The Basics of Combined Heat and Power
An overview of CHP systems and their benefits
Combined heat and power (CHP), also known as cogeneration, is the simultaneous production of electricity and heat from a single fuel source, such as: natural gas, biomass, biogas, coal, waste heat, or oil.
CHP is not a single technology, but an integrated energy system that can be modified depending upon the needs of the energy end user.
• Onsite generation of electrical and/or mechanical power.
• Waste-heat recovery for heating, cooling, dehumidification, or process applications.
• Seamless system integration for a variety of technologies, thermal applications, and fuel types into existing building infrastructure.
The two most common CHP system configurations are:
• Gas turbine or engine with heat recovery unit.
• Steam boiler with steam turbine.
GAS TURBINE OR ENGINE WITH HEAT RECOVERY UNIT
Gas turbine or reciprocating engine CHP systems (Figure 1) generate electricity by burning fuel (natural gas or biogas) to generate electricity and then use a heat recovery unit to capture heat from the combustion system's exhaust stream. This heat is converted into useful thermal energy, usually in the form of steam or hot water. Gas turbines/engines are ideally suited for large industrial or commercial CHP applications requiring ample amounts of electricity and heat.
STEAM BOILER WITH STEAM TURBINE
Steam turbines normally generate electricity as a byproduct of heat (steam) generation, unlike gas turbine and reciprocating engine CHP systems, where heat is a byproduct of power generation. Steam turbine-based CHP systems (Figure 2) are typically used in industrial processes, where solid fuels (biomass or coal) or waste products are readily available to fuel the boiler unit.
CHP technology exists in a wide variety of energy-intensive facility types and sizes nationwide, including:
• Commercial buildings — hotels and casinos, airports, high-tech campuses, large office buildings, nursing homes
• Industrial manufacturers — chemical, refining, ethanol, pulp and paper, food processing, glass manufacturing
• Institutions — colleges and universities, hospitals, prisons, military bases
• Municipal — district energy systems, wastewater treatment facilities, K-12 schools
• Residential — multifamily housing, planned communities
A number of site-specific factors will determine if CHP may be a good technical and economic fit for your facility.
BENEFITS OF CHP
CHP provides efficiency, reliability, environmental, and economic benefits:
• Efficiency benefits — CHP requires less fuel to produce a given energy output, and avoids transmission and distribution losses that occur when electricity travels over power lines.
• Reliability benefits — CHP can be designed to provide high-quality electricity and thermal energy to a site regardless of what might occur on the power grid, decreasing the impact of outages and improving power quality for sensitive equipment.
• Environmental benefits — Because less fuel is burned to produce each unit of energy output, CHP reduces air pollution and greenhouse gas emissions.
• Economic benefits — CHP can save facilities considerable money on their energy bills due to its high efficiency and can provide a hedge against unstable energy costs.
Source: EPA Combined Heat and Power Partnership. For more information, visit www3.epa.gov/chp.
Publication date: 10/19/2015