New proposal of high temperature thermoelectric conversion in power plant

Efficiency of thermoelectric conversion is not high, and therefore this is not used in an usual conventional energy system in spite of the advantages. Even if the product of figure of merit and temperature is improved up to 2.0 and the heat cycle temperature difference is 1000 K, the total efficiency of the conversion is around 23%. This result requests us to find a different way to use this technique in the conventional conversion system. Here, we propose a new system of thermoelectric conversion, which is applied to a steam power plant, in order to improve the total efficiency of the system. This is called the topping system. Since temperature difference between the flame and the pressured steam is large, the loss of exergy is large in the boiler and the thermoelectric conversion is available in this heat cycle. This structure does not lose the energy because the low temperature side of the element is that of the steam. If we insert the element between the inner wall and steam tube of the boiler, the resistance of the heat circuit is increased, but this is not a serious problem if GeSi semiconductor is used. A scale of the thermoelectric generation is 10000 times higher than that of the present generator, and therefore the mass production research is needed. Rough cost estimation has been done and the cost of the thermoelectric conversion is 2.1 US$/Watt, and this is almost one-third of the present price of the element based on bismuth telluride.