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Abstract Thermal energy storage (TES) systems are growing to a relevant role in solar cooling applications. Hence, high energy density is a desirable property of the TES system. Phase change materials (PCM) helps to increase this characteristic. A high temperature pilot plant able to test different types of TES systems and materials was designed and built at the University of Lleida (Spain). This pilot plant is composed mainly of three parts: heating system, cooling system, and different storage tanks. Two identical storage tanks based on the shell-and-tubes heat exchanger, one of them including 196 squared fins in the bundle of the tubes and the other without, were experimentally tested. Hydroquinone was selected as the storage material, having a latent heat of 205 kJ/kg and a phase change temperature between 168 and 173 °C. The aim of this paper is to test experimentally, and compare the average effectiveness of the TES systems analyzed using PCM for solar cooling and refrigeration applications. It was found out that for the same tank configurations (shell-and-tubes) even changing drastically the dimensions of the tank or the number and the diameter of the tubes, the average effectiveness curve proposed in the literature fits well with the results showed here.

Abstract Energy consumption presents increasing trends during last decades, presenting a great challenge. The building sector contributes to a high proportion of the energy consumed and therefore efforts should be focused to improve energy efficiency of buildings. For such purpose, the use of phase change materials in building envelopes has been extensively studied and its benefits were demonstrated. However, there is a lack of simple evaluation tools to assess these benefits. In this paper a previously proposed methodology based on four indicators, which were tested through simulation only are experimentally validated using brick, concrete and timber constructions, incorporating PCM. Results show that the methodology is successful for buildings with heat gains and having low thermal inertia or insulation. However, for highly insulated buildings with significant inertia and low heat gains the method fails to assess the potential benefit of the PCM. Moreover, the ITD indicator is found to be the most accurate in assessing PCM benefits compared to other parameters studied. In this paper the ITD indicator will be modified to take into account an upper and lower comfort temperature levels rather than single set temperature.

The main objective of this paper is to demonstrate experimentally that it is possible to improve the thermal comfort and reduce the energy consumption of a building without substantial increase in the weight of the construction materials with the inclusion of phase change materials (PCM). PCM are a suitable and promising technology for this application. This paper presents an experimental setup to test PCM with various typical insulation and construction materials in real conditions in Puigverd de Lleida (Lleida, Spain). Nine small house-sized cubicles were constructed: two with concrete, five with conventional brick, and two with alveolar brick. PCM was added in one cubicle of each typology. For each type of construction specific experiments were done. In all cubicles, free-floating temperature experiments were performed to determine the benefits of using PCM. A Trombe wall was added in both concrete cubicles and its influence was investigated. All brick cubicles were equipped with domestic heat pumps as Heating, Ventilation, and Air Conditioning (HVAC) system; therefore, the energy consumption was registered, providing real information about the energy savings. Results were very good for the concrete cubicles, since temperature oscillation were reduced by up to 4°C through the use of PCM and also peak temperatures in the PCM cubicle were shifted in later hours. In the brick cubicles, the energy consumption of the HVAC system in summer was reduced by using PCM for set points higher than 20°C. During winter an insulation effect of the PCM is observed, keeping the temperatures of the cubicles warmer, especially during the cold hours of the day.

Abstract Among the research activities that aim at reducing energy consumption in buildings and their impact on the environment is an experimental set-up that has several house-shaped cubicles constructed in Puigverd de Lleida (Spain). Assessing the environmental impact through studying the manufacturing, operational and disposal phases of these cubicles have been done in previous research. The objective of this paper is to investigate the use of esters as PCM in order to estimate its environmental impact in building envelopes in comparison to the use of paraffin or salt hydrates through a theoretical study. The evaluation of the environmental impact of this type of PCM material is conducted using Life Cycle Assessment (LCA) based on the Eco-indicator 99 method. It is found that the impact of ester used as PCM presents slightly better results than the case of using salt hydrates during the manufacturing impact. On the other hand, the use of salt hydrates or ester as PCM in the cubicles results in an impact reduction of 9% and 10.5% respectively, compared to the case of using paraffin.

