Cogeneration

Cogeneration plants, or combined heat and power plants, simultaneously generate both heat and power from the same process. One consequence of the second law of thermodynamics is that when electricity is generated from a high-temperature source, be it combustion, nuclear or whatever, only a portion of the heat drawn can be converted to electricity. The rest must be disposed of in some low temperature reservoir. Large generating stations typically get rid of excess heat either by using cooling towers, by transfering the heat to the atmosphere, or by using water flow from a nearby river or lake. It is the norm in Canada to do this. But new technologies allow us to make use of this extra heat instead.

Approximately 60% of the energy from large coal burning power stations, and approximate 70% of the energy from nuclear stations, is not used. And a great deal more fuel must then be burned to heat houses, factories and commercial buildings. Elsewhere in the world, and particularly in northern Europe, the heat produced is used either in industrial plants, or in district heating systems which distribute heat to communities through pipes carrying steam or hot water. This method of heat distribution reduces greatly the primary energy requirements of the society, and reduces the environmental effects of energy production.

In Canada, cogeneration has begun to appear in industry, where the industry itself utilizes both the electricity and the heat. Large buildings, such as hospitals or hotels, have also begun to install gas turbines or other devices to produce both electricity and heat. The European practice of utilizing the heat from large central power stations through district heating is still rare in North America.

Queen’s University, like most Canadian institutions, has used combustion for campus heating. Now it has replaced these units with cogenerating units, which can provide all of the steam needed for campus heating and generate much of our electrical needs at the same time. This unit is heavily instrumented, and the data made available below for studying both the thermodynamics, the economics, and the environmental impacts of such units.


Cogeneration Facility