Cost benefit of a cooling energy storage system

Since the air conditioner (A/C) load contributes 30% of the peak demand of Taiwan Power Company (Taipower) system during the summer season, load management by A/C load clipping has become one of the most important topics in the Taipower system. Since the eutectic salt is a complete inorganic compound with a freezing point of 47°F and latent heat of 41 Btu/lb, it is a good medium for an energy storage system. An A/C system with an 1800 RT-HR eutectic salt energy storage tank was built on the campus of the National Sun Yat-Sen University (NSYSU) for demonstrating the cooling energy storage (CES) system. By computer simulation, it is found that 41.1% of the electric peak demand has been reduced and 56% of the energy consumption has been shifted from peak hours to off-peak hours by the CES-system. In this paper, the mathematical model of the eutectic salt CES-system has been developed for computer simulation of the energy storage system. It is found that the optimal capacity of the storage tank is determined by the off-peak time period and the largest annual electricity charge saving could be obtained by applying the smallest nominal chiller size under the optimal operating conditions