Thermodynamic research on compressed air energy storage system with turbines under sliding pressure operation

A high-pressure stage turbine will discharge energy under sliding pressure mode in compressed air energy storage system (CAES) if without throttle valve installed upstream the turbine (NV-CAES). In this work, four high-pressure stage turbines A similar to D are designed for NV-CAES with 1-D turbine loss model under four inlet pressures of 5.0 MPa, 7.0 MPa, 9.0 MPa and 11.0 MPa, respectively. Simulation results reveal that Turbine B has relatively wider working operation range and higher performance. Then, another high-pressure stage turbine in NV-CAES is designed with General performance curve (GNV-CAES) under inlet pressure 7.0 MPa. Both thermodynamic model and exergy efficiency model were built to simulation system performance of these NV-CAESs. For comparison, a CAES equipped with throttle valve (V-CAES), in which the turbine train works with constant inlet pressure, is also computed. Compared with V-CAES, GNV-CAES reduces the exergy destruction from 52.25 GJ to 46.29 GJ and improves the exergy efficiency by 3.3%. The thermodynamic comparison among NV-CAESs shows that The CAES with Turbine B shows the best performance with the storage pressure of 4.0-13.0 MPa. Thus, properly choosing design conditions of high-pressure stage turbine plays an important role to enhance performance of CAES with sliding pressure discharging mode. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study compared the performance of high-pressure stage turbines under different inlet pressures in NV-CAES system, demonstrating that turbine B has a wider operating range and higher performance, improving system efficiency. By establishing thermodynamic and exergy efficiency models, the performance of NV-CAES systems can be effectively simulated.