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Special Issue "Solar Thermodynamic Materials Overview"

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

Deadline for manuscript submissions: closed (25 September 2021) | Viewed by 3406

Special Issue Editor

Dr. Anna Castaldo
E-Mail Website
Guest Editor
National Agency for New Technologies, Energy and Sustainable Economic Development, ENEA Department of Renewable Energies, TERIN Solar Thermal and Smart Network Division, STSN Portici, 80055 Naples, Italy
Interests: materials science; applied chemistry; nanotechnology; cool roof materials; nonlinear optical polymers; nanocomposite sensors; thin films sputtering deposition; FT-IR and microRaman vibrational analysis
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Special Issue Information

Dear Colleagues,

I hope this message finds you well.

The journal Energies is currently running a Special Issue entitled "Solar Thermodynamic Materials Overview” that will be a survey of materials engineered in different elements of solar thermodynamic systems, such as concentrating mirrors, receivers, thermovector fluids (transport and storage), and power conversion devices.

Surely, the key coating material of a solar thermodynamic plant is the receiver tube’s spectrally selective absorber, which is devoted to capturing solar energy without heat losses in the infrared region, transferring this energy in thermovector storage fluids utilized to produce high-temperature vapor. A similar renewable mechanism represents a way of feeding thermodynamic cycles between two temperatures for electricity production. At present, the levelized cost of solar thermodynamic energy is high and not competitive with other energy sources, so there is a long way to go. In my opinion, the challenge lies in the research and development of new materials and coatings that can ameliorate the already existing technology, increasing its performance and simultaneously reducing its costs. Concerning the selective absorber, for example, a higher temperature stability of such coating means higher thermal efficiency. This requires new materials with ever better spectrally selective properties (alpha > 95% and epsilon < 5% ) that are stable at relatively high temperatures (300–550 °C) for at least 20 years. The trend of modern research is to obtain coatings with the highest thermal efficiency and lowest emissivity with respect to commercial ones, stable for a longest time to reduce the costs of plant fabrication and maintenance, and possibly stable also in air to avoid the evacuated concentric tube architecture. New frontiers include metamaterials and metasurfaces, such as the metal–dielectric–metal stratifications (interferential filters) tailored to decrease emissivity.

In addition to spectrally selective coating absorbers, other coating materials are very important in contributing to reducing the cost of solar thermodynamic energy: solar mirror coatings; hydrogen barriers for stainless-steel tubes to prevent permeation from diathermic oil subproducts to the vacuum envelope of concentric tubes; innovative materials for getters; coatings for storage tanks; electrodynamic screen coating to avoid dust deposition and reduce O&M operations, and so on.

As the Guest Editor of this Special Issue, I am writing to inquire whether you would consider contributing a communication, article, or review paper on new coating materials for constituent parts of concentrating solar power plants, treating the following topics:

  • Spectrally selective coatings for the receiver tube of solar thermodynamic plants.
  • Metamaterials and metasurfaces with spectrally selective behavior: new intrinsically absorber materials; semiconductors with tailorable bandgap; textured transition metal surfaces; metal-dielectric interferential filters; cermet-based multilayers with sharp cut-off of optical reflectance between absorptive and emissive behavior.
  • Aging of spectrally selective coating: modeling, simulation, experimental tests at the nanoscale.
  • Barrier coatings for fluids and their subproducts in thermodynamic systems.
  • Polymeric front surface solar mirrors.
  • Superhydrophobic coatings for back surface solar mirrors.
  • Self-cleaning solar mirror materials.
  • Electrodynamical coatings for dust accumulation prevention.
  • Materials for hydrogen barrier inside stainless steel receiver tubes, tanks, and other sensible parts of thermodynamic diathermic-oil-based systems.

A multidisciplinary approach will be largely promoted, and we are extending this invitation to contribute not only to field experts but also to researchers with innovative proposals.

Thank you for your kindly attention.

