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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "D1: Advanced Energy Materials".

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 23306

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Special Issue Editors

Dr. Alessandro Cannavale

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Guest Editor

1. Department of Architecture, Construction and Design, Polytechnic University of Bari, Via Orabona 4, 70125 Bari, Italy
2. National Research Council, Institute of Nanotechnology (CNR-NANOTEC), Via Monteroni, 73100 Lecce, Italy
Interests: building integration of innovative technologies; energy saving; building energy
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Ubaldo Ayr

E-Mail Website
Guest Editor

Department of Architecture, Construction and Design, Polytechnic University of Bari, Via Orabona 4, 70125 Bari, Italy
Interests: energy saving; solar energy; wind energy; FEM simulation; acoustics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Nowadays, energy harvesting and saving by means of innovative materials represent a challenge for researchers. In this compelling roadmap, smart materials may play a pivotal role, providing exciting performances and properties, as well as the chance to enhance design opportunities and energy saving through fabrication and operation. Smart materials are defined as highly engineered materials that respond intelligently to their environment with a specialized performance, so as to meet specific users’ needs in a reversible fashion.

Since the beginning of these research activities, worldwide, several classes of materials and devices have been widely proposed and investigated, showing reversibly adaptive properties, namely: shape memory materials, piezoelectric materials; chromogenics; new materials for more efficient solar energy conversion; electro-active polymers for energy harvesting, just to cite some. This Special Issue could help collect contributions of particular scientific results.

It is our pleasure to invite you to contribute to this Special Issue with your valuable manuscripts, sending full papers, reviews, and communications dealing with the design, characterization, and modeling of smart materials and devices for energy saving, for a very wide readership.

Hereafter, a non-exhaustive list of the main topics proposed for this Special Issue is reported:

Energy harvesting and saving;
Chromogenics, mechanotropics, mechanochromics, PCMs, piezoelectrics, and EAPs;
Modelling and simulation of smart materials;
Properties and characterization of smart materials and devices.

Dr. Alessandro Cannavale
Prof. Dr. Ubaldo Ayr
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

energy saving and harvesting
smart materials and devices
chromogenics
electro-active polymers
novel photovoltaics
phase-change materials
piezoelectrics
mechanotropics/mechanochromics

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Published Papers (12 papers)

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Editorial

Jump to: Research, Review

3 pages, 144 KiB

Open AccessEditorial

Smart Materials and Devices for Energy Saving and Harvesting

by Alessandro Cannavale and Ubaldo Ayr

Energies 2024, 17(18), 4684; https://doi.org/10.3390/en17184684 - 20 Sep 2024

Viewed by 405

Abstract

The decarbonisation objectives set for 2050 compel us to envisage any effective strategy in order to reduce the human impact on the planet, drastically reducing greenhouse gas emissions to reduce the effects of global warming [...] Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)

Research

Jump to: Editorial, Review

15 pages, 1867 KiB

Open AccessEditor’s ChoiceArticle

Limitations Imposed Using an Iodide/Triiodide Redox Couple in Solar-Powered Electrochromic Devices

by George Syrrokostas, Sarantis Tsamoglou and George Leftheriotis

Energies 2023, 16(20), 7084; https://doi.org/10.3390/en16207084 - 13 Oct 2023

Viewed by 1183

Abstract

In the present study, an iodide/triiodide (I⁻/I₃⁻) redox couple is used in hybrid electrochromic devices (ECDs), and the effects of the applied bias potential and bias time on device performance are studied. An applied bias potential of ~1 V is sufficient to achieve an initial contrast ratio of 8:1 in less than 5 min. Increasing both the bias potential and bias time results in an enhancement in loss reactions at the WO₃/electrolyte interface, rather than improving optical performance. Moreover, long-term performance depends on the testing procedure (regularly cycling or after storage), while the formation of iodine (I₂) decreases the initial transparency of the ECDs and affects their overall performance. However, its formation cannot be avoided, even without cycling the ECDs, and the restoration of the optical performance can take place only when the electrolyte is replaced with a fresh one. Finally, a new methodology is applied for calculating the loss current, and a suggestion is made to avoid a common mistake in calculating the coloration efficiency of these hybrid ECDs. Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)

