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The current use of buildings is facing an unprecedented increase in energy costs, especially in the European Union. The energy costs can be reduced by energy savings and by increased use of renewable energy represented mostly by energy converted from solar radiation. When solar energy is considered to be utilized in buildings, the mismatch between energy availability and energy demand must be solved by energy storage. This paper describes the principles of the use of latent heat thermal energy storage and the possibility of using bio-based phase change materials as heat storage media. Because the latent heat storage media undergo a change of phase during the charging and discharging, proper encapsulation is necessary. The paper presents the main findings of a study focused on the compatibility between coconut oil and selected plastics as materials of encapsulation. The compatibility of selected plastics and Coconut oil was evaluated by laboratory experiment based on the immersion of plastic samples in coconut oil and calculation of change in weight of samples within 17 weeks lasting test. The negligible weight changes were occurred for polycarbonate and polyethylene terephthalate which proves excellent compatibility with Coconut oil.

Thermal energy storage with phase change materials (PCMs) has attracted a lot of attention in the last several decades. Most PCMs do not change phase at a constant temperature but rather in a certain temperature range. It means that the PCM need to transit through its phase change temperature range to fully change phase from the solid state to the liquid state and vice-versa. The situation, in which the phase transition begins and/or ends within the phase change temperature range (in the mushy zone), is usually called a partial phase transition (or a partial phase change). The partial phase transitions occur quite often in real-life thermal energy storage systems with PCMs; especially when a PCM has a wide phase change temperature range. The behavior of PCMs during the partial phase transitions is poorly understood at the moment, because the experimental techniques used for the characterization of PCMs (such as the differential scanning calorimetry – DSC) are difficult to apply for the study of partial phase transitions. The lack of knowledge in this area influences the accuracy of phase change simulation models. The main goal of the experimental investigations, described in the paper, was to obtain data for the development of a simulation model for partial phase changes. The experimental set up for the investigation of partial phase changes of PCMs has been proposed, assembled, and the pilot measurements have been conducted. The experimental set up consists of two water storage tanks (that can be maintained at different water temperatures), a water-PCM concentric tube type heat exchanger and a data acquisition system. The water flows through the central tube of the heat exchanger while the PCM is located in the annular space of the exchanger. The water storage tanks, maintained at the temperatures within the phase change temperature range of a PCM, allow for the investigations of the heat storage cycles consisting of partial phase changes.

Latent heat storage represents technology with significantly higher energy storage density. The thermal energy storage capacity of building structures and storage units integrated into building services contribute to the energy flexibility of buildings. This paper presents results from laboratory experiments focused on the compatibility of heat storage media represented by phase change materials (PCMs) with materials of container. Material compatibility of selected PCMs with the plastics and metals were tested by a long-term experiment. Two organic-based and two inorganic-based phase change materials were selected for tests of compatibility with selected metals (aluminium, copper and brass) and plastics (PP-H, PE-HD, and PVC-U). Plastic-PCM compatibility was determined by gravimetric method. For evaluation of metal-PCM compatibility, calculation of corrosion rate was applied. The less mass changes and lower penetration of PCMs to the matrix was observed for inorganic-based PCMs compared to organic-based PCMs. In case of compatibility between metals and PCMs, the highest values of corrosion rate were calculated for copper immersed in inorganic-based PCMs Rubitherm SP25. [ABSTRACT FROM AUTHOR]

With the increasing requirements for the energy performance of buildings, there is a demand for internal insulation systems in buildings where it is not possible to apply an external insulation system for legislative reasons. Currently, there has been an upsurge in the development of diffusion-open insulation materials whose properties can compensate for the risks of damage to solid masonry walls insulated with traditional diffusion-closed internal insulation systems. The properties of diffusion-open systems are already well known. This paper focuses on the simulation of the thermal moisture behaviour of a detail of a timber beam embedment in a wall with capillary active thermal insulation in cold climatic conditions of Central Europe.

