SwePub - search: WFRF:(Gomes João 1979 )

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1.	Cabral, Diogo, et al. (author) Electrical and thermal performance evaluation of a district heating system composed of asymmetric low concentration PVT solar collector prototypes 2018 In: PROCEEDINGS OF THE ISES EUROSUN 2018 CONFERENCE - 12TH INTERNATIONAL CONFERENCE ON SOLAR ENERGY FOR BUILDINGS AND INDUSTRY. - Freiburg, Germany : INTL SOLAR ENERGY SOC. ; , s. 755-763 Conference paper (peer-reviewed)abstract Photovoltaic-Thermal (PVT) solar collectors generate electricity and heat from the same gross area. The annual electrical and thermal yields of these systems are dependent on the PVT collector technology, as well as the climate and the type of solar thermal system implemented. This review presents an evaluation of a district heating system composed of 20 asymmetric hybrid low concentrator PVT (C-PVT) solar collector prototypes. The system is installed in a South wall facade in order to maximise the available space (with a tilt of 20 degrees and an orientation of 5 degrees W). The thermal system is connected to the district heating network, thus heating the University buildings. On the other hand, the electrical system is grid-connected, where it feeds the grid directly. Real measurement data has been collected and compared with a thermal (through ScenoCalc tool) and electrical performance models. The annual thermal and electrical yield achieved 86% and 89% of the simulated thermal and electrical yield, respectively.
2.	Costeira, João, et al. (author) Development of a compact and didactic solar energy kit using Arduino 2018 In: PROCEEDINGS OF THE ISES EUROSUN 2018 CONFERENCE - 12TH INTERNATIONAL CONFERENCE ON SOLAR ENERGY FOR BUILDINGS AND INDUSTRY. - Freiburg, Germany : INTL SOLAR ENERGY SOC. ; , s. 1663-1667 Conference paper (peer-reviewed)abstract When the sun rises, so does the key element that will shape the future of the world energy landscape. It is not an understatement to say that the solar energy industry is beginning to lead the path towards a sustainable future for all of us. However, the awareness of the potential of this amazing source of energy must begin from the most basic levels of education all the way to university. The scope of this paper is to display a new compact and didactic solar energy kit with the potential to replace current high cost and complex solar energy kits. These solutions are often too expensive and therefore unavailable for most of Europe’s public schools. As such, an equipment was developed using an open-source platform called Arduino that will enable students to conduct practical experiments in a fast, effective and simple manner and thus allow students to acquire the proper expertise in areas like energy, electronics, and programming.
3.	Furbo, Simon, et al. (author) Best Practices for PVT Technology 2021 In: SWC2021 Proceedings. - Freiburg, Germany : ISES. Conference paper (peer-reviewed)abstract The PVT technology combines solar PV and solar thermal in the same PVT panel. In this way, both electricity and heat are produced by the PVT panel. Compared to the PV technology and the solar heating technology the PVT technology is in the early market stage with only few small and weak industries active. Best practices for the PVT technology, which is still under rapid development, are summarized. Marketed systems with different PVT panel types, different PVT system types with different components for different applications are considered. The potential advantages for PVT systems and the needs for key actors in order to establish a successful sustainable future PVT market are given. Finally, recommendations for a subsidy scheme for PVT systems are given, so that a PVT market can be developed in parallel with the successful PV market.
4.	Torres, João Paulo N., et al. (author) Effect of reflector geometry in the annual received radiation of low concentration photovoltaic systems 2018 In: Energies. - : MDPI AG. - 1996-1073. ; 11:7 Journal article (peer-reviewed)abstract Solar concentrator photovoltaic collectors are able to deliver energy at higher temperatures for the same irradiances, since they are related to smaller areas for which heat losses occur. However, to ensure the system reliability, adequate collector geometry and appropriate choice of the materials used in these systems will be crucial. The present work focuses on the re-design of the Concentrating Photovoltaic system (C-PV) collector reflector presently manufactured by the company Solarus, together with an analysis based on the annual assessment of the solar irradiance in the collector. An open-source ray tracing code (Soltrace) is used to accomplish the modelling of optical systems in concentrating solar power applications. Symmetric parabolic reflector configurations are seen to improve the PV system performance when compared to the conventional structures currently used by Solarus. The parabolic geometries, using either symmetrically or asymmetrically placed receivers inside the collector, accomplished both the performance and cost-effectiveness goals: for almost the same area or costs, the new proposals for the PV system may be in some cases 70% more effective as far as energy output is concerned.
5.	Afzali Gorouh, Hossein, et al. (author) Thermal modelling and experimental evaluation of a novel concentrating photovoltaic thermal collector (CPVT) with parabolic concentrator 2022 In: Renewable energy. - : Elsevier. - 0960-1481 .- 1879-0682. ; 181, s. 535-553 Journal article (peer-reviewed)abstract In the present study, a zero-dimensional thermal model has been developed to analyze a novel low concentration photovoltaic-thermal (CPVT) collector. The model has been developed by driving heat transfer and energy balance equations for each part of the collector and then solving all the equations simultaneously. Moreover, a Monte-Carlo ray-tracing software has been used for optical stimulations of the parabolic trough solar collector. The novel CPVT collector has been experimentally tested at Gävle University (Sweden) and the model has been validated against the experimental results. The primary energy saving equivalent to the thermal-electrical power cogeneration of the CPVT collector has been determined. The effect of glass cover removal, heat transfer fluid (HTF) inlet temperature and mass flow rate on the collector performance has been investigated. The optimum HTF mass flow rates of the collector for maximum electrical yield and overall primary energy saving were determined under specified operating conditions by considering the pump consumption. The effect of mean fluid temperature on the thermal and electrical efficiencies has been studied and the characteristic equation of the thermal efficiency has been obtained. The thermal and electrical peak efficiencies of the collector have been found to be 69.6% and 6.1%, respectively.
