hig.sePublications
Change search
Link to record
Permanent link

Direct link
BETA
Gomes, João
Publications (10 of 15) Show all publications
Torres, J. P., Fernandes, C. A. F., Gomes, J., Luc, B., Carine, G., Olsson, O. & Branco, P. J. (2018). Effect of reflector geometry in the annual received radiation of low concentration photovoltaic systems. Energies, 11(7), Article ID 1878.
Open this publication in new window or tab >>Effect of reflector geometry in the annual received radiation of low concentration photovoltaic systems
Show others...
2018 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 7, article id 1878Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
MDPI AG, 2018
Keywords
Concentrating photovoltaic (C-PV) solar systems, Maximum reflector collector (MaReCo), Ray-tracing, Reflector design, Soltrace, Cost effectiveness, Geometry, Photovoltaic cells, Photovoltaic effects, Ray tracing, Reflection, Solar energy, Solar power generation, Concentrating photovoltaic, Concentrating photovoltaic systems, Concentrating solar power, Concentrator photovoltaics, Conventional structures, Open systems
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-27864 (URN)10.3390/en11071878 (DOI)000441830500262 ()2-s2.0-85051229803 (Scopus ID)
Available from: 2018-09-06 Created: 2018-09-06 Last updated: 2018-09-06Bibliographically approved
Cabral, D., Gomes, J., Dostie-Guindon, P.-A. & Karlsson, B. O. (2017). Ray tracing simulations of a novel low concentrator PVT solar collector for low latitudes. In: ISES Solar World Congress 2017 - IEA SHC International Conference on Solar Heating and Cooling for Buildings and Industry 2017, Proceedings: . Paper presented at SWC 2017: ISES Solar World Congress, SHC 2017: IEA SHC Solar Heating and Cooling Conference 2017; 29 October - 2 November 2017, Abu Dhabi, UAE (pp. 1068-1079). International Solar Energy Society
Open this publication in new window or tab >>Ray tracing simulations of a novel low concentrator PVT solar collector for low latitudes
2017 (English)In: ISES Solar World Congress 2017 - IEA SHC International Conference on Solar Heating and Cooling for Buildings and Industry 2017, Proceedings, International Solar Energy Society , 2017, p. 1068-1079Conference paper, Published paper (Refereed)
Abstract [en]

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. 

Place, publisher, year, edition, pages
International Solar Energy Society, 2017
Keywords
MaReCo CPC geometry, Pure Parabola collector, Symmetric C-PVT, Tonatiuh, C (programming language), Geometry, Optical properties, Photoelectrochemical cells, Photovoltaic cells, Rhenium compounds, Solar collectors, Solar heating, Solar power generation, Solar radiation, Concentrating collector, Concentration factors, Direct solar radiation, Electrical performance, Ray tracing simulation, Ray tracing
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-27631 (URN)10.18086/swc.2017.18.05 (DOI)2-s2.0-85050544604 (Scopus ID)978-3-9814659-7-6 (ISBN)
Conference
SWC 2017: ISES Solar World Congress, SHC 2017: IEA SHC Solar Heating and Cooling Conference 2017; 29 October - 2 November 2017, Abu Dhabi, UAE
Available from: 2018-08-13 Created: 2018-08-13 Last updated: 2018-08-13Bibliographically approved
Francisco Contero, J., Gomes, J., Gustafsson, M. & Karlsson, B. O. (2017). The impact of shading in the performance of three different solar PV systems. In: PROCEEDINGS OF THE 11TH ISES EUROSUN 2016 CONFERENCE: . Paper presented at 11th ISES EuroSun Conference, 11-14 October 2017, Palma, Spain (pp. 1168-1179). INTL SOLAR ENERGY SOC
Open this publication in new window or tab >>The impact of shading in the performance of three different solar PV systems
2017 (English)In: PROCEEDINGS OF THE 11TH ISES EUROSUN 2016 CONFERENCE, INTL SOLAR ENERGY SOC , 2017, p. 1168-1179Conference paper, Published paper (Refereed)
Abstract [en]

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.

