Magnetic Declination

School r ho a u l s o e S Solar Site Analysis

Sun Path Charts are useful for analyzing sites for buildings and photovoltaic systems. By measuring the height and position of shading obstacles like trees and buildings, and graphing them on a Sun Path Chart for your location, you can make a picture of the available sunlight at any time of day throughout the year. Materials • Sun Angle Quadrant (see Appendix A) • Solar Compass Rose (see Appendix B) View video tutorials for this project at: • (2) Sun Path Charts for your location (see Appendix C) solarschoolhouse.org/solarsiteanalysis • Magnetic Declination for your location (see Appendix D) or on the Solar Schoolhouse YouTube Channel • Clipboards or notebooks for the Sun Path Charts • Cardboard backing sheet for Solar Compass Rose • Magnetic compass • Scotch® tape (or other transparent tape) • Pencil Tip: If this activity is done as a group, divide up the tasks: Recorder (plots angles on Sun Path Charts), Sun Angle Quadrant Reader, and Solar Compass Rose operator. What to Do 1. Make a Sun Angle Quadrant and a Solar Compass Rose as shown in Appendix A and Appendix B. 2. Print two Sun Path Charts for your location as shown in Appendix C. Label the charts: Option 1 and Option 2. 3. Find the Magnetic Declination for your location by entering your city and state at this website: https://www.magnetic-declination.com The website shows declination in degrees (º) and minutes (‘). There are 60 minutes per degree. Round the number to the nearest degree. In other words: if the number of minutes is 29 or less round down to zero minutes. If it’s 30 minutes or more round up to the next degree. See Appendix D for further explanation of Magnetic Declination. 4. Draw a site plan of your location (i.e. a bird’s eye view sketch of surrounding buildings/trees/etc). Include two options for placement of your solar device (e.g. solar panel). Draw and label any objects that could shade your proposed solar device location. See example below.

© Rahus Institute-Solar Schoolhouse . OK to reproduce for educational purposes only. page 1 v.20210119 5. Stand at the first place where you are considering installing your photovoltaic device. 6. Correct the Solar Compass Rose orientation for magnetic declination so it points to the True North Pole as described below: a) If your location’s magnetic declination is POSITIVE (EAST), rotate the entire Solar Compass Rose page until the compass needle points to the number of degrees of declination. The ‘N’ now points to the True North Pole. See image on the left. b) If your location’s magnetic declination is NEGATIVE (WEST), subtract that number of degrees from 360. Rotate the the Solar Compass set to 17º East Decli- Compass Rose page so the needle points to nation. ‘N’ points to true north. that number of degrees. NOTE: The needle will be to the left or counterclockwise from ‘N.’ The ‘N’ on the compass now points to the True North Pole. See image on the right. 7. NOTE: BE SURE TO KEEP THE CARDBOARD IN THIS POSITION TO RETAIN THIS TRUE NORTH ORIENTATION WHILE YOU CONDUCT THE REST OF THE ANALYSIS. Compass set to 10º West Decli- 8. Without moving the cardboard backing sheet, rotate the big needle on the nation. ‘N’ points to true north. printed compass rose so one end points true east (or 90º). See example below.

The Solar Compass Rose’s big needle is pointing true east (or 90 º).

© Rahus Institute-Solar Schoolhouse . OK to reproduce for educational purposes only. page 2 v.20210119 Now we’ll measure the height of the tallest shading obstacle in the area of the sky due east of our location. 9. Hold the Sun Angle Quadrant over the Solar Compass Rose, and point the quadrant’s tube in the same direction as the big compass needle (90º or due east). 10. Look through the quadrant tube to see the TOP of any shading obstacle (i.e. tree, house, etc). Remember: DO NOT LOOK AT THE SUN THROUGH THE TUBE! Note the degrees of ALTITUDE indicated on the Sun Angle Quadrant.

11. Draw a dot on the Sun Path Chart at this number of degrees on the 90º Solar Azimuth line. In the example below the dot for the tallest obstacle at 90º has a height (Altitude) of about 25º.

The DOT on the 90º Solar Azimuth line shows the top of the tallest shading obstacle seen through the Sun Angle Quadrant’s tube when facing true east. The top of the tree at 90º has an Altitude of about 25º. (NOTE: Shading obstacles are overlayed on this chart. You don’t need to do this on your charts).

© Rahus Institute-Solar Schoolhouse . OK to reproduce for educational purposes only. page 3 v.20210119 12. Repeat these steps to add a dot for the highest shading obstacle every 15º (at 90º, 105º, 120º, etc.) until you record the shading obstacles measured when facing due west (270º). 13. Use a ruler to draw lines connecting the dots as shown below.

14. Shade in the area under this line as illustrated below. The shaded area of the chart shows the approximate area shaded from the sun at this location throughout the year.

