Proposal for a Thermal Diode with Low-Environmental-Impact Materials for Thermosolar Applications

Abstract

A thermal diode is a component that allows heat flow in one direction while opposing it in the opposite direction. Its applications are wide, for example, it has recently been used for solar energy harvesting and in solar thermal technologies. This work studies a coating made with biomass soot and pine resin, which absorbs and stores captured energy with a preferential heat flow system. The research consists of 3 stages: (a) evaluating the thermal conductivity of soot through experimental arrangements with simple materials and equipment, (b) estimating the thermal rectification of the coating, and (c) applying the soot as a thermal diode in a small-scale system. The results show thermal conductivity values from 0.070 W·mK⁻¹ to 0.095 W·mK⁻¹ for the soot-resin coating, while the rectification factor was 21 % and 53 % for the best coating of 30 % soot–70 % pine resin and the double layer with 10 % soot and 90 % resin, respectively. The soot coating in a small-scale system showed thermal rectification associated with energy charging and discharging, with energy collection efficiency of 34 % and retention efficiency of 17 %. Compared to low-cost paint used in solar technologies, 31.4 % collection efficiency and 8.4 % retention efficiency were achieved. The coating is low-cost, environmentally friendly, and easy to reproduce, showing promise for use in low-power solar thermal technologies, to increase energy storage capacity as a thermal diode.