Search Results (37)

Fossil fuels, including coal, are a basis of energy systems in many countries worldwide. However, coal mining is associated with several difficulties, which include high temperatures within the coal mining area. It causes a need for cooling for safety reasons and also for the comfort of miners’ work. Typical cooling systems in mines are based on central systems, in which chilled water is generated in the compressor or absorption coolers on the ground and transported via pipelines to the air coolers in the areas of mining. The progressive mining operation causes a gradual increase in the distance between chilled water generators and air coolers, causing a decrease in the efficiency of the entire system and insufficient cooling capacity. As a result, it is necessary to increase the diameter of the chilled water pipelines and increase the cooling capacity of the chillers, which is associated with additional investment and technical problems. One solution to this problem may be the use of so-called ice slurry instead of chilled water in the existing mine cooling system. This article presents the cooling system, located in the mine LW Bogdanka S.A., based on ice slurry. The structure of the system and its key parameters are presented. The results show that switching from cooling water to ice slurry allowed the cooling capacity of the entire system to increase by 50% while maintaining the existing piping. This demonstrates the very high potential for the use of ice slurry, not only in mines, but wherever further increases in piping diameters to maintain the required cooling capacity are not possible or cost-effective. Full article

The decarbonization of residential cooling systems requires innovative solutions to overcome the mismatch between the renewable energy availability and demand. Integrating latent thermal energy storage (LTES) with heat pump/air conditioning (HP/AC) units can help balance energy use and enhance efficiency. However, the dynamic behavior of such integrated systems, particularly under low-load conditions, remains underexplored. This study investigates a 5 kW HP/AC unit coupled with an 18 kWh LTES system using a bio-based Phase Change Material (PCM) with a melting temperature of 9 °C. Two configurations were tested: charging the LTES using either a thermostatic bath or the HP/AC unit. Key parameters such as the stored energy, temperature distribution, and cooling capacity were analyzed. The results show that, under identical conditions (2 °C inlet temperature, 16 L/min flow rate), the energy stored using the HP/AC unit was only 6.3% lower than with the thermostatic bath. Nevertheless, significant cooling capacity fluctuations occurred with the HP/AC unit due to compressor modulation and anti-frost cycles. The compressor frequency varied from 75 Hz to 25 Hz, and inefficient on-off cycling appeared in the final phase, when the power demand dropped below 1 kW. These findings highlight the importance of integrated system design and control strategies. A co-optimized HP/AC–LTES setup is essential to avoid performance degradation and to fully exploit the benefits of thermal storage in residential cooling. Full article

Double-skin façades (DSFs) are promising sustainable design elements of buildings. However, they are prone to overheating problems in warm seasons due to high outdoor temperatures and intense solar radiation. Although phase-change material (PCM) blinds have proved to be effective at enhancing the thermal performance of DSFs, the impacts of the design parameters are crucial to the overall thermal performance of the system. This study focused on analyzing the impacts of design parameters on the thermal performance of a ventilated DSF system, which consisted of a macro-encapsulated phase-change material (PCM) blind with an aluminum shell. A simulation study was conducted using ANSYS Workbench FLUENT software, and the temperature distributions of the integrated system were compared with different blind tilt angles and ratios of cavity depth to blind width. The results show that both the blind tilt angle and ratio of cavity depth to blind width had a significant influence on the thermal performance of the DSF system. For instance, lower air-cavity temperatures within the range of 37~40 °C were achieved with the PCM blind at tilt angles of 30° and 60° compared with other selected tilt angles (0° and 90°). In terms of the cavity depth to blind width ratio, a ratio of 2.5 resulted in a lower air-cavity temperature and a better thermal performance by the DSF. With the optimal blind tilt angle and cavity depth to blind width ratio, the integrated DSF and macro-encapsulated PCM-blind system can reduce the cavity temperature by as much as 2.9 °C during the warm season. Full article

Energy savings issues are important in the context of building operation. An interesting solution for the southern external walls of the building envelope is the thermal storage wall (TSW), also known as the Trombe wall. The article considers four variants of the wall structure, including three containing phase change material (PCM). The purpose of this study was to determine the influence of the amount and location of phase change material in the masonry layer on the storage and flow of heat through the barrier. Each wall is equipped with a double-glazed external collector system with identical physical parameters. The research was carried out in specially dedicated testing stations in the form of external solar energy chambers, subjected to real climatic loads. The distribution of the heat flux density values was determined using experimental tests and was subjected to comparative analysis for the various variants considered using statistical analytical methods. A comparative analysis was performed between the heat flux density values obtained for each barrier in the assumed time interval from the one-year research period. The Kruskal–Wallis test and the median test were used for analyses performed in the Statistica 13.3 programme. The purpose of these analyses was to determine the occurrence of significant differences between individual heat flux flows through the barriers tested. The results obtained indicate that the use of PCM in thermal storage walls extends the time required to transfer the accumulated heat in the barrier to the internal environment while reducing the amplitude of the internal air temperature. Full article

