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17 pages, 3613 KiB

Open AccessArticle

A New Methodological Approach for the Evaluation of Scaling Up a Latent Storage Module for Integration in Heat Pumps

by Gabriel Zsembinszki, Boniface Dominick Mselle, David Vérez, Emiliano Borri, Andreas Strehlow, Birgo Nitsch, Andrea Frazzica, Valeria Palomba and Luisa F. Cabeza

Energies 2021, 14(22), 7470; https://0-doi-org.brum.beds.ac.uk/10.3390/en14227470 - 09 Nov 2021

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Abstract

A clear gap was identified in the literature regarding the in-depth evaluation of scaling up thermal energy storage components. To cover such a gap, a new methodological approach was developed and applied to a novel latent thermal energy storage module. The purpose of [...] Read more.

A clear gap was identified in the literature regarding the in-depth evaluation of scaling up thermal energy storage components. To cover such a gap, a new methodological approach was developed and applied to a novel latent thermal energy storage module. The purpose of this paper is to identify some key aspects to be considered when scaling up the module from lab-scale to full-scale using different performance indicators calculated in both charge and discharge. Different normalization methods were applied to allow an appropriate comparison of the results at both scales. As a result of the scaling up, the theoretical energy storage capacity increases by 52% and 145%, the average charging power increases by 21% and 94%, while the average discharging power decreases by 16% but increases by 36% when mass and volume normalization methods are used, respectively. When normalization by the surface area of heat transfer is used, all of the above performance indicators decrease, especially the average discharging power, which decreases by 49%. Moreover, energy performance in charge and discharge decreases by 17% and 15%, respectively. However, efficiencies related to charging, discharging, and round-trip processes are practically not affected by the scaling up. Full article

(This article belongs to the Special Issue Phase Change Materials for Thermal Energy Storage Applications)

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19 pages, 8190 KiB

Open AccessArticle

Numerical Simulation of a Novel Dual Layered Phase Change Material Brick Wall for Human Comfort in Hot and Cold Climatic Conditions

by Atiq Ur Rehman, Shakil R. Sheikh, Zareena Kausar and Sarah J. McCormack

Energies 2021, 14(13), 4032; https://0-doi-org.brum.beds.ac.uk/10.3390/en14134032 - 04 Jul 2021

Cited by 13 | Viewed by 2367

Abstract

Phase change materials (PCMs) have a large number of applications for thermal energy storage (TES) and temperature reduction in buildings due to their thermal characteristics and latent heat storage capabilities. The thermal mass of typical brick walls can be substantially increased using a [...] Read more.

Phase change materials (PCMs) have a large number of applications for thermal energy storage (TES) and temperature reduction in buildings due to their thermal characteristics and latent heat storage capabilities. The thermal mass of typical brick walls can be substantially increased using a suitable PCM primarily based on phase change temperature and heat of fusion for different weather conditions in summer and winter. This study proposed a novel dual-layer PCM configuration for brick walls to maintain human comfort for hot and cold climatic conditions in Islamabad, Pakistan. Numerical simulations were performed using Ansys Fluent for dual PCMs layered within a brick wall for June and January with melting temperatures of 29 °C and 13 °C. This study examined and discussed the charging and discharging cycles of PCMs over an extended period (one month) to establish whether the efficacy of PCMs is hindered due to difficulties in discharging. The results show that the combined use of both PCMs stated above provides better human comfort with reduced energy requirements in Islamabad throughout the year than using a single PCM (29 °C) for summer or winter (13 °C) alone. Full article

(This article belongs to the Special Issue Phase Change Materials for Thermal Energy Storage Applications)

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13 pages, 11378 KiB

Open AccessArticle

Novel Shape-Stabilized Phase Change Material with Cascade Character: Synthesis, Performance and Shaping Evaluation

by Rebeca Salgado-Pizarro, Jose Antonio Padilla, Elena Xuriguera, Camila Barreneche and Ana Inés Fernández

Energies 2021, 14(9), 2621; https://0-doi-org.brum.beds.ac.uk/10.3390/en14092621 - 03 May 2021

Cited by 10 | Viewed by 2276

Abstract

Thermal Energy Storage (TES) materials, such as Phase Change Materials (PCMs) are proven to enhance the energy efficiency in many fields, such as automotive and building sectors, which correspond to the most energy intensive ones. Shape-stabilized PCM and cascade PCM are procedures to [...] Read more.

