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Reflector Optimization for Low Concentration Photovoltaic-Thermal Solar Collectors
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology. (Energy Systems)ORCID iD: 0000-0002-0539-3291
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The alarming new global warming and increasing awareness related to climate change (mainly due to the high emissions of carbon dioxide) in recent decades linked all nations into a common cause, which requires ambitious efforts to combat climate change by adapting energy systems to its effects.

The knowledge gain presented in this dissertation establishes the foundations for the development of a more efficient concentrating photovoltaic-thermal (PVT) solar collector. The presented work provides decision-makers with a broader, more detailed performance assessment of concentrating PVT solar collectors.

A critical issue for concentrating PVT solar collectors lies in the respective reflector shape, which will determine, to some extent, the overall performance of the CPVT collector. Therefore, several symmetrical reflector design concepts were designed and optimized through Monte Carlo ray-tracing software. With the support of a MATLAB script, a simulation test methodology has been developed and optimized, allowing a more thorough analysis of the results regarding the viability of the different reflector shapes, which established the compound parabolic collector (CPC) to be the most appropriate reflector geometry for PVT solar collectors.

Moreover, CPC-PVT solar collectors (based on the findings described above) were designed, built and outdoor tested (under steady-state method guidelines) for their thermal and electrical peak efficiencies, heat losses and incidence angle modifier (IAM) coefficients.

The developments achieved in this dissertation significantly enhanced the annual performance of CPC-CPVT solar collectors, which closes the efficiency/performance gap between mature technologies such as PV modules or ST collectors.

Abstract [sv]

Den alarmerande globala uppvärmningen och den ökande medvetenheten i samband med klimatförändringar på grund av de höga utsläppen av koldioxid har samlat alla nationer till den gemensama uppgiften, att bekämpa klimatförändringarna och effekterna av dem genom anpassning av energisystemen.

Den kunskapsökning som presenteras i denna avhandling utgör grunden för utvecklingen av effektivare koncentrerande solcellsmoduler. Det presenterade arbetet möjliggör en bredare och mer detaljerad analys av prestandan hos koncentrerande PVT-moduler.

En kritisk fråga för den koncentrerande PVT solfångarens prestanda är reflektorns geometri, som i hög grad påverkar verkningsgraden. Därför designades och optimerades flera symmetriska reflektorgeometrier. Med hjälp av en Monte Carlo ray-tracing programvara. Med stöd av ett MATLAB-skript har en simuleringstestmetodik utvecklats vilken möjliggör en mer ingående analys av funktionen hos de olika reflektorformerna. Den visade att compound parabolic collector (CPC) är den mest lämpliga reflektorgeometrin för ej solföljande koncentrerande PVT-solfångare.

Dessutom konstruerades, byggdes och testades CPC-PVT-solfångare, baserat på de resultat som beskrivs ovan, enligt steady-state-metoden, för att få termiska och elektriska verkningsgrader värmeförluster och infallsvinkelberoende.

Den utveckling som uppnåtts i denna avhandling förbättrar den årliga prestanda hos CPVT-solfångare avsevärt, vilket minskar effektivitetsgapet till mognare tekniker som solcellsmoduler och termiska solfångare.

Place, publisher, year, edition, pages
Gävle: Gävle University Press , 2022. , p. 153
Series
Doctoral thesis ; 26
Keywords [en]
Photovoltaic-thermal collector, experimental assessment, collector performance assessment, optical efficiency, concentrating PVT solar collector, ray tracing
Keywords [sv]
Fotovoltaisk-termisk kollektor, experimentell utvärdering, prestandautvärdering, optisk effektivitet, koncentrerande PVT-solfångare, strålgångsanalys
National Category
Energy Systems
Identifiers
URN: urn:nbn:se:hig:diva-37391ISBN: 978-91-88145-81-9 (print)ISBN: 978-91-88145-82-6 (print)OAI: oai:DiVA.org:hig-37391DiVA, id: diva2:1612644
Public defence
2022-01-28, 13:302, Gävle, 09:00 (English)
Opponent
Supervisors
Available from: 2022-01-04 Created: 2021-11-18 Last updated: 2024-07-02Bibliographically approved
List of papers
1. Electrical and thermal performance evaluation of symmetric truncated C-PVT trough solar collectors with vertical bifacial receivers
Open this publication in new window or tab >>Electrical and thermal performance evaluation of symmetric truncated C-PVT trough solar collectors with vertical bifacial receivers
2018 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 174, p. 683-690Article in journal (Refereed) Published
Abstract [en]

One way to reduce solar collectors’ 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/receiver. Symmetrical truncated non-tracking C-PVT trough collectors based on a parabola and compound parabolic concentrator (CPC) geometries have been developed. The collector type has a central vertical bifacial (fin) receiver and it was optimized for lower latitudes. In this paper, the electrical and thermal performance of symmetric truncated non-tracking low concentrator PVT solar collectors with vertical bifacial receivers is analysed, through a numerical ray-tracing model software and a multi-paradigm numerical computing environment. A thermal (quasi-dynamic testing method for liquid heating collectors described in the international standard for solar thermal collectors ISO 9806:2013) and electrical performance models were implemented to evaluate the design concepts. The evaluation was made for heating Domestic Hot Water for a Single Family House in Fayoum (Egypt), where CPC geometries with a concentration factor of 1.6 achieved 8 to 13%rel higher energy yields (in kWh/m2/year) than the Pure Parabola geometries.

