the cooling system of the engine.

After passing through the condenser, the concentrated gases travel into a vertical filter, which snags any remaining particulate matter in layers of woven filament and prevents potential flamebacks from reaching the rest of the system by means of perforated flash traps at both its inlet and outlet. Again, both the condenser and the filter were fabricated in duplicate so that there would be two separate and complete fuel-producing systems, each valved to a common feed pipe leading directly to the engine.

12/30/2014 2:31:09 AM

Hi there , Looks like a very interesting project that could also work here in Europe/ The Netherlands. Could you please provide me with more background and update information on this project? Is it possible to receive some older magazines in one shipment? Thanks in advance. ronald

5/25/2014 9:04:32 AM

We just released an engine that runs directly off of heat - Heat the head of the engine to 400 F and it runs - You can use any type of fuel, wood, solar, propane, natural gas, or waste heat. Check us out at

9/9/2008 2:09:21 PM

Do you have any updates to this experiment?

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