A study on the optimization of control strategy of a thermal energy storage system for building air-conditioning

Abstract

Many new buildings in Malaysia are installed with a centralized air-conditioning system integrated with thermal energy storage system. Building owners are motivated to reduce the operational costs and are being encouraged by the attractive tariff offered by the utility power provider. However, without proper control the operational costs can be even more than the conventional system due to the higher maximum demand charge. This paper describes the results of an investigation on the actual operating data of a centralized air-conditioning plant integrated with thermal energy storage system operated under two different control strategies. Comparisons on the electrical power consumption, overall plant efficiency and chiller coefficient of performance were carried out by using two identical building load profiles. The results show that the supply pressure control is better than delta-temperature control. The electrical power consumption, overall plant efficiency and chiller coefficient of performance for supply pressure control are 30.1%, 33.4% and 33.5% better than the delta-temperature control, respectively. Also from the general observation on the data it was found out that the storage tank is under utilised. The charging capacity is usually less than the nominal storage capacity. In order to further increase the performance characteristic the plant operation schedule need to be revised.