ABSTRACT
Cogeneration of combined heat and power When biomass (or coal, oil or natural gas for that matter) is used as a fuel in a conversion plant to generate electricity, some heat is always produced. This relates to the laws of energy (thermodynamics), as covered in Chapter 1, and is unavoidable. However, if this heat can be usefully used and not ‘wasted’, as it normally is in traditional thermal power generation plants, then the overall system efficiency will be greatly improved. To be classed as ‘cogeneration’ the by-product heat must be put to good use in some way, normally as process heat in a nearby processing plant (Figure 8.1). Producing steam that only drives a condensing turbine (where the waste steam is condensed and the heat rejected into the environment) is not cogeneration.
