Use of PV panels for water heating in Ulbroka research centre

Abstract

Solar energy has been widely used not only in southern countries, but also in Latvia. In Latvia solar energy has been used mainly for heating of water and/or air in summer. In the Ulbroka Research Centre starting with summer of 2008 the vacuum tube solar collector Vitosol 200 SD2 is used for water heating in summer, when the central heating system does not work. Area of this collector is 3m 2 , and it works with 300 l hot water reservoir Vitocell B-100 CVB. Such collector satisfied the demand for hot water till 2013, when severe hail damaged the vacuum tubes of the collector. 9 tubes from 30 were broken. Now we propose photovoltaic (PV) panels for water heating. PV panels have some advantages in comparison with solar collectors: there is no need of the complicated system of heat exchanging and transporting of the heat from the roof of the house, where the solar collector is situated, to the rooms, where the hot water is used; there cooling is not going on, when the sun is covered by clouds; the heating power does not depend on the temperature in the hot water reservoir; it is more simple to ensure tracking to the sun for PV panels than for the solar collector. Measurements of water heating capacity of both stationary and sun tracking PV panels have been done to find out the necessary area of PV panels to satisfy the demand for hot water in the Ulbroka Research Centre. It was obtained that two PV panels Solet 60.6-WF-250, mounted on the tracker ensuring all day perpendicular striking of direct solar beams on the panel's surface, produce in average 4.66 kWh daily in summer. Such amount of energy is sufficient to warm 150 l of water to 26 Celsius degrees.