Global efforts toward carbon neutrality highlight the importance of decarbonizing thermal demand, which accounts for the largest share of final energy consumption. In Japan, more than half of CO₂ emissions from households are attributable to heating, cooling, and hot water supply. Solar water heaters are an effective solution to this problem, but split-type systems consume electricity to operate the pump.In this study, we developed and evaluated a flat-plate LHP by improving the structure of the flat-plate loop heat pipe and placing the evaporator on the upper surface to enable low heat flux operation while directly collecting solar heat.
Matsumura et al. (2025) studied this question.