Technical snags encountered in solar heater are ;

(a) corrosion of various forms has been a nagging problem as efforts have been made to use MS and aluminum with raw water. Use of galvanizing has been resorted to in case of steel absorbers and performance has been reasonably satisfactory, problems in certain localized areas still persist. Use of copper overcomes this problem but shoots up the cost.

(b) Formation of scales in absorbers due to direct use of raw water inhibits flow and increases resistance to heat transfer. The problems is more severe where thin and narrow passages are employed. A scale thickness of 1.22 mm in a 15 mm G.I.Pipe would decrease the collector efficiency by about 1 to 2%, (c) Failure and very poor reliability of the control hardware in the case of forced flow system like (i) A simple thermostat changes calibration over time. Capillary thermostat would provide better performance and reliable operation but are quite expensive (ii) problem with solenoid valve and at times level controllers.

Inadequate attention to controls and their maintenance, compromise made with selection of materials and processing of materials (to bring down initial costs) would severely hamper the commercialisation of solar water heaters.