What Is Cogeneration

Cogeneration is an efficient energy consumption mode that combines heat and power generation. It is also called as combined heat and power (CHP). Corresponding to the cogeneration mode, there are sole power generation mode and sole heat supply mode.

A conventional fuel-fired power plant is of the sole power generation mode. Fuel is burnt in the boiler to generate steam, which is used to drive the turbine. The generator is then driven by the turbine to generate power. The steam will then be condensed into water for reuse. Since the abundance of heat is wasted in the condensation process, the thermal efficiency of a conventional fuel-fired power plant is not high, only 30%-40% for a large coal-fired power plant.

Small industrial coal-fired boilers, which are still commonly used in China, are of the sole heat supply mode. Coal is burnt in the boiler to supply the required steam. It is reported that more than 400 thousand small industrial coal-fired boilers are still operating in China right now.

Since a substantial amount of steam is sold to nearby industrial, commercial and residential users via the heat network, instead of being condensed into water, the cogeneration has higher thermal efficiency than the conventional fuel-fired power generation. Typically, cogeneration plants that are less than 50 MW can reach a thermal efficiency of 45%-90%.

Furthermore, cogeneration plants are more environmentally friendly than small industrial coal-fired boilers, due to their larger capacities and better equipment to reduce emission of air pollutants such as dust and sulphur dioxide.