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SiO2 composite phase change material
Building and Environment 104 (2016) 172e177
Contents lists available at ScienceDirect
Building and Environment journal homepage: www.elsevier.com/locate/buildenv
Investigation on the properties of a new type of concrete blocks incorporated with PEG/SiO2 composite phase change material Tao Xu a, c, Qinglin Chen a, Zhengguo Zhang b, Xuenong Gao b, *, Gongsheng Huang c, * a Guangdong Engineering Technology Research Center for Petrochemical Energy Conservation, School of Chemical Engineering and Technology, Sun Yat-sen University, Guangzhou 510275, China b Key Laboratory of Enhanced Heat Transfer and Energy Conservation (Ministry of Education), School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China c Department of Architecture and Civil Engineering, City University of Hong Kong, Kowloon, Hong Kong
a r t i c l e i n f o
a b s t r a c t
Article history: Received 9 March 2016 Received in revised form 30 April 2016 Accepted 3 May 2016 Available online 6 May 2016
This paper investigates a new type of concrete blocks which integrates a form-stable PEG/SiO2 composite PCM with the melting temperature of 28 C and the latent heat of 113.6 kJ kg1. A comprehensive analysis on the characteristics of sample concrete bricks shows that the properties of PCM concrete bricks are significantly influenced by the quantity of the PEG/SiO2 composite PCM. When the addition of composite is ranging from 0 to 18%, the apparent density, compression strength and thermal conductivity drop from 2.20 to 1.87 g cm3, 23.6 to 0.69 MPa and 0.94 to 0.59 W m1 K1, correspondingly. The optimum amount of PCM in the concrete blocks was determined as 7.5%. The thermal performance of the PEG/SiO2 composite PCM concrete was also evaluated by comparing the temperature variation of a test chamber with PCM concrete and a test chamber without PCM concrete significantly. The results show that the PCM concrete can narrow the indoor temperature swing, which may help to improve the indoor thermal comfort in passive solar chambers. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Novel concrete Phase change material (PCM) Polyethylene glycol (PEG) Thermal performance
1. Introduction With the rapid development of economy and improvement of living standards, the demand of energy is growing fast. According to a report from the U.S. department of energy (DOE) in 2010, the buildings sector accounts for more than 40% of global primary energy consumption [1,2]. This situation, together with the shortage of conventional fossil energy and environmental concerns, has motived the development of sustainable buildings, such as buildings equipped with renewable energy systems [3e5]. During the past few decades, passive solar building, which is one of those expected constructions, has attracted much attention. With the assistance of latent thermal energy storage (LTES) systems by incorporating phase change materials (PCMs) into walls, ceilings, windows or floors, passive buildings can store available heat and coolness in off-peak load conditions to match on-peak demand periods [6e8]. Such benefit offered by the technology of LTES leads
* Corresponding authors. E-mail addresses: [email protected] (X. Gao), [email protected]. hk (G. Huang). http://dx.doi.org/10.1016/j.buildenv.2016.05.003 0360-1323/© 2016 Elsevier Ltd. All rights reserved.
to more efficient energy use and enhances indoor thermal comfort without any expenditure of conventional energy [9]. PCMs, as the core component of the LTES system, are a type of substance that can store or release large amount of latent heat when undergoing a phase transition. To provide a high performance of a passive LTES device in the living space, an appropriate type of PCMs for indoor thermal management is necessary. For building applications, the PCMs should have suitable phase change temperature (18e30 C) to maintain thermal comfort, high enthalpy to make sure a large energy storage capacity and good chemical and thermal stability for long-term use [10,11]. Cost effective and low environmental impact should be favored considering the residential needs. After years of research and development, materials including paraffin waxes [12], fatty acids [13], polyethylene glycol [14] and salt hydrates [15,16] are found to be available in the construction field. Some form-stable composites formed by embedding PCMs into matrix materials in order to solve the leakage problems are considered as potential candidates as well. The polyethylene glycol/silicon dioxide (PEG/SiO2) composite PCM is a good example. Since it is developed in 2009 [17,18], the modifications of its preparation methods [17,18] and thermalphysical properties to accommodate the LTES systems in building
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envelops have attracted the interest from many researchers. However, until now there are very few applications that can be found in current literature although the PEG/SO2 composite PCM has the potential benefits for solar passive buildings. Except the type of PCMs, another important factor that determines the building energy performance is the placement of the LTES systems. As summarized by Soares et al. [10], there are three main methods commonly used to design the LTES components. The first is to encapsulate PCM into wall boards. Aiming at improving the efficiency, different configurations such as PCM wall boards coupling with vacuum isolation panels [19e21] and placement of a PCM composite wall plate within a multiple-layered building envelope [22e25] were proposed recently. The second is to use PCM brick. A hollow thermal-insulation brick, including clay bricks [26], glass bricks [9,27], and gypsum bricks [28] which have holes inside, is suitable to contain PCMs for indoor temperature control. The third is to produce PCM concrete. Many studies, such as Zhang et al. [29], Hunger et al. [30], Jeong et al. [31], Memon et al. [32], Navarro et al. [33] and Ling et al. [34], have investigated the compatibility issue between PCMs and concrete mixture in order to minimize the effects of PCMs on macro thermo-mechanical performance after they are added into concrete mixture. As reported by Baetens et al. [35], the combination of PCMs with concrete mixture can obtain overall heat capacity of 10 times higher than gypsum wall boards. Besides, concrete is the most widely used construction material and can be formed into any shape and size. Therefore it is very valuable to study the properties of PCM concrete. It is noted that although LTES systems in building envelops has been developed [36,37], very few studies focuses on PEG/SiO2 composite PCM concrete block and its potential applications for buildings. Hence, this study proposes a new type of PCM concrete product, i.e. PEG/SiO2 composite PCM concrete block, and investigates its properties and potentials for building applications. The properties of the new concrete will be studied by measuring the apparent density, thermal conductivity and compression strength. To evaluate the performance of the concrete for passive indoor temperature control, passive solar test chambers with the PCM concrete walls will be built and the indoor temperatures will be tested. The ultimate objective of this study is to demonstrate the feasibility of using PEG/SiO2 composite PCM in concrete blocks to increase their thermal inertia and to reduce the energy demand of the building. 2. Experimental setup 2.1. Material preparation The form-stable PEG/SiO2 composite PCM can be prepared by the temperature-assisted sol-gel method. First, the silica sol solution and the PEG solution are made by dissolving silica sol and PEG in water with continuous stirring for 12 h respectively. Then the prepared solutions are mixed at room temperature at the mass fraction of 80%. After that, this mixed solution is heated for 100 min by water bath with quick continuous stirring at 70 C. In this process, PEG will be absorbed into the network of porous silica gel through the reaction of gelatinization. Finally, the form-stable PEG/ SiO2 composite PCM is obtained after a drying procedure in a cabinet at 60 C for 36 h. In order to guarantee the performance stability of composite PCM, some dried sample powder was taken out to carry on leakage test. Firstly, it was put above test paper, and then it was put into the constant temperature chamber with 110 C for 4 h to ensure that no liquid PEG could leak on the test paper. The prepared composite PCM is further incorporated into the conventional concrete to produce a new modified concrete. The detail procedure of the preparation is as follows: to begin with, Slag
