This paper presents the performance of a solar water
heater with evacuated tubes integrated with phase change materials. The results show that phase change material
integrated inside the inner tubes of evacuated tube solar collectors can effectively store energy (in the form of latent
heat) next to the heat pipes and enable a delayed cooling after sunset or late evening. The proposed solar collector utilizes two distinct phase change materials (dual-PCM), namely Tritriacontane and Erythritol with melting temperature 72 °C and 118 °C respectively. The operation of solar water heater with the proposed solar collector is mvestigated during both normal and on-demand operation. The
feasibility of this technology is tested via large scale commercial solar water heaters. This study shows a significant efficiency improvement of dual-PCM solar water heaters
for both normal and stagnation operation, compared with standard solar water heaters that lack phase change materials.