Combined Heat and Power

Converting Waste Heat from Power Generation to Useful Energy

Combined Heat and Power (CHP) — also referred to as cogeneration — is the simultaneous production of electric power and heat from a single fuel source, such as natural gas, coal, oil or biomass. CHP captures thermal energy that would normally be lost in power generation and uses it to provide heating and cooling, which greatly enhances the energy efficiency of power generation.

The Technology

CHP was first used in the United States by Thomas Edison to power the world’s first commercial power plant in 1882. However, early regulations discouraged decentralized power generation, and CHP systems were not widely used until the late 1980s, when new policies to promote energy efficiency encouraged their adoption. Today, the United States has installed more than 82 gigawatts of CHP generation, representing about 8 percent of total capacity, with the widest deployment in energy-intensive industries — including steel, chemical and petroleum-refining plants — and at large institutions such as universities and hospitals. In recent years, smaller systems have also become common in commercial and manufacturing industries.

CHP is not an individual technology but rather an integrated energy system that produces both heat and power for industrial and commercial locations. Unlike traditional systems in which power is generated at a central power plant and then distributed to users, a CHP system allows both electricity and heat to be generated onsite. The two most common CHP systems configurations are a gas turbine, or reciprocating gas engine, with a heat recovery unit or a steam boiler with a steam turbine. In the former, the gas turbine or reciprocating engine generates electricity by burning natural gas or biomass while a recovery unit captures heat from the system’s exhaust stream. In the latter, steam turbines generate electricity as a byproduct of heat generation. In both cases, heat is converted to steam or hot water, which can then be used for heating or cooling a nearby building or for industrial processes.

The Benefits

• Increased efficiency: CHP systems can operate at up to 80 percent efficiency — almost double the national average of 45 percent efficiency for traditional separated heat and power systems.
• Enhanced energy security: CHP increases the resiliency and flexibility of the United States’ energy infrastructure by being able to run when the grid is down, reducing distribution congestion and offsetting transmission losses. In addition, CHP can use both fossil- and renewable-based fuels.

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