Green energy
How Do Solar Panels Work?
- Grades 4-8
- 20 minute activity
- NGSS 4-PS3-2, 4-ESS3-1
Quick answer
A solar panel is made of rows of solar cells, thin slices of silicon that turn light directly into electricity. When sunlight hits a cell, it knocks electrons loose. The cell's two layers push those electrons out one side, around a circuit and back in the other side. That flow of electrons is electricity, with no moving parts, fuel or noise. This is called the photovoltaic effect.
Inside a solar cell
The dark squares on a solar panel are solar cells. Each one is a thin sandwich of silicon, the same material used in computer chips, treated so that the top layer has extra electrons and the bottom layer is missing some. Where the two layers meet, there is a built-in push.
- Light is made of tiny packets of energy called photons.
- When a photon hits the silicon, it can knock an electron loose.
- The built-in push sends loose electrons toward the top, where thin metal lines collect them.
- The electrons flow out through a wire, power your LED, and come back to the metal layer on the bottom.
Solar cells are black because black absorbs the most light. The thin gray lines on top are the metal conductors that carry the electrons away. The photovoltaic effect was discovered in 1839.
Power a dough circuit with the sun
The Squishy Circuits solar panel makes about 6 volts in bright sunlight, the same as the battery holder, so it can power any project. Take out the battery holder and put the solar panel's red and black wires in the same places. On a sunny day it can even run the motor, which takes more power than LEDs.
Try it with dough
Sun-powered circuit
Find out what helps a solar panel make more power. You will need a solar panel, which comes in the Green Engineering Kit.
You need
- Squishy Circuits solar panel
- Conductive (salty) play dough
- 2 or 3 LEDs
- 1 motor with fan (optional)
- A sunny window or a bright lamp
Steps
- Build a simple circuit with an LED, but use the solar panel in place of the battery holder: red wire in one piece of dough, black wire in the other.
- Hold the panel in bright sunlight. The LED should light.
- Slowly tilt the panel away from the sun. When is the LED brightest?
- Cover half the panel with your hand, then all of it. What happens?
- Try a bright lamp or flashlight instead of the sun. Compare the brightness.
- On a sunny day, swap the LED for the motor and see if the fan spins.
What happens
The LED is brightest when the panel faces the sun straight on. Covering the panel dims it or turns it off. A lamp works, but more weakly than sunlight, and may not be enough to run the motor.
Not working?
No light? Move into direct sunlight or put the panel against a sunny window. Check that the long LED leg is on the red-wire side. A mirror or a book wrapped in aluminum foil can bounce extra light onto the panel.
Solar tips and tricks
- Angle: aim the panel so the light hits it straight on. Big solar farms often tilt their panels to follow the sun across the sky.
- Time of day: the sun is strongest around noon, when it is highest in the sky.
- Time of year: winter sunlight is weaker, so panels make less power.
- Lamps and flashlights: sunlight contains every color of light. Many lamps give off only some colors, so the panel converts less of their light into electricity.
Bonus: a motor that makes electricity
A motor turns electricity into motion. Run it backward, by spinning it with your hand, and it turns motion into electricity. That is a generator, and it is how wind turbines and dams make power.
Try it: build a circuit with an LED and the motor, then take out the battery holder. Spin the fan fast with your finger and watch the LED flicker on. Nothing? Spin the other way, since a generator's + and - sides swap when you change direction. Electric cars use the same trick: when they slow down, their motors act as generators and recharge the battery.
Key words
- Solar panel
- A panel of solar cells that turns light into electricity.
- Solar cell
- One thin slice of silicon that makes electricity from light.
- Photovoltaic effect
- Light knocking electrons loose in a material to make electricity.
- Photon
- A tiny packet of light energy.
- Renewable energy
- Energy from sources that do not run out, like sunlight, wind and moving water.
- Generator
- A machine that turns motion into electricity.
For teachers
These activities support NGSS 4-PS3-2 (energy can be transferred by electric currents) and 4-ESS3-1 (energy and fuels come from natural resources, some renewable). Have students design a fair test for panel angle or light source, changing only one thing at a time, and graph LED brightness or motor speed.
The solar panel, a super capacitor battery backup and a wind turbine fan are all part of the Green Engineering Kit, which comes with a 44-page Exploring Green Energy guidebook. For how power gets from power plants to homes, see our article on the electrical grid. Find more lessons on our education page.
Solar panel questions
How do solar panels work in simple terms?
Sunlight knocks electrons loose in the silicon inside each solar cell. The cell pushes those electrons out through a wire, and that flow is electricity.
What are solar panels made of?
Most solar panels are made of silicon cells covered with glass, with thin metal lines on top and a metal layer underneath to carry the electricity.
Do solar panels work on cloudy days?
Yes, but they make much less electricity, because less light reaches them. Shade on even part of a panel can cut its power a lot.
Can a solar panel work with a lamp?
Yes, but not as well as sunlight. A bright lamp or flashlight can light a few LEDs, but may not run a motor, because many lamps give off only some colors of light.
Why are solar panels black?
Black absorbs the most light. The more light a solar cell absorbs, the more electrons it can knock loose.
Is solar energy renewable?
Yes. Sunlight will not run out, and solar panels make electricity without burning fuel or making pollution while they run.
Next, try a project
Build the UFO Project Try it with the solar panel in place of the battery holder.