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[en] Energy storage in the walls, ceiling and floor of buildings may be enhanced by encapsulating suitable phase change materials (PCMs) within these surfaces to capture solar energy directly and increase human comfort by decreasing the frequency of internal air temperature swings and maintaining the temperature closer to the desired temperature for a longer period of time. This paper summarizes the investigation and analysis of thermal energy storage systems incorporating PCMs for use in building applications. Researches on thermal storage in which the PCM is encapsulated in concrete, gypsum wallboard, ceiling and floor have been ongoing for some time and are discussed. The problems associated with the application of PCMs with regard to the selection of materials and the methods used to contain them are also discussed
[en] Highlights: • Night ventilation were tested in combination with PCM-impregnated gypsum boards. • The Price-based method were experimentally used to perform peak load shifting. • Importance of the application of a smart control were experimentally investigated. • A cost and energy saving up to 93% and 92% per day respectively were achieved. - Abstract: In recent years, as a result of the continuous increase in energy demand, the use of energy storage has become increasingly important. To address this problem, the application of phase change materials (PCM) in buildings has received attention because of their high energy storage density and their ease of incorporation in building envelopes. Despite large experimental works conducted on the application phase change materials in buildings, there is very little work done on this application in combination with night ventilation. In this study, the application of night ventilation in combination with PCM-impregnated gypsum boards for cooling purposes was experimentally investigated. Two identical test huts equipped with “smart” control systems were used for testing the concept. One hut was constructed using impregnated gypsum boards, while the other hut was finished with ordinary gypsum board. Initially an air conditioning (AC) unit, without night ventilation, was used in both huts to charge the PCM during low peak period, showing very little savings in electricity. However, when night ventilation was used to charge the PCM instead, a weekly electricity saving of 73% was achieved.
[en] Highlights: • PCM wallboards were used in combination with PCM underfloor heating system. • Price-based method were experimentally used to perform peak load shifting. • Solar irradiation was used to minimize energy consumption. • A cost and energy saving up to 35% and 44.4% respectively were achieved. - Abstract: Phase change materials are used with various building materials in order to increase their thermal mass. This research is on the application of phase change material in the form of DuPont Energain"® wallboards in combination with an underfloor heating system incorporating phase change materials. An experimental study was carried out using two identical test huts at the Tamaki Campus, University of Auckland. Results using a price-based method showed electricity savings in both consumption and cost of up to 35% and 44.4% respectively
[en] This paper presents an analysis of a price-based control system in conjunction with energy storage using phase change materials for two applications: space heating in buildings and domestic freezers. The freezer used for this experimental study was provided with energy storage trays containing a eutectic solution of ammonium chloride (melting point of −15 °C). In the building application, DuPont wallboards were used to provide thermal storage. Experimental results showed that using thermal storage material in conjunction with the proposed price-based control method can improve performance of these systems and lead to a successful peak load shifting. Depending on electricity price trends, cost savings using the proposed strategy can vary. Savings of up to 16.5% and 62.64% per day were achieved for the freezer and building applications respectively, based on New Zealand electricity rates. - Highlights: • Price-based control in combination with PCM storage were suggested. • A freezer and two identical test huts were used for the experimental studies. • Price-based method were experimentally used to perform peak load shifting. • A cost savings up to 16.5% per day were achieved for the freezer experiment. • A cost saving up to 62.64% per day were achieved for the building experiment.
[en] Highlights: • The application of PCM in building was experimentally studied. • Weather forecast data were used in order to improve the energy saving. • The importance of an accurate weather forecast was investigated. • An electrical saving up to 90% per day was achieved. • Successful peak load shifting was achieved. - Abstract: This study experimentally investigated the application of weather forecasting in combination with the price-based control method for solar passive buildings. Two identical lightweight test huts were used for the experimental study, one finished with ordinary gypsum board and the other finished with PCM-impregnated gypsum boards. Based on the experimental results, the application of weather forecast data showed significant energy saving when PCM is used. In some days, an electrical energy saving up to 90% per day was achieved using the proposed method. The results also showed that the application of inaccurate weather forecasts can significantly deteriorate performance of the control system and even lead to more energy consumption in the PCM hut.
