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Chapter 3 - Recent Swedish experiences with operation of vehicles on wood and charcoal gas

3.1 Overview of development work and testing carried out at the national machinery testing institute
3.2 Experiences gained from conversion and operation of modern vehicles
3.3 Producer gas vehicles recently operated in other countries
3.4 Economic evaluation of operation of vehicles on wood gas
3.5 Feasibility of using the vehicle gasifier technology for stationary applications
3.6 Operating hazards

Sweden is today largely dependent on road vehicles using imported petroleum fuels, for transport of goods and people within the country. Roughly 90 percent of the travelling and 50 percent of the goods transport are based on the use of road vehicles.

The dependence on road vehicles is expected to remain. Since no petroleum reserves of importance have been found in Sweden, dependence on imported fuels will continue in the transport sector. Sweden is in this respect in a similar situation to many oil-importing developing countries.

It is obvious that such a large dependence on imported petroleum fuels for an important function in a modern society makes a nation very vulnerable to increased petroleum prices and to supply blockades. The need for an alternative, indigenous fuel supply for the road vehicles and farm tractors was already recognized in Sweden by the late 1930's, and it has since then been the official emergency policy to use wood and charcoal gasifiers in case of a serious supply crisis for petroleum fuels.

This policy was successfully pursued during the Second World War. Most of the road vehicles and farm tractors were then operated with either wood or charcoal gasifiers. As shown in Table 3.1 the introduction of gasifier operation was quite rapid. From less than 1000 vehicles operated on gas in 1939, the number increased to over 70000 in 1942. This rapid introduction would probably not have been possible if there had not been an active interest in the technology since the twenties with a few hundred vehicles in operation during the thirties.

The National Board for Economic Defence, which is the responsible body for emergency planning of the energy supply, still considers conversion of farm tractors, buses, lorries and passenger cars to gasifier operation to be the only realistic alternative in a sustained petroleum fuel supply crisis. Utilization of wood chip-e as fuel, rather than wood blocks and charcoal which were- used during the Second World War, is considered preferable. The reasons for this are that the fuel can be prepared with equipment already available in the paper and pulp industry and large energy losses are avoided. The utilization of wood blocks and charcoal would require investment in new equipment for fuel preparation. This would lead to economic disadvantages and delays in the introduction of the alternative fuel supply. Use of charcoal would inevitably lead to loss of more than 50 percent of the available biomass energy.

Table 3.1 Development of the producer gas vehicle fleet in Sweden 1933-1945.

Since the biomass resources are limited - the maximum utilization of biomass fuels which can be sustained for several years with the present structure of forestry and agriculture can be estimated at some 150 TWh - and since the biomass fuel will also be needed for other purposes in the case of a petroleum supply crisis, utilization of charcoal for vehicle gasifiers will be avoided.

The Swedish interest in wood gasifiers is therefore closely related to the need felt by the Swedish Government to maintain an emergency option for the fuel supply to the transport sector. It is quite clear that wood gasifiers are a realistic alternative to petroleum fuels for rapid introduction only if there is a continuous development of the technology followed by field testing in vehicles of the types given first priority for conversion to-wood gas in case of a petroleum fuel supply crisis.

The results of this research and development work and some of the field testing will be summarized below.

The economy of using wood or charcoal gasifiers for vehicles at present prices for gasoline and diesel oil and the possibility of using this type of gasifier technology in stationary applications is discussed in the last part of this chapter. It should be pointed out, however, that the present economy is not really an issue and that the usefulness of this technology for stationary applications is probably limited to applications where the requirements for compact and lightweight systems are so important that some sacrifices in the form of a fairly short equipment lifetime and additional operator time required for fuel feeding and removal of ash and dust are accepted.

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