Cogeneration or combined heat and power is the simultaneous production of heat and power in a single thermodynamic process that has a history going back several centuries. Originally employed to save labor, its inherent fuel economy took it to the fore-front of the industrial revolution in the nineteenth century. More recently the environmental benefits derived from reduced fuel consumption have made cogeneration a significant factor in global environmental strategies, while current trends towards utility deregulation and distributed power generation continue to bolster the market for this technology.

Cogeneration encompasses several distinct thermodynamic processes of simultaneous heat and power production. One utilizes air as a medium, another steam, a third employs heat rejected from a separate combustion process, such as an internal-combustion engine, and a fourth utilizes a thermochemical process such as found in a fuel cell. Although each process is distinct, they are often combined together...