Passive solar hot water systems are less expensive than active systems because they do without pumps and controls. For much the same reason, passive solar water heaters tend to last longer and require less maintenance. However, they are usually more inefficient. There are two types of passive solar thermal water heaters:
Integral collector-storage (ICS) systems have a batch of black tanks or tubes in an insulated, glazed box. Cold water flows through the collector and heats up. This heated water than flows directly into the house. In this type of system, the water itself collects the solar heat. This type of system is most useful in areas that rarely freeze and are warmer because hot water is only readily available during the day and evening when sunlight is readily available.
ICS systems are the easiest for homeowners to build themselves, as long as only small amounts of water are intended for heating. The tanks, including designs using tubes, usually hold from 30 to 50 gallons of water. This much water is quite heavy so a proper mounting system must be taken into consideration.
ICS systems are often used to supply water to a backup water heating system.
Thermosyphon systems work as water flows the system when warm water rises and cool water sinks. Collectors are installed below the tank in order to facilitate the rise of warm water. Because the heavy tank must be higher than the collector, added care must by taken by the solar contractor to secure the roof against the added weight. This makes thermosyphon systems more expensive than their ICS counterpart.
Passive solar water heating systems usually require a backup system of some kind to pick up the slack on cloudy days.
Thermosiphon is a type of passive solar water heating that utilizes convection to heat water. Water passes through a closed-loop circuit that is vertical and thus needs no mechanical devices or pumps.… Read more »
Integral Collector systems (ICS) are one of three types of solar hot water collectors. What differentiates ICS from evacuated tube and flat plate collectors is that the water itself is the collector.… Read more »