Working principle: When sun rays strike the collector glass cover, three things happen. The cover observes a small portion of the energy, the sun is reflected, and the remaining portion is transmitted through the glazing to reach the absorber and transformed into heat conducted to the water flowing in riser tubes attached to the absorber plate. The water circulates to the storage tank and recirculates to the evening. The circulation occurs either through the natural process (thermo-siphon) /forced of conversion (hot water rises to the top and cold water flows into replace it from the bottom). The tank is well insulated to prevent heat loss by radiation to the atmosphere temperature of the water rises from 25 degrees centigrade to 70 degrees centigrade in a day.
Solar Water Heaters are Two Types
Based on the Flow of Water
Thermo-siphon system: This is a method of passive heat exchange based on natural convection, which circulates liquid without requiring a mechanical pump. This circulation can either be open-loop, as when the liquid in a holding tank is passed in one direction via a heated transfer tube mounted at the bottom of the tank to a distribution point – even one mounted above the originating tank – or it can be a vertical closed-loop circuit with a return to the original vessel. Its intended purpose is to simplify the pumping of liquid and/or heat transfer by avoiding the cost and complexity of a conventional liquid pump. This system is simple, relatively inexpensive and requires little maintenance due to the absence of moving parts. Flat plate Thermo-siphon systems are, however, unsuitable in freezing climates because water remains in the collectors always and may freeze on frigid days resulting in the pipes bursting. These types of systems are suitable for domestic applications with relatively small requirements.
Force flow system: This system is for commercial use and utilizes a pump to circulate water with mechanical help. Pump.
Based on the Type of Solar Collectors
Flat Plate Collector system (FPC): In this system, the solar radiation is absorbed by the flat plate, which consists of an insulated outlet metallic box covered on the top with a glass sheet. Inside are blackened metallic absorber (selectively coated) sheets with built-in channels or riser tubes to carry water. The absorber absorbs solar radiation and transfers the heat to the flowing water.
Technical Specifications
| Overall dimensions | 2132 x 1045 x 95mm |
| Effective absorbed area | TWO +/0.1 M SQ. |
| Glazing material and thickness | 85% and 4 mm thick |
| Absorbed material and thickness | Copper: 0.214 thickness |
| Absorber coating | Block chrome and selective |
| Absorber absorptive and emissivity | >0.96 |
| Expected efficiency | 65% |
| Riser material and size | Copper tube 12.50mm; OD 0.56T |
| Header material and size | Copper tube 25.40 mm; OD 0.71T |
| Method of bonding with absorber | Cu-cu eutectic alloy brazing |
| The ceiling of the collector panel | Neoprene/EPDM rubber gasket with sealant |
| Bottom insulation material and thickness | Pre laminated resin bonded rock wool – 48 Kg/M Cu density – thickness 50mm bottom, 25 mm sides. |
| Collector stand materials | MS angles with epoxy paint as per IS 226 size, 40 x 40 x 6 mm. Vent valves, Gun metal chrome, plated suitably, end connections for connecting two collectors brass flange 65 OD 3mm thickness (according to system capacity), ½ inch expansion bolts will be anchored for collectors. |
| Collector housing | Extruded aluminium section 1.6mm thickness of suitable shape on sides and 0.7mm thickness Al. Sheet at the back shall be used for the collector box. The box should be mounted on an MS stand. Neoprene rubber packing washers shall insulate contact between different metals. |
Evacuated Glass Tube Collector (ETC)
In this system solar collector is made of double-layer borosilicate glass tubes evacuated to provide insulation. The outlet wall of the inner tube is coated with selective absorbing material. This helps the absorption of solar radiation and transfers the heat to the water, which flows through the inner tube.
Technical Specifications
| Output water temperature | 65 t0 70 degrees | ||
| Length of tube | 1500 mm, 1800 mm | ||
| Tube outer diameter | 47 mm, 57 mm | ||
| Inner tube diameter | 37 mm, 47 mm with selective absorption coating | ||
Number of tubes |
|||
| Sl.No. | Capacity in LPD | 1500mm, 37mm & outer 47mm dia | 1800mm, 47mm & outer 57mm dia |
| 1 | 100 | 15 | – |
| 2 | 150 | 22 | – |
| 3 | 200 | 30 | – |
| 4 | 500 | 60 | – |
| 5 | 500 | 70 | – |
| Storage tank volume | 100 litres tank | ||
| Storage tank material | SS 304 – Stainless steel inner | ||
| Support structure | Black power coated – mild steel | ||
| Electric backup | 2 Kw | ||
| Insulation | Poly Urethane foam | ||
| Reflector material | Al | ||