15. Repeat this process to complete the Sun Path Chart for the second option you chose for the placement of your solar device.

© Rahus Institute-Solar Schoolhouse . OK to reproduce for educational purposes only. page 4 v.20210119 Interpreting Your Results Now you can compare the charts to see which location will be best for your solar device. In this example, Option 1 is free of shading from about 10:40am until 3:00pm on December 21. It receives full sunlight all morning from April through August, but is shaded during the late afternoon. On the June 21 it receives shade from about 2:40pm to 3:00pm. (NOTE:Subtract an hour for Daylight Saving Time).

In Option 2 is free of shadows from about 10am to 2pm on December 21. From March to September it receives full sunlight until about 4:30pm. On June 21 there’s no shading.

© Rahus Institute-Solar Schoolhouse . OK to reproduce for educational purposes only. page 5 v.20210119 Determining the Better Location In our example from the last page, we’re assuming our school is choosing a solar panel placement for the new solar fountain. If we want students to be able to interact with the fountain during the Lunch Break from Noon to 1pm, and the Spring After School Program that runs from 3pm to 4pm, which option is better? (ANSWER: Option 2: Both options will have sun during the lunch break, but only Option 2 will have sun during the after school program).

Questions for Your Solar Site Analysis 1) On your chart for Option 1: there will be unshaded sunlight on June 21 from ______AM to ______PM. (NOTE: Remember to subtract an hour for Daylight Saving Time).

1) On your chart for Option 2: there will be unshaded sunlight from on December 21 ______AM to ______PM.

3) Write a short paragraph describing the available sunlight at each of your proposed options for placement of your solar device.

4) Which option will receive the least shading throughout the year? Explain why.

5) A solar battery charger will be placed at this location. To maximize exposure to direct sunlight between 10am and 3pm, is one option better than the other? Explain why.

1. Cut on the outside dotted line A . 2. Cut HALFWAY on the dotted line B . 3. Punch holes for string with a pencil. 4. Fold over on solid line E with the printed side out. 5. Fold in half on solid line F with the printed side out. 6. Tape the sides of the quadrant together, & tape along line E .

7. Roll the square section over a pencil to make a tube & tape it to the quadrant.

8. Thread 1 foot of string thru the hole. Enlarge the hole with a pencil if needed. 9. Thread the string thru 2 paperclips or other weights, & tie the ends. ✄ 10. When the tube’s shadow A forms a circle read the B 1. Cut on this dotted line sun’s altitude on ne d li ✄ the gauge. tte do is th

n 2. cut on this dotted line t o u . C 1 4. Fold this 7. Roll this piece piece over over a pencil to on line 8E . make a tube. Tape it down lengthwise.

3. Punch holes (for string)

4. Fold on this solid line

E E here! 6. Tape along this line Stop

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V w o . . U 7 E s 5. Fold on this solid line e 0 o s S 0 R l u 7 a E S r o s T h H e 6 c l 0 A h o T n o 0 i R o l o h T 6 1 c E lh s A d . o r e C 5 A u la E t 0 T s o R 0 t u e. .s 5 t T or w A o H g ww T d o E S n 40 R n SU E 0 o d N EV 4 t o ! N t 30 u te 30 . C d 1 20 0 lin 2 e 10 10

View the video tutorial at: solarschoolhouse.org/solarsiteanalysis v.20210119 or on the Solar Schoolhouse YouTube channel © Rahus Institute - Solar Schoolhouse. OK to reproduce for educational purposes only. Appendix B: Solar Compass Rose OK to reproduce for educational purposes only. © Rahus Institute-Solar Schoolhouse

Solar CompassSolar Rose

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7 2

2 8

.solarschoolhouse.org

WEST

2 0

0 1

3 0

0 0

4 0

NORTH

SOUTH

0 8

0 0

1. dotted center line & tape the long sides. Attach it to the center of compass rose with a 7 brass brad, using a push pin to make holes. Tape the rose onto a piece of cardboard backing. 0 0 1 Print this page. Cut out the pointer on left side of Fold its

6 0 0 2

1 2

. Tape a magnetic compass on top of the N/S arrow as shown below. 5 0 0 3

1 4 0 0 4 Make sure the ‘N’s are aligned.

1 3 0 0 5 3. EAST 1 Rotate this page until the North end of MAGNETIC

COMPASS needle points to the degrees of Magnetic 20 60

Declination for your location. 110 0 7 100 90 80 NOTE: East declination is to the right of north (or clockwise). the left of north (or counter-clockwise). 4. Now the magnetic compass and Solar Compass Rose are aligned to true north/south. West declination is to N S

v.20210119 © Rahus Institute-Solar Schoolhouse . OK to reproduce for educational purposes only. page 8 v.20210119 School r ho a u l s o e S Appendix C: Sun Path Charts

A Sun Path Chart graphs the sun’s path across the sky at a specific location as it changes over the seasons. These charts are useful for analyzing sites for solar buildings and photovoltaic systems.