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Portland cement (#325), coarse aggregate, fine aggregate sand and water with corresponding mass ratio of 1.00:1.41:1.04:0.48 are mixed for 15 min in order to homogenize the blended components. After that, different amounts of the composites PCM are added into the concrete mixture. Another 10 min are needed to assure the full dispersion of the PCM. Then the desirable PCM concrete will be obtained by drying the mixture mortar to constant weight. In order to investigate the physical properties of the concrete integrated with this composite PCM, a series of concrete blocks with total PEG mass fraction of 0e18% should be fabricated. In this study, Reagent grade polyethylene glycol with an average molecular weight of 1000 was purchased from Guangdong Guanghua Sci-tech Co., Ltd. China. Silica sol was supplied by the Guangzhou Chemical Agent Company (Guangzhou, PR China). Both of them were used as raw materials. 2.2. Property characterization The thermal properties of the PEG/SiO2 composite PCM including the melting point and latent heat of fusion can be measured using a differential scanning calorimeter (Q20, TA Instrument Inc., USA). The samples of the measurements were randomly selected from the different locations of the composite. When tested in DSC, the mass of the sample was in the range of 5e10 mg and sealed in an aluminum pan. The heating and cooling rates were kept constant at 10 C min1, and the temperature was ramped in the range of 20e80 C under the protection of nitrogen. The apparent densities of the PCM concrete can be obtained by
ro ¼
mo Vo
(1)
where ro denotes the apparent density; Vo is the volume of each brick, which was made by pouring the new concrete mixture into a mold with dimensions of 5 cm 5 cm 5 cm; and mo is the mass of each brick, measured after these samples were dried at room temperature for a few hours. The thermal conductivity of the new type of concrete with different content of PEG/SiO2 composite PCM was measured using a hot disk thermal constant analyzer (TPS2500, Hot Disk Inc., Sweden). A probe consisting of a thin nickel foil embedded between two thin layers of Kapton insulated films was employed as both the heating source and the temperature sensor. During the measurement, two concrete blocks with the same content of the composite PCM were placed in contact with the probe. The heating power and scanning time for the tests were set as 0.05 W and 20 s, respectively. The compression strength test of the PCM concrete was carried out with the assistance of a compression testing machine. During this process, the concrete blocks impregnated with different content of the composite PCM were placed in the machine and load was applied without shock and increased continuously at the rate of 0.3 MPa/s until the samples was broken down. 2.3. Thermal performance evaluation The thermal performance of the PEG/SiO2 composite PCM concrete for indoor thermal management in passive solar buildings was investigated using a test chamber, the walls of which were made of the composite PCM concrete. For comparison, another identical chamber with conventional concrete walls was built as well. Fig. 1 shows the schematic diagram of the test chamber, which has the dimensions of 60 cm 60 cm 60 cm. The chamber has a glazing window, three side walls, one floor and one roof. In order to collect the maximum solar radiation throughout the year, the glazing window is 30 south by west oriented. Each of the three
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side walls is constituted by a polyvinyl chloride (PVC) panel of 3 mm thickness, an expanded polystyrene (EPS) panel of 8 mm thickness and a 20 mm thick concrete wall panel with or without PCM. For the roof and floor, the same PVC and EPS panels were used, but no concrete wall panels were placed. During the testing process, the indoor temperature was monitored by one J-type thermal couple. A data logger (34970A, Agilent Inc., USA) was applied to collect the signals generated by the thermal couple and convert them to digital data. The environmental temperature outside the chamber also was recorded. 3. Results and discussion 3.1. Thermal characteristics of the PEG/SiO2 composite PCM The DSC curve of the PEG-1000/SiO2 composite PCM is given in Fig. 2 where the composite PCM contains 80% (mass fraction) of PEG. A single peak during the heating or cooling process was observed, which indicates that the PEG was the only substance that attributes to the latent heat of the fusion of the composite material. The details of the onset of the phase change temperature (Tonset), the peak temperature of the phase change (Tpeak) and the latent heat (DH) can be derived from the DSC curve in Fig. 2, which were determined as 28 C, 36.8 C and 113.6 kJ kg1 respectively; while, in the freezing process, they are 26.6 C, 21.5 C and 115.4 kJ kg1, correspondingly.
apparent density varies smoothly. Since the concrete is a porous media, a part of the composite PCM might be used to occupy the void space within the bricks instead of replacing the concrete volume, which would further cause a slight apparent density drop. This speculation could also explain the rapid decrease of the apparent density at the third stage where the pores in concrete bricks might be completely saturated with PCM.
3.2.2. Thermal conductivity Thermal conductivity of building materials is one of the critical parameters that directly influence the energy performance of buildings. In this work, the thermal conductivity of the concrete with PEG mass fraction ranging from 0 to 18% was measured using a hot-disk thermal constant analyzer. The results were depicted in Fig. 4. With the increase of the quantity of the PEG/SiO2 composite PCM, the thermal conductivity of the concrete bricks exhibits a decreasing trend. For example, the thermal conductivity of the concrete bricks with 1.5% total PEG mass fraction is 0.84 W m1 K1, whereas that it becomes 0.64 W m1 K1 when the total PEG mass
3.2. Properties of the PCM concrete 3.2.1. Apparent density The apparent density of the concrete embedded with the PEG/ SiO2 composite PCM was investigated using concrete blocks with fixed sizes but different PEG mass fraction. Fig. 3 shows the variation of the apparent density of the samples as a function of the total PEG mass fraction. It can be seen that the apparent density of the concrete shows a three-stage decreasing behavior as the PEG content increases. At the first stage, a sharp decline occurs from 0 to 1.5% total PEG mass fraction. This could be due to the presence of the composite PCM, the density of which is much lower than that of the concrete. However, when it comes to the range 1.5e7.5%, the
Fig. 2. DSC thermogram of PEG-1000/SiO2 composite PCM with PEG-1000 mass fraction of 80%.
Fig. 1. Schematic diagram of the test chamber: (a) configuration of the chamber, (b) constitution of the side walls.
