batch solar heater
Passive, batch solar water heater: Cold water enters a pipe and can either enter a solar storage/backup water heater tank or the batch collector, depending on which bypass valve is opened. If the valve to the batch collector is open, a vertical pipe (which also has a spigot drain valve for cold climates) carries the water up into the batch collector. The batch collector is a large box holding a tank and covered with a glaze that faces the sun. Water is heated in this tank, and another pipe takes the heated water from the batch collector into the solar storage/backup water heater, where it is then carried to the house.
A batch solar heater, also known as a bread box system or integral collector storage system, is a simple solar collector consisting of one or more storage tanks placed inside an insulated box that has a glazed side facing the sun. Because the storage tank and the solar absorber act as a single unit, there is no need for other components. A batch collector is mounted on the ground or on the roof (in which case, the roof structure must be strong enough to support it).
Some batch heaters use "selective" surfaces on the tank(s). These surfaces are good absorbers of solar infrared radiation but inhibit radiative loss. On an area basis, batch collector systems are less costly than glazed flat-plate collectors but also deliver less energy per year.