[en] Latent heat storage is one of the most efficient ways of storing thermal energy. Unlike the sensible heat storage method, the latent heat storage method provides much higher storage density, with a smaller temperature difference between storing and releasing heat. This paper reviews previous work on latent heat storage and provides an insight to recent efforts to develop new classes of phase change materials (PCMs) for use in energy storage. Three aspects have been the focus of this review: PCM materials, encapsulation and applications. There are large numbers of phase change materials that melt and solidify at a wide range of temperatures, making them attractive in a number of applications. Paraffin waxes are cheap and have moderate thermal energy storage density but low thermal conductivity and, hence, require large surface area. Hydrated salts have larger energy storage density and higher thermal conductivity but experience supercooling and phase segregation, and hence, their application requires the use of some nucleating and thickening agents. The main advantages of PCM encapsulation are providing large heat transfer area, reduction of the PCMs reactivity towards the outside environment and controlling the changes in volume of the storage materials as phase change occurs. The different applications in which the phase change method of heat storage can be applied are also reviewed in this paper. The problems associated with the application of PCMs with regards to the material and the methods used to contain them are also discussed
[en] Highlights: • The novelty of this research is using PCM microcapsules for thermal storage. • PCM Microcapsules absorb and release the compression heat at higher rates. • Air and tank wall temperatures during compression are predicted successfully. - Abstract: Compressed air energy storage is a useful means of storage since the stored compressed air can be used at any time as a source of mechanical energy for power production. However, if the heat generated during compression is not utilized, the process efficiency will be low, and consequently, additional heat is required to avoid frost formation during the expansion process. The generated heat during compression can be stored in the form of sensible heat in the wall of the high-pressure tank at an elevated temperature. However, this method is undesirable due to (1) less air can be compressed at higher temperatures and (2) heavy insulation would be required to prevent heat loss to the environment over extended time. A solution to this problem is to use Phase Change Material (PCM) which has a melting temperature close to ambient, and hence the heat could be stored as latent heat of melting. PCMs have low thermal conductivity and hence requires to have large contact area with the compressed air so as to be able to release its latent heat rapidly during rapid expansion. This could be achieved through the use of microencapsulated PCM, which provides very large surface area. In this work, a high-pressure tank (2 L, 200 bar) was used for air storage while the commercial microcapsules; Micronal® DS 5038X was used as the latent heat storage material. Both theoretical simulation and experimental measurements made on the system show that the use of PCM microcapsules reduces the maximum increase in air temperature from approximately 45 °C to 27 °C (150 g, Micronal® DS 5038X) during charging. While during discharging, the maximum decrease in temperature was reduced from 48 °C to 28 °C, which prevented air temperature from dropping to below 0 °C.
[en] Highlights: ► The corrosion of materials in contact with some low temperature PCM is studied. ► Copper and carbon steel must be avoided when using the PCM tested. ► Aluminium is not recommended with the tested PCM. ► Stainless steel 316 is recommended when in contact with the tested PCM. ► PP, PS, PET, and HDPE are not affected by a process of degradation by the tested PCM. - Abstract: Transport and storage of low temperature sensitive products is an issue worldwide due to changes of the lifestyle and population increase. In the recent years, thermal energy storage (TES) using phase change materials (PCMs) is being highly studied and developed for cold storage applications. Furthermore, the PCM are normally encapsulated in containers and added in the available systems, usually in food processes. Therefore safety constraints as the compatibility of the PCM with other materials have to take into account. Hence the main goal of the paper is to study the corrosion effect of different metals and polymer materials in contact with some PCM used in low temperature applications. Results show that copper and carbon steel must be avoided as PCM containers, and aluminium is not recommended; stainless steel 316 is recommended when in contact with the tested PCM. Moreover, PP, PS, PET, and HDPE are not affected by a process of degradation and are also compatible with the PCM studied
[en] Highlights: • The corrosion of Cu, Al and stainless steel in contact with inorganic PCM is studied. • Bischofite behavior was compared with the commercial salt MgCl_2·6H_2O. • Strong air-liquid interface corrosion was observed for both inorganic PCM. • Oxide and chloride compounds were determinate as corrosion products. - Abstract: The potential of the use of salt hydrates MgCl_2·6H_2O (bischofite) with typical impurities of the Salar de Atacama as a thermal energy storage material was evaluated with special attention to its corrosion behavior. Bischofite behavior is compared with that of commercial salt MgCl_2·6H_2O. The corrosion tests were conducted with metal sheets (copper, aluminum and stainless steel) partially immersed in molten salt hydrates at a temperature of 120 °C during 1500 h. The results showed minimum corrosion on all the immersed surfaces of all the metals. However, very sever corrosion was observed at the salt/air interface due to a known phenomenon of oxygen enhanced corrosion usually found even with water at ambient temperature. The corrosion products were determined with scanning electron microscopy (SEM-EDX) and X-ray diffraction (XRD) technique. For salts hydrates bischofite and MgCl_2·6H_2O, the results show the formation of cuprite (Cu_2O) and hematite (Fe_2O_3) on copper and stainless steel samples, respectively. For all cases studied in the present work, several chloride compounds were identified as corrosion products.