Thermogenerators (TEG) are devices which convert heat (temperature differences) directly into electrical energy. For the most part, this term is synonymous with "thermoelectric generator" and rarely used in English. They most commonly work on the principle of the Seebeck effect, with typical efficiencies of around 5-10%. Older Seebeck-based devices used bimetallic junctions and were bulky while more recent devices use semiconductor p-n junctions and can have thicknesses in the millimeter range.
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Encyclopedia
Thermogenerators (TEG) are devices which convert heat (temperature differences) directly into electrical energy. For the most part, this term is synonymous with "thermoelectric generator" and rarely used in English. They most commonly work on the principle of the Seebeck effect, with typical efficiencies of around 5-10%. Older Seebeck-based devices used bimetallic junctions and were bulky while more recent devices use semiconductor p-n junctions and can have thicknesses in the millimeter range. These are solid state devices and unlike dynamos have no moving parts other than sometimes a fan. Fuel such as natural gas, propane or kerosene can thus be used to generate DC electricity, which can be converted to AC by an inverter.
Applications
The use of waste heat in combustion engines promises to be a high volume application field. Not only the exhaust but also cooling agents are targeted.
Two general problems exist in such devices: high output resistance and adverse thermal characteristics. In order to get a significant output voltage a very high Seebeck coefficient is needed (high V/°C). A common approach is to place many thermo-elements in series, causing the effective output resistance of a generator to be very high (>10kOhm). Thus power is only efficiently transferred to loads with high resistance; power is lost across the output resistance otherwise. A generator with very high output impedance is effectively a temperature sensor, not a generator. Secondly, because low thermal conductivity is required for a good TEG, this can severely dampen the heat dissipation of such a device. For example its not straight-forward to place a TEG on an essential IC chip that requires cooling. Because of the low thermal conductivity of a TEG device, that IC is cooled at a slower rate.
The effect is employed comercially on the Ecofan, a device intended to sit atop a solid fuel stove, which generates its own power to rotate a small fan which distributes the heat away from the stove.
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