Update: Wood Gas Power

MOTHER EARTH NEWS' researchers have made a few improvements to their wood gas power system. Here is an update.


| September/October 1981



071 wood gas power 4 stationary model2

The redesigned stationary components of the wood gas power system take up a minimum of floor space, and thus leave plenty of sheltered area for scrap lumber storage or for wood heating and drying equipment.


PHOTO: MOTHER EARTH NEWS STAFF

In "Backyard Wood Powered Generator" we described our 10-kilowatt wood gas power plant that uses scrap wood as the fuel for its internal combustion generator. At that time, we promised to update the article as we accumulated more information from the series of controlled—as well as "real world"—tests that followed the completion of the experimental equipment.

As expected, the two-month "trial by fire" brought out both the good and bad features of our cogeneration system, and also gave us an opportunity to try several new concepts that, it now appears, might [1] increase the wood gasifier's efficiency, [2] make it more practical to use, and [3] reduce the maintenance required by the setup.

A Study in Smoke

In a nutshell, our extended testing reinforced what we had already learned about wood gas, but also caused us to examine some of the quirks of the gasification process. For example, after several attempts to come up with an inexpensive and durable filter medium (some that we tested weren't particularly effective in cleaning the smoke, and others tended to clog too easily), we finally took a hard look at the gasifier itself, hoping we might be able to devise modifications that would allow it to burn—rather than pass along—some of the tar and ash that, in the early models, had collected in the condenser and filter chambers.

We also found that the gasification unit on our stationary generator sometimes "slowed down" and couldn't meet the engine's fuel demands, simply as a result of the wood supply's forming a "bridge" over the hearth and blocking the passage of fresh chunks into the combustion zone. Such a situation had rarely occurred in the mobile gasifier fueling our pickup truck (see "Wood Gas Truck: Road Power From Wood Gasification"), because that unit was subject to constant movement.

In addition, we discovered that the excessive summer humidity in our area, coupled with the high moisture content of some types of wood, occasionally resulted in the production of an unusually large amount of steam inside the gas generator. As a result, the temperatures within the hearth weren't always as great as they should've been, and that relative coolness lowered the quality of the gaseous fuel.

So, rather than look for an especially dry fuel to suit the machine, we decided to try to adapt the gasifier to the large supply of moist wood we'd already gathered. We aimed to make the "burn" more efficient by redesigning the air inlet system to include a preheating section that tempers the atmosphere before it enters the combustion zone. The new manifold is made up of a series of sixteen 3/8" black iron pipes, which are evenly spaced around the hearth area and extend from the top of the gasifying chamber (where they're connected, through a distribution ring, to the inlet check valve) to a point about four inches above the restriction at the base of the hearth. This setup allows incoming fresh air to pick up waste heat from the chamber itself, and especially from the area surrounding the combustion zone through which the hot fuel gases pass on their way to the condenser and filter.

stephen wylie
4/5/2009 6:03:16 PM

Stephen Ireland . i have just built a wood chip burner . what my problem is i am getting a lot of black oil type like heavy old oil . what is this an is this of any use . or how best to handle this .


david ponsonby
2/4/2008 7:56:09 PM

I have to say as an old retired engineer, what a pleasure it was to read an article such as I did just then, after I finish re-building 3 water pumping wind mills over here in Tasmania, Aus, I hope to restore an old war time Charcoal using gas producer, I thank you for putting out a very interesting an informative article... Thanks, David Ponsonby...


gary_42
12/27/2007 4:00:24 PM

WHEN ME NEWS WAS BUILDING THEIR FIRSE LARGE STATIONARY SYSTEM WITH THE TWO LARGE ROASTERS , i ALSO BUILT A SYSTEM. mY PRESENT SYSTEM USES A SIMPLE SPECTRIOMITER TI SENSE WATER VAPOR AND AN OSMOSIS SENSOR TO SENSE HYDROGEN. tHE SENSORS ARE HOOKES TO A SIMPLE SENSOR DRIVER FOARD THAT OPERATES A EREMOTE CONTROL SERVO. tHE SERVO CONTROLS THE AIR MIXTRUE. tHE ELECTRONIC SENSOR KEEPS THE CARB RUNING WELL. When the roaster runs out of fues, the carb switshes to propane and the system keeps runing. The mas oxygen seneor actually operates on propane almost as well as the H from the wood gas.






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