Experimental results of a solar hot water system with spontaneous, downward non-freezing heat transport system

Abstract Results are reported on the performance of a solar hot water system fitted with the spontaneous downward heat transport system previously tested at the technical scale. The vertical distance between the collectors (2.8 m 2 ) and the heat exchanger is 8.5 m. The overall efficiency is found to be about the same as expected from a conventional system with a differential thermostat and circulation pump. Moreover, there are the advantages of no maintenance, an extremely high reliability (the system has been in operation now for 1 1 2 yr without any fault) and independence from the availability of electrical energy for the control and pump.