Thermal energy storage based on phase change inorganic salt hydrogel composites

Residential and commercial buildings account for over 40% of the nation’s total energy demand through their consumption of electricity. The DoE’s Building Technologies Office (BTO) supports technologies that could lead to a significant reduction in the energy consumption of buildings. Heating and cooling in buildings and process heating in the industry consume considerable amounts of energy. Storing thermal energy from “waste” heat and using them later, could significantly enhance the efficiency of energy usage in buildings. Thermal energy storage can be achieved using phase change materials (PCMs). The main advantages of PCMs include high thermal storage density and small temperature swing. Paraffin materials are the common PCMs used in building applications. Due to their high cost, low volumetric energy capacities, and high combustibility, alternative PCMs are sought by BTO. Inorganic salt hydrate PCMs are particularly attractive as thermal energy storage materials because of their high volumetric energy densities and optimum transition temperatures, and low costs. However, technical barriers such as inherent supercooling, phase separation, and liquid leakage in solid-liquid phase change must be overcome. Typical methods used to avoid these issues, such as microencapsulation or impregnation of hydrated salts with composites reduce their heat storage density. In the proposed Phase I effort, inorganic hydrate PCMs with superior thermal storage properties and non- leakage characteristics will be prepared by incorporating them into non-toxic hydrogel composites. Nanodimensional additives will also be added to the composites to aid light-to-thermal conversion. The microstructure and thermal properties of inorganic hydrate hydrogel composites will be characterized using a variety of techniques including differential scanning calorimetry and thermogravimetric analysis. The thermal energy storage and the thermal cycling performance will be evaluated to select the best inorganic hydrate PCM. Phase Change materials can efficiently make use of renewable solar energy by storing them as thermal energy that can be used on demand. This will aid in reducing the overall power consumption of HVAC systems and domestic hot water systems. PCMs have been widely used in solar thermal energy storage, air-conditioning systems, energy-efficient buildings, industrial waste heat recovery, temperature-adapted greenhouses, and thermoregulating clothing.