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Advances in Solar Thermal Collectors and Systems: Technological, Efficiency, Energy Storage and Applications

A special issue of Sustainability (ISSN 2071-1050). This special issue belongs to the section "Energy Sustainability".

Deadline for manuscript submissions: 30 June 2024 | Viewed by 7183

Special Issue Editors


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Guest Editor
Mechanical Engineering Department, National Technical University of Athens, 15772 Athens, Greece
Interests: design; simulation; optimization; heat transfer; solar thermal systems; energy saving; energy conservation; hybrid solar collectors (PVT); innovative solar collectors; linear cavity evacuated tube receivers; asymmetrical compound parabolic collectors (ACPCs); evacuated tube collectors (ETCs); parabolic trough collectors (PTCs); flat plate collectors (FPCs); phase change materials (PCMs); nanofluids

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Guest Editor
Thermal Department, School of Mechanical Engineering, National Technical University of Athens, Heroon Polytehniou 9, Zografou, 15773 Athens, Greece
Interests: thermal comfort; solar thermal energy; energy saving; energy conservation; energy efficiency in building; building simulation; green building; energy modeling; renewable energy technologies; energy engineering; solar cooling; thermal engineering; energy conversion; renewable energy and environment protection; energy management; solar radiation; refrigeration & air conditioning; bioclimatic architecture; building technology; green architecture; energy efficiency; building materials; building physics; engineering thermodynamics

Special Issue Information

Dear Colleagues,

It is great pleasure to announce a new Special Issue of Sustainability entitled: Advances in Solar Thermal Collectors and Systems: Technological, Efficiency, Energy Storage and Applications.

In an attempt to lower both carbon emissions and the cost of energy, there is a vital need of substituting conventional energy sources (fossil fuels, etc.) with renewable ones. This need increases every year and sets solar thermal systems utilization in the foreground of our century. There is a great variety of applications which could be supported by Solar Thermal Technology. Some of these are domestic hot water applications, industrial applications, solar cooling, dehumidification, oil recovery, desalination and high-scaled power plants for electricity production.

Given the wide range of applications that could be served by solar energy and the increasing need for renewable energy sources, experts and researchers in solar thermal collectors and systems have to be in continuous vigilance for finding novel and innovative solutions that ensure high performances, low carbon emissions and sustainability.

The present Special Issue (SI) is dedicated to the investigation of Solar Thermal Collectors and Systems in terms of performance (thermal and optical), applications, energy storage and technological advances. This SI will open new gates in the field of Solar Thermal Systems, by giving the opportunity to researchers to propose novel methods, theories and systems considering the environmental impact and the need for long-term sustainability.

In this Special Issue, original research articles and reviews are welcome. Research areas may include (but are not limited to) the following:

  • Thermal and optical analysis of Solar Thermal Collectors
  • Solar Thermal Collectors applications
  • Energy storage in Solar Thermal Systems
  • Solar Cogeneration Technology
  • Enhancement technics in Solar Thermal Collectors
  • Simulation of Solar Thermal Collectors and Systems
  • Experimental investigation of Solar Thermal Collectors
  • Concentrating Solar Thermal Collectors
  • Asymmetric Compound Parabolic Collectors
  • Solar receiver optimization
  • PVT hybrid solar collectors

I look forward to receiving your contributions. 

Dr. Dimitrios N. Korres
Prof. Dr. Christos Tzivanidis
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. Sustainability 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 2400 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 thermal systems
  • energy storage
  • cogeneration
  • concentrating solar collectors
  • asymmetric reflector
  • PV thermal
  • thermal analysis
  • optical analysis
  • performance enhancement
  • computational fluid dynamics

Published Papers (5 papers)

