Successful Field Demonstration of 

Thermal Storage Technology

Many commercial and industrial facilities are cooled using vapor compression systems. The performance of such systems degrades with high outdoor temperatures causing high peak electric demand increase, reduced efficiency and lower cooling capacity. As the number of installed systems increases and the average summer outdoor temperatures rise, electricity consumption and peak demand requirements will become even greater challenges for the utility grid.

 

Installed Integrated Thermal Energy Storage System

Optimized Thermal Systems, Inc. (OTS) recently completed a field study of an Integrated Thermal Energy Storage System (ITESS) developed by Johnson Controls, Inc. (JCI). This system utilizes chilled water to provide additional subcooling for an air conditioning system's condenser, thereby increasing the capacity of the entire system and providing significant reductions in electric demand and consumption. For purposes of the demonstration, the ITESS used a dedicated chiller to cool a thermal storage tank at night when electricity demand and rates are generally lower. The thermal reservoir is then used during the following day to subcool refrigerant leaving the condenser. This additional subcooling increases the cooling capacity and decreases electrical demand during hot days for an existing or new vapor compression system. 

Test results were consistent a theoretical benefit in capacity and peak efficiency of about 25% at an ambient temperature of 90 °F. The cooling capacity of the existing chiller increased on average by 17.7%±5.3%, depending on operating conditions. Furthermore, the ITESS increased existing chiller efficiency on average by 15.0%±4.5%, and reduced power demand on average by 14.0%±2.9. 

The project was conducted in partnership with the New York State Energy Research and Development Authority (NYSERDA). The full report will soon be published on their website. Additional detail about the ITESS can also be found in Kopko, W.L., (2016), Integrated thermal energy storage, 16th International Refrigeration and Air Conditioning Conference at Purdue, July 11-14, West Lafayette, IN, USA.