Thermal Energy Storage (TES) materials, such as Phase Change Materials (PCMs) are proven to enhance the energy efficiency in many fields, such as automotive and building sectors, which correspond to the most energy intensive ones. Shape-stabilized PCM and cascade PCM are procedures to overcome the most important barriers when PCMs are applied since PCMs need to be encapsulated for their technical use: the leakage of the liquid phase, corrosion, low heat transfer and narrow temperature of application. In the present study, a novel shape stabilized PCM with cascade performance (cascade shape stabilized phase change material, CSS-PCM) is synthesized via dissolution, which allows up to 60 wt.% of a paraffin-PCM in the final composition. The novel CSS-PCM is based on a biopolymer, the polycaprolactone (PCL), a low melting temperature polyester as polymeric matrix and RT27 and Micronal DS 5040 acting as PCM. To evaluate the performance of the new TES materials developed, several techniques have been used: Differential Scanning Calorimetry (DSC), and Fourier-Transformed Infrared (FT-IR) spectroscopy were used to evaluate the thermophysical properties and the chemical properties of the different formulations. The CSS-PCM show an increment of storage capacity by increasing the PCM content, and the thermal reliability was also tested: some of the CSS-PCM formulations were stable for up to 500 thermal cycles. Finally, as a potential application of the new polymeric-based PCM 3D, a printing attempt was performed in order to analyze the viability of the formulations to be used as 3D printing material as a first proof of concept. Full article

(This article belongs to the Special Issue Phase Change Materials for Thermal Energy Storage Applications)

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20 pages, 66907 KiB

Open AccessArticle

Latent Heat Thermal Storage of Nano-Enhanced Phase Change Material Filled by Copper Foam with Linear Porosity Variation in Vertical Direction

by Mohammad Ghalambaz, Mohammad Shahabadi, S. A. M Mehryan, Mikhail Sheremet, Obai Younis, Pouyan Talebizadehsardari and Wabiha Yaici

Energies 2021, 14(5), 1508; https://0-doi-org.brum.beds.ac.uk/10.3390/en14051508 - 09 Mar 2021

Cited by 7 | Viewed by 2146

Abstract

The melting flow and heat transfer of copper-oxide coconut oil in thermal energy storage filled with a nonlinear copper metal foam are addressed. The porosity of the copper foam changes linearly from bottom to top. The phase change material (PCM) is filled into [...] Read more.

The melting flow and heat transfer of copper-oxide coconut oil in thermal energy storage filled with a nonlinear copper metal foam are addressed. The porosity of the copper foam changes linearly from bottom to top. The phase change material (PCM) is filled into the metal foam pores, which form a composite PCM. The natural convection effect is also taken into account. The effect of average porosity; porosity distribution; pore size density; the inclination angle of enclosure; and nanoparticles’ concentration on the isotherms, melting maps, and the melting rate are investigated. The results show that the average porosity is the most important parameter on the melting behavior. The variation in porosity from 0.825 to 0.9 changes the melting time by about 116%. The natural convection flows are weak in the metal foam, and hence, the impact of each of the other parameters on the melting time is insignificant (less than 5%). Full article

(This article belongs to the Special Issue Phase Change Materials for Thermal Energy Storage Applications)

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10 pages, 2368 KiB

Open AccessArticle

Evaluation of Formate Salt PCM’s for Latent Heat Thermal Energy Storage

by Samuel Gage, Prashant Sharan, Craig Turchi and Judy Netter

Energies 2021, 14(3), 765; https://0-doi-org.brum.beds.ac.uk/10.3390/en14030765 - 01 Feb 2021

Cited by 3 | Viewed by 2320

Abstract

This work examines formate salts as potential phase change materials (PCMs) for middle-high temperature (≤250 °C) latent heat thermal energy storage applications. The thermophysical properties of three formate salts were characterized: pure sodium formate and binary blends of sodium/potassium formate and sodium/calcium formate. [...] Read more.

This work examines formate salts as potential phase change materials (PCMs) for middle-high temperature (≤250 °C) latent heat thermal energy storage applications. The thermophysical properties of three formate salts were characterized: pure sodium formate and binary blends of sodium/potassium formate and sodium/calcium formate. The stability of formate PCM’s was evaluated by thermal cycling using differential scanning calorimetry where sodium formate and sodium/potassium formate appeared stable over 600 cycles, while sodium/calcium formate exhibited a monotonic decrease in heat of fusion over the test period. A longer test with sodium formate led to gas release and decomposition of the salt. FTIR analysis of the PCM showed degradation of formate to oxalate. T-history experiments with 50-g PCM quantities demonstrated a bulk supercooling of only 2–3 °C for these salts. Thermal conductivity enhancement of over 700% was achieved by embedding aluminum in the solid PCM. Finally, mild carbon steel was immersed in molten sodium formate for up to 2000 h. Sodium formate was found to be non-corrosive, as calculated by mass loss and confirmed by cross-sectional high-resolution microscopy. FTIR analysis of the PCM after 2000 h shows oxidation at the free surface, while the bulk PCM remained unchanged, further indicating a need to protect the formate from atmospheric exposure when used as a PCM. Full article

(This article belongs to the Special Issue Phase Change Materials for Thermal Energy Storage Applications)

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13 pages, 4914 KiB

Open AccessArticle

Dynamics of Melting Process in Phase Change Material Windows Determined Based on Direct Light Transmission

by Dariusz Heim, Michał Krempski-Smejda, Pablo Roberto Dellicompagni, Dominika Knera, Anna Wieprzkowicz and Judith Franco

Energies 2021, 14(3), 721; https://0-doi-org.brum.beds.ac.uk/10.3390/en14030721 - 30 Jan 2021

Cited by 10 | Viewed by 1785

Abstract

Detailed analyses of melting processes in phase change material (PCM) glazing units, changes of direct transmittance as well as investigation of refraction index were provided based on laboratory measurements. The main goal of the study was to determine the direct light transmittance versus [...] Read more.

