Thermal, microstructural and numerical analysis of hempcrete-microencapsulated phase change material composites

Abstract

Biocomposite materials offer the potential to reduce the embodied energy in the construction of buildings significantly. This study develops a new low-carbon heat storage material composed of hempcrete and microencapsulated phase change material (MPCM) that is capable of reducing energy consumption and improving indoor thermal comfort in buildings. Eight hempcrete-MPCM (HPCM) composites were created using: (a) two MPCM types, (b) four MPCM melting temperatures, and (c) two MPCM concentrations. A set of experiments enabled thermophysical and microstructural characterization of MPCM, hempcrete, and HPCM samples. Furthermore, numerical simulations allowed the extension of the experimental results by comparing the performance of timber-frame walls made of hempcrete and HPCM infills with different MPCM concentrations. The findings show that, on the one hand, the developed HPCM formulas have superior heat storage potential compared to the hempcrete owing to their 35% to 85% higher maximum specific heat capacity than hempcrete. On the other hand, HPCM formulas, on average, have lower thermal conductivity than hempcrete due to the low thermal conductivity of MPCMs. As a result, HPCM wall types achieve approximately 5% to 16% and 1% to 36% higher heating and cooling energy savings, respectively, compared to the hempcrete wall. However, the results also indicate that an increase in the percentage share of MPCMs from 9% to 18% in the hempcrete mixture reduces total energy savings and, in particular cooling savings. Therefore, there is a need for a thorough consideration of the operating temperature and percentage share of MPCMs within the hempcrete concerning the specific application and performance objectives. The optimal integration of HPCMs into building envelope might also require changes in the operation of heating and cooling systems.