Long-Term Performance of Anti-Freeze Protection System of a Solar Thermal System

Abstract

In a moderate, transitory climate, to prevent freezing of outdoor pipes and collectors in solar thermal systems, anti-freezing fluids are commonly used. There is little experience of using water without any additives as a solar thermal fluid in such a climate. Based on these findings, to fill the knowledge gap this article presents the long-term results of thermal performance and anti-freeze protection of a solar heating system with heat pipe evacuated tube collectors with water as a solar thermal fluid. The operation of this system under real conditions was analysed for five years in southern Poland. The annual value of solar insolation ranged from 839 to almost 1000 kWh/m2. The monthly efficiency of the solar collectors from March to October was usually higher than 25%, and the lowest was between November and January. The anti-freeze protection system consumed annually from 7 to 13% of the heat generated by the collectors in the installation. Supporting the operation of the central heating system in the building during the winter season highly improved the efficiency of the solar collectors. Results show that it is possible to use water without any additives as a solar thermal fluid in a moderate, transitory climate.

Increasing Energy Self-Consumption in Residential Photovoltaic Systems with Heat Pumps in Poland

“…In Cracow, the lowest average dry bulb air temperatures (−15 • C) are observed from December to February, and the highest ones (30 • C) are from May to August. During the year, 1041 kWh/m 2 of total horizontal solar radiation is available with the highest daily values of 5.0-7.5 kWh/m 2 between the end of May and the beginning of September, which is consistent with the data presented in the study [30]. From 1 April to 30 September, yearly insolation reaches 76%.…”