Phase Change Material Wallboard Research Articles

Combined experimental and numerical evaluation of a prototype nano-PCM enhanced wallboard

In the United States, forty-eight (48) percent of the residential end-use energy consumption is spent on space heating and air conditioning. Reducing envelope-generated heating and cooling loads through application of phase change materials (PCMs) in building envelopes can enhance the energy efficiency of buildings and reduce energy consumption. Experimental testing and numerical modeling of PCM-enhanced envelope components are two important aspects of the evaluation of their energy benefits. An innovative phase change material (nano-PCM) was developed with PCM supported by expanded graphite (interconnected) nanosheets, which are highly conductive and allow enhanced thermal storage and energy distribution. The nano-PCM is shape-stable for convenient incorporation into lightweight building components. A wall with cellulose cavity insulation and a prototype PCM-enhanced interior wallboard was built and tested in a natural exposure test (NET) facility in a hot-humid climate location. The test wall contained the PCM wallboard and a regular gypsum wallboard, for a side-by-side annual comparison study. Further, numerical modeling of the wall containing the nano-PCM wallboard was performed to determine its actual impact on wall-generated heating and cooling loads. The model was first validated using experimental data, and then used for annual simulations using typical meteorological year (TMY3) weather data. This article presents the measured performance and numerical analysis evaluating the energy-saving potential of the nano-PCM-enhanced wallboard.

Parametric analysis of influencing factors in Phase Change Material Wallboard (PCMW)

Incorporating Phase Change Materials (PCMs) into traditional building structures has been considered as an effective way to reduce the mismatch between energy supply and demand and in turn to minimise energy consumption (cooling/heating energy). For building applications, Phase Change Material Wallboards (PCMWs) are of particular interest due to their easy installation to existing buildings for refurbishment. Both interior and exterior PCMWs are investigated in this paper, with a numerical study examining the effects of wallboard thermal properties on its thermal performance. These influencing factors include melting temperature, melting range, latent heat, thermal conductivity and surface heat transfer coefficient. An effective heat capacity model is adopted to consider latent heat with the model validated by an experiment. Inner surface temperature and diurnal energy storage are chosen as the evaluation criteria when comparing the thermal performance between different PCMWs. By analysing the effects of influencing factors on the system thermal performance, this study serves as a useful guide for selection of PCMs in energy-efficient buildings.

Designing building envelope with PCM wallboards: Design tool development

While space conditioning load contributes largely in grid critical peak, shifting a part or full to the off-peak period could have significant economic effects on both energy supply and demand sides. This shifting technique is accomplished by storing energy during off-peak periods to be utilized during peak periods. The wallboard enhanced with PCM can provide latent heat thermal energy storage (TES) distributed in the whole surface area of the building envelope and evade the enhanced thermal mass in light weight buildings. Identifying the best design parameters of the PCM wallboard is the main key to apply this latent heat TES efficiently. The effective dimensionless numbers on the thermal dynamics of a PCM wallboard were identified. Moreover, the impact of the change of those numbers on the time required for the wallboard to become fully charged was evaluated. This parametric study provided a tool to characterize the required thickness of a PCM wallboard which needs to be charged during the off-peak. The tool presents the Fourier number as a correlation of Biot number and Stefan number. Moreover, the impact of melting range on the charging time of a PCM wallboard was investigated.

Evaluation of Thermal Effect of PCM Wallboards by Coupling Simplified Phase Change Model with Design Tool

A simplified PCM wallboard model is coupled to an existing design-oriented model of multi-zone buildings. Using a reference model and a basic simulation configuration, the accuracy of the resulting PCM wallboard-building thermal design tool is evaluated. A new performance indicator, called PCM utilization factor, is then proposed in order to estimate the thermal efficiency of using PCM wallboards in buildings. Using this PCM Utilization factor and a degrees-hours indicator, the ability of the PCM wallboard-building thermal design tool to evaluate the effect of PCM wallboards on heating loads and summer thermal comfort in the early design phase of a project is examined in two real case studies: a family house project and an existing office building. The user-friendliness of this design tool, and the short calculation times it leads to when performing a year-long simulation using a standard office computer, make it a well-adapted tool for sensibility studies or multi-criterion optimization for buildings that contain PCM wallboards.

