"When faced with steamrolling technology, you either become part of the technology or part of the road"
- Lowell Bryan
A Consultancy to Small Scale
As one would imagine, the best applications for small scale cogen are directly related to the amount of heat and electricity they produce. A rule of thumb regarding the relationship between heat and electricity is as follows: Internal combustion engine units produce three times the electrical output. Therefore a 5kw(electric) unit will generate about 15kW (1kW=3412Btu) of heat. A Stirling engine unit can produce up to six times the amount of heat to electricity. Fuel cells vary, but a good estimate would be 1.5-2.0 times the heat out to the electrical output. Microturbines are in the range of four times the heat/electric ratio.
Given this information, one can determine that engine based systems would be best for generating heat, whereas fuel cells would be best for generating electricity - they also have the highest electrical efficiencies - 30% to 50% vs engine systems in the 15% to 25% range.
Typical applications for small scale cogeneration are:
Considering the state of small scale cogeneration technology today, the primary use would be for heat generation. Because of that, the list above reflects applications that need heat - and when the heat is utilized, the electricity comes along as a by-product for very little cost - typically < $0.04/kWh.