Abstract
Residential and commercial buildings consume nearly 40 percent of total USA energy use and account for one-third of total greenhouse gas emissions. The challenges are how to effectively promote energy efficiency in buildings to respond to the high financial burden of energy consumption, while reducing pollution. Phase change materials (PCMs) have been used as passive energy storage for building systems. Along this vein, this study aims to numerically elucidate the design parameters of building envelopes strengthened by PCM layers, and unveil their impacts on building energy efficiency. Critical design variables, such as the thickness of the PCM layer, the latent heat of PCMs, or melting temperature of PCMs were selected for a parametric study, while performance metrics were used to assess building efficiency. Results revealed that PCM-enabled building walls exhibited different levels of improvement, in terms of reduction of peak temperature and temperature swings. Among the variables, the selection of the proper melting point for a PCM was identified as the most crucial parameter for determining building energy efficiency, while the heat of fusion was also observed as a critical property of PCM for building potential. Findings also demonstrated that the placement of the PCM near the interior wall surface could achieve higher efficiency, as compared to other cases. Results also showed that the thermal conductivity of PCM has a minimum contribution to energy storage capacity.
Highlights
Promotion of energy efficiency in the building sector is a pressing need in order to respond to the high financial burden of energy consumption
We could observe the balanced stage near 20 h, as shown in both Figures 7c and 8c, where the indoor temperature was identical to the outdoor, and a certain amount of the heat was only stored by the brick, the thicker thermal mass
Such heat transfer over the wall was cyclically repeated accompanied by the charge and discharge of the phase change materials (PCMs) layer, with cumulative residual heating indoor if without additional heating, ventilation and air-conditioning (HVAC) systems
Summary
Promotion of energy efficiency in the building sector is a pressing need in order to respond to the high financial burden of energy consumption. Lei et al [10] simulated building envelopes integrated with a PCM layer using software EnergyPlus® (National Renewable Energy Laboratory, 15013 Denver West Parkway Golden, CO 80401, USA) and evaluated the energy performance of the building system for cooling load reduction in tropical Singapore Their results showed that PCM can effectively reduce heat gains through building envelopes throughout the whole year, indicating the significant advantage of using PCMs in the buildings located in hot circumstances. Different to the observation by Jin et al [14], Zwanzig et al [15] found that that the centrally located PCM composite wall board performed better under both the heating and cooling seasons, as compared to either externally or internally located PCM walls These studies [12] have demonstrated the improvement of energy efficiency through the use of PCMs for a building environment. It necessitates comprehensive parametric studies, as proposed in this study, that could efficiently assist the building community and stakeholders, from builders, designers, building manufacturers, and to state/local governments, to identify better design
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