Analysis And Optimization Of A Compressed Air Energy Storage-Combined Cycle System

Since the1970s,two issues have become focus points in the whole world’s energy industry. One problem is the crisis of increasingly serious energy shortage and people are urgent to find methods to improve energy efficiency. The other one is that power peaking problems have become so prominent that the security of the power system cannot be guaranteed. Climate change and global warming concerns, coupled with rising oil prices and increasing government support,are driving renewable energy legislation,incentives and commercialization.The use of bulk energy storage technology is an effective method to deal with the intermittency of wind power and to provide reliable and uninterrupted wind or solar-based electricity and thus facilitating higher penetration into the grid.Compressed Air Energy Storage (CAES) is a commercial, utility-scale technology suitable for providing long-duration energy storage with fast ramp rates and good part-load operation. It is one of the most promising storage technologies for balancing large scale penetration of renewable energies such as wind and solar power into the electric grid.In this paper, the Huntorf CAES power plant built in Germany was selected as the research object, the operation process of this CAES system was simulated by Aspen Plus,and analyzed the reasons for its low efficiency.On this basis,two improved CAES systems have been introduced,one of which combines CAES system with a regenerator and another adds absorption refrigeration apparatus to CAES system.Improved systems reuse the waste energy of the CAES system separately from the compression stage and the generation stage, improve the system efficiency and reduce the energy loss effectively.A novel CAES combined-cycle (CAES-CC) system is proposed, which is based on conventional CAES, and combined with a steam turbine cycle by waste heat boiler. The process of simulation and thermodynamic analysis was studied for a conceptual CAES-CC case. Compared with the conventional CAES, it showed that the electricity and heat rates of CAES-CC are lowered by0.13kWh/kWh and0.34kWh/kWh through using high-temperature turbine-exhausting air. Total efficiency of CAES-CC is improved by about10%in comparison to conventional CAES. Compressing inter-cooler heat can keep steam turbine hot standby in CAES-CC system so that its flexibility has been largely improved. This study brought about a new method for the improving efficiency of CAES and provided new thoughts for integrating with other electricity-generating modes.