A central solar domestic hot water system. Performance and economic analysis

A solar-assisted central hot water system was retrofitted onto one of the student dormitory complexes of the Ben Gurion University, Beer Sheva, Israel. The system consisted of twenty commercial solar collectors, of the pipe and plate type (1.78 m²/collector), and a 2 m³ central hot water tank connected to two dormitory buildings-one for singles and the other for couples. The system has two distinct loops: 1. (1) a solar loop, in which the heated water circulates between the collector panels and the central hot water tank, and 2. (2) a consumer loop, where the solar-heated water circulates between the central hot water tank and the dormitory. The solar-heated water circulates through the individual electric hot water tanks (1201. capacity), which existed in each apartment prior to the addition of the solar loop. The latter now serve as individual hot water storage and booster units for each apartment. The mains water is now introduced at the bottom of the central tank to replace consumed water, whereas previously it was introduced at the bottom of the individual tanks. This system has been in operation since November 1976 and its successful operation resulted in many such units being built commercially throughout Israel. The description of the system, the design and its performance, together with an economic analysis, are presented.