What is CHP?
Combined heat and power (CHP), also known as cogeneration, is an efficient, clean, and reliable approach to generating power and thermal energy from a single fuel source. CHP systems capture the heat produced during electricity generation and put it to beneficial use for applications such as space heating, air conditioning, domestic hot water, industrial processes, and more. This dual-output approach significantly improves overall fuel efficiency compared to separate production of electricity and heat.
How CHP Systems Work
A CHP system consists of a prime mover—typically a gas turbine, reciprocating engine or steam turbine—that generates electricity. The heat produced from the electrical generation process is then recovered and used for applications that need both forms of energy. For systems utilizing reciprocating engines or gas turbines, exhaust heat is recovered to produce hot water or steam. Steam turbine CHP systems recover heat from the condenser. The recovered thermal energy can be distributed in the form of hot water or steam through piping networks to buildings to meet their space heating and process steam needs.
The electricity generated can be used on-site to power the facility where the CHP system is located. Any excess power beyond the on-site needs can be exported to the electric grid. On the thermal side, the hot water or steam generated can be used for space heating, domestic hot water, industrial processes, and more. This simultaneous generation of useful electricity and thermal energy makes CHP much more energy efficient than separate heating and power.
Benefits of CHP Systems
In addition to improved overall energy efficiency, CHP offers several other important benefits:
Reliability - By producing power and heat on-site, Combined Heat And Power (CHP) provides a more reliable supply of energy compared to off-site grids alone. The system can act as a backup in the event of electric grid outages.
Cost Savings - By offsetting fuel costs with sales of excess power and from avoiding high electric demand charges, CHP projects can deliver significant cost savings over time. Payback periods are typically 3-5 years.
Resiliency - As on-site distributed generation resources, CHP systems enhance energy resiliency for critical facilities such as hospitals, data centers and more.
Emissions Reductions - CHP combustion systems recapture heat that would otherwise be wasted. This boosts efficiency and cuts carbon emissions compared to conventional separate heat and power. Emission levels are regulated by facilities' air permits.
Applications for CHP
CHP technologies are well-suited for large, continuous baseload operations that require both electricity and thermal energy. Common CHP applications include:
Healthcare facilities – CHP provides reliable power and steam/hot water for hospitals and nursing homes. Over 250 hospitals have installed CHP.
Colleges/universities – Campuses enjoy cost savings from CHP while also boosting sustainability goals. Dozens have installed systems ranging 1-20 MW.
Hotels/casinos – Combined with thermal energy storage, CHP provides efficient HVAC, hot water and power around the clock.
Wastewater treatment plants – CHP generates cost-effective power and steam/hot water demand for operations. Systems of 1-5 MW are common.
Industrial facilities – Process heat and power plants like refineries and chemical plants are ideal CHP host sites. Systems range from 5-50 MW.
Data centers – Constant cooling and power loads make data centers an excellent CHP match for highly efficient operations.
District energy systems – Campus-style developments distribute steam or hot water from centralized CHP plant(s). Examples include military bases, downtown areas and more.
Fuel Options for CHP
CHP prime movers can operate on various fuels depending on availability, emissions regulations and economics. Common fuels include:
Natural gas - Clean-burning and readily available, natural gas is the dominant CHP fuel, accounting for over 90% of current U.S. capacity.
Biogas - Captured from landfills or wastewater treatment, biogas is a renewable option for some systems.
Distillate fuel oil - A backup or transition fuel that stores well on-site. Must meet air permitting.
Renewable natural gas - Upgraded biogas injected into natural gas pipeline to displace fossil gas usage.
While CHP delivers efficiency and economic benefits across many applications and fuel choices, each potential project requires a thorough feasibility analysis to determine optimum system size, configuration and estimated performance based on actual thermal and electric load profiles. With attention to siting, equipment and operations, CHP provides a diverse array of facilities and communities with clean, reliable and cost-effective power and heat.
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