The Capabilites and Barriers of Incorporating Phase Change Material into Residential Building Design

www.seipub.org/ijepr International Journal of Engineering Practical Research (IJEPR) Volume 2 Issue 4, November 2013

The Capabilites and Barriers of Incorporating Phase Change Material into Residential Building Design in Sydney, Australia Rochelle Foran*1, Min Wu2 *1

rochelleforan@uon.edu.au; 2manfred.wu@newcastle.edu.au

Abstract

liquid when the temperature increases from liquid to solid and when the temperature decreases. These organic, inorganic or eutectic compounds impregnated into construction elements, predominately wallboard and concrete to create LHTES systems, display promising results for their widespread adoption and subsequent assimilation into common building practice throughout the built environment.

The building sector’s presence occupiesa large proportion of energy consumption, which is primarily attributed to the control of a comfortable interior thermal environment through the use of heating, ventilating and air‐conditioning (HVAC) systems. These systems, predominantly aim to control and maintain an optimal thermal temperature, however, a promising, alternative solution is latent heat thermal energy storage (LHTES) systems that use phase change materials (PCMs) to form a superior construction material that can produce thermally enhanced conditions, through mitigating temperature swings, whilst remaining appropriate for lightweight residential applications.

The advantages of utilising PCMs include their high energy storage density and relatively low temperature swings. The practical application of PCMs in residential buildings requires their integration within latent heat thermal energy storage (LHTES) systems to form a superior construction material (wallboard or concrete) that can produce thermally enhanced conditions, through mitigating temperature swings, whilst remaining appropriate for lightweight residential applications. Utilising PCMs in residential building design in Sydney, Australia, requires a thorough review on PCMs distinct physical and chemical properties as well as the subsequent effectiveness when incorporated into an LHTES system.

Keywords Phase Change Materials; Latent Heat Thermal Energy Storage Systems; Building Applications

Introduction A prominent concern currently affecting the modern built environment is the requirement for sustainable structures that execute holistic, energy efficient processes through intuitive design. There is a delicate equilibrium between energy supply and demand which requires constant maintenance and conservation to ensure that it does not reach precarious proportions.

The forefront of the rising energy consumption within residential buildings is the demand for an optimal thermal climate resulting in the exploitation of high energy consuming, Heating, Ventilating and Air Conditioning (HVAC) systems. This unfavourable approach presents negative ramifications for the longevity of sustainable structures thus proactive measures are required to mitigate the energy consumption of residential buildings.

The encapsulation methods of microencapsulation as well as shape‐stabilised systems have been developed to surpass their previous counterparts through economic and thermophysical advantages. These evolving processes that integrate PCMs into LHTES systems exude the potential to achieve substantial outcomes if they are holistically examined through the parameters of locational barriers that restrain the suitability of application due to seasonal temperatures.

To improve the thermal efficiency of residential buildings in Sydney, a holistic analysis must pertain to the climatic and economic parameters rigorously associated with each incorporation method’s technical components.

Pioneering the effort to revolutionise the energy efficiency of the built environment is Phase Change Materials (PCMs) that possess the ability to store and release significant amounts of latent heat during their phase change which, as Kuznik and Virgone (2009) outlined, involves a phase change from a solid to

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Phase Change Materials The principle of PCMs constitutes a phase change

International Journal of Engineering Practical Research (IJEPR) Volume 2 Issue 4, November 2013 www.seipub.org/ijepr

kinetic, chemical and economic qualities. The selection of the specific type of PCM to be incorporated into the LHTES system can affect the efficiency of the PCM’s ability to maintain a comfortable interior climate through mitigating temperature swings. The analysis of several commercial grade fatty acids utilised as a solid‐liquid PCM for LHTES systemswas executed by(Sharma et al., 2013)and the thermal properties were calculated by determining the weight percentages of the PCM. These organic PCMs displayed non‐ corrosive, non‐toxic, self‐nucleating characteristics combined with sufficient chemical and thermal stability. The eutectic mixtures, of capric acid with fatty acid, were measured using the Differential Scanning Calorimetry technique and this revealed the latent heat of fusion and melting solidification temperatures. Capric acid combined with stearic acid was viable options for building application due to their latent heat competence and suitable phase change temperature range between 20‐30°C.

from solid to liquid during the charging process where supplied heart increases the temperature of the PCM until its melting point is reached. During this change, significant heat is captured and when the surrounding temperature is less than the PCMs melting temperature, the transformation from a liquid to a solid occurs where the captured heat energy is released (Salunkhe and Shembekar, 2012).

The Development of PCMs Throughout the past decade, much attempt to conceptualise the application of PCM enhanced building materials, as LHTES systems, has increased.

