Introduction to Solar Water Heating
The amount of hot water a solar water heater produces depends on the type and size of the system, the amount of sun available at the site (isolation levels), proper installation, and the tilt angle and orientation of the collectors. To take advantage of solar water heaters, you must have an non-shaded location, where trees and other buildings will not block the suns rays and where the collectors can face south (in the northern hemisphere). The roof of a building is the best location.
In almost all cases, a solar water-heating system works as an auxiliary system alongside conventional gas or electric water-heating systems, which activate when necessary. When a solar hot water system is used, the water being released into your hot water tank (boiler) is already "hot" therefore; the boiler does not need to fire or only needs to fire for a short period of time, thereby saving you money on fuel costs. As hot water from the boiler is used and more is released from the solar system, the water from the solar system will mix with the water already present in the hot water tank. For this reason, to receive the maximum benefit of the solar hot water system, you should have a well-insulated boiler and the size of the tank of your solar system should be equal or smaller than your boiler.
Types of Solar Water Heating Systems
Solar water heaters are characterized as either active or passive:
A. Active systems use an electric pump, valves, and controllers to circulate the heat-transfer fluid (or water) through the collectors and are usually more expensive than passive systems. These systems are usually easier to retrofit than passive systems because their storage tanks do not need to be installed above or close to the collectors.
When characterized as open-loop ("direct"), they use pumps to circulate water through the collectors. This design is efficient and lowers operating costs but must be used with an anti-scaling device if your water is hard as scale quickly disables the system. (Thermosol® model: High-Pressure System for Industries & Swimming Pools)
B. Passive systems move the water through the tank and collectors without pumps. Passive systems have the advantage that electrical outages and electric pump breakdowns are not issues. This makes them generally more reliable, easier to maintain, and possibly longer lasting than an active system.
One type of passive system is called a "thermosiphon system". This type of system relies on warm water rising (convection) to circulate water through the collectors and to the storage tank. In this type of installation, the tank must be above the collector. For smaller systems (Thermosol® has seven sizes) the tank is actually incorporated in the collector. (Thermosol® model: Thermosiphon Systems).For large systems a separate storage tank is required and must be located close and above the collector. (Thermosol® model: Thermosiphon System for Industries).
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