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Research

26 pages, 10894 KiB  
Article
Thermal Performance Analysis of Porous Foam-Assisted Flat-Plate Solar Collectors with Nanofluids
by Xinwei Lin, Yongfang Xia, Zude Cheng, Xianshuang Liu, Yingmei Fu, Lingyun Li and Wenqin Zhou
Sustainability 2024, 16(2), 693; https://doi.org/10.3390/su16020693 - 12 Jan 2024
Viewed by 723
Abstract
This study proposed a model of a porous media-assisted flat-plate solar collector (FPSC) using nanofluid flow. The heightened thermal efficiency of FPSC undergoes numerical scrutiny, incorporating various factors for analysis, including aspects like the configuration of the porous block introduced, Darcy number ( [...] Read more.
This study proposed a model of a porous media-assisted flat-plate solar collector (FPSC) using nanofluid flow. The heightened thermal efficiency of FPSC undergoes numerical scrutiny, incorporating various factors for analysis, including aspects like the configuration of the porous block introduced, Darcy number (Da = 10−5~10−2), types of nanoparticles, volume fraction (φ), and mixing ratio (φc). The numerical findings indicate that the dominant factor in the channel is the global Nusselt number (Nug). As the Darcy number rises, there is an improvement in the heat transfer performance within the channel. Simultaneously, for the case of Re = 234, φ = 3%, and φc = 100%, the Nug in the channel reaches a maximum value of 6.80, and the thermal efficiency can be increased to 70.5% with the insertion of rectangular porous blocks of Da = 10−2. Finally, the performance evaluation criteria (PEC) are employed for a comprehensive assessment of the thermal performance of FPSC. This analysis considers both the improved heat transfer and the pressure drop in the collector channel. The FPSC registered a maximum PEC value of 1.8 when rectangular porous blocks were inserted under conditions of Da = 10−2 and Re = 234 and the nanofluid concentrations of φ = 3% and φc = 100%. The findings can be provided to technically support the future commercial applications of FPSC. The findings may serve as a technical foundation for FPSC in upcoming porous media and support commercial applications. Full article
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36 pages, 10035 KiB  
Article
Dynamic Energy Analysis of Different Heat Pump Heating Systems Exploiting Renewable Energy Sources
by Angeliki Kitsopoulou, Antonis Zacharis, Nikolaos Ziozas, Evangelos Bellos, Petros Iliadis, Ioannis Lampropoulos, Eleni Chatzigeorgiou, Komninos Angelakoglou and Nikolaos Nikolopoulos
Sustainability 2023, 15(14), 11054; https://doi.org/10.3390/su151411054 - 14 Jul 2023
Cited by 5 | Viewed by 1430
Abstract
Renewable energy source-fed heat pumps (HPs) may perform up to very high-efficiency standards, offering a promising tool in the wider residential heat decarbonization effort. In this context, this paper investigates different heating configurations utilizing various renewable thermal sources in conjunction with an HP-based [...] Read more.
Renewable energy source-fed heat pumps (HPs) may perform up to very high-efficiency standards, offering a promising tool in the wider residential heat decarbonization effort. In this context, this paper investigates different heating configurations utilizing various renewable thermal sources in conjunction with an HP-based system in order to determine the optimal configuration in terms of efficiency, using an existing, fully functioning residential building in Zaragoza, Spain, as our case study, comprising 40 dwellings. Four different HP configurations are investigated:, (i) an air-source system, (ii) a ground-source system, (iii) a dual-source system with solar thermal collectors, and (iv) a triple-source system based on solar, geothermal, and ambient sources. For the purpose of such investigation, detailed dynamic energy simulations are conducted through the use of the INTEMA.building tool (developed in Modelica), applying a multi-objective optimization process that aims at minimizing both the annual electricity consumption and the net present cost. It is demonstrated that the renewable thermally driven HPs are more efficient than the conventional, air-source ones, with the seasonal coefficient of performance increasing by 9.98% (ground source), 4.57% (dual source), and 17.40% (triple source), compared to the air-source heat pump system. Finally, it is revealed (via integrated techno-economic analyses) that the most effective and economical design is the dual source system, while the most expensive is the ground-source configuration. These findings can guide the ongoing design efforts on green residential heat solutions at both research and commercial implementation level. Full article
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22 pages, 5204 KiB  
Article
Thermal and Optical Analyses of a Hybrid Solar Photovoltaic/Thermal (PV/T) Collector with Asymmetric Reflector: Numerical Modeling and Validation with Experimental Results
by Dimitrios N. Korres, Theodoros Papingiotis, Irene Koronaki and Christos Tzivanidis
Sustainability 2023, 15(13), 9932; https://doi.org/10.3390/su15139932 - 21 Jun 2023
Cited by 3 | Viewed by 1334
Abstract
This study presents a combined thermal and optical, three-dimensional analysis of an asymmetric compound parabolic collector (ACPC) with an integrated hybrid photovoltaic/thermal (PV/T) receiver with the aim of establishing a sustainable approach in two ways: firstly, by determining the optimal tilt angle for [...] Read more.