The Effectiveness of PCM Wallboards for the Energy Refurbishment of Lightweight Buildings

In order to compensate for the small storage capacity of lightweight buildings, that usually suffer from pronounced overheating in summer, the incorporation of Phase Change Materials (PCMs) into the opaque envelope can be an effective way to enhance thermal inertia and to improve the thermal comfort. In particular, PCM wallboards are recommended during refurbishment, as they have a small thickness and can be easily applied on the inner surface of both the walls and the ceiling.In this paper, a comprehensive study is presented about the effectiveness of PCM wallboards for improving summer thermal comfort in existing lightweight buildings. The study is based on dynamic simulations carried out with the software EnergyPlus on a sample office building. The analysis is repeated in four different locations, ranging from Southern Europe (Catania, Italy) to Northern Europe (Paris, France).The results of the simulations may help designers to make the correct choices in terms of position of the PCM wallboards, scheduled rate of nighttime ventilation and value of the peak melting temperature for the specific PCM.

Simulation of a ventilated cavity to enhance the effectiveness of PCM wallboards for summer thermal comfort in buildings

The present paper proposes and evaluates a novel solution for increasing the effectiveness of phase change materials (PCMs) micro-encapsulated in thin wallboards, in order to improve summer thermal comfort in buildings. The unique feature of this solution consists in realizing a narrow cavity between the wallboards containing the PCM and the partition wall. Here, fresh air might circulate according to appropriate control logics, thus boosting the rate of heat flux exchanged by the PCM, and enhancing its solidification process. This set-up should increase the PCM storage efficiency and the average thermal comfort perceived by the occupants.After introducing a mathematical model to identify the temperature distribution along the ventilated cavity, its actual efficiency is evaluated through a case study, based on simulations performed with EnergyPlus. The evaluation is accomplished by means of newly-introduced indicators that allow a thorough description of the PCM behaviour and its relation with thermal comfort in the room.

Energy refurbishment of existing buildings through the use of phase change materials: Energy savings and indoor comfort in the cooling season

With reference to building applications, recent scientific literature shows good potential in reducing cooling loads by means of phase change materials (PCMs), integrated in the building exterior envelope.This paper proposes a deepening, by investigating if these dynamic components could contribute in reducing building cooling demand in Mediterranean climates. An office building is analyzed, with reference to the entire cooling season (from May 1st to September 30th), in reliable conditions as regards building use, and thus internal gains, occupancy, activation of cooling systems.More in detail, through hourly energy simulation, the achievable cooling energy savings have been calculated, with reference to a well-insulated massive building, refurbished by means of addition of PCM plaster on the inner side of the exterior envelope. Five Mediterranean climates have been taken into account: Ankara (Turkey), Athens (Greece), Naples (Italy), Marseille (France), Seville (Spain). The studies regarded the influences of the phase change temperature, thickness of the PCM wallboard and location of the PCM layer.Beyond the evaluation of the absolute savings of primary energy requests for cooling, the energy saving rate and the not-overheating time have been calculated, respectively by considering an air conditioned building and a naturally ventilated building with free-running indoor temperatures.Starting from the achieved results, through the values of the proposed indicators, this paper would suggest information useful for proper design and selection of phase change materials for building applications.

Applied research on hot water heating wallboard with phase-change material

In this paper, the hot water heating wallboard with phase-change material (PCM) was prepared. PCM was added into the wallboard. Intermittent heating mode was used in the experiment. Heat transfer performance of the wallboards was tested and numerically simulated by ANSYS software. The results showed that the temperature and heat flow on the surface of the PCM wallboard (PCMW) were lower than that of the common wallboard without PCM in the heating process. And the decreasing in the temperature and heat flow of the PCMW was lower than that of the common wallboard. The experimental and simulated results were identical in most cases. PCMW can remain a certain heat flow on the inner surface, so it can control the fluctuation of indoor temperature, and enhanced the comfort of indoor climate. Different influence factors and optimal design of the hot water heating phase-change wallboard were analysed.

A simplified dynamic model of double layers shape-stabilized phase change materials wallboards

A simplified dynamic building model was proposed and validated in this study. The structure of the new wall system is that of a three-layer sandwich-type panel with outer layers consisting of SSPCM wallboards and middle layer consisting of conventional brick. Each layers of the composite wall have different functions: the external layer connected to outside has a higher PCM melting temperature used in summer and the internal layer connected to indoor with a PCM melting temperature near indoor set point used in winter. The middle layer is brick for insulation. Few studies have involved simplified dynamic models of building structures integrated with double layers SSPCMs. The simplified dynamic model represents the brick layer by three resistances and two capacitances (3R2C) and the SSPCM layer by four resistances and two capacitances (4R2C) while the key issue is the parameters identification of the model. The parameters of the simplified model are identified using genetic algorithm (GA) on the basis of the basic physical properties of the brick and SSPCM layer. Validation results show that the simplified dynamic model can represent light weight walls and median weight walls integrated with double layers SSPCMs with good accuracy.