Place, publisher, year, edition, pages
INTL SOLAR ENERGY SOC, 2017
Keywords
Shading; PV-cells; DC-DC; inverter; installation; Impp; Vmpp; Pmax
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-26397 (URN)10.18086/eurosun.2016.08.25 (DOI)000426895100118 ()
Conference
11th ISES EuroSun Conference, 11-14 October 2017, Palma, Spain
Funder
Swedish Energy Agency
Available from: 2018-04-03 Created: 2018-04-03 Last updated: 2018-06-26Bibliographically approved
Gomes, J., Luc, B., Carine, G., Fernandes, C. A., Torres, J. P., Olsson, O., . . . Nashih, S. K. (2016). Analysis of different C-PVT reflector geometries. In: Proceedings - 2016 IEEE International Power Electronics and Motion Control Conference, PEMC 2016: . Paper presented at 17th IEEE International Power Electronics and Motion Control Conference, PEMC 2016, 25-28 September 2016, Varna, Bulgaria (pp. 1248-1255). IEEE, Article ID 7752175.
Open this publication in new window or tab >>Analysis of different C-PVT reflector geometries
Show others...
2016 (English)In: Proceedings - 2016 IEEE International Power Electronics and Motion Control Conference, PEMC 2016, IEEE, 2016, p. 1248-1255, article id 7752175Conference paper, Published paper (Refereed)
Abstract [en]

One of the main advantages of solar concentrating photovoltaic-thermal collectors (C-PVT) is that these systems are all-in-one module type. For this reason, they are associated to less area and material requirements. Nevertheless, these systems require a more complex analysis in order to improve their performances, since the two types of energy conversion are related to the different demands and their cross effects. In the overall analysis, the collector geometry and the used materials for all their components will be crucial to ensure the system reliability. This study presents preliminary work about re-designing the reflector of C-PVT collectors currently produced in the Swedish SME Solarus Sunpower AB with a comparative analysis on an annual basis of the solar radiation that reaches the collector. For the work accomplished, an open-source advanced object-oriented Monte Carlo ray tracing program (Tonatiuh) is used. For low latitudes, two reflector shapes have been selected since they ensure better performances than the current Solarus reflector. These two new designs achieve both the performance and cost-effectiveness objectives: for the same aperture area and for a thinner box, the collector is 7% to 10% more effective and 18% cheaper.

Place, publisher, year, edition, pages
IEEE, 2016
Keywords
MaReCo, ray-tracing, shading, simulation, Symmetric CPC PVT, tilt influence, Tonatiuh, Cost effectiveness, Energy conversion, Geometry, Motion control, Object oriented programming, Power control, Power electronics, Reflection, Reliability analysis, Solar power generation, Ray tracing
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-23529 (URN)10.1109/EPEPEMC.2016.7752175 (DOI)000390590000180 ()2-s2.0-85008259310 (Scopus ID)
Conference
17th IEEE International Power Electronics and Motion Control Conference, PEMC 2016, 25-28 September 2016, Varna, Bulgaria
Available from: 2017-02-06 Created: 2017-02-06 Last updated: 2018-03-13Bibliographically approved
Fernandes, C. A., Torres, J. P., Gomes, J., Branco, P. J. & Nashih, S. K. (2016). Stationary solar concentrating photovoltaic-thermal collector - Cell string layout. In: Proceedings - 2016 IEEE International Power Electronics and Motion Control Conference, PEMC 2016: . Paper presented at 17th IEEE International Power Electronics and Motion Control Conference, PEMC 2016, 25-28 September 2016, Varna, Bulgaria (pp. 1275-1282). IEEE, Article ID 7752179.
Open this publication in new window or tab >>Stationary solar concentrating photovoltaic-thermal collector - Cell string layout
Show others...
2016 (English)In: Proceedings - 2016 IEEE International Power Electronics and Motion Control Conference, PEMC 2016, IEEE, 2016, p. 1275-1282, article id 7752179Conference paper, Published paper (Refereed)
Abstract [en]