T. Xu et al. / Building and Environment 104 (2016) 172e177
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fraction is 7.5%. The relative decrease is 24.2%. According to Li’s work [18], the thermal conductivity of the PEG/SiO2 composite PCM (mass fraction of PEG is 80%) was found to be 0.28 W m1 K1, which is almost 2.5 times lower that of the concrete without PCM. After adding the composite, the thermal conductivity of the concrete is degraded consequently. Fig. 4 shows the variation of the thermal conductivity with respect to the total PEG mass fraction, which indicates that the apparent density of concrete bricks is one of the main effective factors to their thermal conductivity. 3.2.3. Compression strength The compression strength was also tested and the results are presented in Fig. 5. A negative influence of the quantity of the PEG/ SiO2 composite PCM on the compression strength of the concrete can be found. For the concrete without PCM, the compression strength was 23.61 MPa. This value dropped rapidly to 7.5 MPa when the mass ratio of the composite PCM was changed from 0 to 4.5%. The rate of the decline was as much as 68.2%. However, with the further augment of the mass fraction, the compression strength decreased slowly. This downward trend is thought to have been caused by the composite PCM with lower density and compression strength added to concrete. When the mass ratios of the composite PCM are 7.5% and 9%, the global compression strength of the concrete are 4.392 MPa and 3.828 MPa. According to China’s national standard of GB/T 24492-2009 “Nonload Bearing Concrete Hollow Brick”, the lowest compression strength is no less than 4.0 MPa. Thus, the optimum total PEG mass fraction in the concrete walls was determined as 7.5%. 3.3. Thermal performance of the PCM concrete in a passive solar chamber To evaluate the thermal performance of the concrete walls that are impregnated with PEG/SiO2 composite PCM on indoor temperature control, the test chamber shown in Fig. 1, was compared with a chamber without PCM concrete. The heat source was Sun. In the chamber with PCM concrete, the total PEG mass fraction of 7.5% was adopted in these tests considering the requirements of mechanical strength, thermal insulation and heat storage capacity for construction applications. The simultaneous acquisitions of measurements on these two chambers began on 29 September 2012 and lasted for 4 days in Guangzhou, China. Fig. 6 shows the variations of the outdoor and indoor
Fig. 3. Apparent density of the concrete bricks varied with the total PEG mass fraction.
Fig. 4. Thermal conductivity of the concrete bricks varied with the total PEG mass fraction.
temperatures of the two test chambers (with and without the composite PCM). It can be seen that in the daytime, the indoor temperature of the chamber equipped with the PCM concrete walls had a narrow temperature variation than that of the non-PCM chamber. Comparing the peak values in each day, the temperature attenuations of the four days were 4.1, 4.0, 2.7 and 4.6 C, respectively. Conversely, in the case of the night, the minimum indoor temperatures of the chamber with PCM are 1.7, 1.8, 1.1 and 1.5 C higher than that of the non-PCM chamber. These phenomena indicate that the concrete walls embedded with the PEG/SiO2 composite PCM did fulfill their function of narrowing the indoor temperature swing. Fig. 7 presents one measurement period (24 h) extracted from the above data in order to further illustrate the indoor temperature changes. During the heating process, the test point in the chamber with PCM shows a two-step behavior. At the first step where the temperature increases slowly from 27.5 to 33 C, an important part of solar energy was stored in the form of latent heat. This is the way that the composite PCM integrated walls remove heat from the chamber in the daytime. After that, the indoor temperature keeps rising faster due to the increment of solar incomes and the heating
Fig. 5. Compression strength of the concrete bricks varied with the total PEG mass fraction.
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peak is shifted to a later time in comparison to that in the non-PCM chamber. During the cooling process, the discrepancy in the temperature decreasing rate in the two chambers can be observed after the temperature decreases to 30 C. This is because the existence of PCM in the chamber allows the heat release through phase transition to maintain the indoor temperature around the solidifying point, which can explain why the lowest indoor temperature at night is higher than that of non-PCM chamber instead of joining the outside temperature.
4. Conclusions A form-stable PEG/SiO2 composite PCM were prepared and successfully incorporated into concrete and an experimental study was carried out to evaluate the thermal performance of PCM concrete in passive solar chamber. Based on the presented experimental researches, the following major conclusions can be sketched out: 1. The new PEG/SiO2 composite PCM has melting temperature and latent heat of 28 C and 113.6 kJ kg1 respectively. This appropriate phase change point and relatively high latent enthalpy make it potential to applying in passive solar buildings. 2. The properties of PCM concrete bricks were significantly influenced by the quantity of the PEG/SiO2 composite PCM. When the addition of composite PCM is ranging from 0 to 18%, the apparent density, compression strength and thermal conductivity drop from 2.20 to 1.87 g cm3, 23.6 to 0.69 MPa and 0.94 to 0.59 W m1 K1, correspondingly. Combining the percentage variation of the mechanical and thermal properties, the optimum total PEG mass fraction and its corresponding compression strength were 7.5% and 4.392 MPa. The main reason was that the largest storage capability of PCM concrete could be obtained in the conditions of satisfying the lowest compression strength from China’s national standard of GB/T 24492-2009. 3. Thermal performance of passive solar chamber could be markedly improved by using the PCM concrete. Compared with the reference case, the chamber with PCMs represented a gentle fluctuation of temperature, reducing the maximum temperatures by 2.8e4.6 C and improving the minimum temperatures by 1.4e1.8 C. Since the models with relatively small size were tested in this work, a further research with real case was
Fig. 6. Temperature profiles of the test chambers (with and without PCM).
Fig. 7. Temperature variation versus time for one measurement period.
