Molecularly elongated phase change materials for mid-temperature solar-thermal energy storage and electric conversion

The utilization of phase change materials (PCMs) offers state-of-the-art thermal energy storage (TES) developments to overcome the intermittency issues associated with renewable energy sources. Despite the tremendous potential of renewable energy storage at intermediate temperature (100–200 °C), the PCM options for this temperature range are limited, and most available PCM candidates are inadequate for practical applications. Herein, we present a molecular elongation design strategy to develop a series of intermediate-temperature PCMs from naturally occurring fatty materials. By increasing chain length and imparting functional moieties in the molecular backbone, we fine-tune the intermolecular interactions in resulting PCMs to achieve more than two folds higher transition temperature compared with their monomeric analogs. Through a systematic structural analysis, we also probe the fundamental basis at the molecular level for the high TES capacity (up to 228 J g−1) that lies behind the excellent performance of our developed PCMs. Further, by compositing developed PCMs with photo-absorber scaffold, intermediate-temperature solar-thermal energy storage is demonstrated for dispatchable power generation. The prototype experimental results speculate that PCM integrated solar-thermoelectric generators could be an intriguing alternative to battery-coupled photovoltaic systems.