Shadow-tracking solar map
Track shadows on the school roof through the day to find the best place for solar panels.
The big idea
A solar panel only works when the Sun reaches it. Shadows from tanks, trees and buildings can ruin a good roof, so mark them before you plan.
You will need
Tick things off as you gather them.
Step by step
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Step 1: Set up the pole
Fix the stick upright in a stand or a pile of sand on a flat spot in the open. Make sure it stays still all day.
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Step 2: Mark the shadow tip
At 9 am, mark the tip of the stick's shadow with chalk. Write the time next to it.
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Step 3: Repeat every hour
Mark the tip of the shadow every hour until about 4 pm. Notice how the shadow swings round and changes length.
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Step 4: Map the shade
At each time, walk around the roof or playground and note which areas are in shade, and what makes the shade. Sketch these on your plan.
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Step 5: Find the south side
Use a compass to mark which way is south. In India, solar panels face south to catch the most sun across the day.
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Step 6: Colour the best zones
On your plan, colour areas that stay sunny from 9 am to 3 pm. These are the best spots for panels.
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Step 7: Make your recommendation
Pick the best area and explain why. How many panels would fit there?
What to look for
- Shadows are longest in the morning and evening and shortest at noon.
- Some parts of the roof are shaded for hours, even when they look sunny at noon.
- The shadow tips trace a curve across the ground.
Why it works
The Sun rises in the east, climbs high at midday and sets in the west, so shadows move the opposite way. Anything tall, such as a water tank, casts a shadow that sweeps across the roof. A solar panel in shade makes far less power, and when panels are wired together, one shaded panel can drag down the others. Mapping the shadows first saves money later.
Try this next
- Repeat in winter and summer and compare the Sun's height.
- Measure shadow length at noon each month.
- Use your map with the school energy survey to plan a real solar array.
Stay safe
Stay well away from roof edges. Go onto the roof only with a teacher. The playground works just as well.
Link to the grid
Solar developers do this kind of shade study on every site before they build. A good location can make a plant produce a lot more over its life.
Learn how the grid worksMore sun power experiments
Mini solar panel circuit
A small solar panel lights an LED or spins a toy motor. Test it in sun, in shade and at different angles.
Solar cooker
A cardboard box, foil and plastic wrap trap the Sun's heat. Melt chocolate, warm water or cook rice.
Solar water heater
Black-painted bottles or pipe in the Sun heat water. Measure the temperature as it rises.