therefore suggested to evaluate the performance of PCM concrete for indoor thermal management. Acknowledgments This work was financially supported by Guangdong-Hongkong Joint Innovation Project (2016A05050302) and China Fundamental Research Funds for the Central Universities (16lgpy20). References [1] DOE, Buildings Energy Data Book, Office of Energy Efficiency and Renewable Energy (US Department of Energy), 2011. [2] N. Zhu, Z. Ma, S. Wang, Dynamic characteristics and energy performance of buildings using phase change materials: a review, Energy Convers. Manag. 50 (12) (2009) 3169e3181. [3] K. Lin, Y. Zhang, X. Xu, H. Di, R. Yang, P. Qin, Modeling and simulation of under-floor electric heating system with shape-stabilized PCM plates, Build. Environ. 39 (12) (2004) 1427e1434. [4] X. Shi, S.A. Memon, W. Tang, H. Cui, F. Xing, Experimental assessment of position of macro encapsulated phase change material in concrete walls on indoor temperatures and humidity levels, Energy Build. 71 (2014) 80e87. [5] S. Antvorskov, Introduction to integration of renewable energy in demand controlled hybrid ventilation systems for residential buildings, Build. Environ. 43 (8) (2008) 1350e1353. [6] R. Parameshwaran, S. Kalaiselvam, S. Harikrishnan, A. Elayaperumal, Sustainable thermal energy storage technologies for buildings: a review, Renew. Sustain. Energy Rev. 16 (5) (2012) 2394e2433. [7] Y. Zhang, G. Zhou, K. Lin, Q. Zhang, H. Di, Application of latent heat thermal energy storage in buildings: state-of-the-art and outlook, Build. Environ. 42 (6) (2007) 2197e2209. [8] L. Shilei, F. Guohui, Z. Neng, D. Li, Experimental study and evaluation of latent heat storage in phase change materials wallboards, Energy Build. 39 (10) (2007) 1088e1091. [9] A. Bontemps, M. Ahmad, K. Johannes, H. Sallee, Experimental and modelling study of twin cells with latent heat storage walls, Energy Build. 43 (9) (2011) 2456e2461. [10] N. Soares, J.J. Costa, A.R. Gaspar, P. Santos, Review of passive PCM latent heat thermal energy storage systems towards buildings’ energy efficiency, Energy Build. 59 (2013) 82e103. [11] V.V. Tyagi, D. Buddhi, PCM thermal storage in buildings: a state of art, Renew. Sustain. Energy Rev. 11 (6) (2007) 1146e1166. [12] F. Kuznik, J. Virgone, Experimental assessment of a phase change material for wall building use, Appl. Energy 86 (10) (2009) 2038e2046. [13] L. Shilei, Z. Neng, F. Guohui, Impact of phase change wall room on indoor thermal environment in winter, Energy Build. 38 (1) (2006) 18e24. [14] V.V. Tyagi, D. Buddhi, Thermal cycle testing of calcium chloride hexahydrate as a possible PCM for latent heat storage, Sol. Energy Mater. Sol. Cells 92 (8) (2008) 891e899. [15] A. Pasupathy, R. Velraj, Effect of double layer phase change material in building roof for year round thermal management, Energy Build. 40 (3) (2008) 193e203. [16] A.C. Evers, M.A. Medina, Y. Fang, Evaluation of the thermal performance of
T. Xu et al. / Building and Environment 104 (2016) 172e177
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
[26]
frame walls enhanced with paraffin and hydrated salt phase change materials using a dynamic wall simulator, Build. Environ. 45 (8) (2010) 1762e1768. W. Wang, X. Yang, Y. Fang, J. Ding, Preparation and performance of formstable polyethylene glycol/silicon dioxide composites as solideliquid phase change materials, Appl. Energy 86 (2) (2009) 170e174. J. Li, L. He, T. Liu, X. Cao, H. Zhu, Preparation and characterization of PEG/SiO2 composites as shape-stabilized phase change materials for thermal energy storage, Sol. Energy Mater. Sol. Cells 118 (2013) 48e53. M.A. Medina, J.B. King, M. Zhang, On the heat transfer rate reduction of structural insulated panels (SIPs) outfitted with phase change materials (PCMs), Energy 33 (4) (2008) 667e678. e, D. Que nard, Experimental study and nuM. Ahmad, A. Bontemps, H. Salle merical simulation of thermal behaviour of test-cells using light wallboards coupling PCM and VIP, ChemSusChem 5 (10) (2012) 2032e2038. M. Ahmad, A. Bontemps, H. Sallee, D. Quenard, Thermal testing and numerical simulation of a prototype cell using light wallboards coupling vacuum isolation panels and phase change material, Energy Build. 38 (6) (2006) 673e681. A.K. Athienitis, C. Liu, D. Hawes, D. Banu, D. Feldman, Investigation of the thermal performance of a passive solar test-room with wall latent heat storage, Build. Environ. 32 (5) (1997) 405e410. S.D. Zwanzig, Y. Lian, E.G. Brehob, Numerical simulation of phase change material composite wallboard in a multi-layered building envelope, Energy Convers. Manag. 69 (2013) 27e40. R. Ghedamsi, N. Settou, N. Saifi, B. Dokkar, Contribution on buildings design with low consumption of energy incorporated PCMs, Energy Proced. 50 (2014) 322e332. I. Mandilaras, M. Stamatiadou, D. Katsourinis, G. Zannis, M. Founti, Experimental thermal characterization of a mediterranean residential building with PCM gypsum board walls, Build. Environ. 61 (2013) 93e103. T. Silva, R. Vicente, N. Soares, V. Ferreira, Experimental testing and numerical modelling of masonry wall solution with PCM incorporation: a passive
177
construction solution, Energy Build. 49 (0) (2012) 235e245. [27] Y.A. Kara, A. Kurnuç, Performance of coupled novel triple glass unit and PCM wall, Appl. Therm. Eng. 35 (2012) 243e246. [28] S.M. Silva, M.G.d. Almeida, L. Bragança, Evaluation of the Thermal Performance of Hollow Brick Walls with Gypsum-PCM Plasters, 2011, pp. 1e12. [29] D. Zhang, Z. Li, J. Zhou, K. Wu, Development of thermal energy storage concrete, Cem. Concr. Res. 34 (6) (2004) 927e934. [30] M. Hunger, A.G. Entrop, I. Mandilaras, H.J.H. Brouwers, M. Founti, The behavior of self-compacting concrete containing micro-encapsulated phase change materials, Cem. Concr. Compos. 31 (10) (2009) 731e743. [31] S.-G. Jeong, J. Jeon, J. Cha, J. Kim, S. Kim, Preparation and evaluation of thermal enhanced silica fume by incorporating organic PCM, for application to concrete, Energy Build. 62 (2013) 190e195. [32] S.A. Memon, H. Cui, T.Y. Lo, Q. Li, Development of structuralefunctional integrated concrete with macro-encapsulated PCM for thermal energy storage, Appl. Energy 150 (2015) 245e257. [33] L. Navarro, A. de Gracia, A. Castell, S. Alvarez, L.F. Cabeza, PCM incorporation in a concrete core slab as a thermal storage and supply system: proof of concept, Energy Build. 103 (2015) 70e82. [34] A.G. Entrop, H.J.H. Brouwers, A.H.M.E. Reinders, Experimental research on the use of micro-encapsulated phase change materials to store solar energy in concrete floors and to save energy in dutch houses, Sol. Energy 85 (5) (2011) 1007e1020. [35] R. Baetens, B.P. Jelle, A. Gustavsen, Phase change materials for building applications: a state-of-the-art review, Energy Build. 42 (9) (2010) 1361e1368. [36] S. Bourne, A. Novoselac, Improved performance in tube-encapsulated phase change thermal energy stores for HVAC applications, Build. Environ. 98 (2016) 133e144. [37] B. Nghana, F. Tariku, Phase change material’s (PCM) impacts on the energy performance and thermal comfort of buildings in a mild climate, Build. Environ. 99 (2016) 221e238.