The aim of this work is to design the cell string layout in stationary concentrating photovoltaic (PV) or hybrid systems (PVT) in order to minimize the effects of both the longitudinal and transversal shading inherent to concentrating collectors. In this paper it is determined the best configuration of a PV string of cells, composed by several modules, by using a simple mathematical model based on the current vs. voltage of the PV cell. The model calculates the power vs. voltage curves of different possible configurations, in order to identify the optimal one according to efficiency and reliability. The company SOLARUS manufactures PVT collectors with cell strings of 38 solar cells connected in series. Solar cells in the concentrated side of the collector are shaded due to the presence of the aluminium frame of the PVT collector. The effects of shading and non-uniform illumination are minimized by including bypass diodes. Each string has 4 modules of bridged cells, each one associated to a bypass diode. In this work, different combinations of string cells in the collector receiver have been simulated using the free circuit simulation package from Linear Technology Corporation (LTSPICE). Test results are provided by SOLARUS to validate the proposed approach. A comparative analysis is presented at the end, showing that the simulation model is an important tool to define the module configurations that achieve the best energy efficiencies of the PVT panel. 

Place, publisher, year, edition, pages
IEEE, 2016
Keywords
bypass diodes, concentrating collectors, mismatching, PVT systems, shading, Circuit simulation, Diodes, Energy efficiency, Hybrid systems, Motion control, Photovoltaic cells, Photovoltaic effects, Power control, Power electronics, Solar power generation, By-pass diodes, Concentrating collector, Concentrating photovoltaic, Efficiency and reliability, Module configurations, Non-uniform illumination, Solar cells
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-23528 (URN)10.1109/EPEPEMC.2016.7752179 (DOI)000390590000184 ()2-s2.0-85008245566 (Scopus ID)9781509017980 (ISBN)
Conference
17th IEEE International Power Electronics and Motion Control Conference, PEMC 2016, 25-28 September 2016, Varna, Bulgaria
Available from: 2017-02-06 Created: 2017-02-06 Last updated: 2018-03-13Bibliographically approved
Contero, F., Gomes, J., Gustafsson, M. & Karlsson, B. O. (2016). The impact of shading in the performance of threee different solar PV systems. In: : . Paper presented at 11th ISES Eurosun 2016, International Conference on Solar Energy for Buildings and Industry, 11-14 October 2016, Palma, Mallorca.
Open this publication in new window or tab >>The impact of shading in the performance of threee different solar PV systems
2016 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-25761 (URN)
Conference
11th ISES Eurosun 2016, International Conference on Solar Energy for Buildings and Industry, 11-14 October 2016, Palma, Mallorca
Available from: 2017-12-07 Created: 2017-12-07 Last updated: 2018-03-13Bibliographically approved
Nashih, S. K., Fernandes, C. A. F., Torres, J. P., Gomes, J. & Branco, P. J. (2016). Validation of a Simulation Model for Analysis of Shading Effects on Photovoltaic Panels. Journal of solar energy engineering, 138(4), Article ID 044503.
Open this publication in new window or tab >>Validation of a Simulation Model for Analysis of Shading Effects on Photovoltaic Panels
Show others...
2016 (English)In: Journal of solar energy engineering, ISSN 0199-6231, E-ISSN 1528-8986, Vol. 138, no 4, article id 044503Article in journal (Refereed) Published
Abstract [en]

Numerical simulation results and modeling on the electrical features of concentrating photovoltaic-thermal (PVT) using the free circuit simulation package from linear technology corporation (LTSPICE) are presented. The effects of partial shading of cell strings and temperature are analyzed, showing very good agreement with the results obtained experimentally in lab, at Lisbon University, and under outdoor testing using similar receivers, at the SME Solarus Sunpower AB, a Swedish company whose mission is the development, production, and marketing of concentrated solar technology to the world market. The potential of the used methodology for the design of the solar cell configuration is emphasized as an important tool to optimize PV and PVT performances in the energy conversion process. 