Place, publisher, year, edition, pages
Elsevier Ltd, 2018
Keywords
Bifacial receiver, Electrical and thermal yield evaluation, Ray-tracing, Symmetric C-PVT collector
National Category
Energy Systems
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-28322 (URN)10.1016/j.solener.2018.09.045 (DOI)000451499500065 ()2-s2.0-85053808056 (Scopus ID)
Available from: 2018-10-15 Created: 2018-10-15 Last updated: 2021-11-18Bibliographically approved
2. Performance Evaluation of Non-Uniform Illumination on a Transverse Bifacial PVT Receiver in Combination with a CPC Geometry
Open this publication in new window or tab >>Performance Evaluation of Non-Uniform Illumination on a Transverse Bifacial PVT Receiver in Combination with a CPC Geometry
2019 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 194, p. 696-708Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
CPC PVT collector, LCPVT, Transverse bifacial PVT receiver, Irradiation flux distribution, Performance evaluation, Ray-tracing
National Category
Energy Systems
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-30967 (URN)10.1016/j.solener.2019.10.069 (DOI)000502888500067 ()2-s2.0-85074877472 (Scopus ID)
Note

This research was funded by Eureka Eurostars, under project number E10625

Available from: 2019-11-14 Created: 2019-11-14 Last updated: 2021-11-18Bibliographically approved
3. Experimental investigation of a CPVT collector coupled with a wedge PVT receiver
Open this publication in new window or tab >>Experimental investigation of a CPVT collector coupled with a wedge PVT receiver
2021 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 215, p. 335-345Article in journal (Refereed) Published
Abstract [en]

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◦.

Place, publisher, year, edition, pages
Elsevier, 2021
Keywords
Photovoltaic-thermal collector; Experimental assessment; Collector performance; Optical efficiency
National Category
Energy Systems
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-34817 (URN)10.1016/j.solener.2020.12.038 (DOI)000615999900003 ()2-s2.0-85099571668 (Scopus ID)
Funder
European Commission, 814865The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), ME 2018-7559
Available from: 2021-01-25 Created: 2021-01-25 Last updated: 2022-03-01Bibliographically approved
4. Development and performance comparison of a modified glazed CPC hybrid solar collector coupled with a bifacial PVT receiver
Open this publication in new window or tab >>Development and performance comparison of a modified glazed CPC hybrid solar collector coupled with a bifacial PVT receiver
2022 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 325, article id 119653Article in journal (Refereed) Published
Abstract [en]

Innovative concentrating PVT solar collector concepts based on a CPC geometry concept were developed to outperform the asymmetric Solarus CPVT collector and therefore decrease the energy/performance gap between CPVT and PV/ST solar collectors. The updated reflector geometry proved to be the most suitable reflector geometry for CPVTs, where the electrical peak efficiency per gross area reached 10.6%, which is +16.5%rel higher than the electrical peak efficiency of the Solarus CPVT. Optical efficiencies of η0 = 62.3% and η0 = 61.8% for CPC 1 and CPC 2 have been achieved, respectively. A PV module (0.5 m2) combined with an ST solar collector (0.5 m2) system to be able to deliver the same overall energy yield as the newly developed CPVT collector (1 m2) requires on average +0.02 m2 (at 45 °C), −0.06 m2 (at 55 °C) and −0.15 m2 (at 65 °C) of installed area, for a wide range of latitudes. A CPC-PVT system to increase its competitiveness requires a material cost reduction and at the same time an increased overall efficiency. Nevertheless, the energy/performance gap between a system composed of PV + ST technologies and a CPC-PVT decreased significantly.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Bifacial PVT receiver; Collector testing; Glazed CPC-PVT hybrid solar collector; Incidence Angle Modifier
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:hig:diva-39828 (URN)10.1016/j.apenergy.2022.119653 (DOI)000877456000001 ()2-s2.0-85135968615 (Scopus ID)
Funder
EU, Horizon 2020, 814865
Available from: 2022-08-29 Created: 2022-08-29 Last updated: 2024-07-02Bibliographically approved

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