Energy Balance of Solar Water Heaters Thermosyphonic Systems

This work introduces a methodology for determination of energy balance for solar water heater (SWH). Solar legislation in Israel requires installation of solar water heaters in new buildings up to 9 floors from roof. The legislation from year 1980 is based on technology of late 70's. This publication compares old types of installation (steel pipe) with the current common practice (2017) of installation of solar water heaters in Israel. The results are energy losses for circulation pipes, hot water supply pipes and storage tank. The publication introduces also the Israeli system of determination of size of solar water heater and describes the procedure to determine amount of energy gained by the heater every month. It analyzes thermosyphonic systems, but may be helpful to analyze also forced circulation systems. The balance is for demand scenario as determined using national statistics (unique for Israel). The balance shows that in most months of the year SWH supplies more hot water than required for sanitary use. Most of the hot water from solar energy is used for showers while the rest may be used for other applications like washing machines and dishwashers. The balance shows that the main losses of energy are for storage tank envelope, while hot water supply pipes are minor energy users. This work may be helpful for techno-economic evaluation of water heating options and determination of the optimum solutions. It also contains large volume of useful data and information and can serve as solar water heating manual or basic material for solar energy study.