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20 pages, 8875 KiB

Open AccessArticle

Numerical and Parametric Study on Open-Type Ceiling Radiant Cooling Panel with Curved and Segmented Structure

by Minzhi Ye, Ahmed A. Serageldin and Katsunori Nagano

Energies 2023, 16(6), 2705; https://doi.org/10.3390/en16062705 - 14 Mar 2023

Cited by 1 | Viewed by 1507

Abstract

A suspended open-type ceiling radiant cooling panel (CRCP) has been proposed recently. The main challenge is improving its cooling performance to overcome limitations for extensive use. Therefore, this study aims to optimize the design of CRCPs with curved and segmented structure to enhance heat transfer. A three-dimensional CFD model was developed to investigate the cooling capacity and heat transfer coefficient of the CRCPs installed inside a single enclosed room. Panel structure was determined based on four dependent parameters: the panel curvature width (L, m), the panel curvature radius (r, m), the void distance (d, m) between each panel or panel segment, and the panel coverage area (A_c, m²). The panel surface area (A_s, m²) and the ratio of panel curvature width to radius (L/r) were also examined. A total of 35 designs were compared under 7 different cooling load conditions, and 245 cases were carried out. The results show that the nominal cooling capacity and heat transfer coefficient rise with increasing curvature radius and decreasing curvature width. The void distance plays the most crucial role in influencing cooling performance. It is possible to simultaneously improve cooling performance, achieve uniform temperature distribution, and reduce the number of panels through structure optimization. Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)

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15 pages, 4171 KiB

Open AccessArticle

Using a Mine Dewatering System to Increase Cooling Capacity and Energy Recovery of Underground Refrigeration Plant: A Case Study

by Dariusz Obracaj, Nikodem Szlązak and Marek Korzec

Energies 2022, 15(24), 9481; https://doi.org/10.3390/en15249481 - 14 Dec 2022

Cited by 2 | Viewed by 2814

Abstract

Heat stress in deep hot mines is a factor that often determines the possibility of technical mining of natural resources. One of the solutions enabling miners to work in such mines is air cooling. Cooling systems vary, and their selection depends on the type of mine and the mining methods used. Limited air cooling capabilities exist in electric-powered coal mines. The main solution for air cooling is based on movable spot air coolers. Such systems commonly use surface or underground refrigeration plants. An underground refrigeration plant (URP) equipped with compressor chillers does not achieve more than 2.5–3.0 MW of cooling capacity due to the limited heat rejection capacity of return air streams in a typical coal mine. The method discussed in this paper, using mine water to discharge waste heat from the underground refrigeration plant, provides a measurable benefit for optimizing the mine air cooling system. The main purpose of this research is to study the feasibility and effect of water diversion from the actual mine drainage system to the underground refrigeration plant. The water drainage system in an underground mine is called the dewatering system of the mine. The heated water in the condensers of the chillers is directed back to the mine’s central dewatering system. The recovery from water discharged to the surface contributes to optimising energy consumption for a mine air cooling and the sustainable discharge of wastewater. In addition, using the total water flow from the mine dewatering system to reject heat in compressor chillers, compared with the traditional solution, can improve the cooling capacity of URP. These findings may provide beneficial guidance for practical applications in deep hot mines with small natural water inflow. Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)

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16 pages, 4918 KiB

Open AccessArticle

Thermal Performance of Load-Bearing, Lightweight, Steel-Framed Partition Walls Using Thermal Break Strips: A Parametric Study

by Paulo Santos, Paulo Lopes and David Abrantes

Energies 2022, 15(24), 9271; https://doi.org/10.3390/en15249271 - 7 Dec 2022

Cited by 5 | Viewed by 1657

Abstract

Thermal bridges are a very relevant issue for lightweight steel-framed (LSF) construction systems given the high thermal conductivity of steel, which can negatively compromise their thermal behaviour, reduce their durability, and decrease the building energy efficiency. Several thermal bridge mitigation strategies exist, including the attachment of thermal break strips (TBS) to the steel studs’ flanges as one of the most widely employed techniques. In this research, the relevance of TBS to the thermal performance improvement of load-bearing LSF partition walls was assessed by performing a parametric study, making use of a validated 2D numerical model. A sensitivity analysis was performed for five different key parameters, and their importance was evaluated. The assessed parameters included the number of TBS and their thickness, width, and thermal conductivity, as well as the vertical steel stud spacing. We found that these parameters were all relevant. Moreover, regardless of the TBS thermal conductivity, it is always worth increasing their thickness. However, the increase in the TBS width does not always lead to increased thermal resistance; a thermal performance reduction was noted when increasing the width of the TBS at higher thermal conductivities. Therefore, it was concluded that it is more efficient to increase TBS thickness than their width. Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)

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14 pages, 5483 KiB

Open AccessArticle

Metal-Organic Framework Adsorbent Materials in HVAC Systems: General Survey and Theoretical Assessment

by Andrea Rocchetti, Martina Lippi, Luca Socci, Paride Gullo, Vahid Khorshidi and Lorenzo Talluri

