An Innovative Approach to District Heating to Maximize Combined Heat & Power

10:00AM - 6:00PM
Robert Timmerman

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.