Electro/photo to heat conversion system based on polyurethane embedded graphite foam

Organic phase change materials (PCMs) have exhibited many promising potentials for thermal energy conversion and storage, but they are still confronted with many technical bottlenecks for practical application, such as low conductivity, leakage during phase transition process, and lack of functionality. In this article, a highly-efficient electro/photo to heat conversion system of polyurethane@graphite foam (PU@GF) phase change composites was successfully fabricated through in situ polymerization of polyethylene glycol (PEG) in GF. The obtained PU presents solid-solid phase transition behavior that is different from the solid-liquid phase change of original PEG, which can prevent PU from leakage even if it was loaded in micrometer pores in the GF during application. On the other side, PU can improve the thermal stability and decrease the overcooling degree of the composites in effect. Excellent conductive network was provided by the GF, with which the light absorption and thermal conductivity of the composites were enhanced dramatically. Consequently, the solid-solid phase change composites can effectively store electricity or sunlight energy. The electro-heat storage efficiency of the composites can exceed 80% at 1.2 or 1.4 V, meanwhile, the photo-heat storage efficiency can close to 67% under simulated solar illumination. This result presents the highest efficiency for electro-to-heat conversion by PCMs techniques driven by a quite low voltage up to now, and will give rise to a new expectation of functional PCM application for energy conversion and storage.