The ST-5 would enable you to be truly independent only if you produced your own fuel, whether it be wood, agro-residues or gaseous fuels. The amount of fuel required depends on the schedule of engine use. While the volume of space to be heated, amount of insulation and climatic conditions determine your heating requirements, it is likely that the 115,000 BTU/hr of available heat from the ST-5 system will be more than enough for an average home. The objective is to minimize your fuel consumption by matching the ST-5's operation to your daily electricity needs. To determine this, check the charts in the sections on "Cogeneration" and "Uses". Next, determine the extent to which the engine operating time can be reduced by running washing machines, vacuum cleaners, freezers and other such appliances while the ST-5 is in operation. This will minimize the time required to charge batteries, which is a slow process. For the loads assumed in the section on cogeneration, it has been determined that between 9 and 10 cords of oak (with 20% moisture content) would be required for 12 months of operation.

In order to determine the amounts of various kinds of fuel necessary for an hour of operation at full output, it is necessary to know the amount of heat required by the engine and the calorific value per unit of fuel used. The ST-5 requires approximately 38kW (130,000 BTU/hr) of energy input. The second part - the calorific value of the fuel - would vary from fuel to fuel. The table at left lists a few.

From these figures, it is possible to obtain the amounts of fuels required per hour of operation. Some examples are listed below.

Having determined the fuel requirements for your circumstances, we encourage you to ensure a constant supply of fuel. For those using wood, as is the most common case, reasonable management of forest resources is desirable. It has been estimated that maturing forests yield between one third and one half cord of wood per acre per year without detriment to long term forest growth. So, if you anticipate using 9 cords of wood per year and you own 20 acres of forested land, you could quite safely provide for your fuel requirements through reasonable management practices. However, if you do not have established forest acreage, it is suggested that a 'home fuel wood plantation' be started.

There is excellent information available on managing woodlots from your local U.S. Department of Agriculture Forestry Specialist, who can recommend locally specific tree species, land preparation and cultural practices. The U.S. Department of Energy, too, has sponsored and coordinated work on Short Rotation Woody Crops for a number of years and has information available through the Oak Ridge National Laboratory. While most of this information is site specific and has been developed with very large plantations in mind, it is a good starting point for scaling to your home needs.

 

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