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Solar Water Heaters
Solar water heating (SWH) is the conversion of sunlight into heat for water heating using a solar thermal collector. A variety of configurations are available at varying cost to provide solutions in different climates and latitudes.
SWHs are widely used for residential and some industrial applications.
A sun-facing collector heats a water that passes into a storage system for later use. SWH are active (pumped) and passive (convection-driven). They are heated directly . They operate independently or as hybrids with electric or gas heaters.
Flat-plate solar thermal collector
Flat plate collectors are an extension of the idea to place a collector in an 'oven'-like box with glass directly facing
the Sun. Most flat plate collectors have two horizontal pipes at the top and bottom, called headers, and many
smaller vertical pipes connecting them, called risers. The risers are welded (or similarly connected) to thin
absorber fins. Water is pumped from the hot water storage tank or heat exchanger into the collectors' bottom
header, and it travels up the risers, collecting heat from the absorber fins, and then exits the collector out of the
top header.
The type of glass used in flat plate collectors is tempered glass.This glass can withstand significant hail without
breaking, which is one of the reasons that flat-plate collectors are considered the most durable collector type.
Evacuated tube
Evacuated tube collectors (ETC) are a way to reduce the heat loss,inherent in flat plates. Since heat loss due to
convection cannot cross a vacuum, it forms an efficient isolation mechanism to keep heat inside the collector
pipes. Since two flat glass sheets are generally not strong enough to withstand a vacuum, the vacuum is created
between two concentric tubes. Typically, the water piping in an ETC is therefore surrounded by two concentric
tubes of glass separated by a vacuum that admits heat from the sun (to heat the pipe) but that limits heat loss.
The inner tube is coated with a thermal absorber.
Flat plate collectors are generally more efficient than ETC in full sunshine conditions. However, the energy output
of flat plate collectors is reduced slightly more than ETCs in cloudy or extremely cold conditions. ETCs can gather
energy from the sun all day long at low angles due to their tubular shape.
"Our Solar Water Heaters offer Best-in-Class efficiency and our ETC solar water heaters work well even in cloudy conditions ensuring a constant supply of hot water"
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