Keywords
CPC collector, electric efficiency, I-V curves, LTSPICE, PV collector, shading, Circuit simulation, Commerce, Energy conversion, International trade, Photovoltaic cells, Photovoltaic effects, Solar cells, CPC collectors, I - V curve, Collector efficiency
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-22227 (URN)10.1115/1.4033646 (DOI)000381200700017 ()2-s2.0-84975068536 (Scopus ID)
Note

Funding agencies:

FCT through IDMEC under LAETA Grant no: UID/EMS/50022/2013

FCT through IDMEC under IT Grant no: UID/EEA/50008/2013

Available from: 2016-08-16 Created: 2016-08-16 Last updated: 2018-03-13Bibliographically approved
Gomes, J., Bastos, S., Henriques, M., Diwan, L. & Olsson, O. (2015). Evaluation of the impact of stagnation temperatures in different prototypes of low concentration PVT solar panels. In: ISES Solar World Congress 2015, Conference Proceedings: . Paper presented at International Solar Energy Society, ISES Solar World Congress 2015, SWC 2015, 8-12 November 2, EXCODaegu, South Korea (pp. 993-1004).
Open this publication in new window or tab >>Evaluation of the impact of stagnation temperatures in different prototypes of low concentration PVT solar panels
Show others...
2015 (English)In: ISES Solar World Congress 2015, Conference Proceedings, 2015, p. 993-1004Conference paper, Published paper (Refereed)
Abstract [en]

Photovoltaic thermal (PVT) solar panels produce both thermal and electric power from the some area. This paper concerns a PVT design where the series connected strings of cells are laminated using silicone to an aluminium receiver where the heat transfer fluid flows. An evaluation of the impact of reaching high temperatures in the cell structural integrity and performance is presented. Eight small test receivers were made in which the following properties were varied: Size of the PV cells, type of silicone used to encapsulate the PV cells, existence of a strain relief between the cells, size of the gap between cells and type of cell soldering (line or point soldering). These test receivers were placed in an oven for one hour, under eight different monitored temperatures. The temperature of the last round was set at 220°C which well exceeds the highest temperature the panel design can reach. Before and after each round in the oven, the following tests were conducted to the receivers: Electroluminescence (EL) test, IV-curve, diode function, and visual inspection. The test results showed that the receivers made with the transparent silicone and strain relief between cells experienced less micro-cracks and lower degradation in maximum power. No prototype test receiver lost more than 30% of its initial power, despite the large cell breakage shown in some receivers. Prototype receivers with transparent (softer) silicone showed much far less cracks and power decrease when compared to red (harder) silicone receivers. As expected, larger cells are more prone to develop micro-cracks after exposure to thermal stress. Additionally, existing micro-cracks tend to grow in size into larger micro-cracks relatively fast with thermal stress. The EL imaging taken during our experiment leads us to observe that it seems far easier for existing cracks to expand than for new cracks to appear.

Keywords
Concentration, Electroluminescence test, IV-curve, PVT, Stagnation temperature, Concentration (process), Cracks, Cytology, Electroluminescence, Flow of fluids, Heat transfer, Ovens, Photovoltaic cells, Silicones, Solar cell arrays, Solar concentrators, Solar energy, Solar power generation, Soldering, Testing, Thermal stress, High temperature, Highest temperature, I - V curve, Low concentrations, Photovoltaic thermals, Series-connected, Visual inspection, Cells
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-25746 (URN)10.18086/swc.2015.10.14 (DOI)2-s2.0-85017036384 (Scopus ID)9783981465952 (ISBN)
Conference
International Solar Energy Society, ISES Solar World Congress 2015, SWC 2015, 8-12 November 2, EXCODaegu, South Korea
Available from: 2017-12-06 Created: 2017-12-06 Last updated: 2018-03-13Bibliographically approved
Mantei, F., Henriques, M., Gomes, J., Olsson, O. & Karlsson, B. (2015). The night cooling effect on a C-PVT solar collector. In: ISES Solar World Congress 2015, Conference Proceedings: . Paper presented at International Solar Energy Society, ISES Solar World Congress 2015, SWC 2015, 8-12 November 2017, EXCODaegu, South Korea (pp. 1167-1175). International Solar Energy Society
Open this publication in new window or tab >>The night cooling effect on a C-PVT solar collector
Show others...
2015 (English)In: ISES Solar World Congress 2015, Conference Proceedings, International Solar Energy Society, 2015, p. 1167-1175Conference paper, Published paper (Refereed)
Abstract [en]

