Solar-thermal energy conversion and storage technology has attracted great interest in the past few decades. Phase change materials (PCMs), by storing and releasing solar energy, are able to effectively address the imbalance between energy supply and demand, but they still have the disadvantage of low thermal conductivity and leakage problems. In this work, new form-stable solar thermal storage materials by impregnating paraffin PCMs within porous copper-graphene (G-Cu) heterostructures were designed, which integrated high thermal conductivity, high solar energy absorption, and anti-leakage properties. In this new structure, graphene can directly absorb and store solar energy in the paraffin PCMs by means of phase change heat transfer. The porous structure provided good heat conduction, and the large surface area increased the loading capacity of solar thermal storage materials. The small pores and superhydrophobic surfaces of the modified porous G-Cu heterostructures effectively hindered the leakage issues during the phase change process. The experimental results exhibited that the thermal conductivity of the prepared form-stable PCM composites was up to 2.99 W/(m·K), and no leakage took place in the solar-thermal charging process. At last, we demonstrated that the PCM composites as an energy source were easily integrated with a thermoelectric chip to generate electric energy by absorbing and converting solar energy.
Keywords: graphene; phase change materials; solar energy; thermal conductivity.