How is a Solar Hot Water Panel Made?
Solar hot water panels are the means by which the sun’s energy is captured and used to heat water pumped into it. From there, it is distributed into a storage tank for home use. Without panels, solar hot water heaters would not be possible; hence they are the primary components of any system.
There are three basic types of solar hot water panels or solar collectors: flat plate collectors, integral collector storage panels and evacuated tube collectors. By far the most common is the flat plate collector, for it can be applied in both warm and cold climates. Since the flat plate collector is the commonest form of solar collection, its makeup requires the most clarification and is the focus here.
Basic Construction of a Flat Plate Solar Collector
A flat plate collector is a dark metal plate, usually either aluminum or copper. The plate is contained within a metal box and covered with what is known as the glazing. The glazing can be translucent glass or plastic that is designed to allow as much solar energy as possible to get in while preventing it from getting back out. The metal box is fully insulated to protect against the loss of heat. As sunlight passes through the glazing, it is absorbed by the metal plate and converted into heat energy. Depending on the circulatory system of the solar water heater, either water or a different heat transfer liquid is channeled through the panel where it collects the heat thus absorbed by the plate. Once the heat energy has been transferred to the water or other liquid, it is directed into the storage tank for use.
Direct vs. Indirect Circulation
Another major distinction with solar hot water heating systems that use flat plate collectors is between direct and indirect circulation methods. Direct or open-loop systems channel the water for use in the home directly through the flat plate collector to receive the heat energy absorbed by it. Indirect or closed-loop systems circulate a heat transfer liquid–water, antifreeze or some form of oil–through the pipes in the panel. Rather than heat the water directly, the heat transfer liquid is heated, then pumped to the storage tank where, through a process of heat exchange, it is able to heat the water for home use. Both direct and indirect circulation systems work well for use with flat plate collectors. Often, climate is the main factor in deciding which type to use. In cold weather regions, indirect systems work better because there is no chance for the non-water heat transfer liquid to freeze. However, drain back systems which continually drain the collector of any water also work.
Piping in Solar Panels
The pipes that channel the water or heat transfer liquid through the flat plate collector are another important element in the system. In areas where freezing temperatures are of little concern or a heat transfer liquid other than water is used, a common arrangement of the pipes inside the collector is a serpentine S-like pattern that allows for a consistent flow of liquid through the collector. Another type of pipe pattern is a parallel pipe arrangement. Rather that one path the liquid can take as with the S-pattern, the arrangement of parallel pipes offers several, but leaking can be a bigger problem.
The makeup of a flat plate collector solar panel for a solar hot water heater is simple in concept yet ingenious in design. Being the most common type of solar collector for this type of water heater, it is suitable for use in all climates. However, it is modifiable to meet the weather conditions in any particular region.