The paper presents the results from the comparative measurement of indoor environment in two attic rooms. The effect of phase change materials was researched within the operative room temperature. System utilizes simple heating of the material and reversible changes of phase for heat storage. The phase change materials increase the heat storage capacity of the building. This fact has the effect of temperature in the experimental room and its maximum value during the summer. As PCM is used a microencapsulated paraffin in the experimental implementation. Its integration into building structures is a modification of plaster. Activation of phase change materials is carried out by capillary cooling. The paper presents the results of measurements for different modes of operation of passive cooling [ABSTRACT FROM AUTHOR]

The quality of wastewaters is mainly controlled by the legislation based on conventional chemistry. The use of bioassays could produce additional information about the toxicity potential of industrial discharges and effluents. This study presents the results of bioassays performed to evaluate the ecotoxicity of municipal wastewater and wastewaters from a poultry farm and brewery. The ecotoxicological tests were carried out with the aquatic plant Lemna minor, and on the inhibitory effects of Sinapis alba root growth. A luminescent bacterial test based on the inhibition of vitality of marine bacteria Vibriofischeri was added. With tests using Sinapis alba or Lemna minor, the wastewaters were evaluated as minor acutely toxic (brewery and MWWTP influents) or not acutely toxic (the poultry farm influents and all effluents). They also showed the growth stimulation indicating an increased level of nutrients in wastewater (especially in the poultry farm). Difference of sensitivity between the bioassays with Sinapis alba and Lemna minor was observed. The higher sensitivity of bioassays with mustard white seeds Sinapis alba in the wastewater from the poultry farm was found out. Lemna sp. is regarded to be a more sensitive organism but in this study this was not uniquely observed. With the bioluminescence test using Vibrio fischeri, only EC20 values were determined. The higher toxicity was observed for wastewater from the brewery. [ABSTRACT FROM AUTHOR]

Contemporary research stresses the need to reduce mankind's environmental impacts and achieve sustainability. One of the keys to this is the construction sector. New buildings have to comply with strict limits regarding resource consumption (energy, water use, etc.). However, they make up only a fraction of the existing building stock. Renovations of existing buildings are therefore essential for the reduction of the environmental impacts in the construction sector. This paper illustrates the situation using a case study of a rural terraced house in a village near Brno, Czech Republic. It compares the life-cycle assessment (LCA) of the original house and its proposed renovation as well as demolition followed by new construction. The LCA covers both the initial embodied environmental impacts (EEIs) and the 60-year operation of the house with several variants of energy sources. The results show that the proposed renovation would reduce overall environmental impacts (OEIs) of the house by up to 90% and the demolition and new construction by up to 93% depending on the selected energy sources. As such, the results confirm the importance of renovations and the installation of environmentally-friendly energy sources for achieving sustainability in the construction sector. They also show the desirability of the replacement of inefficient old buildings by new construction in specific cases. [ABSTRACT FROM AUTHOR]

The construction and maintenance of building stock is responsible for approximately 36% of all CO2 emissions in the European Union. One of the possibilities of how to achieve high energy-efficient and decarbonized building stock is the integration of renewable energy sources (RES) in building energy systems that contain efficient energy storage capacity. Phase Change Materials (PCMs) are latent heat storage media with a high potential of integration in building structures and technical systems. Their solid-liquid transition is specifically utilized for thermal energy storage in building applications. The typically quite old example is the use of ice that serves as long-term storage of cold. Large pieces of ice cut in winter were stored in heavily insulated spaces and prepared for cooling of food or beverages in summer. In the contemporary use of the principle, the PCMs for building applications and tested in this study must have a melting range close to the desired temperature in the occupied rooms. As the PCMs need to be encapsulated, several types of metal containers have been developed and tested for their thermal conductivity and resistance to mechanical damage, which enhances the performance of these so-called latent heat thermal energy storage (LHTES) systems. Long-term compatibility of metals with PCMs depends, i.e., on the elimination of an undesirable interaction between the metal and the specific PCM. Heat storage medium must be reliably sealed in a metal container, especially if the LHTES is integrated into systems where PCM leaks can negatively affect human health (e.g., domestic hot water tanks). The aim of this study is to evaluate the interactions between the selected commercially available organic (Linpar 17 and 1820) and inorganic (Rubitherm SP22 and SP25) PCMs and metals widely used for PCM encapsulation (aluminum, brass, carbon steel, and copper). The evaluation is based on the calculation of the corrosion rate (CR), and the gravimetric method is used for the determination of the weight variations of the metal samples. The results show good compatibility for all metals with organic PCMs, which is demonstrated by a mass loss as low as 2.1 mg in case of carbon steel immersed in Linpar 1820 for 12 weeks. The exposure of metals to organic PCMs also did not cause any visual changes on the surface except for darker stains, and tarnishing occurred on the copper samples. More pronounced changes were observed in metal samples immersed in inorganic PCMs. The highest CR values were calculated for carbon steel exposed to inorganic PCM Rubitherm SP25 (up to 13.897 mg·cm−2·year−1). The conclusion of the study is that aluminum is the most suitable container material for the tested PCMs as it shows the lowest mass loss and minimal visual changes on the surface after prolonged exposure to the selected PCMs. [ABSTRACT FROM AUTHOR]

