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Additional recommended knowledge
Conversion of energy
Whereas mechanical drives can be designed to run smoothly, with little dissipation of energy to heat, machines for conversion of energy contained in fuels to mechanical work or electric energy necessarily produce large quantities of by-product heat (see: Second law of thermodynamics).
The electrical efficiency of thermal power plants, defined as the ratio between the primary product and input energy, ranges from 30 to 70%. It is often difficult to find useful application for large quantities of low quality heat, so the heat is qualified as waste heat and is rejected to the environment. Economically most convenient is the rejection of such heat to water from a sea, lake or river. If sufficient cooling water is not available, the plant has to be equipped with a cooling tower to reject the waste heat into the atmosphere.
Waste of the by-product heat is avoided if a cogeneration system is used. Limitations to the use of by-product heat arise due to difficulties in heat transport and heat storage.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Waste_heat". A list of authors is available in Wikipedia.|