Getting off-grid: developing a wood gasifier in the woods in darkest Buckinghamshire

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Posted Feb 6 2015 by Ed Morriss of Drawfire
air-jets-and-hourglass-assembled1 Combustion chamber showing air jets and insulation.

As industrial society continues on its capitalist and consumer-led treadmill, its detrimental effect on ecology and the environment are accelerating whilst the returns diminish. As a counter to this, a growing number of people across the world are building communities and working to become independent and to consolidate their own renewable power, water and food supplies. The depth of creativity, endeavour and skill in all of these areas is a constant source of inspiration.

main parts

Main parts ready for assembly.

For our energy needs we are continually developing an off grid power supply to serve lights, computers, central heating pumps, refrigeration and other occasional large and small loads.

hour-glass-inside-reduction-vessel

Underside of combustion (pyrolysis) chamber showing coiled air inlet pipes that pre-heat the air entering the jets above.

We established a 5kW solar power system in 2013 and then a year later a 1kW (max) wind turbine was added to provide extra power during strings of gloomy winter days, both feeding into a 20kWh battery bank. Further to our initial aims we decided that a workshop facility would be an incredibly useful addition and now run workshop equipment including a MIG welder, plasma cutter, compressor etc. from the same system with very occasional use of fossil fuel run generators.

main-unit

Inside completed main unit.

However in order to cut out dependency on fossil fuels altogether and to utilise the immediate resource of the woodland we decided to attempt the incorporation of wood gasification equipment to supply woodgas (syngas) to power a generator.

final-prep

Final preparations of assembled gasifier.

Surprisingly, gasification technology has been around since the late 1800s, and wood gas powered vehicles were used during World War II when petrol became scarce and was rationed. (Wikipedia – Wood_gas_generator.)

flame

First flames…

Basing the design on the open source plans by All Power Labs (see GEK gasifier kits) we have fabricated the reactor and basic filtration components of the process. The photos show the process of fabrication and testing so far, burning the gas in a swirl burner.  The design is an Imbert downdraught gasifier with an expected output of around 10kW.

night-flames

Second run later in the day.

Temperatures and pressures are monitored during operation and well over 800 degC was reached in the pyrolysis chamber on the second run. The next stage is to refine the gas filtration to clean and cool the gas, before attempting to fuel an engine with it.  Suitable engines must be low revving as the flame speed of syngas is slow.  We are planning to use an Onan generator as (most of) these run at 1500rpm compared to 3000rpm for a standard Honda based generator.

More soon. Post any questions below.