The temperature at the Lower Convective Zone (LCZ) of a solar pond (hot water storage section also called LCZ) is measured to be 80 °C while the ambient temperature is 25 °C. A Carnot cycle is assumed to use the heat extracted from the hot water storage section of the pond (at 80 °C) to run a power generation cycle while its condenser rejecting heat to the atmosphere at the surface of the pond (at about 25 °C). 

Assume no heat loss through the wall or the surface of the pond (this is not zero in practice) and also no more energy gain through the sun during the heat extraction period (i.e. night time or cloudy period). At these conditions, the temperature of the hot water section gradually drops from 80 °C down to 25 °C (variable high temperature source), as heat is extracted by the Carnot cycle from the high temperature source. 

Determine the work that can be extracted by this solar pond per kg of hot water stored in the LCZ of the solar pond.