Phase Change Materials for Building Applications: A State-of-the-Art Review

TLDR: In this paper, a state-of-the-art review is given on the knowledge of phase change materials (PCMs) today for building applications, and the authors propose a solution for reducing the energy consumption of buildings.

About: This article is published in Energy and Buildings.The article was published on 2010-09-01 and is currently open access. It has received 784 citations till now. The article focuses on the topics: Energy consumption & Phase-change material.

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Table 4.2 Annual energy balance of the simulated houses in Stockholm and Madison (Wisconsin). House type 1 denotes a reference house, where type 2 denotes a house with PCM enhanced plasterboard [ΔH = 540 kJ/m²]. The simulated conventional house has an average thermal transfer coefficient U of 0.23 W/(m²K) and windows of 1.8 W/(m²K), while both the passive and reference house types have an average thermal transfer coefficient U of 0.12 W/(m²K) and windows of 1.3 W/(m²K). The mentioned Tr denotes the room temperature during the night and the day (Peippo et al. 1991).

Table 4.1 Overview of the main phase change materials (Demirbas 2006).

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Phase change materials for building applications: a state-of-the-art review" ?

Within this work, a state-of-the-art review is given on the knowledge of PCMs today for building applications. 

Q2. What is the advantage of the PCMs?

The PCMs will reduce the temperature rise experienced during early-age curing of massive concrete structures, due to melting of the wax by absorbing energy. 

Q3. What are the advantages of hydrated salts for thermal energy storage?

Hydrated salts are attractive materials for thermal energy storage due to their high storage density of about 240 kJ/kg, their relative high thermal conductivity of about 0.5 W/(mK) and their reasonable cost compared to paraffin waxes. 

Q4. What is the way to define an optimal PCM?

When the optimal transition temperature is known or approximated as function of the application conditions, it should be able to define an optimal PCM. 

Q5. What is the eutectic system for passive solar storage?

The organic eutectic capric-mauric acid seems to be the most suitable for passive solar storage with a melting point of 18°C, a freezing point of 17°C and a heat of fusion of 120 kJ/kg. 

Q6. What is the method of enhancing wallboards with PCMs?

the PCM will show a tendency to migrate to the surface of the paste and cause instability of the paste and a dispersing agent has to be added to ensure good dispersion of PCM in the matrix. 

Q7. What is the important criteria for selecting a PCM?

As previously mentioned is a proper phase change point (or phase change temperature range) one of the most important criteria for selecting PCMs for the application considered. 

Q8. What is the process of enhancing wallboards with PCMs?

The PCM is heated in a flask and at controlled temperature and a weighted quantity of aggregate (the wallboard) is inserted for adsorption of the PCM under vacuum conditions. 

Q9. What are the main factors that affect the performance of the PCM enhanced wallboard?

The performance of the PCM enhanced wallboards will depend on several factors: the melt temperature of the PCM, the temperature range over which melting occurs, the latent capacity per unit area of the wall, how the PCMs are incorporated in the wallboard, the orientation of the wall, climatic conditions, direct solar gains, etc. 

Q10. What is the main advantage of the PCMs in concrete?

concrete strengths were significantly reduced by application of the PCMs (Bentz & Turpin 2007, Castellon 2006) because higher curing temperatures will accelerate hydration and strength gain at early ages, while it may lead to lower long term concrete strengths (Schindler & McCullough 2002). 

Q11. What is the common type of PCM used in building constructions?

Another possibility for applying PCMs in building constructions is PCM-enhanced concrete or the so-called Thermocrete and PCM-enhanced clay tiles. 

Q12. How much heat can be achieved by enhancing gypsum plasterboards?

Having in mind the numbers cited in Ch.4.3.2.a, enhancing concrete with PCMs results in an overall heat capacity of approximately 8 000 kJ/(m²K) at the transition temperature, i.e. 10 times the value achieved for gypsum plasterboards. 

Q13. What is the way to enhance wallboards?

Analysis (Farid 2004) shows that this immersion process has the potential of achieving higher storage capacity than adding filled pellets to wallboard during manufacturing. 

Q14. How many peaks have been observed in the eutectic system?

Binary systems of fatty acids may form a single eutectic point for both melting and freezing, but mixtures with up to four peaks have been noticed (see Fig.4.2) (Feldman et al. 1989). 

Q15. What is the potential of using PCMs in direct contact heat exchange?

The salt/ceramic-based composite thermal storage media offers the potential of using PCMs in direct contact heat exchange and, as a result, shows a potential of cost improvement.