Science Fair 2011-12

ABSTRACT

The Illinois Junior Academy of Science

CATEGORY Environmental Science STATE REGION # ________6________
SCHOOL Adlai E. Stevenson High School IJAS SCHOOL # ___6092__________
CITY/ZIP Long Grove, 60047 SCHOOL PHONE _(847) 415-4000_____
SPONSOR Mrs. Palffy

NAME OF EXHIBITOR* Han Song Huang GRADE 9 NAME OF EXHIBITOR _____________ GRADE

NAME OF EXHIBITOR GRADE

NAME OF EXHIBITOR ______________________ GRADE ___________ * If this project is awarded a monetary prize, the check will be written in this exhibitor’s name, and it will be his/her responsibility to distribute the prize money equally among all participating exhibitors.

PROJECT TITLE The Effect of Dirtiness on Solar Panel Output__
Purpose:
The purpose was to find out how much four years’ worth of grime will affect solar panel output
Procedure:
1. Begin recording output from inverter for dirty solar panels 6 minutes and 35 seconds before apex of sun; record output every 5 seconds until 20 measurements have been recorded. Determine 5-second intervals by looking at stopwatch. 2. Use cleaning cloth and bucket of warm water to clean solar panels completely, taking 10 minutes. Wait for apex to pass. 3. Begin recording output from inverter for clean solar panels 5 minutes after apex; record output every 5 seconds until 20 measurements have been recorded.
Conclusion: As shown in the experiment, the cleaning of the solar panels did result in an increase in output. Therefore, the hypothesis was proven correct. After cleaning, the output of the solar panels increases an average of 3 watts every 5 seconds.

SAFETY SHEET

The Illinois Junior Academy of Science

DIRECTIONS: The student is asked to read this introduction carefully, fill out the bottom of this sheet, and sign it. The science teacher and/or advisor must sign in the indicated space.

SAFETY AND THE STUDENT: Experimentation or research may involve an element of risk or injury to the student, test subjects and to others. Recognition of such hazards and provision for adequate control measures are joint responsibilities of the student and the sponsor. Some of the more common risks encountered in research are those of electrical shock, infection from pathogenic organisms, uncontrolled reactions of incompatible chemicals, eye injury from materials or procedures, and fire in apparatus or work area. Countering these hazards and others with suitable controls is an integral part of good scientific research.

In the box below, list the principal hazards associated with your project, if any, and what specific precautions you have used as safeguards. Be sure to read the entire section in the Policy and Procedure Manual of the Illinois Junior Academy of Science entitled "SAFETY GUIDELINES FOR EXPERIMENTATION" before completing this form. There was no risk involved in this experiment. The experimenter was at least 60cm away from the electrical wire, which was insulated with rubber, at all times. There was an adult in the room to make sure all safety precautions were being followed.

SIGNED_____________________________________________________________
Student Exhibitor(s)

SIGNED_____________________________________________________________
Sponsor*

*As a sponsor, I assume all responsibilities related to this project.

This Sheet Must Be Typed

This form MUST be displayed on the front of the exhibitor’s display board. It may be reduced to half a sheet of paper.

The Effect of Dirtiness on Solar Panel Output

By

Han Song Huang

Table of Contents

Abstract Pg. 1
Safety Pg. 2
Title Page Pg. 3
Acknowledgements Pg. 5
Purpose and Hypothesis Pg. 6
Review of Literature Pgs. 7-12
Materials and Constants Pg. 13
Procedure Pg. 14
Results Pgs. 15-17
Conclusion Pg. 18-19
References Pgs. 20-22

Acknowledgements I would like to thank the people who have helped me for this science fair project. Mr.Wilms helped me to gain access to the inverter and he cleaned the solar panels as well as doing a statistical analysis of the data. He was a major contributor to the effort of this project. Mrs.Ragusa and Mrs.Palffy, my sponsors, helped me to edit, finalize, and take me through the formality steps as well as having helped come up with this topic by combining other possible project ideas that I had.

Purpose and Hypothesis

Purpose: Determine to what extent cleaning affects solar panel power output. This is important because after carrying out this experiment, one can determine whether or not cleaning the solar panels did indeed make a difference. By doing so, people would not have to clean their solar panels as much and therefore reducing the risk of injury.

