Performance Characterization of a Novel Low-Cost Additively Manufactured PCM-Air Polymer Composite Thermal Energy Storage

To meet the increasing building cooling requirements, thermal energy storage (TES) systems are suggested to provide daytime peak-load shifting. Phase-Change Materials (PCMs) can store large amounts of energy with reasonably low-temperature gradients due to their high specific latent energy. However, PCMs need encapsulation and augmented heat transfer before they can be widely applied to Heating ventilation and air conditioning (HVAC) systems. Encapsulation and heat transfer augmentation of PCMs is expensive and usually reduces the energy density of the system, thus requiring special designs to overcome the associated shortcomings.The present study focuses on the development of a novel low-cost additively manufactured polymer composite TES with PCM encapsulated inside the polymer channels. It is fabricated using a customized additive manufacturing technique which involves laying continuous metal wires across the polymer channels. The metal wires provide a low resistance thermal path between the air and the PCM, independent of the conductivity of the polymer. An organic PCM (n-hexadecane) with a phase transition temperature of around 18°C, ideal for building cooling applications, is used. An 0.29 m × 0.26 m × 0.12 m prototype TES unit was designed and additively manufactured. An experimental investigation was performed on the TES heat exchanger capable of storing about 0.75 MJ of energy during the day at typical airflow rates and temperatures utilized in equipment cooling applications. The paper discusses and presents in detail the fabrication process, post-processing technique to obtain a leak-proof construction, experimentally obtained thermal and hydraulic performance results, comparison against analytical-based numerical simulation results. A good agreement between the experimental results and numerical predictions is observed.