Chapter 5 - Solar Water-Heating Systems

Abstract

Chapter 5 is on solar water-heating systems. Both passive and active systems are described. Passive systems include thermosiphon and integrated collector storage systems. The former includes theoretical performance of thermosiphon solar water heaters, reverse circulation in thermosiphon systems, vertical against horizontal tank configurations, freeze protection, and tracking thermosiphons. Subsequently, active systems are described, which include direct circulation systems, indirect water-heating systems, air water-heating systems, heat pump systems and pool heating systems, which include the analysis of various heat losses like evaporation, radiation, convection heat losses, make-up water load, and solar radiation-heat gain. Then the characteristics and thermal analysis of heat storage systems for both water and air systems are presented. The module and array design methods are then described and include the effects of shading, thermal expansion, galvanic corrosion, array sizing, heat exchangers, pipe and duct losses, partially shaded collectors and over-temperature protection—followed by an analysis of the characteristics of differential thermostats. Finally, methods to calculate the hot water demand are given as well as a review of international standards used to evaluate the solar water heaters performance. The chapter includes also simple system models and practical considerations for the setup of solar water-heating systems, which include: pipes, supports and insulation; pumps; valves and instrumentation.