Hypothesis: If a solar panel that has been covered with air pollution particulates collected over a period of 4 years is cleaned, then the power output, measured in watts, will increase significantly.

Review of Literature
What are Solar Panels?
` Photovoltaic technology is the center of solar power. In 1954, Daryl Chapin, Calvin Fuller, and Gerald Pearson developed the first silicon photovoltaic, or PV, cell. In 1959, Western Electric began to sell products that involved PV cells such as dollar bill changers. Sharp Corporation produced practical PV cells in 1963. Throughout the 20th century, many companies have continuously made advancements in solar cell efficiency, with the National Renewable Energy Laboratory achieving 32.3% efficiency for the capacity of the sun able to be absorbed (“The history of,” n.d.). A solar panel is basically a connection of multiple PV cells to generate sufficient electricity. The PV cells are formed by a thin layer of semi-conductors, mainly silicon. Silicon by itself makes a poor conductor, but if treated with phosphorous or arsenic and doped with gallium or boron, then it conducts electricity well. There are two types of silicon semi-conductors used. The N-type is treated with arsenic or phosphorous and makes an electron current, which is negatively charged. The P-type is silicon doped with gallium or boron. “Holes” appear so the electrons have nothing to bond with, and it is positively charged. Once exposed to light, the solar energy from each photon, or light particle will disrupt the electrical neutrality. The electrical field in the cell creates a voltage and further creates power (“How solar panels,” n.d.). Silicon has a very narrow absorption range on the electromagnetic spectrum. In order to be highly effective, the wavelength in nanometers is between 200 and 400nm (“Optical properties of,” n.d.). On the electromagnetic spectrum, the visible light spectrum takes up 400-700nm, with the wavelength of red at 700nm and purple at 400nm. The wavelength range of ultraviolet light is from 250nm to 400nm (“Color and light,” n.d.). Therefore, the absorption range of silicon in terms of type of light emitted is about 75% of ultraviolet light until the range of visible purple light.
Many of the solar cells in use today are made from crystalline silicon. Although silicon is a poor light-absorbing material, it produces very stable cells with 11-16% efficiency. There are three variations of a silicon cell: monocrystalline, polycrystalline, and amorphous. Monocrystalline cells are the most expensive and most efficient; they are made by slicing thin pieces of high purity single crystal rods or boules of silicon. The more cost-friendly type is the polycrystalline, made from melted silicon molded into blocks and then cut into plates. Defects happen during solidification and thus decrease efficiency. The least efficient type is amorphous, where a piece of silicon about 50-100 times thinner than human hair is placed on glass or stainless steel. It is relatively cheap and achieves no more than 8% efficiency. Amorphous PV cells make up about 10% of the current PV market, and some other options to amorphous are copper indium diselenide and cadmium telluride. Scientists are also researching microcrystalline silicon, which combines the efficiency of polycrystalline with the large area capabilities of the amorphous (“What are the,” n.d.). Solar cells have many advantages and disadvantages. Advantages are that once the cost has been recovered, the energy is free. Financial incentives are also available through the government that will reduce cost (“Solar energy advantages,” n.d.). With tax incentives, the initial cost can often be paid back fully in five to ten years (“Solar energy,” n.d.). Also, it is not subject to the supply and demand of gasoline and indirectly reduces health costs by reducing the amount of carbon dioxide in the atmosphere. Solar power gives people jobs and creates a running economy. As long as there is sunlight, then it will continue to supply electricity even in the event of a power outage. However, the main disadvantage is the initial cost, which is extremely expensive. In order to be productive and efficient, a large area is needed to install the solar panels (“Solar energy advantages,” n.d.). Solar panels do not work at night without a storage battery, and weather can make it unreliable during the day (“Solar energy,” n.d.).
