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# Question: insolation latitude time of year and the optimum orientation of...

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Insolation, Latitude, Time of Year, and the Optimum Orientation of Solar Panels

Brief Description: The global pattern of insolation (incoming solar radiation) is a major determinant in the geographic variation of surface air temperatures. Therefore, to understand temperature patterns we must first explain variation in insolation. This exercise uses solar panel orientation as a means to examine the relationship between insolation, latitude, and time of year. For highest efficiency, solar panels need to be pointed in the direction that captures the most sun. Since insolation varies with latitude, a solar panel's "Optimum Tilt" is dependent on its geographic location. Your job in Part A of this assignment is to determine the angle that solar panels in ten different locations need to be pointed in for maximum efficiency. In Part B you will discuss your findings.

Background Information: Recall that the angle at which the sun's rays strike the Earth's surface is highest at the equator and decreases towards the poles. Furthermore, for any one location this angle (also called the angle of insolation) varies throughout the course of the year as the Earth orbits the sun (this is also due to the fact that the Earth's axis is tilted 23.5°). Although other factors play a role (e.g., elevation, coastal vs. interior location, etc.), in general the higher the angle of the sun in the sky the warmer surface temperatures will be.

Part A:

Using Table 1 below, please determine the optimum solar panel orientation for each location in both June and December and fill in the blanks for each location on Table 2.

Note that the angle from horizontal means the angle that the panel is tilted from lying flat to either the north or south. For this chart, if the location is in the Northern Hemisphere, a southward tilt (i.e. the lowest point of the solar panel is to the south and its higher end is to the north) is positive and a northward tilt is negative. If the location is in the Southern Hemisphere, a northward tilt is positive and a southward tilt is negative (see Figure 1).

Also note, June is summer in the Northern Hemisphere, but winter in the Southern Hemisphere and December is winter in the Northern Hemisphere and summer in the Southern Hemisphere.

 Table 1: Latitude Panel Orientation Angle from Horizontal- Summer Panel Orientation Angle from Horizontal- Winter 0-10° -19.7 28.5 11-20° -10.5 37.4 21-30° -1.3 46.3 31-40° 7.9 55.1 41-50° 17.1 64.1

 Table 2: Location Latitude Optimal June Solar Panel Angle Optimal December Solar Panel Angle Cusco, Peru 13°S Bari, Italy 41°N Amman, Jordan 31°N Manila, Philippines 14°N Dunedin, New Zealand 45°S Kumasi, Ghana 6°N Montevideo, Uruguay 35°S Noumea, New Caledonia 22°S Taipei, Taiwan 24°N Port Moresby, Papua New Guinea 9°S

Part B:

Please answer or discuss the following questions. Note that insolation is the incoming solar radiation. In other words, insolation will be highest when the Sun is higher in the sky and in the sky for more hours per day:

1.   a) Which of these locations would receive the greatest insolation over the course of a year based solely on latitude (hint: look at your lecture notes and book)?

b) Which of these locations would receive the least insolation over the course of a year based solely on latitude?

c) Which of these locations would receive the greatest insolation on December 22 based solely on latitude?

d) Which of these locations would receive the greatest insolation on June 22 based solely on latitude?

2. Draw a diagram showing the optimal positioning of the panels on the roof of your house on June 22 if you lived in 1) Montivideo, Uruguay, 2) Kumasi, Ghana, and 3) Storrs, CT. We have given you a sample for Dunedin, New Zealand to get you started. Because Dunedin is in the southern hemisphere, June 22 is the local winter solstice and the sun will be far to the North. Thus, the solar panel angle needs to be at a large angle from horizontal (~64.1 degrees tilted north) to maximize the small amount of winter sunlight. We have drawn in a horizontal line for you to measure the angle from. Please indicate the angle you are using along with your line.