Solar water heaters use solar energy to heat water for a variety of uses, including home, businesses and industrial uses. Swimming pools heating, under-flooring heating, space heating or cooling are other possible uses of solar thermal energy.
Solar hot water systems are composed of solar collectors, which collects energy from the sun. The heat collected is moved, through a fluid system, from the collectors to a storage tank and from there to the point of usage. The system may use electricity for pumping the fluid, or heat convection, depending on the type. The system may include also thermostats and a controller device to control the operation based on temperature differentials and hot water demand. In most cases a solar water heater can provide up to 85% of domestic hot water.
Solar water heaters can be passive and active. Passive solar water heaters, also called thermo-siphon, do not required a circulating pump to move the fluid from the collectors to the tank. The tank is located above the collectors and the fluid circulates by heat convection. This type of solar thermal system is inexpensive, easier to install, and work well in warmer climates.
Active solar hot water systems use a pump to circulate the heat transfer fluid, or water, from the collectors to the storage tank. This type of system is usually more efficient than passive systems, but are also more expensive, and more difficult to install.
Solar water heaters require larger and well-insulated storage tank. It is possible, but not necessary, to keep the existent electric or gas water heater by interconnecting the system already in place to the solar water heater. The solar water heaters pre-heats the water for the conventional water heater reducing the energy required, gas or electricity, to heat the water.
Two types of solar collectors are used for most all applications: flat-plate and evacuated-tube collector. Flat-plate collectors are indicated to warmer climates. Evacuated tube collectors are suitable to colder climates, larger residential or commercial applications. Both types of solar collectors can be used for passive or active systems.
Evacuated tubes are regarded as the most efficient and cost effective solar water heating method of producing natural hot water. As the name suggests the tubes contain a vacuum which has been manufactured with a single, double or triple wall construction. The glass on the inner tube is coated on its outer surface with an absorbent coating, and on its inner surface with a reflective coating. The tubes are vacuums which have a copper heat pipe which runs through the middle of the tube.
The heat pipe carries the heat, which is generated by infra red radiation, up the tube to be collected. The heat pipe contains anti freeze which allows heat to be generated even in freezing temperatures. The heat from the copper pipe is transferred into the Header Pipe through which more antifreeze flows. This heated antifreeze is then pumped through the hot water tank where the water gets hotter and the antifreeze gets cooler. The antifreeze then returns to the solar heating module to be heated again. This flow is constant resulting in the water in the tank becoming hot.
|Specification (Units)||47 Diameter tube||58 Diameter tube|
|Material||Borosilicate glass 3.3||Borosilicate glass 3.3|
|Selective Coating materials||AL/SS/CU||AL/SS/CU|
|tube length (mm)||1500||1800|
|outer tube diameter (mm)||47||58|
|glass thickness (mm)||1.6± 0.15||1.6± 0.15|
|absorption coefficient (pct)||≥0.93（am1.5）||≥0.93（am1.5）|
|emission coefficient (pct)||≤0.065（80±5）||≤0.065（80±5）|
|transmision coefficient (τ) (pct)||≥0.890（am1.5）||≥0.890（am1.5）|
|max strength (mpa)||0.8||0.8|
|vacuum pressure (pa )||≤5.0×10-3||≤5.0×10-3|
|weightof a single tube (kg)||1.3 kg||2.2 kg|
|thermalexpansion (degree)||3.3*10-6 / degree||3.3*10-6 / degree|
|insulation temperature (degree)||200||200|
|resist cold (degree)||-35||-35|
|resist hailstone (mm)||25||25|
|start-up temperature (degree)||<=25||<=25|
Solar flat-plate collectors [ FPC ] are suitable for warmer climates. Flat-plate collectors are affordable and easy to install. For a household size of 4 to 5 people, two flat-plate collectors should be enough to provide 80% of all hot water needs. The first step begins by determining the volume of hot water needed and whether there is area available for the installation. Solar collectors can be installed on the roof or on the ground.
Flat-plate solar collectors specification: Aluminum frame, galvanized steel plate, rock wool insulation, red copper pipes, fin and tube with brazed joints.
|Total area||23.4 sqft|
|Aperture size (m2)||21.2 sqft|
|Absorber size (m2)||21.5 sqft|
|Net Weight||81.6 lbs|
|Flow rate||21 gpm (0.35 gpm)|
|Pressure Loss||160mbar (water, propylene-glycol, 68 F)|
|Collector Connections||2 connectors at top - 3/4 NPT Connector Fittings|
|Absorber Type||12mm / Serpentine, laser-welded to aluminum absorber plate|
|Absorber Coating||Highly selective on aluminum|
|Absorption / Emission||95% / 5%|
|Covering||Low iron, clear, solar safety glass (ESG)|
|Transmission of Covering||88%|
|Cover Impact Resistance||Passed optional impact resistance tests following EN12975-2|
|Insulation||Mineral wool / 1.2"|
|Collector Frame Material||Powder coated aluminum|
|Efficiency||eta 0: 77.6% (relative to aperture area)|
|Heat Loss Coefficient - a1||(k1) 3.95 W/(m2K)|
|Heat Loss Coefficient - a2||(k2) 0.0165 W/(m2K)|
|Maximum Stagnation Temp.||375.8 F (191 C)|
|Maximum Operating Pressure||10 bar|
|Set up angle||20-90 degree|
|Heat loss||5.0w/C m2|
|Flow rate||1.35 GPM|
|Capacity||From 125 litres to 3000 litres and more as per system size.|
|Material of Construction||Stainless Steel 304 L , TIG welded (Argonwelded) with certified Stainless Steel ER308L filler wire.|
|Type||Cylindrical - Horizontal Reinforced Tanks|
|Dimension & Thickness of Plate||
|Pressure Testing||Hydro tested for leakage detection.|
|Insulation|| PUF Insulation with 40Kg. Density (40mm thick)
Glass wool Insulation with 48Kg. Density (100mm thick)
Rockwool Insulation with 100Kg. Density (100mm thick)
|Insulation Covering||26 SWG Aluminium sheet|
|Sealing||Covering completely sealed with Silicone sealant for water proofing of insulation.|