The technology provides stability because there are no moving parts and it is self-sustained. This requires almost no maintenance. Also, there are no products which may pose a threat to humans or the environment and it makes almost no noise. Homes in remote locations use solar power because the electrical network does not extend there. Before, making electricity from the sun has been incredibly expensive (“Solar energy solutions,” n.d.). For example, in the neighborhood of Long Grove with a monthly electrical bill of about $90, the cost is about $32500 for installation and occasional maintenance. It will need a roof space of 466 square feet (“Solar calculator,” n.d.). However, recent increases in efficiency and more environmental awareness have led to wider use of solar panels in Europe, Japan, and the United States (“Solar energy solutions,” n.d.).
Research Done on Factors Affecting Solar Panels
Previous research done in an experiment conducted by the University of Southern California found out that the output of the PV cell decreases as the amount of dust increase. At a dust concentration of 2067 ppm, the sunlight will be completely blocked out (Khemani, n.d.). Assuming it is grain dust, it will cover up to 0.1 cm, or 1 mm of dust (“Particle sizes,” n.d.). This occurs because the dust prevents the photons from the sun from reaching the PV cells and thus creating electricity. Places with frequent dust storms will often render solar panels useless because of the large amount of dust buildup. Some high population locations with dust storms include Texas, Arizona, northern China, and central Australia (“Dust storms, 2010”). In addition, in a recent study, it is stated that the effect of soiling on flat solar panels is that it causes a reduction of 4% in output on average since it produces light scattering at the surface of the PV cells. The scattered photons will be lost because they cannot refocus (Vivar, 2010). Another area that affects the output of solar panels is particulate pollution. This is where particles are carried by the wind and drop onto the tops of objects at random; this is especially a big problem for solar panels in cities. The size of particles varies. Fine, or small, particles are 2.5 micrometers in diameter, and they are so tiny that an electron microscope is required in order to see them; they are about 3% the diameter of a human hair. Fine particles are emitted from a variety of sources. Most are from atmospheric chemical reactions of gases and dust stirred up by vehicles travelling on the roads (“What is pm?,” n.d.).
Factors Affecting This Experiment In this experiment, the apex was chosen as the time around which to take samples. The apex of the sun is usually around noontime. The apex is also when the sun is at its highest point in the sky. Therefore, it is also when the sun releases the most amount of energy. By selecting the month, year, and location on a website that finds out the apex of the sun, sunset, and sunrise, one can easily understand when the solar noon or apex of the sun is. For example, on December 5th, 2011, the apex is at 11:41 AM; also, the apex for December 6th, 2011, is 11:42 AM. By reading the chart provided by the website, one can see when the apex of the sun is at any given day (Thorsen, 1998). The angle of incidence of the sun must also be in the same range when taking samples in order to maintain a constant. The dependent variable in this experiment is power in watts. The watt is a unit that measures electrical energy necessary for an item. For example, a light bulb might be 60 watts while a hair dryer may be 1100 watts. Watts are also used to measure the efficiency of certain devices such as solar panels. The household appliances that consume the most amount of electricity are air conditioning systems, large motors, and small electronics. However, the environment pays a heavy price for it. To produce one kilowatt hour of electricity, approximately one pound of coal is needed. Also, for every megawatt, or 1000 kilowatts, half a ton of coal needs to be mined and one ton of carbon dioxide is released into the atmosphere (Arthur, 2008). The units of this experiment will be watts. In order to measure the output of the solar panels at any given moment, an inverter is needed. The inverter is a machine connected to the solar power grid that gives a reading of solar panel output in watts. Since the sun and weather are unstable, the output readings from the inverter changes very frequently, often around every 2 or 3 seconds. Proper cleaning methods also had to be used to conduct this experiment. Cleaning solar panels is simple. First, make sure there are no cracks. Then, by using a bucket of warm soapy water and a soft sponge, gently scrub the solar panels. Afterwards, dry it with a towel or the grime will just move around rather than being washed away (“How to clean,” n.d.).

