Passive solar water heaters

Passive solar water heaters heat water using only the energy of the sun. Though less efficient, they are more reliable and long-lasting than active solar heaters due to their lack of moving, electrical parts. They are also less expensive.

There are two types of passive solar water heaters. The first is an integral-collector storage system. This is essentially a black storage tank in a well-insulated box. The box includes one clear side facing the sun. As the sun's light and heat is absorbed by the tank, the water inside it is heated.

Thermosyphon systems are the second style of passive solar water heaters. Warm water naturally rises. This process circulates water through the collectors and into a tank above. As this is going on, the cooler water flows to the bottom, enhancing the system's circulation.