Closed System The sun's rays are ideal for moderate to high degree of elevated regions. High-efficiency black polyester powder coated absorber plate collectors are used. Warehouses with polyurethane insulation to maintain hot water for a long time taken by the minimum level of heat loss. Resistant to frost. SOLAR WATER HEATING SYSTEM WITH CLOSED CIRCUIT SOLAREN HOW IT WORKS. ? Closed-circuit solaren heat collectors solar energy absorbed by the system and the heat transfer fluid, antifreeze in the collector passes. As the hot water heater temperature with the principle of natural antifreeze liquid is moving upward through the collector and use the tank water into the jacket around the heat exchanger takes the lead. Here, the heat, drinking water and antifreeze fluid to cool the leads pass. Antifreeze cooling fluid entering the heat exchanger jacket with a hot fluid into the collector by changing the returns to the place. The fluid cooled, back in the collector is heated and rises to convey the warmth of drinking water in storage. This process continues until the warehouse is achieved in the warming of the entire water