Practical applications of Phase Change Materials (PCMs) often require their encapsulation in other materials, such as metals or plastics. This raises the issue of compatibility between PCMs and encapsulating materials, which has still not been sufficiently addressed. The study presented here follows existing research and provides experimental evaluation of the suitability of selected PCMs for proposed integration in building structures. Two organic PCMs, two inorganic PCMs and three representative plastics (polypropylene (PP-H), high density polyethylene (PE-HD) and polyvinylchloride (PVC-U)) were selected for compatibility tests. Evaluation of the results is based on the mass variations of the plastic samples during the test period. Plastic samples were immersed in PCMs and subjected to periodic heating and cooling (for 16 weeks) in a small environmental chamber simulating real operational conditions. The results show that the organic PCMs have a greater ability to penetrate the PE-HD and PP-H compared with the inorganic PCMs. The penetration of all PCMs was most notable during the first four weeks of the experiment. Later it slowed down significantly. Overall, the mass changes in PE-HD and PP-H samples did not exceed 6.9% when immersed in organic PCMs and 1.8% in inorganic PCMs. PVC-U samples exhibited almost negligible (less than 0.1%) mass variation in all cases. [ABSTRACT FROM AUTHOR]

Experiments have been carried out in order to investigate the stabilization of water temperature with a water-PCM heat exchanger. The water-PCM heat exchanger was of a rather simple design. It was a round tube, through which the water flowed, surrounded with an annular layer of PCM. The heat exchanger was divided into one meter long segments (modules) and the water temperature was monitored at the outlet of each of the segments. A paraffin-based PCM with the melting temperature of 42 °C was used in the experiments. The experimental set-up consisted of two water reservoirs kept at different temperatures, the water-PCM heat exchanger, PC controlled valves and a data acquisition system. As the first step a response to a step change in the water temperature at the inlet of the heat exchanger was investigated. Subsequently, a series of experiments with a square wave change of temperature at the inlet of the exchanger were carried out. The square wave temperature profile was achieved by periodic switching between the two water reservoirs. Several amplitudes and periods of temperature square wave were used. The results of experiments show that a water-PCM heat exchanger can effectively be used to stabilize the flowing water temperature when the inlet temperature changes are around the melting range of the PCM.

Simulations of the behaviour of a solar air collector with integrated latent heat thermal storage were performed. The model of the collector was created with the use of coupling between TRNSYS 17 and MATLAB. Latent heat storage (Phase Change Material - PCM) was integrated with the solar absorber. The model of the latent heat storage absorber was created in MATLAB and the model of the solar air collector itself was created in TRNSYS with the use of TYPE 56. The model of the latent heat storage absorber allows specification of the PCM properties as well as other parameters. The simulated air collector was the front and back pass collector with the absorber in the middle of the air cavity. Two variants were considered for comparison; the light-weight absorber made of sheet metal and the heat-storage absorber with the PCM. Simulations were performed for the climatic conditions of the Czech Republic (using TMY weather data).

Highlights: [•] The latent heat thermal storage unit for air-based solar systems was investigated. [•] The CSM panels with the phase change material Rubitherm RT42 were used. [•] The investigations were done both experimentally and numerically. [•] The experimental and numerical results are in a relatively good agreement. [•] Results confirmed a potential of a phase change materials usage in thermal systems. [Copyright &y& Elsevier]