Steam Based Cogeneration

During the operation of a conventional power plant, large quantities of heat are rejected in the atmosphere either through the cooling circuits (steam condensers, cooling towers, etc.) or with the exhaust gases. This is the reason most of the large conventional power generating units have a very low thermal efficiency. The thermal efficiency of most of the conventional power plants is less than 50%. That means over 50% of the heat produced by fuel-burning goes to waste.

Not only that, in many cases this loss of heat actually causes thermal pollution.

In newer systems, most of this waste heat can be recovered and used for other thermal needs. Since heat is used for more than one purpose this type of plants are known as cogeneration systems. These systems increase the efficiency from 30-50% of a power plant to 80-90% of a cogeneration system.

This is actually not new for industrial plants that are equipped with their own power plants. Many of the plants use the exhaust steam for industrial processes. It is estimated that as much as 58% of the total power produced by on-site industrial power plants in the U.S.A. in the early 1900’s was cogenerated.