thermal storage, peak load, demand reduction, chiller efficiency
Many commercial and industrial facilities are cooled using vapor compression cycles (VCC). The performance of such systems degrades with high outdoor temperatures causing high peak electric demand increase, reduced efficiency and lower cooling capacity. An Integrated Thermal Energy Storage System (ITESS) utilizing chilled water provides additional subcooling for a VCC condenser, thereby increasing the capacity of the entire system and providing significant reductions in electric demand and consumption. The ITESS uses a dedicated chiller to cool a thermal storage tank, typically at night when electricity demand and rates may be lower. This thermal reservoir is used during the following day to sub-cool refrigerant leaving the condenser. This additional cooling increases the overall cooling capacity of the chiller without increasing the electrical demand. The following paper outlines the results of a demonstration of the ITESS at an industrial facility in Syracuse, NY. The existing 176-ton chiller, which provides cooling for air conditioning a laboratory space and chilled water for compressor testing, was retrofitted with a 33-ton supplemental chiller, 10,000-gallon water tank, four sub-coolers, and two sub-cooler pumps. The ITESS was instrumented with a number of sensors to measure critical parameters to assess its performance. The test results showed that the cooling capacity of the existing chiller increased by 2.2% - 34.2%, depending on operating conditions, with the addition of subcooling. The ITESS increased existing chiller efficiency between 0.6% - 28.5% and has the potential to reduce power demand by 0.7%-34.3%. Total energy consumption for the system was essentially unchanged, increasing on average by approximately 0.05%, well within the margin of error.