Heat Transfer Technology
Central to McCallum technology are
1) the extraction of heat from an abundant, cheap source of low-grade* heat
2) the processing of that heat, particularly with a heat pump, to obtain much hotter temperatures.
Extraction of Heat from an abundant cheap source:
-Air. This may be from inside or outside air, depending on the circumstances. Electrical equipment operating inside a building often supplies excess heat to its surroundings, and may need cooling as well for it to function well. This is therefore a good source of low grade heat. Sometimes the only air available is outside air. If the air is very cold however, the efficiency of the heat pump may be reduced.
-Water. Water, such as from a pond, lake or the sea, has a large amount of energy in it. More than many other materials, it takes a lot of energy to increase its temperature a little. This also means that a lot of energy can be extracted from the water, with the loss of only a small amount of temperature. Furthermore, water is often abundant, usually not expensive, and can also release this energy even if it is not drinkable. Salt water will do. Water is also safe, and can be pumped easily. Many industries of course use it, so it is often available as a by-product of power production (steam turbines), food processing (milk pasteurisation, beverage processing) and water cooling from manufacturing processes.
-Ground. Ground thankfully happens to be present in most locations. Heat can be extracted from the ground by putting a loop of plastic or metal tube into it (either vertically or horizontally), and circulating fluid through the loop that is cooler than the ground itself. By the time the fluid comes out of the other end of the loop, it will be up to near the ground temperature. It will have become warmer by extracting some heat out of the ground. Not all grounds are as good as each other at releasing heat. Dry sand is not as good as granite for instance. Other things that effect how good the ground is as a source of energy is the heat of the ground, the length of the tube, the surface area of the tube and the conductivity of any grout around the tube. Areas with high heat flow characteristics (eg geothermal areas), are very suitable, as long as the loop is able to withstand the particular temperatures or ground elements. Click Here to learn more about Ground Source Heat from average ground.
Heat Pumps: Most heat pumps use an electric motor to extract a large amount of heat (energy) from a source (such as air, water or ground) and use it to increase the temperature of something else by a large amount. Of course the total amount of energy at the end hasn't increased, but it has been put into a more useful form. Click Here to Download a slide show (727 kb) on basic principles of Heat Pumps and Refrigeration. Properties of gases and liquids are discussed, and how these can be used to advantage in the standard compression-condensation-evaporation heat pump cycle. The new high temperature technology is explained
*In theory, everything above -273 degrees C has some heat available, just that the colder it is, the harder it is to get that heat.