Materials & Constants
Materials:
* Inverter * Cleaning cloth * A bucket of warm, soapy water * 1 printed out Excel spreadsheet * 1 No.2 pencil * 5 solar panels on top of a roof at Adlai E. Stevenson High School, approximately 5 meters wide and 2 meters tall * Stopwatch
Constants:
* Date * Angle of incidence of the sun * Time interval between measurements * Same time from apex

Procedure: 1. Conduct experiment on a sunny and cloudless day so that the sun will not be affected by cloud cover. 2. Go to classroom where inverter is located; make sure that polycrystalline solar panel can be seen from vantage point in front of inverter. 3. Begin recording output every 5 seconds from inverter starting 6 minutes 35 seconds before the apex of the sun. Use stopwatch to determine 5-second intervals. 4. Stop when 20 measurements for the dirty solar panels have been recorded, which is 5 minutes before the apex. 5. Clean the solar panels with a bucket of warm water and a cleaning cloth, should take about 10 minutes. 6. When it is 5 minutes 5 seconds past the apex of the sun, begin recording output every 5 seconds again. Use stopwatch to determine 5-second intervals. 7. Stop when 20 measurements for the clean solar panels have been recorded.

Results
Energy Output of Dirty Solar Panels Prior to the Apex and Clean Solar Panels after the Apex Time (Before Apex), Dirty | Output (Watts) | Time (After Apex), Clean | Output (Watts) | Difference in Output | 6:35 minutes BA | 778w | 6:35 minutes AA | 782w | 4w | 6:30 minutes BA | 761w | 6:30 minutes AA | 781w | 20w | 6:25 minutes BA | 767w | 6:25 minutes AA | 781w | 14w | 6:20 minutes BA | 770w | 6:20 minutes AA | 781w | 11w | 6:15 minutes BA | 772w | 6:15 minutes AA | 781w | 9w | 6:10 minutes BA | 772w | 6:10 minutes AA | 781w | 9w | 6:05 minutes BA | 778w | 6:05 minutes AA | 780w | 3w | 6:00 minutes BA | 776w | 6:00 minutes AA | 781w | 5w | 5:55 minutes BA | 777w | 5:55 minutes AA | 781w | 4w | 5:50 minutes BA | 777w | 5:50 minutes AA | 780w | 3w | 5:45 minutes BA | 778w | 5:45 minutes AA | 781w | 3w | 5:40 minutes BA | 779w | 5:40 minutes AA | 781w | 2w | 5:35 minutes BA | 778w | 5:35 minutes AA | 781w | 3w | 5:30 minutes BA | 779w | 5:30 minutes AA | 780w | 1w | 5:25 minutes BA | 778w | 5:25 minutes AA | 780w | 2w | 5:20 minutes BA | 778w | 5:20 minutes AA | 781w | 3w | 5:15 minutes BA | 779w | 5:15 minutes AA | 780w | 1w | 5:10 minutes BA | 779w | 5:10 minutes AA | 781w | 2w | 5:05 minutes BA | 779w | 5:05 minutes AA | 780w | 1w | Mean for Dirty Solar Panel Power Output= 776 | Mean for Clean Solar Panel Output = 781 | t-value = -4.56p-value = 0.0001 |

Energy Output of Dirty Solar Panels Prior to the Apex and Clean Solar Panels after the Apex

Output (Watts) |
Time (In Relation to Apex)

By drawing a line graph for each set of solar panels (e.g. clean and dirty), one can see that after cleaning the solar panels, the output becomes much more stable and it tends not to have decreases in output at random points in the middle. To test whether this is statistically valid, a t-Test was conducted. The null hypothesis is testing if the means of power output before and after cleaning are the same. If the p-value is less than 0.05, then the null hypothesis is rejected and the two means are shown to be significantly different. The p-value of this experiment is 0.0001. The mean for the dirty solar panels is 776 while the mean for the clean set is 781. This shows that the average output of the clean set is significantly higher than that of the dirty set.