Contents lists available at ScienceDirect
Building and Environment journal homepage: www.elsevier.com/locate/buildenv
Investigation on the properties of a new type of concrete blocks incorporated with PEG/SiO2 composite phase change material Tao Xu a, c, Qinglin Chen a, Zhengguo Zhang b, Xuenong Gao b, *, Gongsheng Huang c, * a Guangdong Engineering Technology Research Center for Petrochemical Energy Conservation, School of Chemical Engineering and Technology, Sun Yat-sen University, Guangzhou 510275, China b Key Laboratory of Enhanced Heat Transfer and Energy Conservation (Ministry of Education), School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China c Department of Architecture and Civil Engineering, City University of Hong Kong, Kowloon, Hong Kong
a r t i c l e i n f o
a b s t r a c t
Article history: Received 9 March 2016 Received in revised form 30 April 2016 Accepted 3 May 2016 Available online 6 May 2016
This paper investigates a new type of concrete blocks which integrates a form-stable PEG/SiO2 composite PCM with the melting temperature of 28 C and the latent heat of 113.6 kJ kg1. A comprehensive analysis on the characteristics of sample concrete bricks shows that the properties of PCM concrete bricks are significantly influenced by the quantity of the PEG/SiO2 composite PCM. When the addition of composite is ranging from 0 to 18%, the apparent density, compression strength and thermal conductivity drop from 2.20 to 1.87 g cm3, 23.6 to 0.69 MPa and 0.94 to 0.59 W m1 K1, correspondingly. The optimum amount of PCM in the concrete blocks was determined as 7.5%. The thermal performance of the PEG/SiO2 composite PCM concrete was also evaluated by comparing the temperature variation of a test chamber with PCM concrete and a test chamber without PCM concrete significantly. The results show that the PCM concrete can narrow the indoor temperature swing, which may help to improve the indoor thermal comfort in passive solar chambers. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Novel concrete Phase change material (PCM) Polyethylene glycol (PEG) Thermal performance
1. Introduction With the rapid development of economy and improvement of living standards, the demand of energy is growing fast. According to a report from the U.S. department of energy (DOE) in 2010, the buildings sector accounts for more than 40% of global primary energy consumption [1,2]. This situation, together with the shortage of conventional fossil energy and environmental concerns, has motived the development of sustainable buildings, such as buildings equipped with renewable energy systems [3e5]. During the past few decades, passive solar building, which is one of those expected constructions, has attracted much attention. With the assistance of latent thermal energy storage (LTES) systems by incorporating phase change materials (PCMs) into walls, ceilings, windows or floors, passive buildings can store available heat and coolness in off-peak load conditions to match on-peak demand periods [6e8]. Such benefit offered by the technology of LTES leads
* Corresponding authors. E-mail addresses: [email protected] (X. Gao), [email protected]. hk (G. Huang). http://dx.doi.org/10.1016/j.buildenv.2016.05.003 0360-1323/© 2016 Elsevier Ltd. All rights reserved.
to more efficient energy use and enhances indoor thermal comfort without any expenditure of conventional energy [9]. PCMs, as the core component of the LTES system, are a type of substance that can store or release large amount of latent heat when undergoing a phase transition. To provide a high performance of a passive LTES device in the living space, an appropriate type of PCMs for indoor thermal management is necessary. For building applications, the PCMs should have suitable phase change temperature (18e30 C) to maintain thermal comfort, high enthalpy to make sure a large energy storage capacity and good chemical and thermal stability for long-term use [10,11]. Cost effective and low environmental impact should be favored considering the residential needs. After years of research and development, materials including paraffin waxes [12], fatty acids [13], polyethylene glycol [14] and salt hydrates [15,16] are found to be available in the construction field. Some form-stable composites formed by embedding PCMs into matrix materials in order to solve the leakage problems are considered as potential candidates as well. The polyethylene glycol/silicon dioxide (PEG/SiO2) composite PCM is a good example. Since it is developed in 2009 [17,18], the modifications of its preparation methods [17,18] and thermalphysical properties to accommodate the LTES systems in building
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envelops have attracted the interest from many researchers. However, until now there are very few applications that can be found in current literature although the PEG/SO2 composite PCM has the potential benefits for solar passive buildings. Except the type of PCMs, another important factor that determines the building energy performance is the placement of the LTES systems. As summarized by Soares et al. [10], there are three main methods commonly used to design the LTES components. The first is to encapsulate PCM into wall boards. Aiming at improving the efficiency, different configurations such as PCM wall boards coupling with vacuum isolation panels [19e21] and placement of a PCM composite wall plate within a multiple-layered building envelope [22e25] were proposed recently. The second is to use PCM brick. A hollow thermal-insulation brick, including clay bricks [26], glass bricks [9,27], and gypsum bricks [28] which have holes inside, is suitable to contain PCMs for indoor temperature control. The third is to produce PCM concrete. Many studies, such as Zhang et al. [29], Hunger et al. [30], Jeong et al. [31], Memon et al. [32], Navarro et al. [33] and Ling et al. [34], have investigated the compatibility issue between PCMs and concrete mixture in order to minimize the effects of PCMs on macro thermo-mechanical performance after they are added into concrete mixture. As reported by Baetens et al. [35], the combination of PCMs with concrete mixture can obtain overall heat capacity of 10 times higher than gypsum wall boards. Besides, concrete is the most widely used construction material and can be formed into any shape and size. Therefore it is very valuable to study the properties of PCM concrete. It is noted that although LTES systems in building envelops has been developed [36,37], very few studies focuses on PEG/SiO2 composite PCM concrete block and its potential applications for buildings. Hence, this study proposes a new type of PCM concrete product, i.e. PEG/SiO2 composite PCM concrete block, and investigates its properties and potentials for building applications. The properties of the new concrete will be studied by measuring the apparent density, thermal conductivity and compression strength. To evaluate the performance of the concrete for passive indoor temperature control, passive solar test chambers with the PCM concrete walls will be built and the indoor temperatures will be tested. The ultimate objective of this study is to demonstrate the feasibility of using PEG/SiO2 composite PCM in concrete blocks to increase their thermal inertia and to reduce the energy demand of the building. 2. Experimental setup 2.1. Material preparation The form-stable PEG/SiO2 composite PCM can be prepared by the temperature-assisted sol-gel method. First, the silica sol solution and the PEG solution are made by dissolving silica sol and PEG in water with continuous stirring for 12 h respectively. Then the prepared solutions are mixed at room temperature at the mass fraction of 80%. After that, this mixed solution is heated for 100 min by water bath with quick continuous stirring at 70 C. In this process, PEG will be absorbed into the network of porous silica gel through the reaction of gelatinization. Finally, the form-stable PEG/ SiO2 composite PCM is obtained after a drying procedure in a cabinet at 60 C for 36 h. In order to guarantee the performance stability of composite PCM, some dried sample powder was taken out to carry on leakage test. Firstly, it was put above test paper, and then it was put into the constant temperature chamber with 110 C for 4 h to ensure that no liquid PEG could leak on the test paper. The prepared composite PCM is further incorporated into the conventional concrete to produce a new modified concrete. The detail procedure of the preparation is as follows: to begin with, Slag