6.	Cabral, Diogo, PhD, 1990-, et al. (author) Experimental Electrical Assessment Evaluation of a Vertical n-PERT Half-Size Bifacial Solar Cell String Receiver on a Parabolic Trough Solar Collector 2023 In: Energies. - : MDPI. - 1996-1073. ; 16:4 Journal article (peer-reviewed)abstract A two-trough parabolic-shaped concentrating photovoltaic solar collector with a vertical half-size ‘phosphorus-passivated emitter rear totally diffused’ bifacial cell string receiver was designed and built for household applications, with the aim of smooth the electrical ‘duck curve’. The study consisted in testing the concentrating photovoltaic solar collector outdoors, under real weather conditions, for its daily electrical peak power and efficiency, as well as for its electrical transversal and longitudinal Incidence Angle Modifier direction. The outdoor testing measurements were conducted in a parabolic trough with low concentration coupled with a central vertical half-size ‘phosphorus-passivated emitter rear totally diffused’ bifacial cell string receiver. Furthermore, the electrical transversal Incidence Angle Modifier showed to be very delicate due to the position and outline of the receiver, which led to an electrical peak efficiency close to 10% at ±25° (i.e., for an electrical power output of around 49.3 W/m2). To validate the measured parameters, a ray-tracing software has been used, where the measured Incidence Angle Modifiers have a very good agreement with the simulated Incidence Angle Modifiers (e.g., deviation of <4%). Consequently, the concentrating solar collector met the objective of lowering the Photovoltaic cell stress and high radiation intensity, by shifting the electrical peak power at normal (e.g., at 0°) to higher incidence angles (e.g., ±25°); this aids the electrical demand peak shaving, by having the highest electrical power production displaced from the highest intensity solar radiation during the day.
7.	Cabral, Diogo, et al. (author) Experimental investigation of a CPVT collector coupled with a wedge PVT receiver 2021 In: Solar Energy. - : Elsevier. - 0038-092X .- 1471-1257. ; 215, s. 335-345 Journal article (peer-reviewed)abstract This paper presents an experimental investigation of a photovoltaic-thermal solar collector (commonly known as PVT) that generates both electricity and heat from the same gross area. PVT solar collectors, in theory, achieve higher combined electrical and heat yields. Additionally, PVT enables a thermal coupling between PV cells and a heat transfer cooling medium. Electrical and thermal outdoor testing measurements have been performed on alow concentration PVT solar collector based on a parabolic reflector geometry with a wedge PVT receiver. Several outdoor experiments have been carried out and presented, such as daily instantaneous electrical and thermal performance efficiency diagrams, as well as optical efficiency charts. Moreover, an electrical IncidenceAngle Modifier (for both transversal and longitudinal directions) assessment has been performed and presented. Furthermore, an overall heat loss coefficient of 4.1 W/m2.◦C has been attained. A measured thermal optical and electrical efficiency of 59% and 8% have been achieved, respectively. Additionally, the placement of the wedge receiver shown to be very sensitive to high incidence angles, as the electrical transversal Incidence AngleModifier factor decreases significantly after reaching its electrical peak efficiency at 10◦.
8.	Cabral, Diogo, et al. (author) Performance Evaluation of Non-Uniform Illumination on a Transverse Bifacial PVT Receiver in Combination with a CPC Geometry 2019 In: Solar Energy. - : Elsevier BV. - 0038-092X .- 1471-1257. ; 194, s. 696-708 Journal article (peer-reviewed)abstract PVT collectors co-generate electricity and heat from the same gross area, thus achieving higher combined heat and electric yields. A comprehensive evaluation has been carried out on non-uniform solar irradiation profile distributions on four symmetric low concentration CPC PVT (LCPVT) solar collector design concepts. Additionally, an electrical and thermal performance evaluation of symmetric truncated LCPVT solar collectors based on a CPC reflector geometry with a central transverse bifacial PVT receiver has been carried out, through a numerical ray-tracing model software and a multi-paradigm numerical computing environment software. A simplified thermal (quasi-dynamic testing method for liquid heating collectors described in the international standard for solar thermal collectors ISO 9806:2017) and electrical performance models were employed to evaluate the LCPVT design concepts. The evaluation was carried out for heating Domestic Hot Water (DHW) for a Single Family House (SFH) in Fayoum (Egypt), where energy yields between 351 and 391 kWh/m2/year have been achieved. The non-uniform solar irradiation assessment showed that the PV cells are exposed to high levels of radiation due to the specific reflector geometry. Furthermore, the study showed that the CPC geometries are very sensitive to the shading effect, as partial shadowing is substantial for high incidence angles.
9.	Cabral, Diogo, et al. (author) Ray tracing simulations of a novel low concentrator PVT solar collector for low latitudes 2017 In: ISES Solar World Congress 2017 - IEA SHC International Conference on Solar Heating and Cooling for Buildings and Industry 2017, Proceedings. - Freiburg, Germany : International Solar Energy Society. - 9783981465976 ; , s. 1068-1079 Conference paper (peer-reviewed)abstract One way to reduce solar collector's production costs is to use concentrators that increase the output per photovoltaic cell. Concentrating collectors re-direct solar radiation that passes through an aperture into an absorber. The current study evaluates electrical performance of symmetric C-PVT solar collectors with a vertical bifacial receiver, through a numerical ray tracing model software, Tonatiuh. Several designs have been analysed, such as the Pure Parabola (PP) and MaReCo CPC geometries, both symmetric. Parameters such as concentration factor, electrical performance, transversal and longitudinal IAM (Incidence Angle Modifier), the influence of optical elements and influence of the length of the reflector in the shadow effect have been studied for different geometries. The simulations were performed for Mogadishu, Somalia and showed good results for the Pure Parabola collector (PPc) annual received energy, 379 and 317 kWh/m2/year for a focal length of 15 e 30 mm, respectively. A symmetrical double MaReCo CPC collector has been simulated with the annual received energy of 315 kWh/m2/year. The addition of the optical elements will decrease the annual received energy of the PPc by around 11.5%, where the optical properties (7.1%) and glass (4.1%) have the biggest impact in the annual received energy. Overall, symmetric geometries proved to be the most suitable geometries for low latitudes applications, being the geometry f1 (focal length of 15 mm) the best one.
