Research Papers

Sun Tracker Performance Analysis for Different Solar Module Technologies in an Alpine Environment

[+] Author and Article Information
Philip Ingenhoven

Institute for Renewable Energy,
European Academy of Bolzano,
Viale Druso 1,
Bolzano 39100, Italy
e-mail: philip.ingenhoven@eurac.edu

Giorgio Belluardo, David Moser

Institute for Renewable Energy,
European Academy of Bolzano,
Viale Druso 1,
Bolzano 39100, Italy

Wolfram Sparber

Head of the Institute
Institute for Renewable Energy,
European Academy of Bolzano,
Viale Druso 1,
Bolzano 39100, Italy

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING. Manuscript received October 14, 2013; final manuscript received December 10, 2013; published online January 10, 2014. Assoc. Editor: Santiago Silvestre.

J. Sol. Energy Eng 136(3), 031005 (Jan 10, 2014) (6 pages) Paper No: SOL-13-1306; doi: 10.1115/1.4026253 History: Received October 14, 2013; Revised December 10, 2013

The objective of this study is to compare the performance of different solar module technologies mounted on a fixed-tilt rack (30 deg) as well as on a single and a dual axis tracker. The data of this study were taken from a 724 kWp multitechnology test field at the Airport of Bolzano in the Italian Alps (position ca.46.46N, 11.33 E), which the European Academy of Bolzano is monitoring. The technologies tested were polycrystalline silicon (p-Si) and heterojunction with an intrinsic thin-layer (HIT). We compared the performance of each system in terms of energy output, as well as the performance ratio of both technologies on the different mounting systems. A detailed shading analysis was performed and losses due to the mountainous environment were determined. Further we analyzed miss-tracking, namely, due to shading of the position sensor on the single axis tracker and further, due to high wind speeds, at which the dual axis tracker moves to a safety position. Identifying these problems helps to maximize the tracker performance and hence the energy harvest. A cost benefit analysis was then performed based on the cost of the trackers, energy price, and by comparing the results with fixed installations.

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Grahic Jump Location
Fig. 1

Average daily energy yield of the HIT (top) and p-Si (bottom) modules for each month and mounting system

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Fig. 2

Performance ratio of the HIT modules on the rack (black), single axis tracker (grey), and the dual axis tracker (white), the inset shows the average daytime module temperature (colour coding is the same as for the PR)

Grahic Jump Location
Fig. 3

Same as Fig. 2 for the polysilicon modules, rack (black), single axis tracker (grey), and the dual axis tracker (white)

Grahic Jump Location
Fig. 4

Pseudoperformance ratio as defined in Eq. (4) for the HIT and p-Si modules, rack (black), single axis tracker (grey), and the dual axis tracker (white), the dual axis tracker performs better most of the year. In July and August, however, the mono-axis tracker performs better, indicating problems with the dual axis tracking.

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Fig. 5

Possible irradiance without the influence of mountain shading as computed (dashed) and the actual measured data (solid) for a clear sky days in April, July, October, and January for all three mounting systems

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Fig. 6

Shading diagram (solid line) and path of the sun at winter (dashed) and summer (dotted-dashed) solstice and at autumn and spring equinoxes (dotted)

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Fig. 7

Losses in percent of the value for the insolation calculated without the influence of mountain shading. The losses are largest for the dual axis tracking system (white) and least for the rack (black). It is interesting to observe that the losses in general are largest in December and January, but for both tracking systems they rise again in summer after dropping in spring.

Grahic Jump Location
Fig. 8

Irradiance data for different days in which miss-tracking occurred. (a) Single axis tracker in winter, the sun position sensor “misses” the sun rise. (b) Due to high wind speeds, the dual axis tracker is driven into a horizontal safety position, where wind speed data are average 3.4 m/s and maximal 6.0 m/s. (c) In summer, the single axis tracker produces more than the dual axis tracker; in theory, it should be the other way around.



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