Dr. Anna Castaldo
Guest Editor

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 2200 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

  • Solar thermodynamics
  • Concentrating solar power
  • Heat-collecting elements
  • Spectrally selective coatings
  • Solar absorber materials
  • Optical filters
  • Thermofluids
  • Self-cleaning solar mirrors
  • Hydrogen barrier materials

Published Papers (5 papers)

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Research

Article
Assessment and Perspectives of Heat Transfer Fluids for CSP Applications
Energies 2021, 14(22), 7486; https://doi.org/10.3390/en14227486 - 09 Nov 2021
Cited by 2 | Viewed by 599
Abstract
Different fluid compositions have been considered as heat transfer fluids (HTF) for concentrating solar power (CSP) applications. In linear focusing CSP systems synthetic oils are prevalently employed; more recently, the use of molten salt mixtures in linear focusing CSP systems has been proposed [...] Read more.
Different fluid compositions have been considered as heat transfer fluids (HTF) for concentrating solar power (CSP) applications. In linear focusing CSP systems synthetic oils are prevalently employed; more recently, the use of molten salt mixtures in linear focusing CSP systems has been proposed too. This paper presents a comparative assessment of thermal oils and five four nitrate/nitrite mixtures, among the ones mostly employed or proposed so far for CSP applications. The typical medium-size CSP plant (50 MWe) operating with synthetic oil as HTF and the “solar salt” as TES was considered as a benchmark. In the first part of the paper, physical properties and operation ranges of different HTFs are reviewed; corrosion and environmental issues are highlighted too. Besides an extensive review of HTFs based on data available from the open literature, the authors report their own obtained experimental data needed to thoroughly compare different solutions. In the second part of the paper, the impact of the different HTF options on the design and operation of CSP plants are analyzed from techno-economic perspectives. Full article
(This article belongs to the Special Issue Solar Thermodynamic Materials Overview)
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Article
Thermal Properties of Shape-Stabilized Phase Change Materials Based on Porous Supports for Thermal Energy Storage
Energies 2021, 14(21), 7151; https://doi.org/10.3390/en14217151 - 01 Nov 2021
Viewed by 515
Abstract
The use of phase change materials (PCM) for thermal energy storage (TES) is of great relevance, especially for the exploitation, in various ways, of the major ecological resource offered by solar energy. Unfortunately, the transition to the liquid state of PCM requires complex [...] Read more.
The use of phase change materials (PCM) for thermal energy storage (TES) is of great relevance, especially for the exploitation, in various ways, of the major ecological resource offered by solar energy. Unfortunately, the transition to the liquid state of PCM requires complex systems and limits their application. The goal of producing shape-stabilized phase change materials (SSPCM) is mainly pursued with the use of media capable of containing PCM during solid/liquid cycles. In this work, four cheap shape stabilizers were considered: sepiolite, diatomite, palygorskite and zeolite and two molten salts as PCM, for medium (MT) and high temperature (HT). The SSPCM, produced with an energy saving method, showed good stability and thermal storage performances. Diatomite reaches up to 400% wt. of encapsulated PCM, with a shape stabilization coefficient (SSc) of 97.7%. Zeolite exhibits a SSc of 87.3% with 348% wt. of HT-PCM. Sepiolite contains 330% wt. of MT-PCM with an SSc of 82.7. Therefore, these materials show characteristics such that they can be efficiently used in thermal energy storage systems, both individually and inserted in a suitable matrix (for example a cementitious matrix). Full article
(This article belongs to the Special Issue Solar Thermodynamic Materials Overview)
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Article
Aluminium Nitride Doping for Solar Mirrors Self-Cleaning Coatings
Energies 2021, 14(20), 6668; https://doi.org/10.3390/en14206668 - 14 Oct 2021
Viewed by 522
Abstract
Soiling severely reduces solar mirror performance, requiring dispendious water consumption for cleaning operations and causing an increase in the levelized cost of energy (LCOE). An emerging technology for facing this problem consists of developing transparent self-cleaning coatings, able to be washed with a [...] Read more.