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Portland cement (#325), coarse aggregate, fine aggregate sand and water with corresponding mass ratio of 1.00:1.41:1.04:0.48 are mixed for 15 min in order to homogenize the blended components. After that, different amounts of the composites PCM are added into the concrete mixture. Another 10 min are needed to assure the full dispersion of the PCM. Then the desirable PCM concrete will be obtained by drying the mixture mortar to constant weight. In order to investigate the physical properties of the concrete integrated with this composite PCM, a series of concrete blocks with total PEG mass fraction of 0e18% should be fabricated. In this study, Reagent grade polyethylene glycol with an average molecular weight of 1000 was purchased from Guangdong Guanghua Sci-tech Co., Ltd. China. Silica sol was supplied by the Guangzhou Chemical Agent Company (Guangzhou, PR China). Both of them were used as raw materials. 2.2. Property characterization The thermal properties of the PEG/SiO2 composite PCM including the melting point and latent heat of fusion can be measured using a differential scanning calorimeter (Q20, TA Instrument Inc., USA). The samples of the measurements were randomly selected from the different locations of the composite. When tested in DSC, the mass of the sample was in the range of 5e10 mg and sealed in an aluminum pan. The heating and cooling rates were kept constant at 10 C min1, and the temperature was ramped in the range of 20e80 C under the protection of nitrogen. The apparent densities of the PCM concrete can be obtained by
ro ¼
mo Vo
(1)
where ro denotes the apparent density; Vo is the volume of each brick, which was made by pouring the new concrete mixture into a mold with dimensions of 5 cm 5 cm 5 cm; and mo is the mass of each brick, measured after these samples were dried at room temperature for a few hours. The thermal conductivity of the new type of concrete with different content of PEG/SiO2 composite PCM was measured using a hot disk thermal constant analyzer (TPS2500, Hot Disk Inc., Sweden). A probe consisting of a thin nickel foil embedded between two thin layers of Kapton insulated films was employed as both the heating source and the temperature sensor. During the measurement, two concrete blocks with the same content of the composite PCM were placed in contact with the probe. The heating power and scanning time for the tests were set as 0.05 W and 20 s, respectively. The compression strength test of the PCM concrete was carried out with the assistance of a compression testing machine. During this process, the concrete blocks impregnated with different content of the composite PCM were placed in the machine and load was applied without shock and increased continuously at the rate of 0.3 MPa/s until the samples was broken down. 2.3. Thermal performance evaluation The thermal performance of the PEG/SiO2 composite PCM concrete for indoor thermal management in passive solar buildings was investigated using a test chamber, the walls of which were made of the composite PCM concrete. For comparison, another identical chamber with conventional concrete walls was built as well. Fig. 1 shows the schematic diagram of the test chamber, which has the dimensions of 60 cm 60 cm 60 cm. The chamber has a glazing window, three side walls, one floor and one roof. In order to collect the maximum solar radiation throughout the year, the glazing window is 30 south by west oriented. Each of the three
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side walls is constituted by a polyvinyl chloride (PVC) panel of 3 mm thickness, an expanded polystyrene (EPS) panel of 8 mm thickness and a 20 mm thick concrete wall panel with or without PCM. For the roof and floor, the same PVC and EPS panels were used, but no concrete wall panels were placed. During the testing process, the indoor temperature was monitored by one J-type thermal couple. A data logger (34970A, Agilent Inc., USA) was applied to collect the signals generated by the thermal couple and convert them to digital data. The environmental temperature outside the chamber also was recorded. 3. Results and discussion 3.1. Thermal characteristics of the PEG/SiO2 composite PCM The DSC curve of the PEG-1000/SiO2 composite PCM is given in Fig. 2 where the composite PCM contains 80% (mass fraction) of PEG. A single peak during the heating or cooling process was observed, which indicates that the PEG was the only substance that attributes to the latent heat of the fusion of the composite material. The details of the onset of the phase change temperature (Tonset), the peak temperature of the phase change (Tpeak) and the latent heat (DH) can be derived from the DSC curve in Fig. 2, which were determined as 28 C, 36.8 C and 113.6 kJ kg1 respectively; while, in the freezing process, they are 26.6 C, 21.5 C and 115.4 kJ kg1, correspondingly.
apparent density varies smoothly. Since the concrete is a porous media, a part of the composite PCM might be used to occupy the void space within the bricks instead of replacing the concrete volume, which would further cause a slight apparent density drop. This speculation could also explain the rapid decrease of the apparent density at the third stage where the pores in concrete bricks might be completely saturated with PCM.
3.2.2. Thermal conductivity Thermal conductivity of building materials is one of the critical parameters that directly influence the energy performance of buildings. In this work, the thermal conductivity of the concrete with PEG mass fraction ranging from 0 to 18% was measured using a hot-disk thermal constant analyzer. The results were depicted in Fig. 4. With the increase of the quantity of the PEG/SiO2 composite PCM, the thermal conductivity of the concrete bricks exhibits a decreasing trend. For example, the thermal conductivity of the concrete bricks with 1.5% total PEG mass fraction is 0.84 W m1 K1, whereas that it becomes 0.64 W m1 K1 when the total PEG mass
3.2. Properties of the PCM concrete 3.2.1. Apparent density The apparent density of the concrete embedded with the PEG/ SiO2 composite PCM was investigated using concrete blocks with fixed sizes but different PEG mass fraction. Fig. 3 shows the variation of the apparent density of the samples as a function of the total PEG mass fraction. It can be seen that the apparent density of the concrete shows a three-stage decreasing behavior as the PEG content increases. At the first stage, a sharp decline occurs from 0 to 1.5% total PEG mass fraction. This could be due to the presence of the composite PCM, the density of which is much lower than that of the concrete. However, when it comes to the range 1.5e7.5%, the
Fig. 2. DSC thermogram of PEG-1000/SiO2 composite PCM with PEG-1000 mass fraction of 80%.
Fig. 1. Schematic diagram of the test chamber: (a) configuration of the chamber, (b) constitution of the side walls.