10.	Chacin, Luís, et al. (author) Impact study of operating temperatures and cell layout under different concentration factors in a CPC-PV solar collector in combination with a vertical glass receiver composed by bifacial cells 2019 In: Proceedings of the ISES Solar World Conference 2019 and the IEA SHC Solar Heating and Cooling Conference for Buildings and Industry 2019. - Freiburg, Germany : International Solar Energy Society. - 9783982040813 ; , s. 836-847 Conference paper (peer-reviewed)abstract Solar Collectors with Compound Parabolic Concentrator (CPC) reflectors redirect solar irradiance into the receiver (placed in optimal position). The concept of such devices is to reduce the installation area and energy costs [1]. This research focuses on the behaviour and efficiency of a stationary CPC-PV solar collector. Each trough of this collector has different concentration factors (1.25 and 1.66) with vertically placed bi-facial cell receivers. An analysis of the electrical efficiency is performed in order to evaluate the viability of a CPC geometry with a vertical bifacial PV receiver. Furthermore, an investigation on bifacial cells performance due to concentration (and consequently increased cell temperature) is carried out. A numerical simulation of the yearly available radiation and the Incident Angle Modifiers (IAM) for each geometry is also conducted. Finally, a comparison between the simulations and the outdoor testing on the prototype collector is detailed. The tests took place in Gävle, Sweden (61º Latitude). The results showed that higher concentration factors led to larger operating temperatures (114ºC for a concentration factor of 1.66 and 96ºC for a concentration factor of 1.25). Although this may compromise the cell performance and shorten the device’s life cycle, it is shown that appropriate ventilation will allow manageable operating temperatures.
11.	Contero, Francisco, et al. (author) The impact of shading in the performance of three different solar PV systems 2016 Conference paper (peer-reviewed)
12.	Francisco Contero, Jose, et al. (author) The impact of shading in the performance of three different solar PV systems 2017 In: PROCEEDINGS OF THE 11TH ISES EUROSUN 2016 CONFERENCE. - Freiburg, Germany : INTL SOLAR ENERGY SOC. ; , s. 1168-1179 Conference paper (peer-reviewed)abstract Partial shading decreases the performance of PV modules due to the series connection between the solar cells. In the recent years, several new technologies have emerged within the photovoltaics field to mitigate the effect of shading in the performance of the PV modules. For an accurate assessment of the performance of these devices, it is required to evaluate them comparatively in different circumstances. Three systems with six series-connected PV modules (each containing 60 cells) have been installed at the University of Gavle. System One comprises a string inverter system with 6 PV modules; System Two features a DC-DC optimizer per panel and a string inverter; System Three incorporates three micro inverters for six modules. A major conclusion of this study was that under partial shading of one (or more) modules both System Two (DC-DC optimizers) and System Three (micro inverters) perform considerably better than System One (string inverter), as long as the Impp of the shadowed module is lower than the Impp of the unshaded string It is also important that the Vmpp in the shaded module is higher than the lowest allowed voltage of the DC-DC optimizer or module inverter. The economic implications of the usage of these devices were also analyzed.
13.	Gallardo, Felipe, et al. (author) Exergoeconomic comparison of conventional molten salts versus calcium based ternary salt as direct HTF-TES in CSP parabolic troughs collectors 2019 In: Proceedings of the ISES Solar World Congress 2019 and IEA SHC International Conference on Solar Heating and Cooling for Buildings and Industry 2019. - Freiburg, Germany : International Solar Energy Society. - 9783982040813 ; , s. 1150-1157 Conference paper (peer-reviewed)abstract This paper presents an exergo-economic comparison of a Concentrated Solar Power (CSP) Parabolic Trough Collectors (PTC) loop using two alternative types of molten salts as direct Heat Transfer Fluid (HTF) and Thermal Energy Storage (TES) based on operational simulations. The plant size and configuration are inspired in the PTC loop with molten salts HTF and TES currently under deployment at University of Evora in Portugal while the molten salts assessed are conventional molten salt (Solar Salt) and a Calcium based ternary salt. The objective of this study is to establish a comparison of exergetic performance and cost contribution per component in the plant for the two types of HTF. The applied methodology allows to identify the suitability of use for the studied salts, to detect challenges in terms of cost and performance at component level and to identify the cost composition of the CSP electricity as final product, according to the exergetic efficiency, investment and operational cost per component for each case.
