Thermodynamic analysis of a novel energy storage system based on compressed CO₂fluid

Abstract

Summary Because of rapidly growing renewable power capacity, energy storage system is in urgent need to cope with the reliability and stability challenges. CO2 has already been selected as the working fluid, including thermo‐electrical energy storage or electrothermal energy storage systems and compressed CO2 energy storage (CCES) systems. In this paper, a CCES system based on Brayton cycle with hot water as the heat storage medium is proposed and analyzed. Thermodynamic model of the system is established for energy and exergy analysis. Sensitivity analysis is then conducted to reveal effects of different parameters on system performances and pursue optimization potential. At a typical transcritical operation condition, round trip efficiency is 60% with energy density of 2.6 kWh/m3. And for the typical supercritical operation condition, the round trip efficiency can reach 71% with energy density of 23 kWh/m3. High round trip efficiency and energy density, which is comparable with those of compressed air energy storage systems, thermo‐electrical energy storage (electrothermal energy storage) systems, and other CCES systems, lead to promising prospect of the proposed system. Copyright © 2017 John Wiley & Sons, Ltd.

Thermodynamic analysis of a novel compressed carbon dioxide energy storage system with low‐temperature thermal storage

“…The default values of the main parameters considered in this novel system are given in Table 4. Most values shown in Table 4 refer to documents 16,20,22,28,29,31 . It should be noted that since we adopt the assumption mentioned in Section 3 (namely, the heat transfer in HX 4 is imperfect), in most cases the minimum internal temperature approach (MITA) in HX 4 has to be higher than that in HX 3 .…”

“…Some assumptions about the system model are as follows 22,28,29,31,44 : The system operates under a steady‐state condition. The leakage of working fluids (ie, CO 2 and water) in the system is negligible. The heat transfer between system components (ie, regenerators, heat exchangers, and TES) and the environment is neglected. Pressure drop and heat dissipation of working fluids in pipes are not taken into account. Pressure change and power consumption in S and LSTs are neglected. Energy conversion efficiencies in motor and generator are neglected. The processes of streams flowing through LSTs are assumed as isothermal and isobaric, and the state changes of CO 2 in LSTs during the charge process and the discharge process are not taken into account. The cooling water tank (CWT) can dissipate heat to the environment, thus the temperature in CWT could be kept constant (ie, 293.15 K). …”

“…In terms of system design and optimization, Zhang et al 22 proposed a novel compressed carbon dioxide energy storage (CCES) system based on Brayton cycle and conducted a sensitivity analysis to reveal the effects of different parameters on system performances. Xu et al 23 proposed a novel liquid carbon dioxide energy storage system with a high‐temperature source.…”

Turbulent heat transfer characteristics of supercritical n ‐decane in a vertical tube under various operating pressures

“…More attention is primarily focused on carbon dioxide, water, refrigerants, and hydrocarbon fuels, particularly for water and carbon dioxide in the view of the heat transfer. In addition, there are also studies on thermodynamic analysis . However, the effect of hydrocarbon fuels at various conditions on heat transfer characteristics gets more attention with the development of scramjet engines .…”

“…In addition, there are also studies on thermodynamic analysis. 16,17 However, Nomenclature: a, the relative deviation of Nusselt number; A, flow cross-sectional, m 2 ; c p , specific heat, J/kg·K; c p , average specific heat, J/kg·K; d, diameter, m; g, gravitational acceleration, m/s 2 ; Gr, Grashof number, gβ (T w -T b )d in 3 /ν 2 ; h, heat transfer coefficient, W/m 2 ·K; H, specific enthalpy, J/kg; I, turbulence intensity, u′/u avg ; L d , the length of downstream section, m; L t , the length of test section, m; L u , the length of upstream section, m; n, the magnitude of exponent; Nu, Nusselt number, hd in /λ; p, pressure, Pa; Pr, Prandtl number, μc p /λ; q w , heat flux, kW/m 2 ; q m , mass flow rate, kg/s; r, radius, m; Re, Reynolds number, ud in /ν; t, temperature,°C; T, temperature, K; T * , nondimensional temperature, (T w -T)/(T w -T b ); u, local velocity, m/s; u′, mean square root of the velocity pulse, m/s; y + , dimensionless wall distance, yρu τ /μ Greek symbol: β, thermal expansion coefficient, K −1 ; λ, thermal conductivity, W/m·K; ν, kinematic viscosity, m 2 /s; ρ, density at the bulk temperature, kg/m 3…”