Abstract
There is an urgent demand to reduce compression power consumption in Compressed Air Energy Storage (CAES) systems. Wet compression has been widely used in gas turbines to reduce compressor power consumption and improve thermal efficiency, but this technology has not been applied yet in the CAES field. In this paper, a centrifugal compressor for CAES was numerically studied to investigate the effect of wet compression on compressor and droplet motion. The results showed that wet compression makes the performance curve shift to a high-pressure ratio/efficiency. Meanwhile, wet compression lowers the stall margin and narrows the stable operation range, and the effect is enhanced with the increase of water injection ratio or the decrease of average droplet diameter. Wet compression can effectively save compressor power consumption during energy storage, and at the designed pressure ratio, the power consumption can be reduced by 1.47% with a water injection ratio of 3% and an average droplet diameter of 5 μm. Influenced by the inertia and secondary flow, the droplets migrate to the impeller pressure and shroud side, thus causing brake loss by impacting on blades. The migration of droplets strengthens with the increase in the average droplet diameter and flow coefficient.
Highlights
Since renewable energy sources such as solar and wind energy are unstable and intermittent, developing energy storage is of great importance for the large-scale use of renewable energy [1].Compressed Air Energy Storage (CAES) has the advantages of a large energy storage capacity, long energy storage period, high efficiency and low investment costs per unit, and it is considered to be one of the most promising large-scale energy storage technologies [2]
Wet compression can effectively save compressor power consumption during energy storage, and at the designed pressure ratio, the power consumption can be reduced by 1.47% with a water injection ratio of 3% and an average droplet diameter of 5 μm
Abdelwahab developed a one-dimensional performance prediction model for centrifugal compressors’ wet compression, and the results showed that wet compression shifts the performance curve towards a higher pressure ratio and larger flow rate [20]
Summary
Compressed Air Energy Storage (CAES) has the advantages of a large energy storage capacity, long energy storage period, high efficiency and low investment costs per unit, and it is considered to be one of the most promising large-scale energy storage technologies [2]. A large-scale Compressed Air. Energy Storage (LSCAES) system requires its compression sub-system to have a high-pressure ratio, large mass flow, high efficiency and wide operating range. An LSCAES system usually adopts multi-stage compression and intermediate cooling to reduce power consumption while achieving a high-pressure ratio. The evaporation latent heat is used to reduce the outlet temperature, and the compression process is closer to isothermal compression [4,5]. This technology, Energies 2019, 12, 906; doi:10.3390/en12050906 www.mdpi.com/journal/energies
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