Testing Bifacial PV Cells in Symmetric and Asymmetric Concentrating CPC Collectors

Gomes João, Henrik Davidsson, Gruffman Christian, Maston Stefan, Karlsson Björn

Division of Energy Engineering, Malardalen University, Vasteras, Sweden.
Energy and Building Design, Lund University, Lund, Sweden.
Finsun AB, alvkarleby, Sweden.
R&D Department, Solarus Sunpower, alvkarleby, Sweden.

DOI: 10.4236/eng.2013.51B034                

Abstract

 

Bifacial PV cells have the capacity to produce solar electricity from both sides and, thus, amongst other advantages, allow a significantly increase both in peak and annual power output while utilizing the same amount of silicone. According to the manufacturer, the bifacial cells are around 1.3 times more expensive than the single-sided cells. This way, bifacial PV cells can effectively reduce the cost of solar power for certain applications.
Today, the most common application for these cells is in stationary vertical collectors which are exposed to sunlight from both sides, as the relative position of the sun changes throughout the day. Another possible application is to utilize these cells in concentrating collectors. Three test prototypes utilizing bifacial PV cells were built. The initial two prototypes were built for indoor testing and differed only in geometry of the reflector, one being asymmetric and the other symmetric. Both prototypes were evaluated in an indoor solar simulator. Both reflector designs yielded positive electrical performance results and similar efficiencies from both sides of the cell were achieved. However, lower fill factor than expected was achieved for both designs when compared to the single cell tests. The results are discussed and suggestions for further testing are presented. A third prototype was built in order to perform outdoor evaluations. This prototype utilized a bifacial PV cells string laminated in silicone enclosed between 2 standard glass panes and a collector box with an asymmetric CPC concentrator. The prototype peak electrical efficiency and temperature dependence were evaluated. A comparison between the performance of the bottom and top sides of the asymmetric collector is also presented. Additionally, the incidence modifier angle (IAM) is also briefly discussed.

 

Keywords

Bifacial PV cells, Symmetric and asymmetric concentrating concentrators; reflector geometry, prototype, NOCT

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	International Renewable Energy Agency, “Renewable Energy Technologies: Cost Analysis Series - Solar Photovoltaic”, Volume 1: Power Sector Issue 4/5, June 2012.
[2]	A. Kr?nzl, R. Kopecek, K. Peter, P. Fath “Bifacial Solar Cells on Multi-Crystalline Silicon with Boron BSF and Open Rear Contact”. Proceedings of the 4th World Conference on Photovoltaic Energy Conversion. May 2006 Vol. 1, pp 968 – 971.
[3]	V. D. Mihailetchi et al. “Screen Printed N-Type Silicon Solar Cells for Industrial Applications”. 25th European Photovoltaic Solar Energy Conference and Exhibition, 6-10 September 2010, Valencia, Spain DOI: 10.4229/25thEUPVSEC2010-2DO.2.2
[4]	C. Duran et al. “Bifacial Solar Cells with Selective B-BSF by Laser Doping”. 24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany. DOI: 10.4229/24thEUPVSEC2009-2CV.5.19
[5]	Alanod, reflector manufacturer, 2012. http://alanod.com.
[6]	Bernardo R. et al., “Measurements of the Electrical Incidence Angle Modifiers of an Asymmetrical Photovoltaic/Thermal Compound Parabolic Concentrating-Collector,” Power and Energy Engineering Conference and Engineering, Sanya, China, Dec 31, 2012 - Jan 2, 2013, unpublished
[7]	Bernardo, L.R et al. Performance evaluation of low concentrating photovoltaic/thermal systems: A case study from Sweden. Solar Energy 2011, 85, 1499-1510
[8]	N. Gentile et al., "Construction of a small scale laboratory for solar collectors and solar cells in a developing country", Power and Energy Engineering Conference and Engineering, Sanya, China, Dec 31, 2012 - Jan 2, 2013, unpublished
[9]	S. Wenham et al, "Applied Photovoltaics", 2nd edition, Earthscan, London, 2007, ISBN 978-1844074013