Highly Efficient Thermo- and Sunlight-Driven Energy Storage for Thermo-Electric Energy Harvesting Using Sustainable Nanocellulose-Derived Carbon Aerogels Embedded Phase Change Materials

It is a challenge to harvest thermoelectric energy in an environment in which temperature is spatially uniform since the temperature gradient is necessary for the Seebeck effect. A sustainable and highly efficient thermo- and sunlight-driven energy conversion and storage material is fabricated by the combination of organic phase change materials (OPCM) with high performance carbon nanofiber aerogels (CNFAs) and proposed as a heat supply to develop an energy harvesting system. The energy harvesting system consists of two different PCM/CNFA composites (stearic acid/CNFA composites (PCM-SA) and 1-tetradecanol/CNFA composites (PCM-1-TD)) and an N and P type semiconductor. It can collect discarded thermal energy and solar energy and convert them into electric energy in an environment with spatially uniform temperature. The high-performance CNFAs are derived from woods and developed by an environmental and economical way. The shape-stabilized PCM/CNFA composites have high latent heat which is comparable to OPCMs, high thermal conductivity (several times higher than OPCMs) and high energy conversion efficiency (82.3% for PCM-SA and 96.2% for PCM-1-TD under sunlight irradiation) which are considered potential materials in the field of energy. The maximum voltages generated by the energy harvesting system are 55 and 80 mV corresponding to the thermo- and sunlight-driven energy harvesting process, respectively, with a maximum power density of 0.50 W/m2 and 1.20 W/m2 in each process, which hold great potential to put low-grade waste heat and solar energy into electricity.