How do solar panels work? - Richard Komp

TED-Ed · May 11, 2026

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Transcript ~688 words · 4:59

0:08

The Earth intercepts a lot of solar power:

0:11

173 thousand terawatts.

0:14

That's ten thousand times more power than the planet's population uses.

0:19

So is it possible that one day

0:20

the world could be completely reliant on solar energy?

0:24

To answer that question,

0:25

we first need to examine how solar panels convert solar energy to electrical energy.

0:31

Solar panels are made up of smaller units called solar cells.

0:36

The most common solar cells are made from silicon,

0:39

a semiconductor that is the second most abundant element on Earth.

0:43

In a solar cell,

0:44

crystalline silicon is sandwiched between conductive layers.

0:48

Each silicon atom is connected to its neighbors by four strong bonds,

0:53

which keep the electrons in place so no current can flow.

0:58

Here's the key:

0:59

a silicon solar cell uses two different layers of silicon.

1:03

An n-type silicon has extra electrons,

1:07

and p-type silicon has extra spaces for electrons, called holes.

1:12

Where the two types of silicon meet,

1:14

electrons can wander across the p/n junction,

1:17

leaving a positive charge on one side

1:19

and creating negative charge on the other.

1:23

You can think of light as the flow of tiny particles

1:26

called photons,

1:28

shooting out from the Sun.

1:30

When one of these photons strikes the silicon cell with enough energy,

1:34

it can knock an electron from its bond, leaving a hole.

1:38

The negatively charged electron and location of the positively charged hole

1:43

are now free to move around.

1:45

But because of the electric field at the p/n junction,

1:48

they'll only go one way.

1:51

The electron is drawn to the n-side,

1:53

while the hole is drawn to the p-side.

1:56

The mobile electrons are collected by thin metal fingers at the top of the cell.

2:01

From there, they flow through an external circuit,

2:04

doing electrical work,

2:06

like powering a lightbulb,

2:07

before returning through the conductive aluminum sheet on the back.

2:11

Each silicon cell only puts out half a volt,

2:15

but you can string them together in modules to get more power.

2:18

Twelve photovoltaic cells are enough to charge a cellphone,

2:22

while it takes many modules to power an entire house.

2:26

Electrons are the only moving parts in a solar cell,

2:29

and they all go back where they came from.

2:31

There's nothing to get worn out or used up,

2:33

so solar cells can last for decades.

2:37

So what's stopping us from being completely reliant on solar power?

2:42

There are political factors at play,

2:44

not to mention businesses that lobby to maintain the status quo.

2:48

But for now, let's focus on the physical and logistical challenges,

2:53

and the most obvious of those

2:54

is that solar energy is unevenly distributed across the planet.

2:58

Some areas are sunnier than others.

3:01

It's also inconsistent.

3:02

Less solar energy is available on cloudy days or at night.

3:07

So a total reliance would require

3:09

efficient ways to get electricity from sunny spots to cloudy ones,

3:14

and effective storage of energy.

3:17

The efficiency of the cell itself is a challenge, too.

3:20

If sunlight is reflected instead of absorbed,

3:23

or if dislodged electrons fall back into a hole before going through the circuit,

3:28

that photon's energy is lost.

3:30

The most efficient solar cell yet

3:33

still only converts 46% of the available sunlight to electricity,

3:38

and most commercial systems are currently 15-20% efficient.

3:43

In spite of these limitations,

3:45

it actually would be possible

3:47

to power the entire world with today's solar technology.

3:50

We'd need the funding to build the infrastructure

3:52

and a good deal of space.

3:54

Estimates range from tens to hundreds of thousands of square miles,

3:59

which seems like a lot,

4:00

but the Sahara Desert alone is over 3 million square miles in area.

4:06

Meanwhile, solar cells are getting better, cheaper,

4:09

and are competing with electricity from the grid.

4:11

And innovations, like floating solar farms, may change the landscape entirely.

4:16

Thought experiments aside,

4:18

there's the fact that over a billion people

4:21

don't have access to a reliable electric grid,

4:24

especially in developing countries,

4:26

many of which are sunny.

4:28

So in places like that,

4:30

solar energy is already much cheaper and safer than available alternatives,

4:34

like kerosene.

4:36

For say, Finland or Seattle, though,

4:38

effective solar energy may still be a little way off.

— end of transcript —

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