Wood Gas Generator For Cars or Electricity Generation

A wonderful low-tech means of providing power off grid is a wood gas generator – or gasifier.  You can use wood gas for cars, electricity generation and heating.

Wood gas is a mixture of gases obtained from the “burning” of wood in an oxygen-starved environment. It all sounds a bit “dirty” but emissions are quite low from well built systems. Done right, gasification of wood fuel IS sustainable!

The best use for wood gas is in combined heat and power systems – coupling micro wood power electricity generation with heat capture – the result is very high fuel efficiency. Like conventional vehicles, using wood gas for cars loses much of the energy as heat out of the engine. Still, it is a handy transitional technology for transportation. Power from wood gas is ideal for self-sufficient living, on a bush block, where timber can be sustainably grown and harvested. And yes, if you’re handy with basic metalworking you can easily build your own gas generator (see below).

How Wood Gas Generators Work

Gasifier designs vary but below is a schematic for an inverted downdraft system – the most suitable setup for internal combustion engines.

inverted downdraft gasifier schematicWood blocks or chips are loaded into the top. Air is fed into the closed system via a manifold with 3 or more nozzles mounted radially about the oxidation zone.

As the wood fuel blocks and chips progress downward toward the oxidation zone (fire), they are first dried then pyrolysed and converted to charcoal by the radiant and rising heat of partial combustion.

Water moisture, tars and volatiles are driven off and drawn downward by the “suction” from an internal combustion engine or electric blower. Temperatures of 800 – 1100 degrees C are achieved in the oxidation zone. Below the oxidation zone is the reduction zone - a hot bed of charcoal becoming gradually cooler toward the bottom.

This “partial” combustion and complex reaction creates producer gas; a mixture of hydrogen, carbon monoxide and small amounts of methane. The gas mixture is suitable for burning immediately or cleaning and feeding to an internal combustion engine.

Build Your Own Wood Gas Generator

Wood gas generators are extremely low-tech, appropriate technology that can be built by a competent metalworker for as little as $200. Much of the material can be sourced from junkyards as scrap metal. Despite the fact that over a million wood gas powered cars were used across Europe and Australia during the fuel shortages of World War 2, finding EXACT plans to follow is now difficult. People who build their own gas generators tend to use guidelines that can be found on the internet and modify ideas and sizes to suit the scrap metal tanks and gas cylinders available

Here are some sources of information…

Wood Gas Generator Plans from Mother Earth News
The only comprehensive plans we could find (at reasonable cost), shows how to build your own wood gas generator from recycled water heaters. Plans include materials list, step-by-step instructions and black-and-white photos. Advanced mechanical and metalworking skills recommended. See http://www.motherearthnews.com/shopping/detail.aspx?itemnumber=762

Yahoo! Groups - Wood Gas
Free subscription to this group of over 3000 enthusiasts is very worthwhile. It will put you in touch with many people actually building wood gas generators for cars and micro cogeneration systems.
http://groups.yahoo.com/group/WoodGas/

Wood Gas as Engine Fuel
This extensive document produced by the FAO (Food and Agriculture Organization) Forestry Department discusses the background, theory of gasification and gasifier types. With a focus on inverted downdraft gasifier design, particularly suited to internal combustion engines, it contains much of theoretical detail required to build an efficient wood gas generator.
http://www.fao.org/docrep/t0512e/T0512e00.htm