Solar Hot Water Systems

Solar Collectors

Flat plate collectors are large shallow boxes that have water moving directly through them and must be positioned to catch the sun. These collectors heat liquid or air at temperatures less than 80°C. They are used primarily in warm climates.

Evacuated tube collectors are able to capture the sun from many different angles because of their 360 degree tubular design. Evacuated-tube collectors can achieve temperatures of 75°C to 175°C. This type of collector is recommended for cooler, cloudy regions.

Collector Placement

If you are thinking about buying a solar hot water system, one of the most important things you need to consider is where to place the solar collector. Solar collectors need to have full or nearly full sunlight all year. They need to be securely mounted to the roof because wind can create a strong lift underneath them. So you need to be sure that the area you choose for the solar collector is large enough and has the proper exposure to the sun.

Tank Size

The tank should hold one day's worth of water for the entire household. When determining what size tank you need: here's a simple table:

System Type

Open Loop Solar Hot Water Systems circulate potable water directly through the solar collector into the storage tank. That means the water that is used in the house is the same water that has circulated through the solar collector. It is called open loop because the system is open to city water pressure. An open loop system is simpler, more efficient and reliable if you live in a warm climate. This type of system is known as a direct circulation system.

Closed Loop Solar Hot Water Systems use a heat transfer fluid to collect heat and a heat exchanger transfers the heat to the water supply.The heat transfer liquid usually consists of a water and antifreeze mixture which circulates through the collectors. This type of system is known as an indirect circulation system.

Climate

If you live in a climate where it rarely freezes, a direct circulation system would be a good choice. Indirect circulation systems use a heat exchanger and are recommended for climates prone to freezing.

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