Cooling, Heating, and Power
Conventional electricity generation is inherently inefficient, using only about a third of the fuel's potential energy. In applications where heating or cooling is needed as well, the total efficiency of separate thermal and power systems is still only about 45%, despite the higher efficiencies of thermal conversion equipment.
Combined cooling, heating, and power (CHP) systems are significantly more efficient. CHP technologies produce both electricity and thermal energy from a single energy source. These systems recover heat that normally would be wasted in an electricity generator, then use it to produce one or more of the following: steam, hot water, space heating, humidity control, or cooling. By using a CHP system, the fuel that would otherwise be used to produce heat or steam in a separate unit is saved.
In conventional conversion of fuel to electricity, two thirds of the energy input is lost to the environment as heat. By recycling and using this waste heat, CHP systems achieve efficiencies of 60% to 80% — a dramatic improvement over the average 33% efficiency of conventional fossil-fueled power plants. These higher efficiencies have an added bonus: reducing air emissions of nitrous oxides, sulfur dioxide, mercury, particulate matter, and carbon dioxide. CHP systems produce much less air pollution than conventional technologies.
CHP isn't new. In the early 1900s, many manufacturing plants operated CHP facilities. However, as a result of improvements in the cost and reliability of electricity generated by the separate electric power industry as well as increasing regulation, the electric generation capacity at most CHP facilities was abandoned in favor of more convenient purchased electricity. A few industries, such as pulp and paper and petroleum refining, continued to operate their CHP facilities, in part driven by high steam loads and the availability of by-product fuels.
In the late 1970s, interest in CHP was renewed in response to the Public Utilities Regulatory Policy Act of 1978 (PURPA) which included measures to promote CHP as an energy efficient technology.
Recent technological advances have resulted in the development of a range of efficient and versatile systems for industrial and other applications. Improvements in electricity generation technologies — in particular advanced combustion turbines and engines — have allowed for new configurations that reduce size yet increase output.
Many of the gas-fueled technologies used for distributed power generation can also be used for CHP. Pursue the following links to learn more about CHP technologies:
Gas-Fired Distributed Energy Resource Technology Characterizations — NREL, November 2003. See the beginning of every chapter for information on the CHP applications of each gas-fired power-generating technology.
Industrial Distributed Energy — This section of the website for the U.S. Department of Energy's Industrial Technologies Program provides extensive information on the performance, cost, markets, and prospects for CHP technologies.