This is because PCMs possess distinct characteristics that allow them to successfully transform the interior climate of a building through their complex yet efficient manner of storing and releasing thermal energy.Tyagi et al. (2011)provided an analytical overview of the microencapsulation process and critically reviewed numerous applications of PCM enhanced wallboard and concrete systems that have been previously carried out. Conclusively, organic PCM incorporated LHTES systems possess desirable storage capabilities and are suitable for their integration in building materials. PCM wallboard is among the most promising developments for use in lightweight residential buildings as they mitigate temperature fluctuations and adequately store heat/ cool energy. These results promote the validity of microencapsulated PCMs and elucidate their potential for use in PCM enhanced building materials.Soares et al. (2013) provided an extensive theory based review of LHTES systems and the diligent role they possess in enhancing a building’s energy performance. The PCMs thermophysical properties are critical components that comprise selecting a suitable PCM due to its temperature range and ensure that a high latent heat transition per unit mass is also achieved. The review consisted of comparison and contrast of PCM enhanced wallboards, wall systems, concrete systems, bricks, trombe walls and shutters and although each system displayed promising indoor temperature controlling results, PCM enhanced wallboards excelled due to their exceptional thermal attributes, economic feasibility and adaptable characteristics.

A significant study of PCM copolymer composite wallboard was experimentally analysed by Kuznik and Virgone (2009)concluded that the selected PCM’s melting and freezing temperature range must be near the average room temperature of the building and additionally, and the day temperature must correlate with the PCMs thermophysical properties. The application of PCMs is widespread, and their effectiveness has been positively demonstrated in plasterboard applications which reveal that gypsum’s 25wt% absorption of PCM decreases overheating thus reducing energy consumption in the residential building experiments carried out. The PCMs tested reduced overeating of wall surface temperatures as well as enhancing the natural convection of room.

Although fatty acids have attractive benefits, certain compositions that form eutectic mixtures having strong odours reducing their applicability for PCM enhanced wallboard use(Kenisarin and Mahkamov, 2007).

Li et al. (2013)prepared a polyethylene glycol/silicon dioxide shape‐stabilised (ss) PCM and aimed at characterising the effects when it was confined in silica gel through analysing the thermal stability and the thermal conductivity of the ss‐PCM against pure polyethylene glycol and different mass fractions of ss‐ PCM. The ss‐PCMs proved thermally reliable and demonstrated appropriate phase change temperatures, adequate thermal conductivities and durable core‐ shell structure thus reinforcing their applicability for use in LHTES systems in building envelopes.

PCM Selection PCM selection is highly regarded as the most important aspect determining the viability and subsequent success of the PCM(Aranda‐Usón et al., 2013). Prominent characteristics that contribute to the effectiveness of PCMs include theirthermophysical,

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determine the effectiveness of the latent heat storage including the dimensions, thickness, temperature range and total latent heat of the PCM.

Climate An imperative factor that predominantly influences the effectiveness of PCMs is the surrounding climate as both the physical and thermal characteristics are largely conditioned by the surrounding environment and the climatic circumstances that prevail. The analysis of three different types of PCMs incorporated in LHTES systems as tiles using the life cycle assessment method was undertaken by Aranda‐Usón et al. (2013) to determine if the energy savings balance out the environmental impact produced from the manufacturing and installing the PCM enhanced wall tiles. Positive results were determined as the environmental implications from the PCM manufacturing, installation and disposal processes did not outweigh the energy savings as the total environmental benefits of 34% with a building that incorporates PCM for up to fifty years.

FIG. 1 MONITORED TEMPERATURES OF PCMM AND REFM(SPRING) (Sá et al., 2012)

Sá et al. (2012) presented a detailed overview of the conception and application of micro encapsulated PCM for internal cement based mortars whereby two tests cells with PCM mortar and regular mortar were analysed under Spring and Summer conditions in Portugal. PCM mortar (PCMM) test cell had a 2.6°C difference compared to the reference mortar (REFM).

Similarly, a difference of 2°C is revealed in FIG. 2 MONITORED

TEMPERATURES

OF

PCMM

AND

FIG. 2 MONITORED TEMPERATURES OF PCMM AND REFM (SUMMER)(Sá et al., 2012)

REFM

Barriers

(SUMMER)(Sá et al., 2012) which further reveals that the

incorporation of PCMs leads to a reduction of peak temperatures and an increase in minimum temperatures thus PCMs act by reducing internal temperatures during the day, levelling them and turning them closer to comfort temperature levels for Summer and Spring conditions.

Although the applications of PCMs in LHTES systems have received considerable attention due to their thermal energy storage behaviour, their commercial feasibility is limited by the economic costs of their integration as well as a lack of consistent research (Sharma et al., 2013). This critical disadvantage hinders the progression ad subsequent integration of PCMs into common building practice as they lack widespread availability to all areas of the construction materials market due to their expensive attributes.

