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As energy can neither be created nor destroyed, why can’t we conserve energy by converting low grade heat directly into electricity?

As energy can neither be created nor destroyed, isn’t there is a real opportunity to conserve energy and make efficient use of power by converting low grade heat directly into electricity. This concept has wide applications from data centres to factories and ultimately even in the home with domestic appliances, assuming the processes involved could be made efficient enough to be economic on such a small scale. Is there any research being carried out into the development of this concept?
John Woolley from Oxfordshire (Age 55+)


One Response

  1. There is, in two instances that I am aware of. On a domestic scale, Combined Heat and Power systems are used – as the name suggests – to generate heat and electricity from the same source. The hot water or air in a boiler drives turbines when it is circulated to the rest of the heating system, generating power. A CHP system can be 70% efficient in its production of useful heat and electricity, comapred to about 40% for standard powerstation. CHP systems can also be scaled down for use in normal family homes or in larger factories.

    There are other techs which reclaim heat, rather than making more use of it in the first place. When a conductor has different temperatures at each end, a voltage is generated across it as the electrons in the hot end gain more energy and spread out, pushing the others along. To use this voltage, a second conductor has to be connected, which will generate its own voltage in the opposite direction. If these are the same type of conductor, the effect cancels out, but since the voltage generated for a given temperature depends on the material, you can combine different conductors to create a device that gives out voltage when exposed to temperature differences. These are called thermocouples, and are commonly used as measuring devices, but they can be used to generate power. The pilot light on most boilers is powered thermoelectrically. Also, the Cassini and Huygens probes use thermocouples to convert the heat generates by the radioisotopes inside them to power for their interplanetary journeys. But thermocouples aren’t commonly used as power sources on Earth because they have a low efficiency when the temperature difference is small. People are working on this though: check out this page at Caltech if you’re interested. http://www.thermoelectrics.caltech.edu/

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