Peak power shaving in heating systems can be achieved using heat accumulators, traditionally implemented in the form of water storage tanks. Their heat capacity can be increased by using a phase change material (PCM) instead of water, which, however, usually requires a change in the tank design. The innovation of this paper is an interesting concept to use plastic capsules filled with a PCM that replace part of the water volume in an existing heat accumulator. The aim of this paper is to compare the cooling rate of the same volume of water as that of the water mixed with the PCM capsules to initially verify the heat storage potential of the capsules. The results of pilot experimental studies on a laboratory scale are presented and discussed, showing the potential of this idea for heat storage. The partial replacement of water with capsules (40% of the total volume) results in significantly faster heat accumulation with the same tank volume (3.85 times at the beginning of the process) and more heat stored (decrease in the temperature of water alone by 14 K and water with PCM capsules by 26 K in the same period of time), which gives promising perspectives for the use of this solution on a semitechnical scale and further in a real-size heating system. Full article

With a growing number of PCMs and new, suitable PCM candidates, an overview is not only important, but also increasingly complex. Classification of PCM was thus changed significantly in the past decades. A review of classification of PCMs from recent years shows that not only different classification criteria are used, but more important that they are often mixed, used inconsistently, even without a clear goal. Focusing on the main goal of current classification schemes, to give an overview of the material options for the search for new, suitable PCM candidates, including already established PCMs, a consistent classification is developed in a desktop study. For this, first, the general options for classification criteria are reviewed, and then the appropriate ones selected. Then, based on them a new, revised PCM classification is suggested. It is specifically detailed with regard to mixtures; for binary mixtures it is based on a literature review performed within the study. The result also stresses the importance of specific R&D: for pure substances the sources and the chemical modification, and for mixtures their optimization by new compositions, additives, etc. Full article

Phase-change cold storage technology is recommended as a solution for energy conservation and carbon neutrality in air conditioning systems of buildings. This study focuses on the development of binary composite phase-change materials comprising octanoic acid–tetradecanol (OA-TD). To enhance its thermal conductivity, expanded graphite (EG) was employed as an additive carrier, and the surface modification of EG particles using hexadecyltrimethoxysilane (HDTMOS) was attempted to make up for the instability and further to improve the performance of OA-TD/EG CPCMs. The OA-TD/EG-HDTMOS CPCMs were synthesized by EG mixed with EG-HDTMOS at a 1:1 mass ratio. The thermal performance and stability of the OA-TD/EG-HDTMOS CPCMs were thoroughly evaluated by multi-cycle melting–solidification and thermal conductivity measurements. The results revealed that the OA-TD mixture, when at a mass ratio of 77:23, exhibited a phase-transition temperature of 11.4 °C and a latent heat ranging from 150 to 155 J/g. Then, the OA-TD/EG-HDTMOS composite material, at a 12:1 mass ratio of OA-TD to EG-HDTMOS, solidified and melted at temperatures of 9.2 °C and 11.2 °C, with a latent heat ranging from 138 to 143 J/g, and significantly improved the thermal conductivity to 0.7 W/(m·K), representing a remarkable 133% increase compared to that of OA-TD alone. Even after undergoing 100 melting–solidification cycles, the OA-TD/EG-HDTMOS maintained superior phase-change thermal performance and stability, making it suitable for cold storage and energy conservation in air conditioning. Full article

As the impact of climate change intensifies, meeting the energy demand of buildings in China’s cold regions is becoming increasingly challenging, particularly in terms of cooling energy consumption. The effectiveness of integrating phase change material (PCM) into building envelopes for energy saving in China’s cold regions is unclear. The aim of this study is to assess the effectiveness of PCM integration in building enclosures for energy efficiency in these regions. The research monitored and recorded indoor temperature data from typical residential cases from May to September. This measured data was then used to validate the accuracy of EnergyPlus22-1 software simulation models. Subsequently, the calibrated model was utilized to conduct a comparative analysis on the effects of PCM on indoor temperatures and cooling energy consumption across these regions. The results of these comparative analyses indicated that PCM can alleviate indoor overheating to varying degrees in severe cold regions of China. Focusing on north-facing bedrooms, applying PCMs reduced the duration of overheating in non-air-conditioned buildings in severe cold regions of China by 136 h (Yichun), 340 h (Harbin), 356 h (Shenyang), and 153 h (Dalian). In terms of cooling energy consumption, the energy saved by applying PCMs ranged from 1.48 to 13.83 kWh/m². These results emphasize that the performance of PCM varies with climate change, with the most significant energy-saving effects observed in severe cold regions. In north-facing bedrooms in Harbin, the energy-saving rate was as high as 60.30%. Based on these results, the study offers guidance and recommendations for feasible passive energy-saving strategies for buildings in severe cold and cold regions of China in the face of climate change. Additionally, it provides practical guidance for applying PCMs in different climatic zones in China. Full article

