Solar Hot Water Systems
2012 Solar hot water heating systems can be comprised of a number of technologies, most of which have been accepted in nearly all countries for a number of years. There are two basic types of solar hot water systems. The passive system, also known as a “close-coupled” system, uses a natural process called “Thermo-siphon” to draw the hot water into a horizontally mounted tank, directly above the solar panels. Another system is a “Pump-circulated” system. This system is considered an active system, since water is pumped through the solar collector. This is the most commonly used solar hot water system in use today. The main difference in these two systems, is the active system has a circulation pump, normally mounted on the ground floor, where the passive one doesn't.
There are various designs in Solar Collectors (solar panels). These are not at all like the photovoltaic panels used to create electricity. Some of these panels are a simple insulated glass topped box, which contain copper pipes, attached to sheet metal. The metal parts are all painted black, which help absorb more energy from the sun. Other types of solar collectors use a set of metal tubes which are near vacuum in pressure. These are surrounded by a glass cylinder. The heat transfer that takes place within a solar collector is normally achieved through a separate loop of fluid, containing both anti-freeze and a corrosion inhibitor.
For commercial and industrial applications, a parabolic mirror is sometimes used to concentrate the sunlight onto the tube. Heated water is stored in a hot water storage tank. This tank may need to be fairly large to hold sufficient water during inclement weather.
In both kinds of systems, as water passes through the solar collectors, it is heated. Both solar hot water systems are designed to deliver an optimum amount of hot water throughout most of the year. In some parts of the country, other types of water heaters may be needed during the cold months of the year. Although the global solar thermal market is dominated primarily by China, Japan, Europe, and India; the United States is starting to play a larger role in this market.