14.	Gomes, João, 1979- (author) Assessment of the impact of stagnation temperatures in receiver prototypes of C-PVT collectors 2019 In: Energies. - : MDPI AG. - 1996-1073. ; 12:15, s. 2967-2967 Journal article (peer-reviewed)abstract Concentrating Photovoltaic Thermal (C-PVT) solar collectors produce both thermal and electric power from the same area while concentrating sunlight. This paper studies a C-PVT design where strings of series-connected solar cells are encapsulated with silicone in an aluminium receiver, inside of which the heat transfer fluid flows, and presents an evaluation on structural integrity and performance, after reaching stagnation temperatures. Eight test receivers were made, in which the following properties were varied: Size of the PV cells, type of silicone used to encapsulate the cells, existence of a strain relief between the cells, size of the gap between cells, and type of cell soldering (line or point). The test receivers were placed eight times in an oven for one hour at eight different monitored temperatures. The temperature of the last round was set at 220 °C, which exceeds the highest temperature the panel design reaches. Before and after each round in the oven, the following tests were conducted to the receivers: Electroluminescence (EL) test, IV-curve tracing, diode function, and visual inspection. The test results showed that the receivers made with the transparent silicone and strain relief between cells experienced less microcracks and lower power degradation. No prototype test receiver lost more than 30% of its initial power, despite some receivers displaying a large number of cell cracks. The transparent and more elastic silicone is better at protecting the solar cells from the mechanical stress of thermal expansion than the compared silicone alternative, which was stiffer. As expected, larger cells are more prone to develop microcracks after exposure to thermal stress. Additionally, existing microcracks tend to grow in size relatively fast under thermal stress. EL imaging taken during our experiment leads us to conclude that it is far more likely for existing cracks to expand than for new cracks to appear. [ABSTRACT FROM AUTHOR]
15.	Gomes, João, 1979-, et al. (author) Defining an Annual Energy Output Ratio between Solar Thermal Collectors and Photovoltaic Modules 2022 In: Energies. - : MDPI. - 1996-1073. ; 15:15 Journal article (peer-reviewed)abstract Photovoltaics (PV) and Solar Thermal (ST) collectors are sometimes competitors, as investment capacity, energy demand, and roof space are limited. Therefore, a ratio that quantifies the difference in annual energy output between ST and PV for different locations is useful. A market survey assessing the average price and performance both in 2013 and 2021 was conducted, showing a factor of 3 cell price decrease combined with a 20% efficiency increase, while ST showed negligible variation. Winsun simulations were conducted, and the results were plotted on the world map. Despite variations due to local climate, the ratio of energy production (ST/PV) increases at lower latitudes mainly due to (a) higher air temperature increasing ST output but decreasing the PV output; (b) solar radiation reducing ST efficiency to zero while having a minor impact on PV efficiency. The ratio was calculated for several ST operating temperatures. For latitudes lower than 66 degrees, the ratio of a flat plate at 50 degrees C to a PV module ranges from 1.85 to 4.46, while the ratio between a vacuum tube at 50 degrees C and a PV module ranges from 3.05 to 4.76. This ratio can support the decision between installing ST or PV while combining different factors such as energy value, system complexity, and installation cost.
16.	Gomes, João, 1979- (author) Development of Concentrating Photovoltaic-Thermal Solar Collectors 2021 Doctoral thesis (other academic/artistic)abstract Fossil fuels have greatly improved human living standards and saved countless lives. However, today, their continued use threatens human survival, as CO2 levels rise at an unprecedented pace to levels never seen during human existenceon earth.This thesis aims at gathering knowledge on solar energy in general and photovoltaic thermal (PVT) and concentrating photovoltaic thermal (C-PVT) in particular. This thesis establishes several key research questions for PVTs and C-PVT collectors and attempts to answer them.A comprehensive market study of solar thermal (ST), photovoltaic (PV) and PVT was conducted to obtain prices and performance. Simulations of the energy output around the world were conducted. A ratio between ST and PV annual output was defined to serve as a tool for comparison and plotted on a world map.A key issue for PVT collectors is how to encapsulate the solar cells in a way that, amongst other things, protects the cell from the thermal expansion of the receiver, has a high transparency, and insulates electrically while at the same time conducts the heat to the receiver. In order to be useful, this analysis must also consider the impacts on the production processes. Several prototypes were constructed, a test methodology was created, and the analysis of the results enabled several conclusions on the validity of the different silicon encapsulations methods.This thesis relies heavily on collector testing with 30 different prototypes of C-PVTs being designed and constructed. Most testing was conducted using steady state method but quasi dynamic was also carried out. From this work, several guidelines were created for the design of collectors in terms of reflector geometry, cell size, string configuration, encapsulation method and several other design aspects. These analyses were complemented with thermal simulations (COMSOL & ANSYS), string layout (LT SPICE) and evaluation of existing installations. Two novel design ideas came from this thesis work, which the author will patent in the coming year. Additionally, raytracing work has been conducted and a new reflector geometry more appropriate for C-PVTs has been found to significantly improve the annual performance. Finally, the current and future position of PVTs in the global energy market is discussed.
17.	Gomes, João, 1979-, et al. (author) Minimizing the impact of shading at oblique solar angles in a fully enclosed asymmetric concentrating PVT collector 2014 In: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 57, s. 2176-2185 Journal article (peer-reviewed)abstract PVT collectors produce both electricity and heat from the same area. PVT collectors with low concentration factor allow both stationary and tracking configurations. For stationary or single axis tracking, the daily variation in the solar incidence angle can cause significant shading in concentrating collectors. Shading has a larger impact on PV than on thermal collectors and thus the evaluations was more focused on the electrical part. Several prototype versions of a novel design for a concentrating asymmetric PVT collector have been tested and compared. One tested improvement was replacing the reflective end gables with transparent end gables. Another improvement was to use different cell sizes. These actions were expected to minimize the impact of the shading at oblique solar incidence angles. The second action was found to be more beneficial than the first. Measurements were also performed in the solar simulator to fully understand the impact of shading in cell strings with 1/6 the size of standard cells. The latest version of the PVT was found to have, at 25 °C and 1000w/m2, a collector efficiency of 13,7%, a cell area efficiency of 20,3% and an electrical power output of 237W. Lower side of the receiver was producing 58% of the total power.
