Roof Mount Closed Loop Thermosiphon Solar Hot Water Systems

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Closed loop roof mounted or Closed loop thermo syphon flat panel heaters can be the most reliable type of solar hot water system because they have minimal moving parts that may need replacing. Closed loop thermo syphon systems are recommended for frost areas. Split solar hot water systems where you have the solar hot water collector on the roof and the tank on the ground need a solar hot water circulating pump and solar controller to operate which makes these system more efficient the roof mount systems.

  1. The inner hot water storage tank holds hot water for domestic use only. The heat transfer fluid in the outer tank (9) and the domestic hot water never mix. Conduction of heat from heat transfer fluid in the outer tank to the domestic hot water in the inner hot water storage tank occurs through the wall of the inner hot water storage tank.
  2. The domestic hot water outlet pipe. Hot water is forced out of the inner hot water storage tank (1) by the incoming mains pressure cold water (3). This happens when a hot tap is opened.
  3. The cold water inlet pipe. Mains pressure cold water forces its way into the inner hot water storage tank (1) through the cold water inlet pipe. This happens when a hot tap is turned on.
  4. Arrows show the direction of the flow or current as the heated heat transfer fluid rises from the top of the Flat panel collectors (8) into the outer tank (9).
  5. Arrows show the direction of the flow or current as the cooled heat transfer fluid drops from the outer tank (9) into the bottom of the panels (8) to be re heated by the sun.
  6. The Pressure and Temperature Relief Valve (PTRV). When water is heated it expands. The PTRV releases excess water pressure cause by the expanding water in the inner storage tank (1). It also releases water that is hotter than 99°C
  7. The insulated outer jacket stops the heat transfer fluid in the outer tank (9) as well as the Domestic hot water in the inner hot water storage tank (1) from loosing heat.
  8. The Flat panel collectors as well as the outer tank (9) are filled with heat transfer fluid. Flat Panel Solar Collectors absorb heat energy from the sun. This energy is transmitted into the heat transfer fluid. As the heat transfer fluid is heated in the panels by the sun its density decreases causing it to rise into the outer tank (9).
  9. Once in the outer tank, the heat in the heat transfer fluid is exchanged through the wall of the inner hot water storage tank through a process called conduction. As the heat is released from the heat transfer fluid its density increases causing it to drop out of the outer storage tank and back to the bottom of the panels (8). This natural reoccurring current is called thermo syphoning. This current will continue to flow as long as the water in the inner hot water storage tank (1) is cooler than the fluid in the out tank.