4. A 10 MWe Solar Pond in Israel uses an Organic Rankine Cycle ORC power conversion system to generate electricity. The ORC is a closed cycle that uses R134a as the working fluid to power the expander turbine. The cycle is pictured here: Warm pond water return Evaporator Cool pond water in Pump Warm pond water in Expander 10 MWe Generator Regenerator 6 Condenser Cool pond water return Attached is a T-S diagram of the power cycle. Lines of constant enthalpy h kJ/kg are shown on the diagram. Assume that the thermodynamic properties of pond water are the same as pure water. a. The efficiency of the electric generator is 0.90. The efficiency of the expander turbine is 0.8 with respect to R&A efficiency. Find the mass flowrate of R134a in the system from values of the enthalpy of the expanded R123a vapor. [Answer: 605 kg/s.] b. The condenser is cooled by pumping the cooler water at 25 C from the solar pond through tubes in the condenser, the R134a condenses on the tubes. Condensation takes place at 33 C, which is the temperature of the return water to the pond. Calculate the flowrate of water needed to cool the condenser by calculating the heat removed from the condenser. [Answer: 2430 kg/s.] c. R134a is evaporated with a heat exchanger that evaporates the R134a with the heat from the warm pond water. The temperature warm pond water is 80 C, evaporation takes place at 70 C. Find the mass flow rate of warm pond water through the heat exchanger. [Answer: 1710 kg/s] d. Natural gas is burned to superheat the vapor out of the evaporator, step 4-5 in the cycle. Calculate the heat rate of natural gas combustion needed to superheat the vapor. [Answer: 6.05 MW] e. What is the purpose of the regenerator in the cycle?