18.	Hosouli, Sahand, et al. (author) Evaluation of a solar photovoltaic thermal (PVT) system in a dairy farm in Germany 2023 In: Solar Energy Advances. - : Elsevier. - 2667-1131. ; 3 Journal article (peer-reviewed)abstract Livestock farms are a major contributor to CO2 emissions. The use of renewable energy sources (RES) is an important step to mitigate emissions from farms. This paper develops and evaluates a market-integrated, cost-effective, and case-sensitive RES solution for livestock farms. For this purpose, the dairy farm at LVAT-ATB in Germany; which includes three barns for milk production with a total area of 3950 m2, was considered. A solar PVT system is designed to most effectively use the heat recovery of the milk coolers and to use the thermal heat from the PVT system to lift the inlet temperature of an electric boiler (E-boiler) and reduce grid electricity consumption. The performance and monthly thermal output of the designed PVT system are evaluated using two different PVT collectors; Solarus (concentrated) and Dual Sun (flat plate). A preliminary analysis was performed to determine the PVT collector most suitable for the livestock farm here studied. The DualSun collector generated a higher electricity output than the Solarus C-PVT, however, the C-PVT was able to reach higher temperatures. Since the LVAT-ATB farm site included an existing heat recovery system, the integration point was carefully defined and a semi-automated system was incorporated to (1) use the heat from the heat recovery system as the inlet heat for the PVT system and (2), to use the PVT buffer tank as additional storage to store excess heat from the heat recovery system. Using this approach, a maximum amount of thermal energy can be stored. The PVT system would further raise the temperature from the heat recovery system and thus minimize the electricity consumption of the E-boiler. Furthermore, a draft layout of all the components and outdoor enclosure was presented. 24 Solarus PVT collectors running at mean temperature of 45 °C meet 16% of the annual hot water demand of the dairy farm by direct solar heat and this number of PVTs can supply up to 38% of hot water demand in summer months. The payback period for this system is less than 6 years and annual electrical energy utilization ratio and highest solar thermal fraction are 9.7 and 51.9%, respectively. Furthermore, 24 PVTs on an annual basis, generate slightly more than 4,200 kWh of electricity that can be used to offset electricity consumed by electric boilers in the LVAT farm.
19.	Hosouli, Sahand, et al. (author) Mitigating PV cell cracking in solar photovoltaic thermal collectors with a novel H-pattern absorber design 2024 In: Applied Thermal Engineering. - : Elsevier. - 1359-4311 .- 1873-5606. ; 242 Journal article (peer-reviewed)abstract This paper introduces a novel absorber design for a Solar Photovoltaic Thermal (PVT) collector, specifically addressing the persistent issue of cell cracking induced by thermal expansion. Despite considerable research efforts to advance PVT technology, cell cracking remains a critical challenge, contributing to decreased collector efficiency. In contrast to previous studies, this research adopts a unique approach. A novel PVT design is proposed, featuring an aluminium alloy structure with a distinctive 'H'-shaped pattern of expansion cavities positioned between Photovoltaic (PV) cells and the absorber. This innovative design is engineered to mitigate thermal expansion and optimize the overall performance of the collector.A 3-D Computational Fluid Dynamic model, simulated using ANSYS software, validates the proposed PVT design against experimental data from a reference collector. A parametric study explores various H-pattern cavity dimensions, revealing that the 2 mm H-pattern plate cavity design achieves the lowest directional expansion, minimizing the risk of breakage. Results show that the proposed design outperforms the reference collector by 10 %, 2 %, and 8 % in thermal, electrical, and overall efficiency, respectively. Furthermore, the H-pattern design reduces thermal expansion by 20 %, enhancing structural resilience and minimizing the likelihood of PV cell cracking. This study represents a significant advancement in PVT technology, providing a practical and easily implementable solution to the critical issue of cell cracking and presenting an optimal design for real-world applications.
20.	Hosouli, Sahand, et al. (author) Optimizing photovoltaic thermal (PVT) collector selection: A multi-criteria decision-making (MCDM) approach for renewable energy systems 2024 In: Heliyon. - : Elsevier. - 2405-8440. ; 10:6 Journal article (peer-reviewed)abstract In the realm of renewable energy systems, the effective selection of Photovoltaic Thermal (PVT) collectors is important. This study delves into the intricacies of choosing optimal PVT collectors available in the market, emphasizing the utility of Multiple Criteria Decision Making (MCDM) methodologies. PVT collectors are differentiated based on various aspects such as their transparent front cover presence and the medium—liquid or air—used for heat transfer. The study methodologically identifies commercially available PVT collectors and establishes key performance indicators for comparison. Using an 11-point fuzzy scale, a weight matrix is determined. Subsequently, advanced MCDM techniques, including PROMETHEE II, TOPSIS, EDAS, and VIKOR, are employed to rank the alternatives. This research not only provides a systematic approach to PVT collector selection but also extends to a MATLAB-based tool for facilitating the process. The results underscore the value of the proposed methodologies in refining the selection of PVT collectors and their potential adaptability to other applications, such as PVT collector design.
21.	Hosouli, Sahand, et al. (author) Performance Assessment of Concentrated Photovoltaic Thermal (CPVT) Solar Collector at Different Locations 2021 In: SWC2021 Proceedings. - Freiburg, Germany : ISES. Conference paper (peer-reviewed)abstract The double MaReCo (symmetric reflector geometry) solar collector (DM-CPVT) has been designed and developed by MG Sustainable Engineering AB (MG) and the University of Gävle (HiG). Performance and overall electrical and thermal parameters of the collector have been studied and presented. The outdoor tests have been performed in both Sweden during the summer months of 2020 and Greece in September of 2020. The goal of the studied designs is to optimize the incoming solar radiation that can be collected without the need for tracking. This is possible due to the use of a symmetric reflector geometry with low concentration factor and lower collector depth. The use of a symmetric reflector geometry allows higher annual outputs worldwide. Furthermore, a low concentration factor is necessary to avoid tracking and a lower collector depth to reduce the shading, which is particularly important for the electrical production of these DM-CPVT design concepts. The testing facilities in both locations are also described in this paper. The information on the thermal performance of a collector is important for the prediction of the energy output of any solar system. The thermal properties assessment of the DM-CPVT collector followed the procedures of the ISO 9806:2017 standard and reported. The outdoor testing results have been validated with a deviation of 2.8% and 2.4% for both thermal and electrical peak efficiencies between the testing facilities, respectively. Regarding the Incidence Angle Modifier testing results, the deviation is negligible for all angles of incidence, which shows that outdoor testing procedures can be fairly accurate when tracking systems are not available.
