Batch solar water heaters, also called integral collector-storage (ICS) systems, are made up of a water tank or tubes inside an insulated, glazed box. Cold water flows through the solar collector. The water is heated and then continues on to the backup water heating storage tank. Some water can be stored in the collector until it is needed. ICS systems are a type of direct solar water heating system which circulates water to be heated, rather than using a heat transfer fluid to capture the solar radiation.
Photo Credit: Florida Solar Energy Center
Batch systems are only suitable for warmer climates. The collector itself and any outdoor pipes are susceptible to freezing in cold weather, and the batch collector can become very hot if the water is not drawn during the day. Batch systems lose heat during the night time. Nevertheless, batch systems are very good for heating water during the day. They are best for households with most hot water demand during the day and evening.
Cost and Durability
ICS systems can be quite heavy when filled with water and may require extra roof support. But aside from that, batch solar water heaters are simpler than other types of solar collectors, and are correspondingly less expensive. These can be one of the most cost-effective solar water heating systems for warm, sunny climates. Colder climates require additional components to the system, in which case another type of solar collector is likely more economical.