PCM-based High-density Thermal Storage Systems for Residential and Small Commercial Retrofit Applications

Environmental cooling loads comprise 11% of overall electric usage in the United States, and during peak cooling months in hot/humid climates these cooling loads can comprise more than 50% of peak electric energy loads. Thermal storage systems can shift these environmental cooling loads to non-peak hours, making better use of baseload generation capacity as well as reducing the need for expensive and environmentally inefficient peak power plants. Residential and small commercial buildings generate much of the cooling responsible for peak electric load, but these structures may not have the space or facilities to support conventional sensible energy thermal storage systems, such a chilled water thermal storage tanks. For these applications a compact, high-density, retrofittable thermal storage system is needed. This paper investigates the development, testing, and modeling of a compact, scalable PCM (phase change material) based latent thermal storage system for these applications. The results show that a simple tube-encapsulated, tetradecane PCM-based thermal storage system can reduce the size of a thermal store by at a factor of between 2 and 4 while providing acceptable energy recovery rates.