Cogeneration performance and potential.

• Author: Chiu, Amanda
• Position: VITAL SIGNS - Report

Just over 8 percent of world electrical generating capacity uses cogeneration (also known as combined heat and power, or CHP), an integrated energy system that produces both electricity and useful heat. Cogeneration plants have a total global installed electricity capacity of some 325,000 megawatts (MW).

CHP captures waste heat from electricity generation and recycles it to provide another energy service, or captures waste energy from industrial processes and recycles it into useful electricity and thermal power. Conventional systems simply exhaust waste heat into the environment and so require additional fuel to provide the same amount of heat to industry or buildings; CHP is thus significantly more efficient. An average coal-fired power plant converts 33 percent of its fuel to usable energy services, and the most efficient natural gas-fueled plant has a conversion efficiency of 60-64 percent. In contrast, CHP systems have efficiencies of 75-90 percent.

Key uses of CHP, besides electricity generation and heat for industrial processes, include district heating and cooling systems. District heating and cooling either heats buildings by means of steam carried in well-insulated pipe networks or cools them by funneling the steam through absorption chillers that distribute cool water. CHP can also be used to supply electricity and heat to individual or dense groups of residential and commercial buildings. In North America, this application is most often found in universities and hospitals.

Most CHP systems are found in energy-intensive sectors, including paper and printing, chemicals, metal and oil refining, and food processing, which together account for 80 percent of world installed capacity. Because CHP relies on diverse technologies that use a variety of fuels, including renewables, it can be a climate-friendly way of producing power. Recent data indicate that natural gas accounts for 53 percent of world CHP capacity, coal 36 percent, and oil 5 percent. Renewable fuels like biomass and high-temperature geothermal supply 6 percent but are starting to get more attention.

The regions that rely the most on CHP are Western and Eastern Europe. More than half of Western Europe's CHP-generated electricity is produced in publicly owned facilities connected to district heating and cooling systems. Denmark is the global leader, with CHP meeting 52 percent of its...