The growing availability and decreasing cost of microencapsulated phase change materials (PCMs) present an opportunity to develop innovative insulation materials for latent heat energy storage. By integrating PCMs with traditional insulation materials, it is possible to enhance the thermal capacity of a building by up to 2.5-times, virtually without increasing the building’s mass. To improve buildings’ indoor structural performance, as well as improving their energy performance, microencapsulated PCMs are integrated into wallboards. The integration of microencapsulated PCMs into the wallboard solves the PCM leakage problem and assures a good bond with the building materials to achieve better structural performance. The novelty of this research is the application of encapsulated phase change material dispersion and technology for its incorporation into the structure of hemp shives and longitudinally milled wood chip-based insulation boards, using cold pressing technology to reduce the energy consumption of board production. As a result, low-density insulation boards for indoor application were produced by varying their structure and the amount of phase change materials in the range of 5% to 15% by board mass. The obtained board prototypes can be used as microclimate and thermoregulation elements of interiors, as well as functional aesthetic elements of interior design. Full article

Energy retrofit solutions that concern a building’s roof structure play a significant role in the enhancement of a building’s thermal behaviour. This study investigates the integration of phase change materials (PCMs) with cool coatings (CCs) or thermochromic coatings (TCCs), namely, a PCM roof, a PCM-CC roof, and a PCM-TCC roof, as alternative and novel tactics for the simultaneous control of solar heat transfer and solar heat reflection. An energy simulation analysis with the DesignBuilder tool is conducted for a one-story residence and the climatic conditions of Athens. The simulation results indicate that, compared to the existing concrete roof construction, the PCM roof, PCM-CC, and PCM-TCC roof systems demonstrate energy savings that reach up to 13.55%, 16.04%, and 21.70%, respectively. The systematic analysis reveals that the increase in PCM’s thickness leads to an increase in the total electricity savings of the buildings, but in the case of PCM-CC and PCM-TCC roof systems, they merely effect the cooling thermal loads. The mean phase transition temperature that favours the cumulative electricity savings is 28 °C in the case of PCM and PCM-TCC roof systems and 35 °C in the case of PCM-CC roof systems. The methodology of this study allows the design of efficient, integrated roof systems with advanced thermal and optical properties as energy retrofit solutions for Mediterranean climatic conditions. Full article

For artificial snowfall, snow particle size can have a direct impact on snow quality. The operating conditions of the snow-makers and environmental factors will influence the atomization and crystallization processes of artificial snow making, which consequently affect snow particle size. This paper investigates the size distribution of snow particles during artificial snow making under different operating conditions and environmental parameters. For this purpose, an environmental chamber is designed and structured. The laser scattering method was used to measure the size distribution of snow under different parameters in the room. The results show that the distribution of snow crystal particle size aligns closely with the Rosin–Rammler (R-R) distribution. The higher the height of the snowfall, the longer the snow crystals grow and the larger the snow crystal particle size. It has been found that a higher air pressure favors atomization, while the opposite is true for water pressure, which results in a higher air–water pressure ratio, producing smaller snow particle sizes. Additionally, an ambient temperature in the range of −5 °C to −15 °C contributes to the snow crystal form transforming from plates to columns and then back to plates; the snow particle size first decreases and then increases. Snow crystal particles at −10 °C have the smallest size. Outdoor snow-makers should be operated at the highest possible air–water pressure ratio and snow height, and at a suitable ambient temperature. Full article

This article presents the use of phase-change material (PCM) thermal storage within the Horizon 2020 HEART project (Holistic Energy and Architectural Retrofit Toolkit), aimed at decarbonising the European building sector through the retrofitting of existing structures into energy-efficient smart buildings. These buildings not only reduce energy consumption, but also incorporate advanced technologies for harnessing green energy, thereby promoting environmental sustainability. The HEART project employs state-of-the-art technologies for electricity production/dispatching and heat generation/storage, managed by a cloud-based platform for the real-time monitoring of parameters and optimising energy utilisation, enabling users to control their environmental comfort. The article provides a detailed examination of one of the project’s demonstration sites in Italy, focusing on various components such as heat pumps, photovoltaic systems (PV), controllers, and particularly emphasising the significance of storage tanks. The study involved the measurement and analysis of three heat storage tanks, each with a total volume of 3000 L. These tanks utilised PCM modules for latent heat storage, significantly enhancing overall heat accumulation. Water served as the heat transfer fluid within the tanks. Through meticulous calculations, the article quantifies the accumulated heat and presents a comparative evaluation between PCM-based storage tanks and conventional water tanks, showcasing the advantages of PCM technology in terms of increased heat retention and efficiency. Full article

