An engineer has proposed that compressed air be used to “level the load’ in an electrical-generation and distribution system. The proposed system is illustrated in Fig. P7–199E. During those times when electrical-generation capacity exceeds the demand for electrical energy, the excess electrical energy is used to run the compressor and fill the storage tank. When the demand exceeds the generation capacity, compressed air in the tank is passed through the turbine to generate additional electrical energy. Consider this system when the compressor and turbine are isentropic, the tank’s temperature stays constant at 70°F, air enters the compressor at 70°F and 1 atm, the tank volume is 1 million cubic feet, and air leaves the turbine at 1 atm. The compressor is activated when the tank pressure is 1 atm, and it remains on until the tank pressure is 10 atm. Calculate the total work required to fill the tank and the total heat transferred from the air in the tank as it is being filled.

Transcribed Image Text:

Turbine Compressor 4 Storage tank