Thermoelectric generators in photovoltaic hybrid systems

The supply of distant electric devices that cannot be connected to the public electricity grid for reasons of cost, waiting time or due to the need of local flexibility has been a major problem. To date, the power supply of such stand-alone systems has been based mainly on battery-buffered fossil-fueled motor-generators. Apart from the consumption of limited fossil fuel reserves, the disadvantages of these systems include the creation of noise and exhaust gases, the constant need to obtain fuel and, most important, the high amount of maintenance and repairs. For these reasons, and due to the progress in regenerative energy conversion made in the last decade, battery-buffered PV power systems are used more and more often. Their advantages are high reliability and low cost of repairs. However, far away from the equator, where solar radiation is very low during the winter, large PV generators are needed to guarantee sufficient reliability. Therefore, system costs are high. Another disadvantage is that the battery lifetime in PV power systems is significantly reduced compared to its lifetime in fossil fueled systems. To avoid these disadvantages, the PV generator can be combined with fossil fueled power generators. In the medium power range, from 10 W up to several hundred W, thermoelectric generators appear to be particularly qualified because of their reliability and lifetime. In this paper, a (so called) "photovoltaic hybrid system" is compared to a purely PV power system on the basis of model calculations starting with the solar radiation situation on the Earth's surface.