Conclusion The hypothesis of this experiment was that if a solar panel that has been covered with air pollution particulates collected over a period of 4 years is cleaned, then the power output, measured in watts, will increase significantly.
The experimental hypothesis was supported because the mean power output of the dirty solar panels was 776 and the mean power output of the clean solar panels was 781. The p-value when these means were compared using a t-test was .0001, which means the power output of the clean was significantly higher than that of the dirty panels.
There were some possible areas of error. The thickness of the atmosphere was not the same during the same amount of time on either side of the apex, and that would have made the output readings on either side of the apex different. After cleaning the solar panels, the water may not have been completely dried off, so the output readings for the clean solar panels may have been lower than actual. Since there are special products made for cleaning solar panels, using water may not have been the best way that made a difference, so it would not have been the most effective way to increase the output. The weather may not have been stable. For example, a cloud may have passed overhead and therefore produced an outlier. After conducting this experiment, the hypothesis has been proven correct. Cleaning the solar panels did cause a significant increase in power output. This shows that cleaning once about every four years is necessary for the solar panels to be kept at their peak performance level. Unfortunately, since solar panels will have to be cleaned occasionally, the risk of injuries and fatalities will be greater than if solar panels do not have to be cleaned at all. Also, since there were outliers in both sets of data, the one in the dirty set was 759 and the one in the clean set was 771, and they were both in the same angle of incidence in relation to the sun before and after the apex, they were taken out so a statistical analysis could be conducted.
I used the solar panels provided by the school to conduct this experiment. Therefore, I only had one set of solar panels to work with and could not conduct multiple trials. Since only one trial was conducted, I would like to find a way to somehow simulate the natural air pollution particulates that build up on solar panels over time so multiple trials can be conducted. Therefore, the data would be much more reliable and consistent. In addition, since grime will continue to build up until I conduct another experiment, I would like to clean the solar panels again exactly a year from the day which I cleaned it. Then, I could determine how one year of grime affects the output compared to four years of air pollution particulates.

References

Arthur, A. (2008, February 22). What is a watt?. Retrieved from http://andyarthur.org/fodder/energy/watt.html Color and light. (n.d.). Retrieved from http://www.optics4kids.org/Home/TeachersParents/Articles/Color-and-Light.aspx Dust storms. (2010). Retrieved from http://www.osei.noaa.gov/Events/Dust/

How solar panels work. (n.d.). Retrieved from http://www.siemenssolar.com/how-solar-panels-work.html How to clean a solar panel. (n.d.). Retrieved from http://www.practicalenvironmentalist.com/green-building/how-to-clean-a-solar- panel.htm

Khemani, A. (n.d.). California state science fair. Retrieved from http://www.usc.edu/CSSF/History/2010/Projects/J1017.pdf Optical properties of silicon. (n.d.). Retrieved from http://pveducation.org/pvcdrom/appendicies/optical-properties-of-silicon Particle sizes. (n.d.). Retrieved from http://www.engineeringtoolbox.com/particle-sizes-d_934.html Solar calculator. (n.d.). Retrieved from http://www.findsolar.com/index.php?page=rightforme Solar energy advantages and disadvantages. (n.d.). Retrieved from http://facts-about-solar-energy.com/solar-energy-advantages-disadvantages.html Solar energy. (n.d.). Retrieved from http://environment.nationalgeographic.com/environment/global-warming/solar-power-profile/ Solar energy solutions. (n.d.). Retrieved from http://www.siemenssolar.com/solar-panels.html The history of solar. (n.d.). Retrieved from http://www1.eere.energy.gov/solar/pdfs/solar_timeline Thorsen, S. (1998, May 24). Sunrise and sunset in chicago. Retrieved from http://www.timeanddate.com/worldclock/astronomy.html?n=64&month=12&year=2011&obj=sun&afl=-11&day=1 What are the common types of solar cells?. (n.d.). Retrieved from http://www.siemenssolar.com/types-solar-cells.html What is pm?. (n.d.). Retrieved from http://www.epa.gov/airnow/airaware/day1-PM.html

Solar powered solutions. (n.d.). Retrieved from http://webpages.csus.edu/~bmw97/

Vivar, M., Herrero, R., Anton, I., Martinez-Moreno, F., Moreton, R., Sala, G.,
Blakers, A. W., & Smeltink, J. (2010, March 31). Effect of soiling in cpv systems.. Retrieved from http://web.ebscohost.com/ehost/detail?vid=9&hid=12&sid=dcb63af3-3ada-4b68-b612-9db1273fd30f%40sessionmgr112&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=aph&AN=51150691

References: Arthur, A. (2008, February 22). What is a watt?. Retrieved from http://andyarthur.org/fodder/energy/watt.html Dust storms. (2010). Retrieved from http://www.osei.noaa.gov/Events/Dust/ How solar panels work Thorsen, S. (1998, May 24). Sunrise and sunset in chicago. Retrieved from http://www.timeanddate.com/worldclock/astronomy.html?n=64&month=12&year=2011&obj=sun&afl=-11&day=1 Blakers, A. W., & Smeltink, J. (2010, March 31). Effect of soiling in cpv systems.