Fora hundred years, simple solar batch heaters have been used in theUnited States. The term ICS (integrated collector storage) tells usthat the collector and storage tank are combined into one unit. A tankof water, enclosed in an insulated box covered with glass, is placed inthe sun facing south. Cold water is piped to the bottom of the tank;hot water is taken off the top. Whenever there´s a call for hot water,water pressure from the home moves hot water from the top of the solarbatch heater as cold water is pushed into the bottom.
Since thepotable water is heated directly, this is an open-loop system. Andsince no pump is used to move the water from collector to end use, itis passive. The batch heater is a popular choice for homes in moderateclimates where freezing is not much of an issue. Commerciallymanufactured batch heaters are relatively low cost. Crude batch heaterscan even be homemade. If batch heaters are installed on the roof,weight has to be taken into account. Commercial batch heaters can weigh200 pounds (90 kg) dry, and when filled with 40 gallons (150 l) ofwater, more than 320 pounds (145 kg) is added.
Because oftheir relatively low cost and simplicity, for those living in moderateclimates with good sunshine available, the batch heater is probably thebest value for heating domestic water.
The illustration includes the primary components of any solar batch heater system.