HALLOYSITE CLAY NANOTUBES WITH PCM FOR THERMAL ENERGY STORAGE AND EFFICIENCY

摘要

There is opportunity to achieve energy savings and increasing energy sustainability through new techniques addressing thermal storage challenges. New materials may be useful to a wide variety of applications including solar thermal as well as building heating and cooling systems. This present work focuses on new thermal storage technology that may be utilized across a wide spectrum of structures. The technology itself relies on implementation of a phase-change insulation material that combines unique characteristics of naturally occurring hal-loysite clay nanotubes with low-cost eicosane-type waxes. This combination results in a microtube skeleton supported material. This allows for material shape preservation during phase transition heat conversion. Investigations further consider the addition of thermal conductivity enhancement via graphite-based nano particles or tubes. In this manner a unique material is presented that is capable of maintaining shape during wax phase change while exhibiting increase in thermal conductivity. Unlike wax-based phase change material systems that allow the wax to change structure during phase change, the use of halloysite nanotubes also maintains the overall thermal conductivity increase through numerous phase change cycles. Multiple material combinations that vary included percentages of both halloysite and conductivity enhancement are investigated. Thermal conductivity of wax-halloysite-graphite (45/45/10 %) composite showed increased conductivity to 1.35 W/mK. This was nearly 3 times higher than the base wax-halloysite composite. Wax-halloysite-graphite-carbon nanotubes (45/45/5/5 %) composite showed thermal conductivity of 0.83 W/mK while maintaining original shape until 81°C (above the wax melting point).