Thermal Stability and Physicochemical Properties of Zn(NO3)2·6H2O-Based Heat Storage Materials

Phase-change heat storage materials (PCMs) based on Zn(NO3)2·6H2O, which undergoes phase transition in the range 25–40°C, were developed. The most stable composition was the one comprised of Zn(NO3)2·6H2O/Co(NO3)2·6H2O/expanded graphite/CMC. Its heat of crystallization with account for the heat capacity in the supercooled region was determined as 146.0 ± 7.3 and 140.6 ± 7.0 J/g and was comparable with the heats of melting before and after 500 thermal cycling cycles, equal to 147.4 ± 4.4 and 130.6 ± 3.9 J/g, respectively. The composition tested in a prototype electric underfloor heating film showed that the energy consumption for heating was 67% lower than for the heating film without the developed material.