Waste Heat to Power Systems Page: 1 of 9
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" EPA COMBINED HEAT AND
WASTE HEAT TO POWER SYSTEMS
Waste heat to power (WHP) is the process
of capturing heat discarded by an existing
industrial process and using that heat to
generate power (see Figure 1). Energy-
intensive industrial processes-such as
those occurring at refineries, steel mills,
glass furnaces, and cement kilns-all
release hot exhaust gases and waste
streams that can be harnessed with well-
established technologies to generate
electricity (see Appendix). The recovery of
industrial waste heat for power is a largely
untapped type of combined heat and
power (CHP), which is the use of a single
fuel source to generate both thermal
energy (heating or cooling) and electricity.
Fuel is combusted
Fuel as part of an
Figure 1: Waste Heat to Power Diagram
CHP generally consists of a prime mover, a generator, a heat recovery system, and electrical interconnection
equipment configured into an integrated system. CHP is a form of distributed generation, which, unlike central
station generation, is located at or near the energy-consuming facility. CHP's inherent higher efficiency and its
ability to avoid transmission losses in the delivery of electricity from the central station power plant to the user
result in reduced primary energy use and lower greenhouse gas (GHG) emissions.
The most common CHP configuration is known as a topping cycle, where fuel is first used in a heat engine to
generate power, and the waste heat from the power generation equipment is then recovered to provide useful
thermal energy. As an example, a gas turbine or reciprocating engine generates electricity by burning fuel and
then uses a heat recovery unit to capture useful thermal energy from the prime mover's exhaust stream and
cooling system. Alternatively, steam turbines generate electricity using high-pressure steam from a fired boiler
before sending lower pressure steam to an industrial process or district heating system.
Waste heat streams can be used to generate power in what is called bottoming cycle CHP-another term for
WHP.1 In this configuration, fuel is first used to provide thermal energy in an industrial process, such as a furnace,
and the waste heat from that process is then used to generate power. The key advantage of WHP systems is that
they utilize heat from existing thermal processes, which would otherwise be wasted, to produce electricity or
mechanical power, as opposed to directly consuming additional fuel for this purpose.
The Opportunity for WHP
Industrial energy use represents the largest potential source of WHP generation.2 In 2009, the industrial sector
used the largest share of energy in the United States, accounting for more than 28 Quads, or 30 percent of all
1 Title 18: Conservation of Power and Water Resources; Part 292-Regulations under Sections 201 and 210 of the Public Utility
Regulatory Policies Act of 1978; Subpart A - General Provisions, 292.101 Definitions.
2 Waste heat streams in other segments are generally either too low in temperature (power generation) or too small in
volume (commercial and residential) to represent viable WHP sources.
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United States. Environmental Protection Agency. Combined Heat and Power Partnership. Waste Heat to Power Systems, text, May 30, 2012; Washington, D. C.. (digital.library.unt.edu/ark:/67531/metadc949408/m1/1/: accessed November 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.