Soiling severely reduces solar mirror performance, requiring dispendious water consumption for cleaning operations and causing an increase in the levelized cost of energy (LCOE). An emerging technology for facing this problem consists of developing transparent self-cleaning coatings, able to be washed with a small amount of water by virtue of the modulation of surficial wetting properties. Nevertheless, the beneficial effects of coatings decrease in the first year, and coated mirrors show even higher soiling than non-coated ones. Moreover, it is important that coating production processes are economically convenient, consistent with the intended reduction of overall costs. The aim of this work is the research and development of a cheap and scalable solution, compatible with mirror fabrication steps and, in such a sense, economically advantageous. It involves the substitution of the alumina last layer of solar mirrors with more hydrophobic, potentially auxetic aluminum compounds, such as nitrides. In particular, 2D inorganic aluminum nitride thin films doped with metals (such as aluminum and silver) and non-metals have been fabricated by means of reactive sputtering deposition and characterized for the purpose of studying their self-cleaning behavior, finding a trade-off between wetting properties, optical clarity, and stability. Full article
(This article belongs to the Special Issue Solar Thermodynamic Materials Overview)
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Article
Solar Coatings Based on Ag Infrared Reflector with High Stability at Medium and High Temperature
Energies 2021, 14(18), 5910; https://doi.org/10.3390/en14185910 - 17 Sep 2021
Viewed by 477
Abstract
The manufacturing of thermally stable solar coatings with high photo-thermal performance represents a key factor for the further deployment of the CSP technology. Since 2005, ENEA has been developing solar coatings suitable for medium and high temperature applications based on the technology of [...] Read more.
The manufacturing of thermally stable solar coatings with high photo-thermal performance represents a key factor for the further deployment of the CSP technology. Since 2005, ENEA has been developing solar coatings suitable for medium and high temperature applications based on the technology of double nitride cermet, by employing silver and tungsten as infrared reflectors, respectively. Thanks to the high infrared reflectance of silver, the corresponding coatings have better optical performance than those with tungsten; however, the high diffusivity of silver compromises its use at high temperature. In order to improve the structural and chemical stability at medium and high temperature of coatings based on silver, this infrared reflector was placed between compact and uniform layers of metal and cermet manufactured by using high-energy and fast deposition processes. In particular, an Unbalanced Magnetron cathode was adopted to promote an ion-assisted deposition process that improved uniformity and compactness of the metal and cermet films. The new coating shows no photo-thermal parameters degradation after 25 years of service at the operating temperature of 400 °C, while its photo-thermal conversion efficiency decreases by only 1.5% after 25 years of service at an operating temperature of 514 °C. Full article
(This article belongs to the Special Issue Solar Thermodynamic Materials Overview)
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Article
High-Temperature Chloride-Carbonate Phase Change Material: Thermal Performances and Modelling of a Packed Bed Storage System for Concentrating Solar Power Plants
Energies 2021, 14(17), 5339; https://doi.org/10.3390/en14175339 - 27 Aug 2021
Cited by 2 | Viewed by 623
Abstract
Molten salts eutectics are promising candidates as phase change materials (PCMs) for thermal storage applications, especially considering the possibility to store and release heat at high temperatures. Although many compounds have been proposed for this purpose in the scientific literature, very few data [...] Read more.
Molten salts eutectics are promising candidates as phase change materials (PCMs) for thermal storage applications, especially considering the possibility to store and release heat at high temperatures. Although many compounds have been proposed for this purpose in the scientific literature, very few data are available regarding actual applications. In particular, there is a lack of information concerning thermal storage at temperatures around 600 °C, necessary for the coupling with a highly efficient Rankine cycle powered by concentrated solar power (CSP) plants. In this contest, the present work deals with a thermophysical behavior investigation of a storage heat exchanger containing a cost-effective and safe ternary eutectic, consisting of sodium chloride, potassium chloride, and sodium carbonate. This material was preliminarily and properly selected and characterized to comply with the necessary melting temperature and latent enthalpy. Then, an indirect heat exchanger was considered for the simulation, assuming aluminum capsules to confine the PCM, thus obtaining the maximum possible heat exchange surface and air at 5 bar as heat transfer fluid (HTF). The modelling was carried out setting the inlet and outlet air temperatures at, respectively, 290 °C and 550 °C, obtaining a realistic storage efficiency of around 0.6. Finally, a conservative investment cost was estimated for the storage system, demonstrating a real possible economic benefit in using these types of materials and heat exchange geometries, with the results varying, according to possible manufacturing prices, in a range from 25 to 40 EUR/kWh. Full article
(This article belongs to the Special Issue Solar Thermodynamic Materials Overview)
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