Sun Path Charts for your location are available online from the University of Oregon at: http://solardat.uoregon.edu/SunChartProgram.html. At this website specify your location by zip code and select your time zone in parenthesis. For example: (PST) = Pacific Standard Time, (MST) = Mountain Standard Time, etc. Choose to plot the data between solstices from either December to June or June to December, and plot the hours in Local Standard Time. Accept the rest of the default settings and click the “create chart” button. How to Read Sun Path Charts There are two basic measurements used to describe the sun’s position: altitude and azimuth. The sun’s ALTITUDE altitude is its height above the horizon in degrees from 0º to 90º, measured up from 0º at the horizon. East South 90 180 The sun’s Azimuth describes the compass direction at which it

270 can be found. At any instant, a vertical line from the sun to the 0 horizon would intersect a degree of a circle measuring clockwise North West from north at 0º. This degree measures the sun’s azimuth angle. AZIMUTH The sun path chart below has two sets of curved lines: the solid lines chart the days of the year; the dotted lines chart the hours of the day. The intersection of the two curved lines shows the position of the sun at a precise time of day on a particular date. For example: The large ‘X’ on the chart below marks the sun’s position at eleven o’clock in the morning on January 21st (and November 21st). To find the sun’s altitude at that moment, follow the nearest grid line to the y-axis on the left. It reads about 25º above the horizon. Follow the nearest grid line down to the x-axis to find the sun’s azimuth at that time: about 158º. Note: During Daylight Savings Time subtract an hour from the time line you read. For example: At 1pm on June 21st, the sun’s position would be found on the 12pm line in the chart below. (Note: Daylight Savings Time is in effect from the 2nd Sunday in March to the 1st Sunday in November). 1. In the chart below what is the sun’s altitude & azimuth at 5pm on September 21st? Solar Altitude: Solar Azimuth:

90º Sun Path Chart Lat: 44º; Long: -123º (Standard) time zone: -8 75º 12 PM June 21 Eugene, Oregon 11 AM 1 PM May & Jul 21 2 PM 10 AM 60º Apr & Aug 21 3 PM 9 AM 45º Mar & Sep 21 4 PM 8 AM Feb & Oct 21 5 PM 30º 7 AM Jan & Nov 21 Solar Elevation (Altitude) 6 PM 6 AM December 21 15º

5 AM 0º 7 PM 60º 75º 90º 105º 120º 135º 150º 165º 180º 195º 210º 225º 240º 255º 270º 285º 300º

East Solar Azimuth West

Remember: Subtract an hour for Daylight Time. Daylight for hour an Subtract Remember: Answer: Solar Altitude: ~26; Solar Altitude: ~245 Altitude: Solar ~26; Altitude: Solar Answer:

S Appendix D: Magnetic Declination - page 1

You might be surprised to know that a magnetic compass does not usually point to the true north pole. The compass needle actually points to a different place called the magnetic north pole. The magnetic north pole is in northern Canada. Not only that, the magnetic north pole is moving! It’s traveling in a northwesterly direction at about 26 miles per year. The magnetic pole also wanders daily around an average position. The angle between the magnetic north pole and the true north pole is called magnetic declination. This angle changes over the course of time, and the values shown here may be different whe you read this. 13° east The angle between magnetic north and true north also depends on where you are on the Earth’s surface. San Francisco

Viewed from San Francisco, the magnetic north pole is about 13° to the east of the true north pole.

East Declination Suppose you were in San Francisco, and wanted to find the true north pole with a compass. 13° east If you pointed the “N” of the compass toward the true north pole, the compass needle would point 13 degrees to the right (or east) of north.

We say that the magnetic declination in San Francisco is 13 degrees east.

In San Francisco a compass needle REMEMBER: These measurements are constantly reads 13° east when the “N” (north changing. When you read this San Francisco’s cardinal point) points true north. declination may be different.

S Appendix D: Magnetic Declination - page 2

West Declination At the time of this writing, in Boston magnetic north is about -14 degrees to the left or west of true north. This is also called west declination of 14 degrees.

-14° (west) Boston In Boston, a compass needle points about 14 degrees west of north when the Viewed from Boston, the magnetic north pole is “N” points toward the true north pole. about 14° to the left of the true north pole.

Finding Magnetic Declination for Your Location To find true north or south for any location, visit one of these online magnetic declination calculators: https://www.magnetic-declination.com or: https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml#declination Current magnetic declination maps are also available online at the National Geophysical Data Center: https://www.ngdc.noaa.gov/geomag/WMM/image.shtml

courtesy of NOAA: https://www.ngdc.noaa.gov/geomag/WMM/data/WMM2020/wmm_north_america_2020.pdf