In pressurized water heaters, the inlet to the Solar Tank is through a Pressure Pump. Such systems do not have an air vent (as with normal atmospheric vented systems), but have a safety valve instead, to release the pressure build-up inside the tank. The tanks used in these systems have a dished-end construction and are of a higher thickness to withstand a working pressure of 8 kg/sq.cm. Typical inlet pressure from pressure pumps is around 3-5 kg/sq.cm.
This type of solar water heating system is used when the original cold water (from the source) contains dissolved minerals and is therefore hard water. A Thermal fluid is filled through a make-up tank in to the outer tank. In turn, this fluid gets circulated through the solar collector fins and tubes and goes back into the top of the outer tank. This fluid acts as a medium for heat transfer and prevents clogging of the copper tubes due to mineral contents in the original water source.
The inner tank gets filled with cold water from the original cold water source. Since the inner tank is immersed within the outer tank, the heat gets transferred to the inner tank through thermal conductivity and convection methods. The water in the inner tank then gets heated up and is available for various applications.
You can significantly reduce the cost of heating your swimming pool(s) by installing a solar pool heater. These come in both gas and heat pump varieties pool heaters, and are cost-effective incurring very low, annual operating costs.
Pool water is pumped through the filter and then through the solar collector(s), where it is heated before it is returned to the pool. In hot climates, the collector(s) can also be used to cool the pool during peak summer months by circulating the water through the collector(s) at night.