Performance of a small‐scale compressed air storage (CAS)

Abstract

Summary The use of renewable energy, such as wind and solar, has significantly increased in the last decade. However, these renewable technologies have the limitation of being intermittent; thus, storing energy in the form of compressed air is a promising option. In compressed air energy storage (CAES), the electrical energy from the power network is transformed into a high‐pressure storage system through a compressor. Then, when the demand for electricity is high, the stored high‐pressure air is used to drive a turbine to generate electricity. The advantages of CAES are its high energy density and quality, and for being environmentally friendly process. In the existing facilities of University of Auckland, New Zealand, air cavern is not available; thus, a high‐pressure tank is used to store the compressed air, which could provide an excellent opportunity for small size applications. There is a limited literature available on the temperature and pressure profiles in a typical high‐pressure tank during charging and discharging processes. Therefore, this research investigates how temperature and pressure inside a high‐pressure tank change during charging and discharging processes. It will provide a better understanding for heat transfer in such system. Furthermore, it will provide the necessary information needed for the designing of an efficient small‐scale CAES. In this work, air is compressed to a maximum pressure of 200 bar and stored into a 2 L tank, which is fully fitted with a pressure transducer and a thermocouple suitable for high‐pressure measurements. The charging and discharging process is theoretically modeled, and the results are compared with the experimental measurements, showing a good agreement. The heat balance on the system is used to validate the steady‐state condition, while dynamic analysis is used to predict the transient change of compressed air and tank wall temperatures. The theoretical modeling is undertaken by solving the differential equations describing the transient change in temperature of both air and tank wall. The results of this study show that air temperature rises from 24°C to 60°C at 100 bar and from approximately 17°C to over 60°C at 200 bar. During discharging process, air temperature drops from ambient to 5°C at starting pressure of 100 bar and to −20°C at starting pressure of 200 bar.

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“…An experimental and theoretical study has been conducted for a high-pressure compressed air tank storage system in which the experimental data was used to assess the wall and air temperatures in the pressurized storage tank of 100 bar. The results showed that the tank wall should be taken into account in the thermal analysis of CAES systems [21]. In another study, a compressed air energy storage is integrated with a biomass-driven power plant with thermal energy storage subsystems.…”

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“…An experimental and theoretical study has been conducted for a high-pressure compressed air tank storage system in which the experimental data was used to assess the wall and air temperatures in the pressurized storage tank of 100 bar. The results showed that the tank wall should be taken into account in the thermal analysis of CAES systems [21]. In another study, a CAES system integrated with a biomass-driven power plant with thermal energy storage was studied and the effects of heat loss in the cavern and the temperature of the soil around the cavern on the performance of the system were investigated [22].…”

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