Imants Ziemelis

Solar tracking stand for solar panels and collectors

The conversation of solar energy into electricity using photovoltaic panels and into heat energy using solar collectors is the challenge of the time. Presently widely used fossil energy is unfriendly to the earth environment and its amount is limited. Both solar panels and solar collectors produce more energy, if direct solar radiation strikes its working surface perpendicularly during all the operation time. For that special device – the sun tracking stands or trackers, automatically keeping their working surface perpendicular to the sunbeams, are used. Different constructions of solar trackers and actuators are known: trackers based on the clockwork principle, based on the principle of freon evaporation and condensation, based on the principle of spring made of shape-memory alloys and others. The trackers act on a control unit and actuator, changing the position of the panels or collectors in azimuth, or azimuth and zenith plane. Different constructions of the actuators are in operation. Driving mechanisms with one electric motor (turning only in one plane) or with two electric motors (turning in two planes) are widely used. In the Ulbroka Research Centre a solar tracking stand of a new construction has been developed. There only one electric motor with a gearbox and a crank mechanism simultaneously is turning solar panels in two planes (Latvia patent LV 15245 A, 2017). The device has been made, experimentally investigated in field conditions on the roof of a house and positive results have been obtained. The amount of electric energy produced by two solar panels placed on the developed stand during the summer time of 2017 has been compared with the gain of electricity produced by in the same conditions working stationary fixed panels of the same type. Tracking the sun panels had produced around 1.48 times more electric energy than the fix ones, but in September 1.3 times more.

Use of PV panels for water heating in Ulbroka research centre

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.