R W Timmermam & Associates
Conventional district heating systems are designed around the load, and its required temperature, with special purpose plants built to supply the load.
This approach leads to heat supplied at fairly high temperatures, limiting amounts of combined heat and power. An alternate approach would be to design
around potential heat sources, including the waste heat from power plants. While power plant cooling systems are optimized for low temperatures, American
turbines are designed for back pressures of 5" of mercury (133.75F), which allows heating district heating water to at least 120F. This water can be distributed
in inexpensive uninsulated pipes, and used for district heating. This heat source has several advantages. It uses the full heat rejection of conventional
power plants, permitting the maximum amount of combined heat and power, and does not require construction of special purpose combined heat and power plants
- every utility plant can be a combined heat and power plant, and revert to normal power generation in summer when heat is not required. This paper describes
the system in detail, and the prototype installation. It discusses piping methods, comparing insulated with non-insulated pipe, and with lightly insulated
cast iron pipe. It presents an economic comparison of insulated versus non-insulated pipe, and the advantages of omitting insulation. It describes methods
of adapting existing buildings to low temperature water, including work done to adapt an existing steam heated building to use 165F water from a seasonal
solar storage plant. It presents the results of preliminary cost studies of proposed systems. Finally, it will discuss methods of obtaining heat from power
plants, including plants that do not run continuously.