Detailed analyses of melting processes in phase change material (PCM) glazing units, changes of direct transmittance as well as investigation of refraction index were provided based on laboratory measurements. The main goal of the study was to determine the direct light transmittance versus time under constant solar radiation intensity and stable temperature of the surrounding air. The experiment was conducted on a triple glazed unit with one cavity filled with a paraffin RT21HC as a PCM. The unit was installed in a special holder and exposed to the radiation from an artificial sun. The vertical illuminance was measured by luxmeters and compared with a reference case to determine the direct light transmittance. The transmittance was determined for the whole period of measurements when some specific artefacts were identified and theoretically explained based on values of refractive indexes for paraffins in the solid and liquid state, and for a glass. The melting process of a PCM in a glass unit was identified as a complex one, with interreflections and refraction of light on semi layers characterized by a different physical states (solid, liquid or mushy). These optical phenomena caused nonuniformity in light transmittance, especially when the PCM is in a mushy state. It was revealed that light transmittance versus temperature cannot be treated as a linear function. Full article

(This article belongs to the Special Issue Phase Change Materials for Thermal Energy Storage Applications)

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20 pages, 4702 KiB

Open AccessArticle

Identification of Phase Fraction–Temperature Curves from Heat Capacity Data for Numerical Modeling of Heat Transfer in Commercial Paraffin Waxes

by Tilman Barz, Johannes Krämer and Johann Emhofer

Energies 2020, 13(19), 5149; https://0-doi-org.brum.beds.ac.uk/10.3390/en13195149 - 02 Oct 2020

Cited by 11 | Viewed by 2949

Abstract

The area-proportional baseline method generates phase fraction–temperature curves from heat capacity data of phase change materials. The curves describe the continuous conversion from solid to liquid over an extended temperature range. They are consistent with the apparent heat capacity and enthalpy modeling approach [...] Read more.

The area-proportional baseline method generates phase fraction–temperature curves from heat capacity data of phase change materials. The curves describe the continuous conversion from solid to liquid over an extended temperature range. They are consistent with the apparent heat capacity and enthalpy modeling approach for the numerical solution of heat transfer problems. However, the curves are non-smooth, discrete signals. They are affected by noise in the heat capacity data and should not be used as input to continuous simulation models. This contribution proposes an alternative method based on spline approximation for the generation of consistent and smooth phase fraction–temperature, apparent heat capacity–temperature and enthalpy–temperature curves. Applications are presented for two commercial paraffins from Rubitherm GmbH considering heat capacity data from Differential Scanning Calorimetry and 3-layer-calorimetry. Apparent heat capacity models are validated for melting experiments using a compact heat exchanger. The best fitting models and the most efficient numerical solutions are obtained for heat capacity data from 3-layer-calorimetry using the proposed spline approximation method. Because of these promising results, the method is applied to melting data of all 44 Rubitherm paraffins. The computer code of the corresponding phase transition models is provided in the Supplementary Information. Full article

(This article belongs to the Special Issue Phase Change Materials for Thermal Energy Storage Applications)

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39 pages, 6548 KiB

Open AccessReview

A Critical Review on the Control Strategies Applied to PCM-Enhanced Buildings

by Gohar Gholamibozanjani and Mohammed Farid

Energies 2021, 14(7), 1929; https://0-doi-org.brum.beds.ac.uk/10.3390/en14071929 - 31 Mar 2021

Cited by 29 | Viewed by 3173

Abstract

The incorporation of phase change materials (PCM) in buildings has the potential to enhance the thermal efficiency of buildings, reduce energy cost, shift peak load, and eventually reduce air pollution and mitigate global warming. However, the initial capital cost of PCM is still [...] Read more.

The incorporation of phase change materials (PCM) in buildings has the potential to enhance the thermal efficiency of buildings, reduce energy cost, shift peak load, and eventually reduce air pollution and mitigate global warming. However, the initial capital cost of PCM is still high, and thus the establishment of a control strategy has become essential to optimize its use in buildings in an effort to lower investment costs. In this paper, an extensive review has been made with regard to various control strategies applied to PCM-enhanced buildings, such as ON/OFF control, conventional control methods (classical control, optimal, adaptive, and predictive control) and intelligent controls. The advantages and disadvantages of each control strategy are evaluated. The paper further discusses the opportunities and challenges associated with the design of PCM-enhanced buildings in combination with control strategies. Full article

(This article belongs to the Special Issue Phase Change Materials for Thermal Energy Storage Applications)

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