22.	Hosouli, Sahand, et al. (author) Performance Evaluation of Novel Concentrating Photovoltaic Thermal Solar Collector under Quasi-Dynamic Conditions 2023 In: Solar. - : MDPI. - 2673-9941. ; 3:2, s. 195-212 Journal article (peer-reviewed)abstract Concentrating Photovoltaic Thermal (CPVT) collectors are suitable for integration in limited roof space due to their higher solar conversion efficiency. Solar sunlight can be used more effectively by CPVT collectors in comparison to individual solar thermal collectors or PV modules. In this study, the experimental investigation of a novel CPVT collector called a PC (power collector) has been carried out in real outdoor conditions, and the test set-up has been designed based on ISO 9806:2013. A quasi-dynamic testing method has been used because of the advantages that this method can offer for collectors with a unique construction, such as the proposed collector, over the steady-state testing method. With a quasi-dynamic testing method, it is possible to characterize the collector within a wide range of incidence angles and a complex incidence angle modifier profile. The proposed novel collector has a gross area of 2.57 m2. A maximum power output per collector unit area of 1140 W is found at 0 °C reduced temperature (1000 W/m2 irradiance level), while at a higher reduced temperature (70 °C), it drops down to 510 W for the same irradiance level. The data have been fitted through a multiple linear regression method, and the obtained efficiency curve coefficients are 0.39, 0.192, 1.294, 0.023, 0.2, 0, −5929 and 0 for Kθd, b0, c1, c2, c3, c4, c5 and c6, respectively. The experimental characterization carried out on the collector proved that the output powers calculated by using the obtained parameters of the quasi-dynamic testing method are in good agreement with experimental points.
23.	Kurdia, Ali, et al. (author) Quasi-Dynamic Testing of a Novel Concentrating Photovoltaic Solar Collector According to ISO 9806:2013 2018 In: PROCEEDINGS OF THE ISES EUROSUN 2018 CONFERENCE - 12TH INTERNATIONAL CONFERENCE ON SOLAR ENERGY FOR BUILDINGS AND INDUSTRY. - Freiburg, Germany : INTL SOLAR ENERGY SOC. ; , s. 1262-1273 Conference paper (peer-reviewed)abstract Testing and certification of solar thermal collectors has been widely researched and improved over the years, however, many of the developments in the test standards has been focused primarily on generic flat plate collectors. In this study, the focus was on depicting the applicability of the current standard in characterizing the performance of a novel concentrating solar collector of design. The applicability of the Quasi-Dynamic Testing (QDT) method for collector certification, by the ISO 9806:2013, is studied to be used in characterizing the novel concentrating PVT collector, and to point out the weaknesses observed, and essential additions required.
24.	Lanca, Miguel, et al. (author) Numerical Simulation of the Thermal Performance of Four Concentrating Collectors with Bifacial PV Cells 2018 In: PROCEEDINGS OF THE ISES EUROSUN 2018 CONFERENCE - 12TH INTERNATIONAL CONFERENCE ON SOLAR ENERGY FOR BUILDINGS AND INDUSTRY. - Freiburg, Germany : INTL SOLAR ENERGY SOC. - 9783982040806 ; , s. 810-821 Conference paper (peer-reviewed)abstract Bifacial photovoltaic cells can produce electricity from the incoming solar radiation on both sides. Used in combination with concentrating solar technology, bifacial photovoltaic cells can see its electrical output further augmented, thus decreasing the cost per kWh. It is known, however, that the efficiency reduction when these cells are exposed to increased temperatures is a relevant factor. This can happen, for example, when they are mounted on a glassed collector or receiver. In this study, a thermal analysis is carried out on four prototypes of concentrating collectors with bifacial PV cells. Results show that, as expected, when glass and gables are removed from the collector, much better heat dissipation is achieved, thus resulting in favorable cell operation conditions.
25.	Lança, Miguel, et al. (author) Thermal performance of three concentrating collectors with bifacial photovoltaic cells part I – Experimental and computational fluid dynamics study 2024 In: Proceedings of the Institution of mechanical engineers. Part A, journal of power and energy. - : Sage. - 0957-6509 .- 2041-2967. ; 238:1, s. 140-156 Journal article (peer-reviewed)abstract Bifacial photovoltaic cells can produce electricity from incoming solar radiation on both sides. These cells have a strong potential to reduce electricity generation costs and may play an important role in the energy system of the future. However, today, these cells are mostly deployed with one side receiving only ground reflection, which leads to a profound sub-optimal utilization of one of the sides of the bifacial cells. Concentration allows a better usage of the potential of bifacial cells, which can lead to a lower cost per kWh. However, concentration also adds complexity due to the higher temperatures reached which add the requirement of cooling in order to achieve higher outputs. This way, this paper focuses on the effectiveness of forced air circulation methods by comparing the thermal performance of three specific concentrating bi-facial collector designs. This paper developed a computational model, using ANSYS Fluent intending to assess the thermal performance of a covered concentrating collector with bifacial Photovoltaic (PV) cells. These results have then been validated by outdoor measurements. Results show that even a simple natural ventilation mechanism such as removing the side gable can effectively reduce the receiver temperature, thus resulting in favourable cell operation conditions when compared to the case of an airtight collector. Therefore, compared with a standard model, a decrease of 13.5% on the cell operating temperature was reported when the side gables are removed. However, when forced ventilation is apllied a 22.8% reduction on temperature is found compared to the standard air-tight model. The validated CFD model has proven to be a useful and robust tool for the thermal analysis of solar concentrating systems.
