Science Buddies: "Ask an Expert"

I did a web search for "solar panel effective angle" and came up with nothing, so I don't know exactly what you mean. I think you mean to ask, "What angle for the panel yields the most output in a day of operation?"
The concept of a control group is used when your study consists of a number of different entities that may be measured only once. For example, a person contracts or does not contract the flu when he does XXX. You need to have a group of people who did XXX and a group of people who did not XXX (the control group). In your experiment you are making as many measurements of the solar cell output as you wish. Each measurement is made on the same solar cell, is rather accurate, you know the angle for each, and uncontrolled factors have little influence. You are just measuring a single variable (angle) to see what is best.
Yes, you should make a large number of measurements to cover all the possibilities. Be sure to note all the potentially important factors in each measurement: time-of-day, date, latitude, longitude, cloud cover, temperature (maybe your solar cell efficiency is affected by temperature), etc. Relate your results to what you expect to find by the analysis you refer to. Did the maximum output occur at the expected angle? Explain why. If not, what theory can you formulate to explain why not.
Good luck.

Yes, I suppose that you can use the measurements for your panel at any fixed angle as the control and the measurements at all other angles as your experimental group. In an experiment like yours, I might refer to the control measurements as "calibrating" the equipment, but it's also certainly properly referred to as a control. In fact, if you measure the panel output at the control angle every time you measure at some other angles, it will help to sort out chnages due to cloud cover, haze, etc.
By all means you want to conform to the format dictated for your project. I think the terminology of using a control is properly emphasized in science projects because control, calibration, reference, comparison, or whatever one calls it is so fundamental to doing good science.

You unfortunately have picked a VERY DIFFICULT project to test from a "control" standpoint and the teacher is intentionally pressing you on this issue to get you to think about the problem.

From a simple geometry perspective, for any given locale and day, the sun will rise up over the horizion at one point and will set down below the horizon at another. If the goal is to find the optimal three angles, azimuth, altitude, and rotation for a stationary rectangular solar panel on that day, you have a dilemma on how to provide controls and how to control the uncontrollable.

One expensive way would be to utilize a large number of calibrated solar panels set at different angles and compare the total power produced.

If the sky was always clear and had uniform transmittance, one could calculate by using an azimuth and altitude calculation and a site survey to find the sunrise and sunset points for your exact locale and assume that the best azimuth choice would be the bisection of the angle between the sunrise and sunset points. You could then assume that the mean between the maximum altitude and the average of the sunrise and sunset points would be the optimal altitude angle. Coming up with the optimal rotation is probably some function of the slope of the sunrise to sunset point and the chosen azimuth angle.

If it is cloudy in the morning and clear in the afternoon, then the optimal azimuth angle for that day would be skewed to the afternoon.

-Craig

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dvscrobe wrote:designed his home in such a way that his roof faces the sun's trajectory or Southern Hemisphere. The angle of the roof was also designed to be at the latitude angle of around 40 degrees.

This optimal design answer for that installation is for a different Scientific question. The homeowner's Scientific/Engineering question did NOT involve a "particular day". In many ways, that makes it simpler for most locales because it is intended for a much longer period of time over which there will be a wide variance of cloud conditions and the best assumptions are that any time of day cloud variations will average themselves out. For places like the east or west coast of florida with sea breeze driven afternoon thunder storms in the rainy season, there might be some historical data that might bias those assumptions as sea breeze driven thunderstorm arrival and departure times for east sea breeze dominant days and west sea breeze dominat days are about typically about three hours different on each coast.

Slight changes in the Scientific/Engineering question being asked can dramatically increase or reduce the complexity and/or results.

Dvscrobe,

I recommend that you do a web search to learn a bit more about the optimum angle for solar panels. Not to argue with your neighbor, but I think his recipe of using the latitude is definitely not optimum. A quick Google search turned up Optimum Orientation of Solar Panels and Solar Angle Calculator.
No matter how you formulate the research project, I think you or your daughter would need to spend a several days taking many readings of the panel output along with other observations such as cloud cover, fog, etc.

You need two angles. An inclination angle measured with a protractor with a level as the base reference of the protractor. The other angle you need can be measured with a magnetic compass. If you were to make a setup with a post in the ground that is vertical with a board that you can level and that will rotate and stay level, then you can hinge another board off one of its edges with a sliding support and locking mechanism to hold the boards at an angle. You can set a compass the horizontal base board to measure the azimuth. You can measure the inclination with a protractor or an inexpensive plastic QuickSquare available at your favorite building supply store as the angle between the two boards.

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IMO: IF/THEN hypothesis are not appropriate for this grade level. The danger in all IF/THEN hypothesis is that the IF clause turns out to always be false. Theses kinds of hypothesis are really only appropriate for second level problems where previous experiments have shown that multiple outcomes exist and you want to experiment ONLY on one class of outcomes specified by the IF clause.

Questions are NEVER appropriate in a well formed hypothesis.

Hypothesis are best formed as statements that are to be proved to be TRUE, FALSE, or UNDETERMINED if your testing methods and equipment are inconclusive. There is another rather sophisticated and specialized "NULL HYPOTHESIS"; however, that is well beyond what most teachers and science fair judges know how to deal with and its primary purpose is in research studies where direct experiments aren't possible.