Environmental Engineering Reference
In-Depth Information
11
11
Heat Pumps - from Cold to Hot
Due to the steep rise in oil and petrol prices during recent years and rising public
awareness of climate problems, alternatives such as wood pellet heating, solar
thermal systems and heat pumps are becoming more prominent. Manufacturers of
heat pump systems have seen a boom in sales since 2000.
Yet the whole principle behind the heat pump is far from modern. Lord Kelvin, a
British physics professor, already proved the principle of the heat pump in 1852.
He also recognized that a heat pump uses less primary energy to provide heat than
a system that heats directly. A heat pump uses a heat source with low temperatures
and increases it to a higher level of temperature (Figure 11.1). This process requires
an electric, mechanical or thermal drive.
Figure 11.1
Energy fl ow with a heat pump process.
11.1 Heat Sources for Low-Temperature Heat
A heat pump is basically a machine in which a mechanically or electrically driven
pump generates heat from a low-temperature source. This heat is then used to
provide heating or to produce hot water. Before a heat pump can even function, a