Energies 2022, 15(23), 8908; https://doi.org/10.3390/en15238908 - 25 Nov 2022

Cited by 2 | Viewed by 2304

Abstract

In this paper, the use of Metal-Organic Framework (MOF) materials as an option for the energy efficiency enhancement of HVAC systems is investigated. In particular, the possibility of using MOFs as dehumidifying materials to reduce the latent load associated with the moisture content of the airflows is studied. A literature review is proposed, highlighting the benefits of using MOFs instead of other adsorbents (e.g., silica-gel) and discussing the unique features (high water uptake capacity and low regeneration temperatures) that make MOFs a preferential desiccant. The possibility to finely tune these properties is also underlined, reporting some explicative examples. A theoretical proposal of a psychrometric transformation, to be performed in a HVAC system equipped with a MOF-Assisted Dehumidifier (MAD), is presented. This transformation is compared with a traditional one (cooling and dehumidification operated by a cooling coil with low temperatures of the coolant). The preliminary numerical simulations, conducted on a reference case study in Florence, Italy, show an estimated energy saving of 30–50%, leading us to consider the use of this technology as a very competitive one in the air-conditioning sector. Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)

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16 pages, 4318 KiB

Open AccessArticle

Aging of Polymeric Insulators under Various Conditions and Environments: Another Look

by Xinhan Qiao, Yue Ming, Ke Xu, Ning Yi and Raji Sundararajan

Energies 2022, 15(23), 8809; https://doi.org/10.3390/en15238809 - 22 Nov 2022

Cited by 11 | Viewed by 3246

Abstract

Polymeric insulators have lightweight, excellent hydrophobicity and convenient transportation and installation. They are widely used in the external insulation for distribution and transmission lines. However, due to the long-term effects of pollution, ultraviolet radiation, discharge, temperature, humidity, altitude and other natural and complex environmental and service factors, the silicone rubber and other materials of polymeric insulators gradually age and lose their hydrophobicity and electrical insulation characteristics. The operability is significantly reduced, which seriously affects the safety and reliability of the power system. Hence, there is a need for assessing and evaluating the long-term aging and degradation of polymeric insulators under various operating conditions and environments. In this review, the various aging and characterization techniques of the polymeric insulators and their aging performance under the action of multiple factors are discussed. To enhance the performance of polymeric insulators, nano-coating, surface treatment and other techniques are also indicated. In addition, future potential fields that should be explored from a high-voltage electrical insulation perspective are also presented. Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)

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19 pages, 2410 KiB

Open AccessFeature PaperArticle

Solid–Gas Sorption System for Ammonia Storage and Delivery Driven by Engine Waste Heat for NOx Reduction of Diesel Engine

by Chenjue Wang, Shi Chen, Long Jiang, Yaodong Wang and Huashan Bao

Energies 2022, 15(22), 8376; https://doi.org/10.3390/en15228376 - 9 Nov 2022

Cited by 1 | Viewed by 1742

Abstract

A new design of a sorption-selective catalytic reduction (SCR) system is proposed to improve ammonia storage density and meet the ammonia demand for high NOx conversion efficiency at a relatively lower temperature (<100 °C) compared to urea-SCR systems. The major components are a main unit and a start-up unit that each contain a metal halide ammine as the sorbent. The start-up unit can operate without any external heat source, but spontaneously releases ammonia at the ambient temperature and is only used when the main unit is being warmed up for action. The selection criteria for the metal halide ammine for each unit is discussed. The working pair of SrCl₂ as the main ammine and NH₄Cl as the start-up ammine is further analyzed as an example to be used in the sorption-SCR system for a diesel engine, the NOx emissions of which were experimentally measured in different operation modes. Based on the experimental data of engine emissions and kinetic models of the chemisorption between ammines and ammonia, the dynamic performance of the sorption system with a total capacity of 180 L sorbent composite in different layouts was investigated and compared. It was found that the achievable desorption conversion degree was lower in smaller reactors and was more sensitive to operating conditions in smaller reactors compared to larger reactors. This suggests that a system using a small reactor layout requires some extra volume to completely meet the required capacity compared to a larger reactor layout. However, because systems with large reactors tend to respond slowly, as they have more thermal mass and take a longer time for preparation, there is a design trade-off required to have optimal performance and balance between the main unit and the start-up unit. In the case studied in this work, a system using three rechargeable reactors with a volume of 60 L each was found to be the preferable layout; it could have about a 90% desorption conversion degree and required around 10 min of warm-up time. Meanwhile, the coupled start-up unit should have a capacity of around 165 mL at least. Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)

