• Energy Research

Abstract The use of phase change material as an efficient way to use building energy has recently been discovered as this material occupies 40 % of the total carbon emissions through energy used in the building sector. In order to apply phase change materials to buildings, phase stabilization must first be achieved; some researchers have developed shape-stabilized phase change material (SSPCM). In this study, the enthalpy-temperature function based on the thermal properties of 22 types of SSPCMs were analyzed and applied to a dynamic energy simulation program. The SSPCM was applied to improve the low heat storage performance of wooden buildings along with building energy savings. The SSPCM was applied to the inner side of a 20-mm-thick external wall in a case study concerning the inside and outside of an external wall. An analysis of the annual energy consumption of buildings showed that applying SSPCM resulted in average savings of 5 %. To confirm the improvement in the heat storage performance of buildings, the indoor temperature behavior during the heating and cooling periods was analyzed. Maintaining the thermal inertia of SSPCM was found to have reduced the peak temperature in summer by 4.1 °C.

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.

Abstract Among the PCMs, Bio-based PCMs are considered one of the most promising candidates, due to their large latent heat, low vapor pressure in the melt, good chemical stability, self-nucleating behavior, safety, and commercial availability at low cost. However, the leakage problem and low thermal conductivity of Bio-based PCM limit its application, to some extent. Therefore, porous materials with a high thermal conductivity, such as boron nitride, are promising candidates for simultaneously solving these two problems. In this study, we prepared Bio-based PCM with boron nitride, by using the vacuum impregnation process. We analyzed the microstructure, chemical bonding, heat capacity, thermal resistance and Thermal conductivity of Bio-based PCM with boron nitride, by SEM, FTIR, DSC, TGA and TCi analyses. From the analyses, we expect Bio-based PCM with boron nitride to be useful in applications in various fields, due to its high thermal properties.

AbstractAs recent buildings become more air tight, the natural ventilation rate is significantly reduced and it leads to difficulty in removing accumulated moisture in buildings. Hot and humid weather in summer and the large amount of moisture caused by indoor activity are the major factors of moisture problem in Korea. The hygrothermal performance of building environment has to be considered carefully to reduce condensation risk and mold growth potential, and comfortable indoor environment. In this study, heat and moisture performance of two different wall structures mainly used in Korea were investigated using WUFI simulation program. The water content of the various building materials, hygrothermal behavior of the wall structure, condensation risk and mould growth potential were identified to design comfort building environment.

Abstract In this experiment, we used a vacuum impregnation method to prepare shape stabilized PCM that contained sodium montmorillonite (Na-MMT) and Exfoliated graphite nanoplatelets (xGnP), to improve the thermal conductivity of PCMs, and prevent leakage of the liquid state of PCMs. Na-MMT has low cost and natural abundance, high adsorption and absorption capacities, and fire retardant heating rate. In the used materials, xGnP, usually produced from graphite intercalated compounds, are particles consisting of several layers of graphene sheets. As a result, we found that the FTIR adsorption spectra of paraffinic PCMs did not change, and there was no chemical interaction between paraffinic PCMs and xGnP/Na-MMT mixture. From the DSC analysis, xGnP made an impact on the thermal properties of the paraffinic PCMs/Na-MMT composites. The oxidation rate of paraffinic PCMs based composite with xGnP was greater than that of the composite without xGnP. FTIR, DSC, TGA and TCi were used to determine the characteristics of the paraffinic PCMs/Na-MMT composites.

Globally, humanity is at risk from the coronavirus disease (COVID-19). To address the shortage of beds in quarantining those infected with COVID-19, hospitals have prepared temporary beds. However, for temporary hospital beds, it is difficult to maintain a comfortable temperature due to lack of insulation and heat storage. Phase change materials (PCMs) are used to provide temperature stability and control for temporary structure. Therefore, this study aimed to conduct experiments that analyze the effect of room temperature stabilization using a PCM. The method of macro packed PCM (MPPCM) was used to apply the PCM to buildings. The MPPCM installation location was selected and the effect of reducing the box temperature was analyzed, according to the strength of the heat source. As a result, a maximum reduction of 4.9 °C in the box temperature was achieved. Therefore, the application of MPPCM to buildings give to stabilize the box temperature. And the result showed the possibility of providing a comfortable indoor space for temporary hospital beds.

Abstract High insulation fire door (HIFD) was designed using the design process of vacuum insulation panels (VIPs) and frames to improve the insulation performance of fire doors. To improve the insulation and airtightness performance of HIFDs, the frame was designed using a 3D heat transfer program. The thermal performance of the HIFD could be improved through ceramic board application, gasket positioning, and frame design for cavity applications. The final designed HIFD exhibited a heat transmittance value of 0.872 W/m 2 K. To assess the applicability of the HIFD to buildings, tests were conducted using the test object produced for the optimal design derived from the simulation data. The tests included fire resistance, airtightness, and condensation tests. Despite the high insulation performance, a fire resistance performance of more than 60 min was achieved. Due to the application of graphite covering tapes, fire resistance and airtightness improved, and the exhibited condensation performance could be applied in the −20 °C area.

Various policies for carbon reduction are being promoted due to the increase in energy consumption and changes in the global environment. However, the low-income household of South Korea are still living in old houses with poor energy performance; thus, they require a lot of money for heating. In response, the government is subsidizing the cost of remodeling houses as an energy welfare project. From the 2020 low-income household energy welfare project, out of approximately 30,000 households, 24 households were selected based on factors such as the construction method, region, year of construction, and floor area. These houses were visited before and after modification to measure and analyze heat loss and airtight performance. Instead of diagnosing with simple drawings or dimensions, the accuracy of the results was improved by placing the numerical values obtained before and after energy retrofit of the actual house into the simulation. Retrofit cases consist of three types of modifications: insulation wall construction, window replacement, and both. With a budget of about $2,500, we analyzed the heating energy savings of 24 households and the cost before and after the retrofit through three retrofit cases. The average annual heating energy demand of 24 households was reduced by 22.61%, and the average budget was supported by $2314.14. In addition, the retrofit cost required to reduce the heating energy demand of 24 households by 1 kWh/m2·a was $ 37.09 on average.

Abstract The main objective of this study was to develop a heat storage gypsum-cement board (G/C board) by using vacuum impregnation method and evaluate its physical and thermal properties. In particular, this paper analyzed the chemical property, heat capacity, thermal resistance, thermal conductivity, and heat transfer performance of the heat storage G/C board based on results of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), TCi, and dynamic heat transfer analyses. Especially, dynamic heat transfer analysis was focused in this study to determine time-lag effect and thermal efficiency property of the developed heat storage G/C board with PCMs. As a result, it was confirmed that PCM containing heat storage G/C boards had time lag effect. Such heat storage G/C board could be used to reduce energy consumption of buildings. In the analysis of building energy consumption through energy simulation, the energy reduction effect is larger when the G/C board with n-octadecane was applied, because n-octadecane has more suitable phase change temperature. Especially, when n-octadecane was applied, it is effective to reduce the cooling load during cooling season.