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fraction is 7.5%. The relative decrease is 24.2%. According to Li’s work [18], the thermal conductivity of the PEG/SiO2 composite PCM (mass fraction of PEG is 80%) was found to be 0.28 W m1 K1, which is almost 2.5 times lower that of the concrete without PCM. After adding the composite, the thermal conductivity of the concrete is degraded consequently. Fig. 4 shows the variation of the thermal conductivity with respect to the total PEG mass fraction, which indicates that the apparent density of concrete bricks is one of the main effective factors to their thermal conductivity. 3.2.3. Compression strength The compression strength was also tested and the results are presented in Fig. 5. A negative influence of the quantity of the PEG/ SiO2 composite PCM on the compression strength of the concrete can be found. For the concrete without PCM, the compression strength was 23.61 MPa. This value dropped rapidly to 7.5 MPa when the mass ratio of the composite PCM was changed from 0 to 4.5%. The rate of the decline was as much as 68.2%. However, with the further augment of the mass fraction, the compression strength decreased slowly. This downward trend is thought to have been caused by the composite PCM with lower density and compression strength added to concrete. When the mass ratios of the composite PCM are 7.5% and 9%, the global compression strength of the concrete are 4.392 MPa and 3.828 MPa. According to China’s national standard of GB/T 24492-2009 “Nonload Bearing Concrete Hollow Brick”, the lowest compression strength is no less than 4.0 MPa. Thus, the optimum total PEG mass fraction in the concrete walls was determined as 7.5%. 3.3. Thermal performance of the PCM concrete in a passive solar chamber To evaluate the thermal performance of the concrete walls that are impregnated with PEG/SiO2 composite PCM on indoor temperature control, the test chamber shown in Fig. 1, was compared with a chamber without PCM concrete. The heat source was Sun. In the chamber with PCM concrete, the total PEG mass fraction of 7.5% was adopted in these tests considering the requirements of mechanical strength, thermal insulation and heat storage capacity for construction applications. The simultaneous acquisitions of measurements on these two chambers began on 29 September 2012 and lasted for 4 days in Guangzhou, China. Fig. 6 shows the variations of the outdoor and indoor
Fig. 3. Apparent density of the concrete bricks varied with the total PEG mass fraction.
Fig. 4. Thermal conductivity of the concrete bricks varied with the total PEG mass fraction.
temperatures of the two test chambers (with and without the composite PCM). It can be seen that in the daytime, the indoor temperature of the chamber equipped with the PCM concrete walls had a narrow temperature variation than that of the non-PCM chamber. Comparing the peak values in each day, the temperature attenuations of the four days were 4.1, 4.0, 2.7 and 4.6 C, respectively. Conversely, in the case of the night, the minimum indoor temperatures of the chamber with PCM are 1.7, 1.8, 1.1 and 1.5 C higher than that of the non-PCM chamber. These phenomena indicate that the concrete walls embedded with the PEG/SiO2 composite PCM did fulfill their function of narrowing the indoor temperature swing. Fig. 7 presents one measurement period (24 h) extracted from the above data in order to further illustrate the indoor temperature changes. During the heating process, the test point in the chamber with PCM shows a two-step behavior. At the first step where the temperature increases slowly from 27.5 to 33 C, an important part of solar energy was stored in the form of latent heat. This is the way that the composite PCM integrated walls remove heat from the chamber in the daytime. After that, the indoor temperature keeps rising faster due to the increment of solar incomes and the heating
Fig. 5. Compression strength of the concrete bricks varied with the total PEG mass fraction.
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peak is shifted to a later time in comparison to that in the non-PCM chamber. During the cooling process, the discrepancy in the temperature decreasing rate in the two chambers can be observed after the temperature decreases to 30 C. This is because the existence of PCM in the chamber allows the heat release through phase transition to maintain the indoor temperature around the solidifying point, which can explain why the lowest indoor temperature at night is higher than that of non-PCM chamber instead of joining the outside temperature.
4. Conclusions A form-stable PEG/SiO2 composite PCM were prepared and successfully incorporated into concrete and an experimental study was carried out to evaluate the thermal performance of PCM concrete in passive solar chamber. Based on the presented experimental researches, the following major conclusions can be sketched out: 1. The new PEG/SiO2 composite PCM has melting temperature and latent heat of 28 C and 113.6 kJ kg1 respectively. This appropriate phase change point and relatively high latent enthalpy make it potential to applying in passive solar buildings. 2. The properties of PCM concrete bricks were significantly influenced by the quantity of the PEG/SiO2 composite PCM. When the addition of composite PCM is ranging from 0 to 18%, the apparent density, compression strength and thermal conductivity drop from 2.20 to 1.87 g cm3, 23.6 to 0.69 MPa and 0.94 to 0.59 W m1 K1, correspondingly. Combining the percentage variation of the mechanical and thermal properties, the optimum total PEG mass fraction and its corresponding compression strength were 7.5% and 4.392 MPa. The main reason was that the largest storage capability of PCM concrete could be obtained in the conditions of satisfying the lowest compression strength from China’s national standard of GB/T 24492-2009. 3. Thermal performance of passive solar chamber could be markedly improved by using the PCM concrete. Compared with the reference case, the chamber with PCMs represented a gentle fluctuation of temperature, reducing the maximum temperatures by 2.8e4.6 C and improving the minimum temperatures by 1.4e1.8 C. Since the models with relatively small size were tested in this work, a further research with real case was
Fig. 6. Temperature profiles of the test chambers (with and without PCM).
Fig. 7. Temperature variation versus time for one measurement period.
