Long-term performance of a solar water heating system with a novel variable-volume tank

Abstract

A novel variable-volume tank is lately designed to cater for the varying needs of tank volume. Based on the validated models of collector and the novel tank, a mathematical model for the solar heating system with the novel tank is proposed in this paper. The system is designed for space heating and consists of solar collector, variable-volume water tank and auxiliary heat source. A case of office building using the solar heating system for space heating is studied. The thermal behaviour of the system during a 4-month heating season is simulated and investigated. The studied case shows that the novel tank system has clear advantage in providing 11.6% more useful heat and reducing 19% system heat loss compared to a conventional system. A parametric study is also conducted to analyse the impacts of tank insulation, tank volume and collector size on the long-term system performance. The results show that the long-term performance of the novel tank system is more resilient to a degraded tank insulation or an oversized tank volume, which contributes to a robust heating system to cope with extreme operating conditions.