Operating characteristics of constant-pressure compressed air energy storage (CAES) system combined with pumped hydro storage based on energy and exergy analysis

Potential and Evolution of Compressed Air Energy Storage: Energy and Exergy Analyses

“…Micro-CAES with an air cycle heating and cooling system can use the heat of compression and the cooling effect of expanding air with good efficiency as a multipurpose system [10]. Constant-pressure CAES combined with pumped hydro storage can eliminate throttling loss in the existing CAES plants with varying air storage pressure and reduce the volume of air storage [11,12]. This paper reviews the main drawbacks of the existing CAES systems and the advantages of innovative CAES concepts such as adiabatic CAES, isothermal CAES, micro-CAES combined with air-cycle heating and cooling, and constant-pressure CAES combined with pumped hydro storage by energy and exergy analyses.…”

“…The thermal exergy of 0.77 kWh in Figure 3 is not chemical exergy but a total thermal exergy added in form of heat during the multistage expansion with reheating. In general, the energy efficiency of the CAES system can be calculated by adding the heat input by natural gas, Q , to the electric input as follows [13,16,17]: (11) But, this value may not be considered a useful measure of electrical storage efficiency, because the heat input is not equivalent to the electric input. Rather, it may be seen as a mixed efficiency of the electrical storage efficiency and thermal efficiency of a power plant.…”

“…(a) Each compression and expansion is assumed to occur at a steady state with a steady flow and constant-pressure air storage, have negligible potential and kinematic energy effects, and exhibit no chemical reaction; (b) For simplicity, the pressure drop in all heat exchangers is neglected; (c) Air pressure in the storage cavern (or vessel) is assumed to remain constant at 5 MPa by adoption of constant-pressure air storage [10,11]. The designed pressure ratios of the compressor and expander are 50, with isentropic (adiabatic) efficiencies of 85%.…”

“…The designed pressure ratios of the compressor and expander are 50, with isentropic (adiabatic) efficiencies of 85%. The air-storage pressure is optimized by energy density and efficiency of the system and the general value of air-releasing pressure for CAES gas turbine is around 5 MPa [10,11]; (d) The efficiencies of the motor and generator are assumed to be 95%.…”

A Novel Pumped Hydro Combined with Compressed Air Energy Storage System

“…The results are shown in Table 2, from which we can see the total cost of PHCA is less than that of the other two. Compared with CAES [11,12,17], the PHCA has the advantages listed below:…”