therefore suggested to evaluate the performance of PCM concrete for indoor thermal management. Acknowledgments This work was financially supported by Guangdong-Hongkong Joint Innovation Project (2016A05050302) and China Fundamental Research Funds for the Central Universities (16lgpy20). References [1] DOE, Buildings Energy Data Book, Office of Energy Efficiency and Renewable Energy (US Department of Energy), 2011. [2] N. Zhu, Z. Ma, S. Wang, Dynamic characteristics and energy performance of buildings using phase change materials: a review, Energy Convers. Manag. 50 (12) (2009) 3169e3181. [3] K. Lin, Y. Zhang, X. Xu, H. Di, R. Yang, P. Qin, Modeling and simulation of under-floor electric heating system with shape-stabilized PCM plates, Build. Environ. 39 (12) (2004) 1427e1434. [4] X. Shi, S.A. Memon, W. Tang, H. Cui, F. Xing, Experimental assessment of position of macro encapsulated phase change material in concrete walls on indoor temperatures and humidity levels, Energy Build. 71 (2014) 80e87. [5] S. Antvorskov, Introduction to integration of renewable energy in demand controlled hybrid ventilation systems for residential buildings, Build. Environ. 43 (8) (2008) 1350e1353. [6] R. Parameshwaran, S. Kalaiselvam, S. Harikrishnan, A. Elayaperumal, Sustainable thermal energy storage technologies for buildings: a review, Renew. Sustain. Energy Rev. 16 (5) (2012) 2394e2433. [7] Y. Zhang, G. Zhou, K. Lin, Q. Zhang, H. Di, Application of latent heat thermal energy storage in buildings: state-of-the-art and outlook, Build. Environ. 42 (6) (2007) 2197e2209. [8] L. Shilei, F. Guohui, Z. Neng, D. Li, Experimental study and evaluation of latent heat storage in phase change materials wallboards, Energy Build. 39 (10) (2007) 1088e1091. [9] A. Bontemps, M. Ahmad, K. Johannes, H. Sallee, Experimental and modelling study of twin cells with latent heat storage walls, Energy Build. 43 (9) (2011) 2456e2461. [10] N. Soares, J.J. Costa, A.R. Gaspar, P. Santos, Review of passive PCM latent heat thermal energy storage systems towards buildings’ energy efficiency, Energy Build. 59 (2013) 82e103. [11] V.V. Tyagi, D. Buddhi, PCM thermal storage in buildings: a state of art, Renew. Sustain. Energy Rev. 11 (6) (2007) 1146e1166. [12] F. Kuznik, J. Virgone, Experimental assessment of a phase change material for wall building use, Appl. Energy 86 (10) (2009) 2038e2046. [13] L. Shilei, Z. Neng, F. Guohui, Impact of phase change wall room on indoor thermal environment in winter, Energy Build. 38 (1) (2006) 18e24. [14] V.V. Tyagi, D. Buddhi, Thermal cycle testing of calcium chloride hexahydrate as a possible PCM for latent heat storage, Sol. Energy Mater. Sol. Cells 92 (8) (2008) 891e899. [15] A. Pasupathy, R. Velraj, Effect of double layer phase change material in building roof for year round thermal management, Energy Build. 40 (3) (2008) 193e203. [16] A.C. Evers, M.A. Medina, Y. Fang, Evaluation of the thermal performance of
T. Xu et al. / Building and Environment 104 (2016) 172e177
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
[26]
frame walls enhanced with paraffin and hydrated salt phase change materials using a dynamic wall simulator, Build. Environ. 45 (8) (2010) 1762e1768. W. Wang, X. Yang, Y. Fang, J. Ding, Preparation and performance of formstable polyethylene glycol/silicon dioxide composites as solideliquid phase change materials, Appl. Energy 86 (2) (2009) 170e174. J. Li, L. He, T. Liu, X. Cao, H. Zhu, Preparation and characterization of PEG/SiO2 composites as shape-stabilized phase change materials for thermal energy storage, Sol. Energy Mater. Sol. Cells 118 (2013) 48e53. M.A. Medina, J.B. King, M. Zhang, On the heat transfer rate reduction of structural insulated panels (SIPs) outfitted with phase change materials (PCMs), Energy 33 (4) (2008) 667e678. e, D. Que nard, Experimental study and nuM. Ahmad, A. Bontemps, H. Salle merical simulation of thermal behaviour of test-cells using light wallboards coupling PCM and VIP, ChemSusChem 5 (10) (2012) 2032e2038. M. Ahmad, A. Bontemps, H. Sallee, D. Quenard, Thermal testing and numerical simulation of a prototype cell using light wallboards coupling vacuum isolation panels and phase change material, Energy Build. 38 (6) (2006) 673e681. A.K. Athienitis, C. Liu, D. Hawes, D. Banu, D. Feldman, Investigation of the thermal performance of a passive solar test-room with wall latent heat storage, Build. Environ. 32 (5) (1997) 405e410. S.D. Zwanzig, Y. Lian, E.G. Brehob, Numerical simulation of phase change material composite wallboard in a multi-layered building envelope, Energy Convers. Manag. 69 (2013) 27e40. R. Ghedamsi, N. Settou, N. Saifi, B. Dokkar, Contribution on buildings design with low consumption of energy incorporated PCMs, Energy Proced. 50 (2014) 322e332. I. Mandilaras, M. Stamatiadou, D. Katsourinis, G. Zannis, M. Founti, Experimental thermal characterization of a mediterranean residential building with PCM gypsum board walls, Build. Environ. 61 (2013) 93e103. T. Silva, R. Vicente, N. Soares, V. Ferreira, Experimental testing and numerical modelling of masonry wall solution with PCM incorporation: a passive
177
construction solution, Energy Build. 49 (0) (2012) 235e245. [27] Y.A. Kara, A. Kurnuç, Performance of coupled novel triple glass unit and PCM wall, Appl. Therm. Eng. 35 (2012) 243e246. [28] S.M. Silva, M.G.d. Almeida, L. Bragança, Evaluation of the Thermal Performance of Hollow Brick Walls with Gypsum-PCM Plasters, 2011, pp. 1e12. [29] D. Zhang, Z. Li, J. Zhou, K. Wu, Development of thermal energy storage concrete, Cem. Concr. Res. 34 (6) (2004) 927e934. [30] M. Hunger, A.G. Entrop, I. Mandilaras, H.J.H. Brouwers, M. Founti, The behavior of self-compacting concrete containing micro-encapsulated phase change materials, Cem. Concr. Compos. 31 (10) (2009) 731e743. [31] S.-G. Jeong, J. Jeon, J. Cha, J. Kim, S. Kim, Preparation and evaluation of thermal enhanced silica fume by incorporating organic PCM, for application to concrete, Energy Build. 62 (2013) 190e195. [32] S.A. Memon, H. Cui, T.Y. Lo, Q. Li, Development of structuralefunctional integrated concrete with macro-encapsulated PCM for thermal energy storage, Appl. Energy 150 (2015) 245e257. [33] L. Navarro, A. de Gracia, A. Castell, S. Alvarez, L.F. Cabeza, PCM incorporation in a concrete core slab as a thermal storage and supply system: proof of concept, Energy Build. 103 (2015) 70e82. [34] A.G. Entrop, H.J.H. Brouwers, A.H.M.E. Reinders, Experimental research on the use of micro-encapsulated phase change materials to store solar energy in concrete floors and to save energy in dutch houses, Sol. Energy 85 (5) (2011) 1007e1020. [35] R. Baetens, B.P. Jelle, A. Gustavsen, Phase change materials for building applications: a state-of-the-art review, Energy Build. 42 (9) (2010) 1361e1368. [36] S. Bourne, A. Novoselac, Improved performance in tube-encapsulated phase change thermal energy stores for HVAC applications, Build. Environ. 98 (2016) 133e144. [37] B. Nghana, F. Tariku, Phase change material’s (PCM) impacts on the energy performance and thermal comfort of buildings in a mild climate, Build. Environ. 99 (2016) 221e238.