On the addition of heat to solar pond from external sources

This brief note addresses the method of adding heat to a solar pond from an external source which is used to enhance the performance of a solar pond. Heat energy collected by Evacuated Tube Solar Collectors (ETSC) is transferred by circulating fluid from the Lower Convective Zone (LCZ) of a solar pond. While adding the heat, a strange phenomenon is observed here which is against the intuition that higher the amount of heat added to the pond higher will be the temperature of the pond always. It is noticed that in the case of no or low heat extraction from the pond the heat is actually lost from the pond to the circulating heat adding fluid in specific periods of time which causes a drastic downfall of solar pond temperature. Moreover, it is observed that larger the capture area of the ETSC, larger is the heat loss from the pond. A strategy to control the heat loss from the solar pond by installing temperature sensors and flow controller in LCZ and the circulating fluid exiting ETSC is discussed here.