Commercially Viable Thermochemical Heat Storage Materials for Energy Storage in Buildings

The Department of Energy Office of Energy Efficiency and Renewable Energy is seeking advances in thermal energy storage for buildings, particularly thermochemical materials with low desorption temperatures that can maximize the capacity and efficiency of thermal storage. Several salt hydrates and their composites were identified in literature as potential sorbents capable of reducing the instability of thermochemical materials at the material level. However, general issues persist, including (1) reduced mass transport within the matrix pores, (2) poor recyclability and (3) salt deliquescence or over-hydration with possible leaking of the active material resulted. In addition, for composites, the small pore sizes of the host matrix in the sorption process lead to low salt filling in the matrix, which results in low storage capacity. During the proposed project, the company will develop an inorganic salt impregnated matrix composite as an effective thermal storage material with high energy density, good recyclability and low regeneration temperatures. Embedded additives in the composite will be optimized to increase the porosity of the matrix enabling incorporation of optimal amount of salt, reduce the pressure drop and increase the mass transport. In addition, these additives will increase the conductivity to enable uniform temperature throughout the reaction bed. Further, the materials used in the composite will be non-toxic, non-corrosive and economical. They will have no secondary reactions and small volume variation during reaction. In Phase I, the company will create an extensive database of various composites and salts from literature and develop the composite by adding highly conductive material to a highly porous matrix and impregnating an inorganic salt in it. Specific surface area, apparent porosity, sorption isotherms and specific energy density will be characterized and evaluated. Further, the inorganic salt impregnated matrix composite will be tested for efficiency by determining the regeneration temperature and recyclability using an in-house developed experimental setup. Feasibility will be demonstrated in a sorption prototype and the results will be used to optimize the composite in Phase II. The inorganic salt impregnated matrix composite will offer an effective and cost-competitive solution by lowering energy usage in residential and commercial buildings as well as lowering operating costs. Advantages of using this inorganic salt composite in an energy system include increasedoverall efficiencyandbetterreliability,reductionsininvestment andrunningcosts, andfewer CO2emissionspollutingthe environment.