Energy, exergy and economic analysis of utilizing the supercritical CO(2)recompression Brayton cycle integrated with solar energy in natural gas city gate station

摘要

The pressure of natural gas stream must be reduced in city gas station. The natural gas has to be preheated before pressure reduction takes place usually through throttling valves. In conventional city gas stations, the natural gas is preheated by indirect water bath heaters, which burn a large amount of the natural gas as fuel. In this study, the rejected heat from a supercritical carbon dioxide recompression cycle using solar energy is recovered for preheating the natural gas. The novel design of this system generates uniform electricity as well as preheats the natural gas in city gate station. The proposed system is simulated for Birjand city gas station as a case study, and a thorough techno-economic analysis is performed in Engineering Equation Solver for evaluating the system performance. The results of this study demonstrate that parabolic trough collectors with 25 rows are the most efficient solar system while the annual average of thermal and exergy efficiency of the system is 0.56 and 0.41, respectively. The exergetic analysis of the system shows that the highest average exergy destruction takes place in the throttling valve and the second highest in the solar collectors. Also, the total amount of fuel saving is estimated at 4.87 million cubic meters annually and the net power output is equal to 2.86 MW. From the economic point of view, the value of the payback period is estimated 4 years and, based on the net present value method, after 8 years, the initial investment could be returned.