Night cooling consists in running a fluid through a solar panel during the night in order to reduce the fluid temperature which can be used for cooling applications. Radiative heat losses can allow the fluid to reach temperatures below ambient while conduction and convection works to equalize the collector with the ambient temperature. This paper analyzes the possibility of using an asymmetric concentrating photovoltaic thermal solar collector (C-PVT) for cooling applications during the night by losing heat through convection, conduction and irradiation. The cooling performance of the C-PVT collector has been measured during the night at different inlet temperatures in the interval of 13 to 38°C which corresponded to a AT (between the collector average and the ambient) from 6 to 28°C. The performance of the tested C-PVT collector has been measured at different inlet temperatures in an interval of 13 to 38°C. During all performed measurements, the radiation losses did not drive the collector temperature below ambient temperature. With high AT (between the inlet and the ambient) of 30°C, a 1,85°C temperature decrease in the fluid was obtained. For AT of 14°C, the temperature decrease was only 0,88°C. The measurements showed a night U-value for the Solarus C-PVT of 4,2 W/m2K This correlates well with previous papers showing measurements taken during the day. Heat losses seem to be dominated by convection and conduction due to the existence of the glass in the collector. Despite this, a measurable relation between heat losses and cloudiness factor exists. This shows that the irradiance losses are not negligible. Only very specific applications can be suited for night cooling with this collector design, since it is not so common to have applications that require low grade cooling during the night time or justify storing this energy. However, if the C-PVT design was made without a glass cover, the results could potentially be very different for locations with many clear nights.

Place, publisher, year, edition, pages
International Solar Energy Society, 2015
Keywords
Asymmetric collector, Collector testing, Concentrating PVT, CPC-collector, Night cooling, Glass, Heat convection, Heat losses, Solar collectors, Solar energy, Solar power generation, Temperature, Asymmetric collectors, CPC collectors, Cooling
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-25747 (URN)10.18086/swc.2015.10.33 (DOI)2-s2.0-85016956998 (Scopus ID)9783981465952 (ISBN)
Conference
International Solar Energy Society, ISES Solar World Congress 2015, SWC 2015, 8-12 November 2017, EXCODaegu, South Korea
Available from: 2017-12-06 Created: 2017-12-06 Last updated: 2018-03-13Bibliographically approved
Davidsson, H., Bernardo, R., Gomes, J., Gentile, N., Gruffman, C., Chea, L. & Karlsson, B. (2014). Construction of laboratories for solar energy research in developing countries. Paper presented at 2013 ISES Solar World Congress, 3-7 November 2013, Cancún, Mexico. Energy Procedia, 57, 982-988
Open this publication in new window or tab >>Construction of laboratories for solar energy research in developing countries
Show others...
2014 (English)In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 57, p. 982-988Article in journal (Refereed) Published
Abstract [en]

A large number of PV-systems have been installed in developing countries around the world duringnumerous projects. The aim is often to improve the quality of life in rural areas, often lacking electricity.Many of these installations provide important services such as lighting and charging of different devices.However, when the projects are finished, there is a large risk that maintenance is not carried out properlyand that malfunctions are never repaired. This situation can leave an otherwise well functioning systemunusable. A key problem is that there are not enough trained technicians that can maintain and repair thesystem locally. One reason to this is the lack of practical education in many developing countries.Furthermore, the availability of spare parts is essential for the long term effectiveness.During 2011 a group of researchers from Lund University in Sweden built a small scale laboratory inMaputo, Mozambique, together with local researchers. The project was successful and today thelaboratory functions both as a teaching facility and as a measurement station for solar energy research forlicentiates, masters and PhD students.The main goal is now to widen the project in order to incorporate more universities in developingcountries. We are now looking for new interested partners in developing countries that believe that such alaboratory could strengthen their possibility to teach practical work and to perform research at the localuniversity. Partners for planning and executing the project are also needed.

Keywords
Sustainable Development; Solar Laboratory; Research and Education
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-18535 (URN)10.1016/j.egypro.2014.10.081 (DOI)
Conference
2013 ISES Solar World Congress, 3-7 November 2013, Cancún, Mexico
Available from: 2014-12-13 Created: 2014-12-13 Last updated: 2018-03-28Bibliographically approved
Organisations

Search in DiVA

Show all publications