26.	Lança, Miguel, et al. (author) Thermal performance of three concentrating collectors with bifacial PV cells. Part II – parametrical study 2024 In: Proceedings of the Institution of mechanical engineers. Part A, journal of power and energy. - : SAGE. - 0957-6509 .- 2041-2967. Journal article (peer-reviewed)abstract One of the problems in using PV cells to extract energy from sunlight is the temperature effect on PV cells. As the solar panel is heated, the conversion efficiency of light to electrical energy is diminished. Moreover, successive temperature elevations can cause dilatations in the array of cells which may also contribute to the degradation of the receiver. Some of the operating temperature mitigation approaches may include air-flow ventilation. In this study, data obtained by experimental and numerical simulations of a collector with bifacial PV cells is compared to the expressions found in the literature for the estimation of the heat transfer coefficient. Forced ventilation was applied to the studied collector as it accounts for much better heat dissipation. A new correlation for the estimation of the heat transfer coefficient is developed for such a geometry, for inlet velocities ranging between 3 and 8 m/s. Values of heat transfer coefficient estimated in the present work have been compared with studies of other researchers.
27.	Loris, Alexander, et al. (author) Evaluation of the Use of Concentrated Solar Photovoltaic Thermal Collectors (CPVT) in a Dairy and Swine Farm in Europe 2021 In: SWC2021 Proceedings. - Freiburg, Germany : ISES. Conference paper (peer-reviewed)abstract The use of CPVT collectors in combination with other renwable energy sources (RES) has been evaluated for a dairy and swine farm in view of fossil-free farming practises. Electrical and thermal heat demands have been analysed for the LVAT-ATB dairy farm in Germany, and for the ILVO swine farm in Belgium. A CPVT collector produced by Solarus has been tested and modelled the thermal and electrical performance output for each of the farms. Taking into consideration the demands of the farms, the use of the CPVT in a fossil-free energy system for the farm has been evaluated. Analysis of the swine farm suggested to use the CPVT as a heat source to improve the system efficiency for two heat pumps that would provide the final heating. A similar result was obtained in the dairy farm where the CPVT would raise the temperature of the incoming water to the heat recovery system of the milk cooler.
28.	Meramveliotakis, George, et al. (author) Innovative Coupling of PVT Collectors with Electric-Driven Heat Pumps for Sustainable Buildings 2020 In: PROCEEDINGS OF THE ISES EUROSUN 2020 CONFERENCE - 13TH INTERNATIONAL CONFERENCE ON SOLAR ENERGY FOR BUILDINGS AND INDUSTRY. - Freiburg, Germany : International Solar Energy Society. - 9783982040820 ; , s. 440-451 Conference paper (peer-reviewed)abstract An innovative renewable- energy based system is examined for covering the heating and cooling demand in residential buildings. This system adopts an alternative solar-assisted heat pump configuration, developed around its two main components: the PVT collectors and a dual-source heat pump. The heat produced by the collectors can be either used directly for covering the heating needs or stored in a buffer tank for supplying the heat pump with low-temperature heat, exploiting all solar heat and operating the heat pump with an elevated performance for a longer period during the day. Once the stored heat in the buffer tank is discharged, the heat pump is supplied by ambient heat. The same configuration can also operate at cooling mode during summer, with the heat pump reversing its operation. The current work examines the main system parameters, in order to evaluate its performance for covering a large share of the building's energy needs.
29.	Murali, Damu, et al. (author) Experimental assessment of a solar photovoltaic-thermal system in a livestock farm in Italy 2024 In: Solar Energy Advances. - : Elsevier. - 2667-1131. ; 4 Journal article (peer-reviewed)abstract This paper presents an experimental evaluation of the performance of a solar photovoltaic-thermal (PVT) system in a swine farm at Mirandola in Italy. In this project named RES4LIVE, funded by the EU’s Horizon 2020 program, a PVT system is installed to replace fossil fuel consumption in one of the barns on the farm. The electrical energy from the collectors is utilized to operate the heat pump and provide electricity to the barn, whereas the thermal energy from the collector is stored in a borehole thermal energy storage (BTES) for further use by a 35 kW heat pump. The hybrid solar field consists of 24 covered PVT flat plate collectors (7.68 kWel and 25 kWth) with a total aperture area of 39.3 m2, which can increase the temperature of the heat transfer fluid (HTF) to up to 40 °C. The PVT system is connected to a modular solar central (SC) with a standardized design that can also be used for other similar applications. The hybrid solar system complemented by energy storage is expected to save approximately 20,850 kg CO2/year . The data collected from the PVT system, SC, and BTES are rigorously analyzed to evaluate its overall performance. A comprehensive performance assessment reveals the capability of the solar system to reduce carbon emissions and effectively replace fossil fuel consumption in the agricultural sector.