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10 pages, 3207 KiB

Open AccessArticle

AC Loss Characteristics of HTS Novel Twisted Cables Composed of Soldered-Stacked-Square (3S) Wires

by Zhuyong Li, Zhixuan Zhang, Mingshuo Wang, Yingying Lv and Kyungwoo Ryu

Energies 2022, 15(20), 7454; https://doi.org/10.3390/en15207454 - 11 Oct 2022

Cited by 2 | Viewed by 1622

Abstract

Compared with traditional cables, superconducting multi-stage cables have the natural advantages of greater transmission power and less energy loss, which have gradually attracted attention. However, conventional multi-stage cables are based on low temperature superconducting (LTS) technology and there is considerable scope for improvement in their performance. In this paper, a novel structure of the multi-stage high temperature superconducting (HTS) twisted cable prepared by the soldered-stacked-square (3S) wire is proposed. The AC loss characteristics of the twisted cable are deeply studied by experiments and simulation. Through the experiment, the influence of the voltage-leads on the AC loss measurement accuracy is eliminated, and frequency dependent is shown in the AC loss of the twisted cable. Besides, the simulated value of AC loss is consistent with the experimental value, which verifies the accuracy of the simulation. The AC loss of twisted cable is only 20% of that of the thin strip model, which reveals its outstanding advantages in AC loss. Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)

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13 pages, 1972 KiB

Open AccessArticle

Photovoltaic Performance of Dye-Sensitized Solar Cells with a Solid-State Redox Mediator Based on an Ionic Liquid and Hole-Transporting Triphenylamine Compound

by Minseon Kong, Da Hyeon Oh, Baekseo Choi and Yoon Soo Han

Energies 2022, 15(8), 2765; https://doi.org/10.3390/en15082765 - 9 Apr 2022

Cited by 3 | Viewed by 1698

Abstract

An ionic liquid, 1-methyl-3-propylimidazolium iodide (MPII), was solidified with an organic hole-transporting material, 4,4′,4″-tris[(3-methylphenyl)phenylamino]triphenylamine (m-MTDATA), and the resulting solid-state redox mediator (RM) (m-MTDATA-solidified MPII) was employed in solar devices to realize solid-state dye-sensitized solar cells (sDSSCs). Solar devices with only MPII or m-MTDATA as an RM showed almost 0 mA/cm² of short-circuit current (J_sc) and thus 0% power conversion efficiency (PCE). However, an sDSSC with the m-MTDATA-solidified MPII exhibited 4.61 mA/cm² of J_sc and 1.80% PCE. It was found that the increased J_sc and PCE were due to the formation of I₃⁻, which resulted from a reaction between the iodie (I⁻) of MPII and m-MTDATA cation. Further enhancement in both J_sc (9.43 mA/cm²) and PCE (4.20%) was observed in an sDSSC with 4-tert butylpyridine (TBP) as well as with m-MTDATA-solidified MPII. We attributed the significant increase (about 230%) in PCE to the lowered diffusion resistance of I⁻/I₃⁻ ions in the solid-state RM composed of the m-MTDATA-solidified MPII and TBP, arising from TBP’s role as a plasticizer. Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)

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16 pages, 3688 KiB

Open AccessArticle

Modeling of Dielectric Electroactive Polymer Actuators with Elliptical Shapes

by Jakub Bernat and Jakub Kołota

Energies 2021, 14(18), 5633; https://doi.org/10.3390/en14185633 - 8 Sep 2021

Cited by 5 | Viewed by 1925

Abstract

Dielectric electroactive polymers have been widely used in recent applications based on smart materials. The many advantages of dielectric membranes, such as softness and responsiveness to electric stimuli, have lead to their application in actuators. Recently, researchers have aimed to improve the design of dielectric electroactive polymer actuators. The modifications of DEAP actuators are designed to change the bias mechanism, such as spring, pneumatic, and additional mass, or to provide a double cone configuration. In this work, the modification of the shape of the actuator was analyzed. In the standard approach, a circular shape is often used, while this research uses an elliptical shape for the actuator. In this study, it was shown that this construction allows a wider range of movement. The paper describes a new design of the device and its model. Further, the device is verified by the measurements. Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)

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Review

Jump to: Editorial, Research

23 pages, 3084 KiB

Open AccessReview

Effectiveness of Daytime Radiative Sky Cooling in Constructions

by Alessandro Cannavale, Marco Pugliese, Roberto Stasi, Stefania Liuzzi, Francesco Martellotta, Vincenzo Maiorano and Ubaldo Ayr

Energies 2024, 17(13), 3210; https://doi.org/10.3390/en17133210 - 29 Jun 2024

Viewed by 939

Abstract

In this paper, we have carefully studied the scientific literature dealing with the use of passive radiative surfaces within the construction industry. The aim of this paper is to highlight technologies and materials for daylight radiative cooling under study today—or already on the market—and to report their main characteristics, performance and, where possible, costs. Following a review of the available scientific literature, the advantages and limitations of such an option were highlighted, seeking to capture opportunities and future lines of research development. This review also provides the physical laws that evaluate the energy balance of passive radiative surfaces as well as the criteria to quantify all the terms of these equations. Full article

(This article belongs to the Special Issue Smart Materials and Devices for Energy Saving and Harvesting)

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