The feasibility analysis of the performance of the phase change material wallboard used in Southwest China

The feasibility analysis of the performance of the phase change material wallboard used in Southwest China

On an experimental innovative setup for the macro scale thermal analysis of materials: Application to the Phase Change Material (PCM) wallboards

This work deals with the assessment of a novel experimental methodology to investigate the thermal storage properties of materials in “macro” scale. The experimental device developed in the present research was used for the thermal characterization of wallboards containing Phase Change Materials labeled “PCM wallboards”. In general, PCM wallboards can contribute to the improvement of the thermal comfort and the energy saving when integrated in the building envelope. In this study, the developed experimental device operates in convection mode without need to sophisticated accessories. First, several “blank” tests were performed with different scenarios of temperatures and air flows. This step was useful to determine the thermal signature of the experimental device and especially the thermal losses occurring during the heat transfer. Then, a validation step was achieved on a “school case” using steel panels with known thermal properties. It was shown that the relative specific heat obtained by the means of the experimental device correlates well with the available information derived from literature. Also, an exploitation phase is performed using PCM wallboards (Energain). Finally, in order to allow comparison of the experimental results of the bench test, a “semi-analytical” approach based on DSC (differential scanning calorimetry) measurements and a simplified homogenization schema (mixture law) was carried out. It was noticed that the results derived from the experimental device measurements (specific heat and latent heat) present a good approximation in comparison with the different approaches of DSC technique and homogenized schemes.

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

Phase change materials (PCMs) have the capability to store/release massive latent heat when undergoing phase change. When impregnated or encapsulated into wallboard or concrete systems, PCMs can greatly enhance their thermal energy storage capacity and effective thermal mass. When used in the building envelope PCM wallboard has the potential to improve building operation by reducing the energy requirement for maintaining thermal comfort, downsizing the AC/heating equipment, and shifting the peak load from the electrical grid. In this work we numerically studied the potential of PCM on energy saving for residential homes. For that purpose we solved the one-dimensional, transient heat equation through the multi-layered building envelope using the Crank–Nicolson discretization scheme. A source term is incorporated to account for the thermal-physical properties of the composite PCM wallboard. Using this code we examined a PCM composite wallboard incorporated into the walls and roof of a typical residential building across various climate zones. The PCM performance was studied under all seasonal conditions using the latest typical meteorological year (TMY3) data for exterior boundary conditions. Our simulations show that PCM performance highly depends on the weather conditions, emphasizing the necessity to choose different PCMs at different climate zones. Comparisons were also made between different PCM wallboard locations. Our work shows that there exists an optimal location for PCM placement within building envelope dependent upon the resistance values between the PCM layer and the exterior boundary conditions. We further identified the energy savings potential by comparing the performance of the PCM wallboard against the performance of a building envelope without PCM. Our study shows that PCM composite wallboard can reduce the energy consumption in summer and winter and can shift the peak electricity load in the summer.

Experimental Research on the Heat Transfer and Mechanical Property of Phase Change Material Wallboards

This paper investigated the heat transfer and mechanical property of phase change material (PCM) walls and common wall. Three mixtures of liquid paraffin-46# paraffin, liquid paraffin- lauric acid and capric-myristic acid were prepared and mixed respectively with high-density polyethylene (HDPE) to prepare shape-stabilized phase change materials. Then direct mixing method was used to add these materials into cement mortar in order to make phase change walls. The results shows that the temperatures and heat flow on phase change walls’ surface are all lower than those of common wall; PCMs of different thermal properties have a more and more obvious distinction in heat storage performance with the increasing content of them added in the wall; PCM walls have lower compressive strength than the common one. Results can provide the basis for the application of phase change material walls in real buildings.

A methodology for investigating the effectiveness of PCM wallboards for summer thermal comfort in buildings

The present paper describes a methodology for the comprehensive evaluation of the effectiveness of Phase Change Materials (PCMs) for the improvement of summer thermal comfort in lightweight buildings.To this aim, a series of indicators is firstly introduced, that allow a precise description of both the PCM behaviour (frequency of melting, storage efficiency) and the intensity and duration of the thermal comfort perceived by the occupants. Then a case study is proposed, based on simulations, that consists in the application of newly developed wallboards, containing organic PCMs, on the partition walls of a lightweight office building.The approach presented in the study can be useful for assisting the detection of the most appropriate PCM and its installation pattern as a function of the climatic operating conditions and of the comfort requirements.

