Question:

What is meant by "cogeneration" and "combined cycle"? Is there a connection between the two?

Answer:

Cogeneration is the production of electricity and heat from the same fuel: natural gas, biogas (from municipal solid waste, for example), coal, fuel oil... The combustion of these fuels powers a thermal engine connected to an electric generator. The exhaust gas from the engine, which can reach temperatures of more than 450 °C, is recovered in a boiler that supplies heat locally, for example to an urban heating system, industrial facilities or hospitals. Electricity-generating household heating systems that operate with natural gas are also becoming available.
The combined cycle uses a gas turbine fueled by a mixture of compressed air and natural gas. Here, too, the heat is recovered, but in this case it is recycled to a second turbine to generate more electricity. The combined cycle thus means more electricity for the same amount of fuel, and therefore fewer CO₂ emissions. This type of plant supplies additional power during peak demand.