AME 20213 LEX-4 Solar Panels Week 2-3 TA: Dustin Coleman Email: dcolema4@nd.edu LEX-4 website : www.nd.edu/ dcolema4/homepage/ame 20213.html Report Due: May 3, 2011 Last Revised: April 18, 2011 Overview Weeks 2 and 3 will be an independent study of solar panel characterization and practical operation. This study will include panel output as a function of angle of incidence and as a function of time of day. These parameters will be used to draw a conclusion on the practicality of using the given solar panels to power the student s dorm room. The student will also develop a further study of their choosing. 1 Measurement Procedure It is suggested that the student use a Fluke handheld multimeter for the outside experiments. For the lab it is suggested to use the HP 3468A Multimeter for all measurements, however, if time resolution is of concern or interest the student may use the LabQuest system. Proper operations for both are listed below. 1.1 HP 3468A Multimeter Current: Set the toggle switch to short and unplug everything from the V posts. Connect the meter leads to the I posts. Current is measured with the black lead in the LO connector, and the red lead in the A (bottom) connector on the meter. Voltage: Set the toggle switch to short and place a shortening plug in the I posts. Connect the meter leads to the V posts. On the multimeter, the black lead should be in the LO socket, while the red prong should be in the HI connector. 1.2 LabQuest Data Acquisistion Please refer to the LabQuest Reference Guide found on the TA s website. 2 Power Output vs. Angle of Incidence First, the student will study the effect on varying angle of incidence on power output of the panel. In order to determine the solar panel s orientation with respect to irradiant 1
sunlight, several quantities describing the relationship between the Earth and the Sun must be determined. These parameters include: 2
Latitude (φ): South Bend s latitude is 41.68. Declination (δ): Declination is the angle between the line joining the centers of the Earth and the Sun and its projection on the equatorial plane. It is defined as, [ ] 360 δ = 23.45 sin (284 + n), 365 where n is the day of the year (i.e., n = 1 on January 1 and n = 32 on February 1). Hour angle (ω): The angular displacement of the Sun east or west of the local time zone s meridian. The hour angle is zero at solar noon, negative in the morning and positive in the afternoon for the northern hemisphere. It can be calculated from, ω = (ST 12[hr]) 15[ /hr] where ST is the Solar Time (time based on the apparent angular motion of the sun across the sky, with solar noon denoting the time the sun crosses the meridian of the observer). Since we re taking these measurements now, in April, we need to account for daylight savings time, which means subtract 1 hour from our current time to get the standard time. The difference between solar time and our standard time is plotted in Figure 1, shown over the duration of this lab. -41.5 Solar time - Stanard time [min] -42-42.5-43 -43.5-44 -44.5 108 110 112 114 116 118 120 122 day of year, n Figure 1: Solar time difference from standard time (April 18 - May 2, South Bend, Indiana) Slope (β): The angle between the panel surface and the horizontal plane. This angle requires measurement. 3
Azimuth (γ): The angle between the line due south of the surface under consideration and the projection of the surface s normal onto the horizontal plane. This angle requires measurement. These quantities can be used to determine the angle of incidence, θ, between the solar panel s normal direction and the irradiant sunlight, as shown in (1)[1]. cos θ = (cos φ cos β + sin φ cos γ) cos δ cos ω + cos δ sin ω sin β sin γ + sin δ (sin φ cos β cos φ sin β cos γ) (1) It is suggested that the student measure the power output in a parametric sweep for at least 4 β values and 4 γ values, however, a finer resolution of both angle effects will result in an optimum incidence angle for maximum power. A sample test matrix may look something similar to Table 1: Sample Test Matrix Slope, β Azimuth, γ I sc [ma] V oc [V] P=VI [mw] 0 90 0 45 0 45 0 90 30 90 30 45 30 45 30 90 60 90 60 45 60 45 60 90 90 90 90 45 90 45 90 90 3 Power Output vs. Time of Day This part of the study will essentially be testing the effect of the hour angle, ω, on power output. For this testing the student should repeat the previous study for at least 4 different times during a single day. Note the weather conditions during each time. Ideally the best measurements would come from a day with homogenous conditions throughout. 4
4 Practical Use of Solar Panel During this part of the exercise the student will assess the practicality of using photovoltaic solar panels to power their dorm room. First, the student must estimate the total power usage of their dorm room on a typical day. Next, use the information from part 2 and 3 to determine the maximum power output that can be achieved on a given day. Assuming that we have devices to store as much energy as possible, the student must estimate how many solar panels are needed to power their dorm room based on the peak power during the day. Finally, given a cost per solar panel and the price of kwh for a dorm, the student must compute the payback period of the solar panels (i.e., given an initial start-up cost of buying the panels, how long until they pay for themselves?). 5 Further Studies To receive full credit in the report the student should investigate an interesting topic further and weave it seamlessly into the previous investigations. Topics could include: a comparison of the transient response of the given solar panels, both with the flood light and with the sun, the efficiency of the solar panels, a prediction for the total emissive power of the sun, a discussion of the panels behavior with temperature, a further investigation on the financial analysis of solar panels, a discussion on intermittent conditions in South Bend and its effect on panel behavior (are they practical to use in this area?), a discussion of other ways to take advantage of solar energy (thermal properties, etc.) could the solar panel be calibrated for use as a light meter? These are just a few examples of further studies that could be done, however, the student is encouraged to be extremely creative and put effort towards developing a unique experiment/study. Most of all have fun with the last two weeks of lab! References [1] G. N. Tiwari. Solar Energy: Fundamentals, Design, Modelling and Applications. CRC Press, 2002. 5