How do Solar Hot Water Systems Work?
Using the sun to heat water seems simple enough. As a garden hose produces scalding hot water when left out in the garden during the hot summer, heating water that is enclosed is a simple enough task. But to produce hot water for every need in a home without scalding anyone is more complicated. Another major complication factor for your solar water-heating system is the colder temperatures that come with winter.
When water freezes, it can expand as much as 9 percent and exert a force that equals at least 100,000 psi. Thus, water piping of even the strongest copper or metal is bound to crack with such a strong force exerting on it. If you happen to live in an area that does have freezing nighttime temperatures, then consider a direct-gain solar water-heating system to heat up all the water required for your household needs.
Direct-Gain System
Direct-gain refers to the method of harnessing the sun’s energy at a sunny spot outside of your home, usually the roof, where the water is heated and stored in a tank for later use for all household needs, such as hot showers, washing, cooking and the like. The storage tank for the hot water is also usually placed on the roof so that the heating process can be performed the hot water is stored away, typically in an insulated and glazed black box.
Alternatively, the water can be heated using either of two methods: flat-plate or evacuated tube. The water is then stored in a tank that is located somewhere in the home, often the basement. These simple systems of heating water use water pressure to move the water, which is cheap and easy to perform.
A batch collector or integrated collector storage is the simplest of the direct-gain systems, as it requires no extra solar collectors to heat and store the hot water on the roof easily and cheaply. However, the main disadvantages of such a system are the weight from the extra tank of water on a small portion of the roof, and the loss of heat in the tank when there is no sunlight.
The main difference between batch systems and direct-gain systems is that batch systems function best when most of the required hot water is used in the later part of the day, while direct-gain systems function best when most of the required hot water is used in the early morning part of the day because of its insulated tank and solar collectors.
A standard requirement of USDA hardiness with at least zone 8 must be confirmed before any home can be installed with any kind of direct-gain solar heating system. In areas the microclimate may not permit the installation.
Heat Exchange System
In climates that have freezing temperatures, you can use a system that has a heat exchanger to prevent any damage to the pipes, collectors or any related component during freezing weather.
There are two types of heat exchange methods: closed loop and drain-back. The heated propylene glycol fluids