Design and Analysis of Energy, Exergy and Economy of the Sub-cooled Compressed Air Energy Storage System (SCAES)

In this paper, a sub-coled CAES unit has been investigated to produce electricity and cooling demand during peak times, and energy efficiency and payback period have been calculated in different operational conditions. For this purpose, a computer code has been developed in MATLAB software by solving the relevant equations in repetition process with appropriate time step. The results showed that by increasing the compression and expansion stages, the energy efficiency improves. Also, increasing in compression’s stages, the system payback period has been decreased, while increasing in expansion’s stages, the system’s payback period has been increased. The system has the best its performance when the temperature of tank is equal to that of ambient. In the study of a real sample that provides 900 kW of output power over a period of 4 hours, the payback period for the average price of electricity consumed was 15 cents per kWh, excluding the 8-year inflation rate, but based on the current net value method After 11 years, the proposed system becomes profitable.