Using Phase Change Materials (PCMs) to Reduce Energy Consumption in Buildings

The building sector is known to make a large contribution to total energy consumption and CO2 emissions. Phase change materials (PCMs) have been considered for thermal energy storage (TES) in buildings. They can balance out the discrepancies between energy demand and energy supply, which are temporally out of phase. However, traditional PCMs need special latent storage devices or containers to encapsulate the PCM, in order to store and release the latent heat of the PCM. The proper design of TES systems using a PCM requires quantitative information and knowledge about the heat transfer and phase change processes in the PCM. In Korea, radiant floor heating systems, which have traditionally been used in residential buildings, consume approximately 55% of the total residential building energy consumption in heating. This article reviews the development of available latent heat thermal energy storage technologies and discusses PCM application methods for residential building using radiant floor heating systems with the goal of reducing energy consumption.

Improving the energy efficiency of passive PCM system using controlled natural ventilation

Residential buildings account for a large portion of total energy consumption in the United States. Residential energy usage can be dramatically reduced by improving the efficiency of building envelope systems. One such method is to incorporate thermally massive construction materials into the building envelope. This benefits building operation by reducing the energy requirement for maintaining thermal comfort, downsizing the AC/heating equipment, and shifting the time of the peak load on the electrical grid. Phase change materials (PCMs) are promising material for that purpose. When impregnated or encapsulated into wallboard or concrete systems, PCMs can greatly enhance their thermal energy storage capacity and effective thermal mass. In this work, a numerical study is conducted to investigate the characteristics of PCMs in building applications. For that purpose a one-dimensional, transient heat equation for a multilayered building envelope is solved using the Crank-Nicolson scheme. The effect of PCM is modeled with a latent heat source term. The code also incorporates sun loading and uses real weather data. Using this code a PCM composite wallboard incorporated into the walls and roof of a residential building was examined. The PCM performance was studied under all seasonal conditions using TMY3 data for exterior boundary conditions. Comparisons were made between different PCM wallboard locations. This work shows that there is an optimized location for PCM placement within building envelope and the location depends on the thermal resistance of the layers between the PCM and the exterior boundary. The energy savings potential was identified by comparing the performance of the PCM wallboard with the performance of a building envelope without PCM. This work shows that a PCM composite wallboard enhanced building can reduce the annual cooling load from the walls by as much as 19.7% and from the roof by as much as 8.1%. Similarly, the annual heating loads can be reduced by as much as 6% and 6.4% for the walls and roof respectively. It was also shown that the peak electricity load can be shifted by as much as three hours in the summer for a south facing wall. Studies are also conducted to compare the PCM performance across three climate zones. This work shows that PCM performance varies significantly across these zones.

Simulation-based optimization of PCM melting temperature to improve the energy performance in buildings

Effect of microstructure on melting in metal-foam/paraffin composite phase change materials

Using molecular dynamics (MD) simulation, the thermal efficacy of phase change materials (PCMs) in solar energy applications and solar thermal energy storage was evaluated. In order to achieve this objective, an investigation was conducted into the structure's temperature (Temp), velocity, and density profiles, heat flux, thermal conductivity, charge and discharge time, and thermal stability. Three models of tube, shell, and shell-tube were adopted to scrutinize the atomic behavior and thermal performance (TP) of PCMs. The results show that the maximum density of the tube model, shell model, and shell-tube model was 0.042, 0.036, and 0.033 atom/A3, respectively. Other numerical results showed that the maximum velocity for the three structures of tube model, shell model, and shell-tube model under the initial Temp of 300 K was 0.0066 Å/fs, 0.0059 Å/fs, and 0.0054 Å/fs, respectively. The structure in the tube model manifested more optimal atomic behavior compared to other models. The TP of simulated structures revealed that the heat flux of the samples reached 5.69, 4.85, and 4.15 W/m2, respectively. Finally, the thermal conductivity of the structures approached 1.35, 1.32, and 1.31 W/m.K, respectively. The results suggested that the tube model had the most thermal stability and showed the optimal thermal behavior in the simulation. The findings of this study, particularly the optimal atomic behavior and thermal stability of the tube model, can be useful in designing and optimizing PCMs for solar energy applications. In general, this research had the potential to significantly advance the field of solar energy system efficiency and cost-effectiveness.

Energy demand in the building sector has drastically increased due to rising occupant comfort requirements, accounting for 30% of the world’s final energy consumption and 26% of global carbon emissions. Thus, to improve building efficiency in heating and cooling applications, phase change material (PCM)-based passive thermal management techniques have been considered due to their energy storage capabilities. This study provides a comprehensive review of the research on PCM applications, types, and encapsulation forms. Various solutions have been proposed to enhance PCM performance. In this review, the authors suggest new methods to improve PCM efficiency by using the multilayered wall technique, which involves employing two layers of a hybrid bio-composite—specifically, the hybrid hemp/wood fiber-reinforced composite with a polypropylene (PP) matrix—along with a layer of PCM made from spent coffee grounds (SCGs). Previous studies have shown that oil extracted from SCGs demonstrates good thermal and chemical stability, as it contains approximately 60–80% fatty acids, with a phase transition temperature of approximately 4.5 ± 0.72 °C and latent heat values of 51.15 ± 1.46 kJ/kg.

Numerical simulation of phase change material composite wallboard in a multi-layered building envelope

An experimental and numerical study on phase change material melting rate enhancement for a horizontal semi-circular shell and tube thermal energy storage system

Energy performance of phase change materials integrated into brick masonry walls for cooling load management in residential buildings

Effect of melting point on thermodynamics of thin PCM reinforced residential frame walls in different climate zones

In this work, a numerical evaluation of the melting/solidification performance of phase change material (PCM) filled inside a triplex‐tube latent heat storage unit has been carried out. To enhance the melting/solidification performance, the porous Cu metal foam (MF) was embedded inside PCM (termed as composite PCM). Alternative segments of pure PCM and composite PCM have been allocated in such a way that both the pure PCM and composite PCM occupy the equal annular area (i.e., equal volumes). Influence of increasing number of segments was delineated on the melting/solidification rate, complete melting time, and thermal energy storage/recovery enhancement. The comparisons were drawn with reference to the model having two segments of PCM and composite PCM. The results show that the model containing 64 segments with alternate allocations of PCM and composite PCM has a faster melting/solidification rate than other models. With 32 alternate segments of MF, the full melting/solidification time reduced by 23%/77% with respect to the case with one segment of MF only. The melting/solidification performance gets saturated beyond 32 segments (M‐5) and negligible variation (only ~1%) in the thermal performance was noticed upon further segmentation. Finally, the model M‐5 proved as the best model considering the aspects of augmented melting/solidification rate and associated complexities. Moreover, the heterogeneity of MF applied in 32‐segment model confirmed that the anisotropic MF results in an increased melting rate and leads over other random isotropic distributions of MF.

Combined effects of heat input and clamping pressure on the thermal performance of phase change thermal interface materials for electronics cooling applications

A novel method to evaluate phase change materials' impact on buildings' energy, economic, and environmental performance via controlled natural ventilation

Recent progress on Carbon-based nanomaterial for phase change materials: Prospects and challenges