This paper presents the development of a methodology for using simulation to test decentralised façade ventilation systems with PCM exchangers and its validation with experimental data. Two approaches were compared to simulate the operation of an exchanger filled with phase-change material. In Method A, the geometry consisted of an air domain and a phase-change material domain, located in the cylinders of the exchanger. In this method, the phase transition was not modelled, but the specific heat was made temperature-dependent, wherein within the limits of the melting point, the specific heat is increased to a level that mimics the amount of latent heat from melting and solidification of the phase-change material. In Method B, the geometry consisted only of the air domain, and the temperature was set on the cylinder wall surfaces at each time step using UDFs. When comparing the methods, the temperature difference at the individual measuring points was no greater than 1 K and the resulting exchanger efficiencies did not differ by more than 5%. It was noted that when the phase-change material was modelled in the software with Method A, the results provided better representation of the values obtained in the experiment. Validation of the models was carried out by comparing the experimental results from the real tests with the simulation results of methods A and B. It demonstrated that both models correctly reflected the operation of the exchanger, and that the efficiency results achieved did not differ by more than 6% compared to the experiment. A comparison of supply temperatures and exchanger efficiencies with numerical simulations using two methods is presented. Visual comparison of the temperature distribution in the flowing air and the temperature distribution on the cylinder walls is also presented. This article adds to existing scientific knowledge of computer simulation of exchangers used in façade ventilation units with phase-change material. Full article

Choosing the right phase change material (PCM) for a thermal energy storage (TES) application is a crucial step in guaranteeing the effectiveness of the system. Among a variety of PCMs available, the choice for a given application is established by several key factors, e.g., latent heat, stability, and melting point. However, phenomena such as subcooling—for which PCM cools in a liquid state below its solidification point—can lead to a reduction in the amount of energy stored or released, reducing the TES overall effectiveness, and also in some inaccuracies when modeling the problem. Thus, understanding the effects of subcooling on PCM performance is crucial for modeling and optimizing the design and the performance of TES systems. To this end, this work analyzes the PCM discharging phase in a cold thermal energy storage coupled to a chiller system. A first conduction-based predictive model is developed based on enthalpy–porosity formulation. Subcooling phenomena are encompassed through a control variable formulation, which takes its cue from the operation of a thermostat. Then, thermal properties of the PCM, i.e., the phase change range and specific heat capacity curve with temperature, are evaluated by using differential scanning calorimetry (DSC), in order to derive a second predictive model based on these new data, without including subcooling, for the sake of comparison with the first one. Experimental results from the storage tank confirm both model reliability and the fact that the PCM suffers from subcooling. Between the two numerical models developed, the first one that considers subcooling proves it is able to predict with satisfactory accuracy (RMSE < 1 °C) the temperature evolution on different tank levels. Full article

Due to their excellent thermophysical properties and high stability, inorganic salts and Forsalt mixtures are considered promising thermal energy storage materials for applications operating at high temperatures. A mixture of binary salts, such as CaCl₂ (58 wt.%)-LiCl (42 wt.%), was investigated in this work to understand their thermal properties and stability for use in TES systems. Thermophysical properties, such as onset melting and crystallization temperature, enthalpy of fusion, and crystallization enthalpy, were all investigated experimentally via the use of a simultaneous thermal analyzer. The experimental findings demonstrated a suitable onset melting temperature of 488 °C and a solidification temperature of 480 °C. The heat of fusion was observed as 206 J/g, whereas the heat of crystallization was recorded as 180 J/g. Thermal repeatability tests indicated little variations in melting temperature; however, fusion enthalpies changed significantly over the course of 30 heating-cooling cycles. Additionally, the results obtained from the thermogravimetric analysis showed relatively weak thermal stability with considerable mass changes. This might be caused by the salts decomposing at elevated temperatures. In order to validate this, a high-temperature in-situ X-ray diffraction technique was used to verify the thermal instability of the binary salt mixture with and without thermal cycling. The thermal decomposition of parent salts and the subsequent formation of new phases with the formation of voids were shown to be the cause of thermal instability. It is concluded that the binary mixture of chloride salt showed suitable thermal properties but relatively weak thermal stability, which may limit its use in practical applications. Full article