Power
Summary
Conventional district heating systems are generally designed around the load. However, an alternate approach would be to design around potential heat sources, including the waste heat from power plants. Many steam turbines are designed for backpressure of 5 in. of mercury, which allows heating water to at least 120F, suitable for district heating.
With the recent emphasis on renewable energy, thermal energy has been neglected, even though fossil fuels (natural gas, fuel oil, and propane) make up 46% of the energy used by buildings in the U.S. Most of these fuels are used for space heating and domestic hot water. This is an energy load that has largely been ignored in developing district heat in the U.S., although in Europe, district heating has been used for apartment buildings.
An Ignored Heat Source
While cogeneration plants have been used to supply heat for district heating for many years, most of the ones in the U.S. have been special purpose plants, using extraction turbines to supply high-pressure steam to district steam systems with limited cogeneration.
There are two principal conventional technologies that have higher cogeneration potential. There is European technology, using 180F water provided by central power plants with extraction turbines, and smaller-scale plants, using internal combustion engines or combustion turbines to make 180F to 220F hot water for local use.
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