The utilization of microencapsulated phase change material wallboards for energy saving

Wallboards with micro encapsulated phase changing material (micro PCM) were used to investigate the performance and the energy saving characteristics as building materials in winter and summer climate conditions. The test house consisted of a boiler with under floor heating system, an air conditioner, micro PCM wallboard room and conventional wallboard room. The outer temperature of the rooms could be artificially controlled at the temperature range of −12 to 35 °C. Micro PCM content in wallboards was 0–4 kg/m2. The melting temperature and latent heat of Micro PCM are 23 °C and 211 J/g. Also, micro PCM shows stable mechanical strength under 500 psi. As micro PCM content increased, the temperature fluctuations decreased. In case of micro PCM wallboard, temperature profiles in the room show stable and comfortable ranges. The optimum amount of micro PCM in wallboard to maximize energy saving efficiency was around 3 kg/m2.

Energy and environmental performance of building façades integrated with phase change material in subtropical Hong Kong

In the past decade, the application of phase change material (PCM) wallboard in building façade has gained wide attention around the world. For successful application of PCM integrated building façade, a number of crucial factors including thermo-physical properties of PCM, outdoor climate condition, operating schedule of building, investment cost and tariff structure should be taken into account. In this study, a typical residential flat with PCM integrated external walls constructed in the living room and bedroom was modeled and the thermal/energy performance was investigated. The effect of PCM integrated wall's orientation was also evaluated. Through computer simulations, it was found that the living room of a residential flat with west-facing integrated external wall could perform better. It gave a comparatively higher decrease in the interior surface temperature up to a maximum of 4.14%. Moreover, an annual energy saving of 2.9% in air-conditioning system was achieved. However, a long cost payback period of 91 years makes the PCM integrated building façade economically infeasible. On the other hand, the energy payback period was estimated as 23.4 years for this building case, indicating that the energy saving can surpass the embodied energy of PCM wallboard and mitigate the greenhouse gas emission.

Mechanical and Thermal Properties of PCM Wallboards Based on Gypsum and Paraffin

This paper studied on preparation, mechanical and thermal properties of two PCM wallboards made of gypsum and paraffin composite, PCM particles wallboard and PCM bag packed wallboard. Density, flexural and compressive strength and thermal conductivity of PCM particles wallboards deceased as PCM particles dosage increasing. Only PCM particles wallboard with PCM particles dosage 30% is suitable. Thermal comparison between PCM wallboards and pure gypsum wallboard shows that two PCM wallboards have better thermal properties and PCM wallboards can be used in building envelope to cut down building energy-consumption.

Inorganic Phase Change Materials in Building Energy Saving

The applications of inorganic phase change materials (PCMs) in building energy saving have been investigated within the past decades. In this paper, the contents of operative principles of applying inorganic PCMs in buildings, incorporation methods, and its applications in building energy saving in the fields of PCM wallboards, floors, and roofs and so on were summarized in details. Finally, some problems and new trends in the future are also discussed.

Effects of wallboard design parameters on the thermal storage in buildings

The phase change material (PCM) could be added to the wallboard to increase the thermal mass to decrease in indoor temperature fluctuation and improve thermal comfort. In this study, experimentally validated simulation was performed to investigate the effects of various parameters of PCM including the nominal average phase change temperature, its range, the convective heat transfer coefficients and the wallboard thickness on the thermal storage performance of the wallboard such as the thermal energy storage and the time shift.It was found that the average phase change temperature should be close to the average room temperature to maximize the thermal heat storage in the wallboards. The phase change temperature should be narrow to maximize the thermal heat storage in the PCM wallboards. The thermal heat storage increased with the convective heat transfer coefficient, and the optimal average phase change temperature to maximize the storage shifted a bit to a higher temperature with it. The time shift was found to decrease with the convective heat transfer coefficient and the phase change temperature range.

Performance of shape-stabilized phase change material wallboard with periodical outside heat flux waves

Numerical simulations were carried out to investigate the performance of shape-stabilized phase change material (SSPCM) wallboard with sinusoidal heat flux waves on the outer surface and compared with traditional building materials – brick, foam concrete and expanded polystyrene (EPS). One-dimensional enthalpy equation was solved using control volume-based implicit finite-difference scheme. Time lag ( φ) , decrement factor ( f) and phase transition keeping time ( ψ) of inner surface were applied to analyze the effects of PCM thermo-physical properties, inner surface convective heat transfer coefficient and thickness of SSPCM wallboard. The results showed that for SSPCM, there exist two flat segments within one wave length period of inner surface heat flux lines and it has larger time lag and lower decrement factor than those three ordinary building materials. It was found that melting temperature and thermal conductivity of SSPCM have little effects on φ, f and ψ, which is different from the case of temperature waves; for a certain outside heat flux wave, there exist critical values of latent heat of fusion and thickness of SSPCM above which the heat flux wave amplitude can be diminished to zero; inner surface convective heat transfer coefficient is one important factor which significantly influences the decrement factor; and the phase transition zone leads to small fluctuations of the original flat segments of inner surface heat flux line.