Water heating with tracking to sun solar batteries

Abstract

Traditionally it has been considered that solar collectors are more effective for water heating than solar batteries (PV) because of changing of energy from heat to electricity and then back to heat in the case of batteries. But there are some aspects why solar batteries can be more effective for water heating than solar collectors, especially in northern countries, where ambient temperature is low. The first of them is negative impact of temperature difference between the absorber of the solar collector and ambient air on the efficiency of the solar collector. Therefore, efficiency of the solar collector importantly decreases with increasing of the temperature of the obtained hot water. The efficiency of solar batteries only slightly depends on temperature and, opposite to the case of solar collectors, is higher at lower ambient temperature. The same situation is at the heat exchanger traditionally used with the solar collector: the amount of heat given from the heat carrier to usable water depends on the temperature difference between them. Electricity from solar batteries heats water independently on its temperature. Also tracking to sun is more complicated for solar collectors than for solar batteries. Water heating using tracking to sun solar batteries has been studied in this work. Two photovoltaic panels Solet P6.60-WF-250 with surface area 3.25 m2 each, mounted on a dual axis tracking device, were used for water heating with electrical resistance heaters. Measurements were carried out from 1 of August till 22 of October 2016. The results show that the measured power of batteries on sunny October day is approximately 500 W and 28 1 reservoir without heat insulation of water has been heated up to 50...70 °C, or by 30 °C during 2h what corresponds to 490 W received power. An opposite dependence of the photovoltaic efficiency on ambient temperature also has been observed.