The question is: Consider a thermal battery - a device for storing mechanical energy. Use two large containers as heat reservoirs where one contains ice and water in equilibrium and the other contains steam and water in equilibrium. Both are held at pressure=1atm. Energy is stored by using a carnot cycle to transfer heat from the colder reservoir to the hotter - how much ice is created and how much vapor is created when 1kW*hr of energy is stored? I know that a refrigerator is essentially a heat pump in reverse so we can consider a Carnot engine where heat is transferred from the cold reservoir. Work is done in order to do this, and the work for the refrigerator is negative. Since I don't know the temperatures, and n=only the pressure of the systems and the energy stored, I know I can't use the COP or efficiency in the problem but I am unsure where to go next. Any help is appreciated.