SPONTANEOUS DOWNWARD HEAT TRANSPORT SYSTEM Quantitative determination of the overall efficiency in comparison to a conventional circuit with circulation pump

ABSTRACT The new system for the spontaneous downward transport of heat has been implemented in one of two equal hot water solar circuits, the other-one being a conventional forced circulation circuit. Purpose of the tests is the comparison of the performance of the two systems. Each circuit comprises 4 m 2 of thermal collectors and a water reservoir of 200 dm 2 placed about 9 m below the collectors. The two circuits are operated exactly in the same conditions. The parameters varied during the outdoor tests were: the amount of water extracted and its minimum delivery temperature, the hours of the day when the water was extracted, the setting of the differential thermostat. The results have shown that the efficiency of the forced circulation system is slightly better only in the low temperature range (temperature of the water store below about 30°C) or with low daily irradiation values. In the other cases, and particularly for a single water draw-off at the end of the day, the efficiency of the spontaneous system is better. This performance is obtained in addition to the exceedingly high reliability and to the property of working without the need of electrical energy.