Batch water heaters are the simplest of all solar water heaters. These are also known as integral tank and collector heaters. Batch water heaters use tanks between 30-80 gallons. The tank is placed within a weatherproof, insulated enclosure with one side having a transparent or translucent glazing(s), normally two layers of glass. The side of the tank facing the glazing is painted black to absorb the solar energy which is conducted directly to the water in the tank.
Batch solar water heaters work great in the tropics. Due to nightime heat losses we do not reccomend them in climates above approximately 35 degrees latitude. The only thing on one side of the collector between the hot tank and the cold air outside is 2 layers of glass. In climates harsher than this, throughout the winter months the heater tends to lose at night most of the daytime energy gained. Batch water heaters are simple, reliable, easy to install and are tipically low cost. They can provide 50-90% of hot water needs depending on usuage and climate. The piping to and from the heater is the weak link in the chain. It should be well insullated and heat tape should be installed in harsh climates.