Turning light into electricity
A solar panel turns sunlight directly into electricity, with no moving parts, no fuel and no noise. Solar panels power homes, satellites, calculators, road signs and entire cities. Solar is now one of the cheapest and fastest-growing sources of electricity in the world.
The invention of solar cells
| Year | Event |
|---|---|
| 1839 | French physicist Edmond Becquerel, age 19, discovers the photovoltaic effect: light creates electricity in certain materials |
| 1883 | Charles Fritts makes the first solar cell from selenium coated with gold; about 1% efficient |
| 1905 | Albert Einstein explains how light knocks electrons loose (the photoelectric effect), later winning a Nobel Prize |
| 1954 | Bell Labs scientists Daryl Chapin, Calvin Fuller and Gerald Pearson create the first practical silicon solar cell, about 6% efficient |
| 1958 | The satellite Vanguard 1 uses solar cells; it’s still in orbit today |
| 1970s | Oil crises spark interest in solar energy |
| 2000s–2020s | Mass production makes panels far cheaper |
How a solar cell works
- A solar cell is made of two thin layers of silicon, a semiconductor.
- One layer is treated (doped) with phosphorus, giving it extra electrons (n-type). The other is treated with boron, creating "holes" where electrons are missing (p-type).
- Where the layers meet, an electric field forms.
- When sunlight hits the cell, light energy knocks electrons loose.
- The electric field pushes the freed electrons in one direction, creating a flow of electricity.
- Metal contacts on the top and bottom collect the current.
Each cell produces only about 0.5 volts, so many cells are connected in a panel.
From cell to power system
| Component | Job |
|---|---|
| Solar cells | Make electricity from light |
| Solar panel (module) | Many cells wired together under protective glass |
| Solar array | Many panels connected |
| Inverter | Converts direct current (DC) to alternating current (AC) for homes and the grid |
| Battery (optional) | Stores energy for night or cloudy days |
| Meter | Measures electricity made and used |
Efficiency
Efficiency is the percentage of sunlight energy a panel converts into electricity.
| Type | Typical efficiency |
|---|---|
| Monocrystalline silicon | About 20–24% |
| Polycrystalline silicon | About 15–20% |
| Thin-film | About 10–18% |
| Multi-junction cells (space and research) | Over 40% |
| Perovskite (newer research) | Rapidly improving in labs |
Even at 20%, a typical rooftop system can supply much of a home’s electricity.
What affects output?
| Factor | Effect |
|---|---|
| Sunlight intensity | More sun = more power |
| Angle | Panels facing the Sun directly produce the most; in Canada, panels usually face south and tilt at an angle close to the local latitude |
| Temperature | Cooler panels work better |
| Shade and snow | Even partial shade reduces output |
| Dust and dirt | Reduce output |
The falling cost of solar
Solar panel prices have dropped about 90% since 2010. In many places, solar is now the cheapest source of new electricity. Global solar capacity has grown many times over in the past decade.
Solar in Canada
- Canada gets plenty of sunshine, especially on the Prairies. Regina and Calgary are among the sunniest cities in Canada.
- Cold weather improves panel efficiency, and snow can reflect extra light onto panels.
- Many remote and Indigenous communities in the North use solar to reduce reliance on expensive, polluting diesel generators.
- Large solar farms operate in Alberta, Ontario and elsewhere.
Advantages and disadvantages
| Advantages | Disadvantages |
|---|---|
| Renewable and abundant | No power at night |
| No emissions while operating | Less power on cloudy days and in winter |
| Few moving parts; low maintenance | Needs storage or backup |
| Panels last 25–30 years | Manufacturing uses energy and materials |
| Can go on rooftops, near users | Recycling old panels is still developing |
Solar in space
Solar panels power almost all satellites and the International Space Station, whose huge solar arrays cover an area about the size of a football field. Canada’s satellites, like the RADARSAT Constellation, also run on solar power.
Common mistakes
- Thinking solar panels need heat. They need light and actually work better in the cold.
- Thinking panels store energy. Batteries store it.
- Thinking solar panels produce nothing on cloudy days. They produce less, but still some.
Try it yourself
- Connect a small solar panel to a motor or LED. Measure how it performs in direct sun, shade and under a lamp.
- Tilt a small panel at different angles toward the Sun. Which angle works best?
- Use an online tool to estimate how much electricity panels on your school roof could make.
Quick recap
- Solar panels convert light directly into electricity using the photovoltaic effect.
- Becquerel discovered the effect in 1839; silicon cells were developed in 1954.
- Doped silicon layers create an electric field that moves freed electrons.
- Inverters convert DC to AC; batteries store energy.
- Solar costs have fallen dramatically, and solar works well in Canada.