Photovoltaic Analysis of a Solar Tracker

Daniel Conway

Department of Electrical and Computer Engineering, Iowa State University, IA - 50011

Background

Methods Further Work

Conclusions Results

Acknowledgements

Introduction

CONTACT

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Daniel Conway

Email: dycsms@gmail.com

Ankeny Centennial High School

Photovoltaics is the conversion of

light into electricity using semi-

conductive materials. This term is

most commonly known to be

attached to solar panels. Most

individuals have heard of the

concept of these solar cells, but

most to not know that there are

different types and methods of

collecting light. The data on this

poster deals with two different

encapsulations as well as

methods of collecting photons.

The goal of the research

conducted is to analyze the

difference in output of a stationary

solar cell and one on a tracker to

determine the best and most

efficient way of utilizing solar cells.

As shown in figure 1 below, the decay of the lensed

stationary cell is much higher than the flat cell on the

tracker. The efficiency of the solar tracker proved to

be superior, never going below 85% efficiency during

the course of a day. A small dip is expected for two

main reasons. One, the tracker was only single axis:

not receiving full range of motion to be perfectly

perpendicular to the sun. Second, the solar flux

naturally decreases as it moves away from solar

noon and vice versa as rays will start to be blocked

from reaching the surface as the sun moves away

from solar noon, decreasing solar flux.

The lensed cell, even with assistance from the

lensing reached 33% and was continuing to crash.

With the sun rising and setting, the cell, while

creating more power at its peak, decreases output

heavily as the sun moves away from solar noon,

creating less photons hitting the solar cell as well as

changing the angle of entry to a non-perpendicular

angle, decreasing efficiency.

The data shows for the tracker to be more

efficient at creating power in the same conditions as

a cell that is flat down on a surface, even with the aid

of lensing.

The incredibly superior efficiency of the sun

tracker from the data collected leads to the

observer to conclude that solar tracking is a

better way of increasing the output of a solar cell

compared to lensing.

Although a test of a stationary flat panel

was not conducted, it would not make sense for

that trial to produce data that shows greater

efficiency than even the lensed panel. A

continuation of the stationary lensed panel

would show greater declination of current while

the flat tracker panel continues steadily. After

normalization, the minimum efficiency of the

tracker is over 50% greater than the flat lensed

panel.

The conclusion of superior efficiency from

the data collected can be easily determined as

the tracker is far more superior. This conclusion

can be used when analyzing how a consumer

would best create the greatest efficiency of a

solar cell or panel in the local area as data will

change with location.

The steps to achieve results include:

•Gain a basic understanding of photovoltaics

•Program the stepper motor using Python to

rotate the solar panel so that it is perpendicular

to the sun throughout the day

•Construct a frame to hold the hardware and to

protect it from environmental factors such as

high winds and rain fall

•Use a wireless multimeter to log current of the

solar cell for each trial

•Convert the text file into a spreadsheet using

Microsoft Excel

Future work mainly includes further testing. Only

one trial was able to be gathered in the allowed

amount of time. Further trials would create a

more accurate conclusion when averaging data.

A control trial of a stationary flat solar panel

would be useful in gaining more information on

the benefits of applying a single axis tracker.

Finally, sophisticated hardware would increase

data logging times and reduce interruption.

Photovoltaic cells, or solar cells, convert light

into electricity. While the analysis of the output

of a tracking solar panel has been performed,

none have been conducted in this area.

Because of this, testing in the local area will

create more accurate results to use as reference

in future related experiments.

The “Flat” photovoltaic (solar) cell refers to a

solar cell that is encapsulated with a flat plastic

A “Lensed” cell contains concentrator cells which

use a plastic Fresnel lens to focus sunrays onto

the surface of the cell, increasing power output.

Thanks is given to the Young Engineers and Scientists program and Iowa State for making this opportunity possible and allowing access to the campus and its resources. I would also like to thank Vikram Dalal and Istiaque Hossain for providing guidance and funding along the process as well as Liang Zhang for programming assistance and Max Noack for hardware support.

The entire solar tracker unit

Figure 1: Graphed current throughout half of a day

Lensed Solar Panel

Flat Solar Panel

Microcontroller and Raspberry bi used to control The material presented here is based upon work supported by the Nation Science Foundation under Award No. EEC-0813570. Any opinions, findings, and conclusions

or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.