Thermal optimization of an integrated LV battery energy storage station

In the framework of an R&D project called “Smart Storage”, Enexis has developed a boxed electricity storage system called the Smart Storage Unit (SSU). The SSU is a concrete housing in which a set of batteries and DC/AC converters is pre-assembled. After local installation, 50% of the SSU is below ground level. The thermal concept of the system has been chosen to minimise reliance on active cooling. This paper presents the design considerations, discusses the thermal balance on various time scales, and describes the chosen solution. Extensive functional and cyclic testing of the assembled system was performed in KEMA´s Flex Power Grid Laboratory in Arnhem in March-April 2012. These tests have led to modifications on the internal air flow, which have been implemented and have been put to test in December 2012. The paper presents the results and discusses the achieved performance improvements.