September 1997 Cogen from the Engine up C ogeneration is the generation of electricity and useful heat from the same primary fuel, thus making more efficient use of the fuel consumed. Cogeneration installations allow a large proportion of the waste heat to be captured and used as steam or hot water. The relative amounts of electricity and heat produced can be tailored to the needs of the business. The choice of plant will depend on the requirements of the business.
Natural gas is the most common fuel for cogeneration.
Waste materials can also make good fuels for cogeneration if a waste disposal charge is levied. Then using a waste stream as fuel may have a very low cost or even produce an immediate saving. However, in some cases, cogeneration can increase emissions of nitrogen oxides and noise. As a rule of thumb, cogeneration plants with an electrical output below about 100kW are not likely to be economic, so this represents an approximate lower limit on the scale of investment that could be considered. Installations with outputs from around 100kW and up to about 10MW of electricity are considered to offer the most promise as viable investments at this stage.