Cogeneration: How Power Plants Save Energy and the Environment

When a power plant produces electricity to power turbines, an enormous amount of heat energy is lost in that process.

Until recently, this was a reality of power plant generation. Now, many power plants are using a process called cogeneration which seeks to make use of that lost heat energy.

Cogeneration – also known as combined heat and power - is an approach where a power plant takes some of the heat typically lost when making electricity and uses it for heating rather than losing it. In doing so the plant does not need to get its heating power from a separate system.

The California Energy Commission is conducting research on cogeneration through its Research and Development Division. Current research activities are focusing on improving small systems.

In its latest tracking progress report on cogeneration the Commission found that California has 7,796 megawatts of onsite cogeneration installed making it the second largest cogeneration state in the country, after Texas.

While the conventional method of producing usable heat and power separately has a typical combined energy efficiency of 45 percent, cogeneration systems can operate at levels as high as 80 percent efficiency.

The benefits of cogeneration are many. Cogeneration can reduce the strain on the electric grid, it can lower greenhouse gas emissions at plants, and can lessen the need for new transmission and distribution infrastructure.

And since much of the energy of a cogeneration system is consumed on-site (as a form of distributed generation), less energy is lost through transmission. This leads to even more energy savings.

Further, the process is well suited to using abundant clean domestic energy sources such as natural gas and biomass.

Cogeneration can also provide opportunities to use renewable fuels. For example, wastewater treatment plants are ideal for developing cogeneration systems as they use the waste heat on-site to warm digesters and export excess renewable electricity to the grid.

Sites that use cogeneration electricity on-site reduce the need for grid electricity, thereby affecting the retail electric sales forecast and the amount of renewable generation needed to meet California’s Renewables Portfolio Standard requirements.