Abstract Thermal energy storage and conversion aims to improve the high inefficiency of the industrial processes and renewable energy systems (supply versus demand). Chemical sorption processes and chemical reactions based on solid–gas systems are a promising way to store and convert thermal energy for heating or cooling applications and, thereby to increase the efficiency of the processes and to reduce the greenhouse effect. Although more efforts are required to bring this technology to the market, some important breakthrough have been made regarding to system efficiency. Over the last two decades, the experimental research in this field has increased largely to validate these advances under practical conditions. Therefore, this paper gives a state-of-art review of performances obtained under practical conditions by the different prototypes built over the last two decades. In addition, the main advantages and disadvantages of solid–gas chemical sorption processes and chemical reactions are summarized.

Abstract It is well known that it is necessary to insulate the buildings to decrease the thermal demand and to decrease the use of heating and cooling. Due to the high cost of fossil fuels and to the necessity to reduce CO 2 emissions, and also due to the new building regulations more attention is paid to the insulation of buildings. Different insulation materials are available in the market. Usually, they are compared by their thermal conductivity and with theoretical calculations, but there are no experimental comparisons available, where the behavior of such insulation materials in a building is compared over time. This is why the authors started a comparison of three typical insulation materials, polyurethane, polystyrene, and mineral wool. For this purpose, four house-like cubicles were constructed (with a size of 2.4 m × 2.4 m × 2.4 m) and their thermal performance throughout the time was measured. The cubicles were built under a conventional Mediterranean construction system, differing only in the insulation material used. During 2008 and the first months of 2009 the performance of these cubicles was evaluated, and the results are presented in this paper.

Abstract A new type of ventilated facade (VF) with macro-encapsulated phase change material (PCM) in its air cavity is presented in this paper. The thermal performance of this special building envelope is experimentally tested to analyze its potential in reducing the cooling demand during the summer season in the Continental Mediterranean climate. Two identical house-like cubicles located in Puigverd de Lleida (Spain) were monitored during summer 2012, and in one of them, a ventilated facade with PCM was located in the south wall. Six automatized gates were installed at the different openings of the channel in order to control the operational mode of the facade. This versatility allows the system to be used as a cold storage unit, as an overheating protection system or as a night free cooling application. The experimental results point out the night free cooling effect as the most promising operational sequence to reduce the cooling load of the cubicle. On the other hand, the thermal resistance of the outer skin of the facade must be increased; otherwise the cold storage system cannot be used efficiently.

Abstract This work presents the results of an experimental set-up to test phase change materials with two typical construction materials (conventional and alveolar brick) for Mediterranean construction in real conditions. Several cubicles were constructed and their thermal performance throughout the time was measured. For each construction material, macroencapsulated PCM is added in one cubicle (RT-27 and SP-25 A8). The cubicles have a domestic heat pump as a cooling system and the energy consumption is registered to determine the energy savings achieved. The free-floating experiments show that the PCM can reduce the peak temperatures up to 1 °C and smooth out the daily fluctuations. Moreover, in summer 2008 the electrical energy consumption was reduced in the PCM cubicles about 15%. These energy savings resulted in a reduction of the CO2 emissions about 1–1.5 kg/year/m2.

Abstract In a recent meeting of IEA's Annex 23, several members presented their conclusions on the modeling of phase change materials behavior in the context of building applications. These conclusions were in agreement with those of a vast review, involving the survey of more than 250 journal papers, undertaken earlier by the group of Ecole de technologie superieure. In brief, it can be stated that, at this point, the confidence in reviewed models is too low to use them to predict the future behavior of a building with confidence. Moreover, it was found that overall thermal behaviors of phase change material are poorly known, which by itself creates an intrinsic unknown in any model. Models themselves are most of time suspicious as they are often not tested in a very stringent or exhaustive way. In addition, it also appears that modeling parameters are somewhat too simplified to realistically describe the complete physics needed to predict the real life performance of PCMs added to a building. As a result, steps are now taken to create standard model benchmarks that will improve the confidence of the users. Hopefully, following these efforts, confidence will increase and usage of PCM in buildings should be eased.