This study presents a combined thermal and optical, three-dimensional analysis of an asymmetric compound parabolic collector (ACPC) with an integrated hybrid photovoltaic/thermal (PV/T) receiver with the aim of establishing a sustainable approach in two ways: firstly, by determining the optimal tilt angle for operations, and secondly, by introducing an innovative simulation method which reduces computational cost while calculating thermal performance. Initially the Incident Angle Modifier (IAM) was calculated for a wide range of incident angles, and the ray-tracing results were verified using three different simulation tools (Tonatiuh, COMSOL, and SolidWorks) with mean deviations being lower than 4%. The optimal tilt angle of the collector was determined for seven months of the year by conducting a detailed ray-tracing analysis for the mean day of each month considering whole day operation. In the thermal analysis part, the authors introduced novel numerical modeling for numerical simulations. This modeling method, designed with sustainability in mind, enables lighter computational domains for the air gap while achieving accurate numerical results. The approach was established using two distinct simulation tools: COMSOL and SolidWorks. From the optical analysis, it was found that in all months examined there is a four-hour time range around solar noon in which the optimum tilt angle remains constant at a value of 30°. The numerical models constructed for the thermal analysis were verified with each other (6.15% mean deviation) and validated through experimental results taken from the literature regarding the examined collector (<6% mean deviation). In addition, the two simulation tools exhibited a deviation of around 6% between each other. Finally, the thermal performance of the collector was investigated for the mean day of September at solar noon by adopting the optimal tilt angle for that month according to the optical analysis, considering inlet temperatures from 20 °C up to 80 °C. Full article
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17 pages, 4561 KiB  
Article
Experimental Study of Simultaneous Charging and Discharging Process in Thermocline Phase Change Heat Storage System Based on Solar Energy
by Xinming Xi, Zicheng Zhang, Huimin Wei, Zeyu Chen and Xiaoze Du
Sustainability 2023, 15(9), 7322; https://doi.org/10.3390/su15097322 - 28 Apr 2023
Viewed by 1428
Abstract
As a renewable energy power generation method, concentrating solar power generation has a broad application prospect. Weather and fluctuation significantly affect the output power of concentrating solar power generation. A heat storage system can stabilize this fluctuation and generate continuous and stable power. [...] Read more.
As a renewable energy power generation method, concentrating solar power generation has a broad application prospect. Weather and fluctuation significantly affect the output power of concentrating solar power generation. A heat storage system can stabilize this fluctuation and generate continuous and stable power. Therefore, the research on heat storage systems is of great significance to the development of concentrating solar power generation. This paper mainly studies the operating characteristics of the heat storage system based on solar energy in simultaneous charging, the influence in the change in solar radiation intensity on the charging power and the discharging outlet temperature, and the feasibility of the heat storage tank as an inertial link to stabilize the fluctuation in solar energy and the discharging outlet temperature. In this study, an experimental system for heat storage was established, in which solar energy was used as the heat source, water was used as the heat transfer fluid, and paraffin was used as the phase change heat storage material. When the initial temperature is 50 °C and the charging flow rate is maintained at 0.7 m3/h, at the same time the discharging flow rate is 0.1 m3/h, 0.3 m3/h, and 0.5 m3/h, respectively. The results show that when the solar radiation intensity is lower than 548 W/m2, the curve of heat storage power is almost parallel to the curve of solar radiation intensity; when the solar radiation intensity is lower than 535 W/m2, the moving direction of the thermocline will change; the average discharging outlet temperature in each case is higher than the phase change temperature of the phase change material and this system can continuously supply hot water at more than 69 °C for more than 3 h 32 min; and increasing the discharging flow rate will increase the whole charging and discharging time, thicken the thermocline, and disturb the temperature field in the tank. The experimental analysis will be conducive to profoundly understanding the operation characteristics of the thermocline heat storage tank under the solar heat source and has reference value for the subsequent design of a more efficient heat storage system. Full article
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17 pages, 3801 KiB  
Article
Investigation of a Compound Parabolic Collector with a Flat Glazing
by Evangelos Bellos, Dimitrios N. Korres and Christos Tzivanidis
Sustainability 2023, 15(5), 4347; https://doi.org/10.3390/su15054347 - 28 Feb 2023
Cited by 6 | Viewed by 1542
Abstract
The compound parabolic concentrator is a promising technology for efficient solar irradiation exploitation at low- and medium-temperature levels. This collector type can be used in a series of applications, such as solar cooling, desalination, and industrial process heat applications. This work presents a [...] Read more.
The compound parabolic concentrator is a promising technology for efficient solar irradiation exploitation at low- and medium-temperature levels. This collector type can be used in a series of applications, such as solar cooling, desalination, and industrial process heat applications. This work presents a novel compound parabolic concentrator that presents satisfying efficiency and low cost due to the use of flat glazing and not an evacuated tube receiver. More specifically, the goal of the present investigation is based on the energy and exergy analysis of a compound parabolic collector with flat glazing, which has a concentration ratio of 2.81. The collector is examined thermally and exegetically, aiming to calculate the efficiency of different operating inlet temperatures. Moreover, the solar unit is studied by a developed computational fluid dynamics model in the SolidWorks Flow Simulation tool. Emphasis is given to the calculation of the convection losses of the receiver tube with the internal air inside the collector. The heat convection coefficient is calculated, and the distribution of the thermal losses, convection, and radiation is presented. Furthermore, the temperature levels of the absorber, the cover glass, and the top thermal loss coefficient are found. The thermal efficiency of the solar unit was 77.4% for inlet temperature at 10 °C and 32.6% for inlet temperature at 110 °C. It was calculated that the maximum exergetic performance of the solar unit is 10.19% for operation at 90 °C, while the thermal efficiency for this case is 41.57%. Additionally, the temperature distributions for different cases are included in the present work. Full article
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