Another prominent issue that obstructs the positive reputation of PCMs is the inadequate correlation between building specifications and PCM selection as currently, the undeveloped rules and regulations create inconsistencies, which generates negative connotations. This flawed relationship between PCMs and current building regulations has deterred their ease of integration into common building practice.

The performance of PCMs are significantly influenced by the surrounding climate and this concept has been investigated through a numerical seasonal comparative analysis of PCM wallboard performed by Zwanzig et al. (2013). The results were obtained through using the Crank‐Nicolson discretization scheme and revealed that the location and placement of the PCM is an important aspect and centrally located PCM composite wallboards are more efficient than external or internal PCM placement. Similarly, Heim (2010) investigated an isothermal heat storage system encapsulated with PCMs that stores heat energy and releases it in the cold period. The systems analysed were PCM‐ impregnated gypsum plasterboard and transparent insulation which were compared against a non PCM case. The results revealed the critical parameters that

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Microencapsulated PCMs have consistently surpassed the macro‐encapsulation method. Salunkhe and Shembekar (2012) highlighted the advent of nano‐ encapsulated PCMs which have paved the way for the

International Journal of Engineering Practical Research (IJEPR) Volume 2 Issue 4, November 2013 www.seipub.org/ijepr

future progression of PCMs. However the current research on nano‐encapsulation methods is limited to laboratory experiments prohibiting a thorough investigation on their physical and chemical characteristics due to the lack of practical applications and experiments. Another problem is the impregnation of PCMs within the building material especially wallboard and concrete and this method can be expensive which does not promote an attractive possibility. Eutectics have adverse characteristics due to their strong odour which rules them out of contention for use in PCM enhanced wallboard (Kenisarin and Mahkamov, 2007). A deterring occurrence, initiated by PCM manufacturers, reveals that data provided about the capabilities of PCMs appears to be erroneous and overzealous allowing for inconsistent results to flourish throughout the thermal energy sector (Soares et al., 2013).

building construction. Renewable Energy, 35, 788‐796.

KENISARIN, M. & MAHKAMOV, K. 2007. Solar energy storage using phase change materials. Renewable and Sustainable Energy Reviews, 11, 1913‐1965.

KUZNIK, F. & VIRGONE, J. 2009. Experimental assessment of a phase change material for wall building use. Applied Energy, 86, 2038‐2046.

LI, J., HE, L., LIU, T., CAO, X. & ZHU, H. 2013. Preparation and characterization of PEG/SiO2 composites as shape‐ stabilized phase change materials for thermal energy storage. Solar Energy Materials and Solar Cells, 118, 48‐53.

SÁ, A. V., AZENHA, M., DE SOUSA, H. & SAMAGAIO, A. 2012. Thermal enhancement of plastering mortars with Phase Change Materials: Experimental and numerical approach. Energy and Buildings, 49, 16‐27.

SALUNKHE, P. B. & SHEMBEKAR, P. S. 2012. A review on

Conclusions

effect of phase change material encapsulation on the

To make a holistic understanding of PCM micro‐ encapsulation within LHTES system, the synthesis of the physical and chemical characteristics displayed by PCMs was combined with the analysis of barriers that hinder their widespread utilisation. Predominant economic challenges are an intrinsic factor that has limited their integration of PCMs into the built environment.

thermal performance of a system. Renewable and Sustainable Energy Reviews, 16, 5603‐5616.

SHARMA, A., SHUKLA, A., CHEN, C. R. & DWIVEDI, S. 2013. Development of phase change materials for building applications. Energy and Buildings, 64, 403‐407.

SOARES, N., COSTA, J. J., GASPAR, A. R. & SANTOS, P. 2013. Review of passive PCM latent heat thermal energy storage systems towards buildings’ energy efficiency.

A thorough analysis on previous studies with the focus on the characteristics of PCMs and their integration with LHTES systems has been conducted to extricate the pertinent parameters that contribute to the performance of these systems and thus the building’s energy efficiency. From the results obtained in the studies, the microencapsulation of PCM within gypsum wallboards was proved to be the most efficient LHTES system through its performance in mitigating both the peak cooling and heating loads as well as reducing off peak seasonal energy consumption.

Energy and Buildings, 59, 82‐103.

TYAGI, V. V., KAUSHIK, S. C., TYAGI, S. K. & AKIYAMA, T. 2011. Development of phase change materials based microencapsulated technology for buildings: A review.

Renewable and Sustainable Energy Reviews, 15, 1373‐1391.

ZWANZIG, S. D., LIAN, Y. & BREHOB, E. G. 2013.

Numerical simulation of phase change material composite wallboard in a multi‐layered building envelope. Energy Conversion and Management, 69, 27‐40.

Rochelle Foran, Bachelor of Construction Management, Newcastle University, a junior project manager and contract administrator at BDM Constructions, located in Wauchope NSW, Australia.

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