GAS-L: 21st Century Wood Gas Car

[Ken Boak <kenboak@stirlingservice.freeserve.co.uk>]

Tom and gas Listers,

I read with interest your last posting about the development of a 21st Century Woodgas Car.

Do you mean a C21 gasifier fitted to a standard automobile, or a C21 gasifier fitted to a vehicle where the engine and powertrain, aerodynamic design, and vehiclular systems have been optimised to extract the best efficiency from the fuel source?

There is, as you will appreciate, a very big difference in the two approaches.

For the gasifier to be used in conjucnction with an existing IC engine in a typical automotive duty cycle, it has to be responsive to the demands from the engine, and as such needs to have a quick response time, and a high degree of automatic control. Last week, I read with interest, an article from 1942, describing such a gasifier - by Kalle. I am sure that you already know of this piece of work, but here is the link for your convenience:

http://www.artech.se/~joacim/gengas/kg_eng.html

This was of course a charcoal gasifier, which featured a novel CO2 feedback system, a means of producing very fine charcoal dust at the heart of the reaction zone, and a response which tracked the demand from the engine.

I believe that any thermal process is likely to have a fairly poor response time, and matching the size of the gasifier to meet the peak demands of the IC engine will result in an oversize gasifier for most of the time.

It may be a better approach to decouple to gasifier and IC engine systems from the demands of acceleration by means of an electric propulsion system, the peak load being handled by a modest sized battery pack. In this way the gasifier and IC engine can be scaled down to meet the mean demads of power, and run almost continuously at maximum efficiency. They can then become a tightly coupled system, matched in the same way that an generator set is matched to the optimum rpm of the IC engine.

It may well be thet the IC engine is not the best candidate as the primemover for a system running on wood gas. Other engine types may be better suited, particularly when run at constant power output in a series hybrid mode. Ones to consider are Stirling engine (a very nice 11kW engine is available from Solo Kleinmotoren of Stuttgart - and would be easily converted from propane/natural gas to a woodgas burner). Such an approach would allow the vehicle to run on autogas, LPG, CNG or propane, if wood was temporarily not available - a true multifuel vehicle.

Modern lightweight steam engines are also possible candidates - capable of 22% thermomechanical efficiency. The most interesting option I think would be a rotary turbine of some kind optimised to being able to handle the wood gas combustion conditions (variable calorific value, water and ash content etc). There are 2 designs which spring to mind for such a turbine. It could be directly coupled to a high speed brushless dc generator, thus dispensing with additional complexities of gearboxes, and has the means of being lightweight, compact and efficient.

Fuel handling is going to be a major issue with any woodgas fired vehicle, either a whole industry evolves producing pelletised fuel, charcoal beans, cubed timber or sawdust briquettes. It may be possible to put the fuel into a standard cartridge, and this is just loaded into a receptacle on the car - without the owner coming into contact with the fuel. A similar cartridge approach could be used for the ash collection - this is just a variation on ideas borrowed from laser/inkjet printer technology.

The 21st century woodgas car needs to compete against contempory vehicles in terms of range and perceived performance. It also has to meet stringent emission controls that just weren't present in 1940's war torn Scandinavia.

Best of luck with your project,



Ken Boak





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