Sustainability | Renewable Energy

Combined heat and power (CHP, Cogeneration)

CHP makes productive use of otherwise wasted heat from power generation; other industrial processes

Fuel sources for combined heat and power vary from project to project, country to country; but always make use of otherwise wasted heat and energy from the energy production process, or other industrial processes. Combined heat and power (CHP - also known as cogeneration) is the simultaneous production of energy and heat in a CHP power plant from: natural gas, coal, oil, sources of biomass/ biofuel, biogas (gas from landfills, or sourced from organic matter in anaerobic digesters), solar, other renewable energy sources, and other waste heat.

Waste heat for use in CHP plants can be defined as:

  • waste heat from power generation,
  • heat from municipal waste incineration,
  • industrial/ commercial manufacturing waste heat.

How Effective is CHP?

CHP significantly reduces greenhouse gas emissions. CHP is significantly more efficient than conventional power generation, requiring less fuel to produce a given energy output. CHP can produce electricity and thermal energy on-site, avoiding the grid and avoiding energy losses that occur via standard transmission and distribution, as well as avoiding power outages.

The high efficiency inherent in CHP saves businesses and consumers money on their utility bills, offering a reliable source of high-quality energy and HVAC. CHP will maximize the use of energy in the production process (for energy production, manufacturing, etc...), and in the process increase other efficiencies, like cost efficiency, reducing long-term costs.

CHP plants can reduce wasted energy from power production and other industrial processes by 50% or more, by using the maximum amount of the heat and energy generated during industrial processes; thereby increasing the energy efficiency and cost efficiency of industrial processes. CHP is used in tandem with power generation, district heating, manufacturing, and/ or waste treatment, just to name a few applications for CHP.

Here is a simple diagram of how the combined heat and power process works, compared to a traditional power plant without CHP (more information at Explain That Stuff!)>>>

combined heat and power diagram
Combined Heat and Power vs. conventional power plant

Whereas conventional energy production just treats waste heat as an inevitable loss, CHP treats heat from energy production as thermal energy which must be recycled in the energy production process, even if it's for adjunct energy uses. For example, in Iceland, the dominant source for CHP is geothermal energy production.

Examples of CHP throughout the world

Over half the energy use in Reykjavik, Iceland, which has the highest energy use (per capita) of any nation in the world, is geothermal, and much of it is CHP. CHP power plants in Reykjavik produce energy for electricity, and heated water/ steam for fish farms, pools, etc…and also for geothermal district heating. As another example, Copenhagen turns waste into district heating to provide heat for 97% of the city's heating needs; using surplus heat from waste incineration, and a natural gas and biomass-fueled CHP power plant.

As seen in the above examples with Reykjavik and Copenhagen; as well as many other European cities, such as Vaxjo, Sweden - CHP can be seamlessly integrated with a number of energy production technologies including natural gas, biogas and other renewable energy generation, waste incineration, and on-site energy generation at industry locations such as manufacturing companies. Often, energy production systems are developed exclusively for the onsite generation of electrical and/ or mechanical power, in addition to HVAC and water heating.

These energy production systems can all be developed with or without CHP, although increased energy efficiency is always seen with CHP. CHP is most often developed with a gas turbine and a heat recovery unit or a steam boiler with a steam turbine- however, CHP exists in industrial and commercial buildings, institutional campuses, municipal facilities (district energy systems, wastewater treatment facilities, etc…), and is even implemented for farms and residential properties.

Here is a snippet from Explain That Stuff about the promising future of CHP in the global energy market-

'...there seems to be a growing consensus that cogeneration is the way forward for large-scale electricity and heating supplies, and we're likely to see thousands more CHP plants appearing all over the world in the coming decades...massive potential for expansion into a much wider range of large buildings, from retail stores and universities to office complexes, hotels, and hospitals."


Please also see: district heating

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