30.	Nasseriyan, Pouriya, et al. (author) Numerical and Experimental Study of an Asymmetric CPC-PVT Solar Collector 2020 In: Energies. - : MDPI. - 1996-1073. ; 13:7 Journal article (peer-reviewed)abstract Photovoltaic (PV) panels and thermal collectors are commonly known as mature technologies to capture solar energy. The efficiency of PV cells decreases as operating cell temperature increases. Photovoltaic Thermal Collectors (PVT) offer a way to mitigate this performance reduction by coupling solar cells with a thermal absorber that can actively remove the excess heat from the solar cells to the Heat Transfer Fluid (HTF). In order for PVT collectors to effectively counter the negative effects of increased operating cell temperature, it is fundamental to have an adequate heat transfer from the cells to the HTF. This paper analyzes the operating temperature of the cells in a low concentrating PVT solar collector, by means of both experimental and Computational Fluid Dynamics (CFD) simulation results on the Solarus asymmetric Compound Parabolic Concentrator (CPC) PowerCollector (PC). The PC solar collector features a Compound Parabolic Concentrator (CPC) reflector geometry called the Maximum Reflector Concentration (MaReCo) geometry. This collector is suited for applications such as Domestic Hot Water (DHW). An experimental setup was installed in the outdoor testing laboratory at Gävle University (Sweden) with the ability to measure ambient, cell and HTF temperature, flow rate and solar radiation. The experimental results were validated by means of an in-house developed CFD model. Based on the validated model, the effect of collector tilt angle, HTF, insulation (on the back side of the reflector), receiver material and front glass on the collector performance were considered. The impact of tilt angle is more pronounced on the thermal production than the electrical one. Furthermore, the HTF recirculation with an average temperature of 35.1C and 2.2 L/min flow rate showed that the electrical yield can increase by 25%. On the other hand, by using insulation, the thermal yield increases up to 3% when working at a temperature of 23 C above ambient.
31.	Panchal, Rajan, et al. (author) Evaluation of Symmetric C-PVT Solar Collector Designs with Vertical Bifacial Receivers 2019 In: Proceedings of the ISES Solar World Congress 2019 and IEA SHC International Conference on Solar Heating and Cooling for Buildings and Industry 2019. - Freiburg, Germany : International Solar Energy Society. - 9783982040813 ; , s. 165-176 Conference paper (peer-reviewed)abstract Photovoltaic thermal (PVT) solar collectors can be an effective solution for system output improvement. Photovoltaic thermal collectors naturally have a more expensive receiver than simpler photovoltaic or thermal only collectors, therefore making concentration a more appealing solution to achieve cost reduction. However, concentrating systems need careful analysis on the design phase in order to optimize the annual output. In addition, for stationary (non-tracking) collectors, it is critical to determine the incidence angle modifier (IAM).For this reason, a reflector study was carried out to determine suitable reflector designs for a stationary concentrating PVT collector. The reflectors were simulated using a Monte Carlo raytracing software called Tonatiuh. The two selected reflectors designs were named “pure parabola” (PP) and “compound parabolic concentrator” (CPC). The concentration ratio of 1.2 and 1.6 were selected for each reflector designs, which means a total of 4 collector troughs. The next step involved the construction of the two selected C-PVT collector designs, which were built and subsequently tested by the authors. The IAM was assessed and discussed by simulation and outdoor testing in detail.The IAM results show similar decreases in longitudinal IAM for both the PP and the CPC CPVT collector for the 1.2 concentration factor. For the transversal IAM with 1.2 of concentration factor, the CPC over performs. For the 1.6 concentration prototype collectors, the results are fairly similar. Lastly, the annual output was also simulated and presented.
32.	Yildizhan, Hasan, et al. (author) Alternative work arrangements: Individual, organizational and environmental outcomes 2023 In: Heliyon. - : Elsevier. - 2405-8440. ; 9:11 Journal article (peer-reviewed)abstract Flexible working models are widely used around the world. Furthermore, several countries are currently transitioning to a 4-day workweek. These working models have significant effects on organizational behavior and the environment. The study investigates the employees' attitudes and behaviors toward flexible working and 4-day workweek and the impact on the environment. The semi-structured interview method was used in the study to determine employee attitudes and behaviors; the carbon footprint calculation method was used to determine the environmental impact of a 4-day workweek. According to the study's findings, it has been discovered that there would be a positive impact on socialization, happiness, stress factor, motivation, personal time, mental health, comfort, work-life balance, time-saving, willingness, positive working environment, personal time, and physical health. Furthermore, a 4-day workweek reduced commuting emissions by 20%, resulting in a 6,07 kg tCO2e reduction per person. As a result, the study attempted to draw attention holistically to the positive effects of the flexible working model and 4-day workweek. The study is intended to serve as a tool for decision-makers and human resource managers.
33.	Yılmaz, Sıdıka Ece, et al. (author) The Drivers and Barriers of the Solar Water Heating Entrepreneurial System: A Cost–Benefit Analysis 2023 In: Sustainability. - : MDPI. - 2071-1050. ; 15:20 Journal article (peer-reviewed)abstract Sustainable development objectives place a high priority on entrepreneurship and renewable energy. Supporting entrepreneurial activities in the renewable energy industry can provide economic growth and employment to accomplish the Sustainable Development Goals Agenda 2030. Solar water heating systems can provide clear benefits for both the environment and economic growth. There is a gap in the literature regarding the study of the factors hindering or driving the development of the solar water heating system industry. This study aims to investigate the solar water heating system industry's challenges and attempts to define the drivers to further develop the industry. Thus, solar water heating entrepreneurship parameters can be identified. Additionally, energy savings and carbon dioxide emissions were calculated for the region to raise awareness among consumers. This study used the qualitative analysis method through semi-structured interviews with 40 business owners in Adana/Turkey. The findings showed that the industry has administrative, production, political, and economic issues; there is a need for economic support and expanding education and control mechanisms. Also, the payback period is 1.63 similar to 3.27 years for a solar water heating system and this system prevents 800.75 kg of CO2 emission. The study has implications for policy-making, practice, scientific research, and the SDGs Agenda 2030.

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