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Combined heat and power

by Linda Bertelsen
Amagervaerket Power Station producing electricity and DH for customers in Copenhagen Metropolitan area

Combined Heat and Power (CHP) is a technology that allows the simultaneous production of electricity and useful heat from a single energy source, such as natural gas, biomass, or waste heat.

CHP is also known as cogeneration, but there are some differences between the two terms. Cogeneration refers to using a simple cycle gas turbine to generate electricity and steam. At the same time, CHP refers to using a combined cycle power plant that uses steam to drive a steam turbine and produce more electricity.

CHP is more efficient than cogeneration because it utilizes more thermal energy in the fuel. CHP can also provide cooling by using absorption chillers that use the waste heat to produce chilled water.

CHP – energy-efficient and environmentally friendly

CHP is an energy-efficient and environmentally friendly way of generating power and heat for various applications, such as industrial processes, district heating and cooling, and buildings. CHP can reduce energy costs, increase power reliability, and decrease carbon emissions by avoiding the losses associated with separate electricity and heat generation.

CHP can also reduce the strain on the transmission and distribution grid by providing distributed generation close to the point of consumption.

CHP systems vary a great deal

CHP systems can vary in size, fuel type, prime mover, and configuration depending on the specific needs and preferences of the user. Some examples of prime movers for CHP systems are reciprocating engines, combustion turbines, steam turbines, microturbines, and fuel cells.

Each prime mover has advantages and disadvantages regarding efficiency, cost, maintenance, noise, emissions, and flexibility. The choice of prime mover depends on factors such as the required power-to-heat ratio, the quality and quantity of heat demand, the availability and price of fuel, and environmental regulations.

CHP district heating

Cogeneration is a more efficient use of fuel or heat because otherwise-wasted heat from electricity generation is put to some productive use. Combined heat and power (CHP) plants recover otherwise wasted thermal energy for heating. This is also called combined heat and power district heating. Small CHP plants are an example of decentralized energy.

By-product heat at moderate temperatures (100–180°C can also be used in absorption refrigerators for cooling. The supply of high-temperature heat first drives a gas or steam turbine-powered generator. The resulting low-temperature waste heat is then used for water or space heating. At smaller scales (typically below 1 MW), a gas engine or diesel engine may be used.