ACTIVE SYSTEMS
 Active systems use pumps to circulate water or other heat transfer fluid through the system. When sunlight heats one or more solar collectors sufficient for water heating, sensors and a controller activate a pump to circulate a fluid - either potable water from the storage tank or a food-grade antifreeze solution in climates exposed to freezing conditions.An active system also has a flat-plate collector on the roof and a solar storage tank which is usually located in a garage or utility room. An electric pump circulates the water between the collector and the indoor solar storage tank whenever solar energy is available and needed to increase the temperature of the water in the solar storage tank. |