The Calculation of the Amount of Energy Needed to Keep the Solar Collector Absorber Surface above the Freezing Point of Water in the Polish Climate All Year Round

One of the simplest methods of employing solar energy is using the heat generated in solar collectors for the heating of household water. When there is a lack of heat collected from the tanks holding the water, while a large amount of sunlight is present on the collectors, stagnation occurs. One of the main effects of stagnation is faster degradation of solar fluid. Our paper suggests that changing the solar fluid to water can bring benefits, as it is non-toxic, publicly available, and allows for easy dosing of the system. The main objective of this paper is the calculation of the amount of energy needed to keep the temperature of the water in the installation above freezing throughout the year. This allows the comparison between water and antifreeze as energy carriers. In the current paper, we only consider the use of the installation for hot water, because the demand for it is generally constant throughout the year. The use of water is advantageous during filling, since it is cheaper and non-toxic. It is more convenient for supplementing, filling, and emptying the installation. If water is left in the plant all year round, however, the user must bear in mind the energy costs of maintaining the collectors at temperatures above 0 °C, and the increased cost of providing the pump drive to the collector during these cold periods. In the case of flush installations for the winter, these costs are not incurred.