Compressed Air Energy Storage (CAES, watch video on YouTube channel) is considered as one of the cheapest Energy Storage (ES) technologies in terms of capital cost ($/kWh) and maintenance cost ($/kW-year). CAES works in the process as: the ambient air is compressed via compressors into one or more storage reservoir(s) during the periods of low electricity demand (off-peak) and the energy is stored in the form of high pressure compressed air; during the periods of high electricity demand (on-peak), the stored compressed air is released, heated by a heat source from the combustion of fossil fuels or other methods, and then the energy stored in compressed air is captured by turbines/expanders to generate electricity. The major concern in deployment of CAES is its relatively low cycle efficiency compared with other ES technologies.
IMAGES project carried out the CAES whole system analysis via simulation study to identify the major energy losses which are important in improving the whole system efficiency. The results confirm that the current relative low efficiency of CAES systems can be improved to address the main concern of CAES system design and deployment. From our study, it is confirmed the following:
- The isentropic efficiencies of compressors and turbines and the heat transfer rates of HEXs are the key parameters to give the dominant influences on the system efficiency.
- The system configuration is another key factor in system efficiency improvement.
- A-CAES charging and discharging time regulation via flow control can also lead to different system efficiencies. These are considered as the important factors for efficient system design in practice.
- The results from optimal design study of low temperature A-CAES systems show that the system cycle efficiency and the heat energy recycle efficiency can potentially reach to around 68% and 60% respectively.
The results are reported in “Modelling study, efficiency analysis and optimisation of large-scale Adiabatic Compressed Air Energy Storage systems with low-temperature thermal storage” (LINK)