Performance of precooled CAES system using ORC-VCR to recover compression heat
The energy storage process in a conventional diabatic compressed air energy storage(D-CAES)system usually uses more than four compressor units to reduce the consumption of air compression work.However,this leads to a substantial discharge of low-grade compression heat into the environment and serious energy waste.To solve this problem,this study proposes a precooled CAES system that uses organic Rankine cycle-steam compression refrigeration(ORC-VCR)for compression heat recovery(ORC-VCR-CAES).In the proposed system,the compressor inlet air is precooled by recovering the compression heat generated during the air compression stage.This approach further reduces the consumption of air compression work and improves the round-trip efficiency of the system.The thermodynamic and economic analysis of the ORC-VCR-CAES coupling system are also performed.Results show that the choice of ORC-VCR cycle working medium considerably influences system performance.The ORC-VCR-CAES system using R152a as a cycle working medium exhibits the best performance,achieving a system cycle efficiency of 64.15%,which is 5.94%higher than that of the conventional D-CAES system.Moreover,considering external waste heat energy input,the ORC-VCR-CAES system attains an energy efficiency of 51.90%,which is 4.81%higher than that of the conventional D-CAES system.Although the energy loss in coolers is effectively reduced through the recovery of compression heat,the energy loss from compressor units is still large,which is a key equipment for further system optimization.Economic analysis shows that with peak and valley electricity prices at 1.26 and 0.30 CNY,the net present value of the ORC-VCR-CAES system increases by 9.64%compared to the conventional D-CAES system.Compared with the conventional D-CAES system,the percentage increase in the net present value of the ORC-VCR-CAES system is higher when the peak and valley electricity price difference is smaller.
compressed air energy storageorganic Rankine cyclevapor compression refrigerationthermodynamic analysiseconomic analysis
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