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Minimizing the impact of shading at oblique solar angles in a fully enclosed asymmetric concentrating PVT collector
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.ORCID iD: 0000-0002-8156-2587
Instituto Superior Tecnico, Av. Rovisco Pais, Lisboa, Portugal .
Energy and Building Design, Lund University, Lund, Sweden .
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
2014 (English)In: Energy Procedia, ISSN 1876-6102, Vol. 57, p. 2176-2185Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2014. Vol. 57, p. 2176-2185
Keywords [en]
Asymmetric CPC collector; PVT hybrid; shading; Transparent / Reflective end gables; Electrical Efficiency; Cell Size;
National Category
Energy Systems
Identifiers
URN: urn:nbn:se:hig:diva-18519DOI: 10.1016/j.egypro.2014.10.184ISI: 000348253202033Scopus ID: 2-s2.0-84922311436OAI: oai:DiVA.org:hig-18519DiVA, id: diva2:770935
Conference
2013 ISES Solar World Congress, 3-7 November 2013, Cancún, Mexico
Available from: 2014-12-11 Created: 2014-12-11 Last updated: 2023-08-28Bibliographically approved
In thesis
1. Development of Concentrating Photovoltaic-Thermal Solar Collectors
Open this publication in new window or tab >>Development of Concentrating Photovoltaic-Thermal Solar Collectors
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Abstract [sv]

Denna avhandling syftar till att samla kunskaper om solenergi i allmänhet och PVT-hybrider som ger både el och värme i synnerhet. Särskilt stort intresse riktas mot koncentrerande C-PVT-hybrider.

Avhandlingen ställer ett flertal viktiga forskningsfrågor för PVT och CPVT solfångare och försöker svara på dem. En omfattande marknadsstudie av solvärme (ST), solceller (PV) och PVT har genmförts för att erhålla priser och prestanda.

Studien användes som underlag för energiutbytessimuleringar runt om i världen. Ett förhållande för kvoten mellan energiutbytena för ST och PV definierades för att användas som ett verktyg för en jämförelse mellan systemen och ritades in på världskartan.

En viktig fråga för PVT-solfångare är hur man kapslar in solcellerna på ett sätt som bland annat skyddar solcellen från absorbatorns värmeutvidgning, har hög transparens och isolerar elektriskt samtidigt som den leder värmen till absorbatorn. För att vara användbar måste denna analys också ta hänsyn till produktionsprocesserna. Flera prototyper konstruerades, en testmetod utarbetades och analysen av resultaten möjliggjorde ett antal viktiga slutsatser om funktionen hos de olika silikoninkapslingsmetoderna.

Denna avhandling baseras på verkningsgradstestning av 30 olika prototyper av C-PVT. De flesta testerna utfördes med den statiska testmetoden, men kvasidynamisk testning har också använts. Från denna testning utarbetades riktlinjer för konstruktionen av solfångarna när det gäller reflektorgeometri, cellstorlek, strängkonfiguration och inkapslingsmetod. Dessa analyser kompletterades med termiska simuleringar (COMSOL & ANSYS), stränglayout (LT SPICE)och utvärdering av befintliga installationer. Ett antal nya designidéer kommer att patenteras under de kommande åren. En ny reflektorgeometri för C-PVT som förbättrar det årliga energiutbytet har utarbetats och testats. Slutligen diskuteras PVTs nuvarande och framtida position på den globala marknaden försolenergisystem.

Place, publisher, year, edition, pages
Gävle: Gävle University Press, 2021. p. 194
Series
Doctoral thesis ; 21
Keywords
Solar Energy, Photovoltaic-Thermal (PVT), Concentration, Collector Testing, Silicon Cell Encapsulation, Ray Tracing, Market Survey, String Layout, Prototype Collectors, Solenergi, Fotovoltaisk-termisk (PVT), Koncentration, Solfångarprovning, Inkapsling av kiselceller, Strålgångsberäkning, Marknadsundersökning, Strängdesign, Solfångarprototyper
National Category
Energy Engineering
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-35411 (URN)978-91-88145-67-3 (ISBN)978-91-88145-68-0 (ISBN)
Public defence
2021-08-27, Room 13:111, Kungsbäcksvägen 47, Gävle, 10:15 (English)
Opponent
Supervisors
Available from: 2021-06-17 Created: 2021-03-09 Last updated: 2024-08-29Bibliographically approved

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Gomes, JoãoKarlsson, Björn

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