How do solar panels work? - Richard Komp
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0:08 - 0:11The Earth intercepts a lot of solar power:
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0:11 - 0:15173 thousand terawatts.
-
0:15 - 0:19That's ten thousand times more power
than the planet's population uses. -
0:19 - 0:21So is it possible that one day
-
0:21 - 0:24the world could be completely
reliant on solar energy? -
0:24 - 0:26To answer that question,
-
0:26 - 0:32we first need to examine how solar panels
convert solar energy to electrical energy. -
0:32 - 0:36Solar panels are made up of smaller units
called solar cells. -
0:36 - 0:39The most common solar cells
are made from silicon, -
0:39 - 0:43a semiconductor that is the second
most abundant element on Earth. -
0:43 - 0:45In a solar cell,
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0:45 - 0:49crystalline silicon is sandwiched
between conductive layers. -
0:49 - 0:54Each silicon atom is connected
to its neighbors by four strong bonds, -
0:54 - 0:58which keep the electrons in place
so no current can flow. -
0:58 - 0:59Here's the key:
-
0:59 - 1:04a silicon solar cell uses
two different layers of silicon. -
1:04 - 1:07An n-type silicon has extra electrons,
-
1:07 - 1:12and p-type silicon has extra spaces
for electrons, called holes. -
1:12 - 1:14Where the two types of silicon meet,
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1:14 - 1:18electrons can wander across
the p/n junction, -
1:18 - 1:20leaving a positive charge on one side
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1:20 - 1:23and creating negative charge on the other.
-
1:23 - 1:27You can think of light
as the flow of tiny particles -
1:27 - 1:28called photons,
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1:28 - 1:30shooting out from the Sun.
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1:30 - 1:34When one of these photons strikes
the silicon cell with enough energy, -
1:34 - 1:39it can knock an electron from its bond,
leaving a hole. -
1:39 - 1:43The negatively charged electron and
location of the positively charged hole -
1:43 - 1:46are now free to move around.
-
1:46 - 1:49But because of the electric field
at the p/n junction, -
1:49 - 1:51they'll only go one way.
-
1:51 - 1:53The electron is drawn to the n-side,
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1:53 - 1:56while the hole is drawn to the p-side.
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1:56 - 2:02The mobile electrons are collected by
thin metal fingers at the top of the cell. -
2:02 - 2:05From there, they flow through
an external circuit, -
2:05 - 2:06doing electrical work,
-
2:06 - 2:08like powering a lightbulb,
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2:08 - 2:12before returning through the conductive
aluminum sheet on the back. -
2:12 - 2:15Each silicon cell only puts out
half a volt, -
2:15 - 2:19but you can string them
together in modules to get more power. -
2:19 - 2:23Twelve photovoltaic cells are enough
to charge a cellphone, -
2:23 - 2:26while it takes many modules
to power an entire house. -
2:26 - 2:29Electrons are the only moving parts
in a solar cell, -
2:29 - 2:32and they all go back where they came from.
-
2:32 - 2:34There's nothing to get worn out
or used up, -
2:34 - 2:37so solar cells can last for decades.
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2:37 - 2:43So what's stopping us from being
completely reliant on solar power? -
2:43 - 2:45There are political factors at play,
-
2:45 - 2:49not to mention businesses that lobby
to maintain the status quo. -
2:49 - 2:53But for now, let's focus on the physical
and logistical challenges, -
2:53 - 2:54and the most obvious of those
-
2:54 - 2:59is that solar energy
is unevenly distributed across the planet. -
2:59 - 3:01Some areas are sunnier than others.
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3:01 - 3:03It's also inconsistent.
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3:03 - 3:07Less solar energy is available
on cloudy days or at night. -
3:07 - 3:10So a total reliance would require
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3:10 - 3:14efficient ways to get electricity
from sunny spots to cloudy ones, -
3:14 - 3:17and effective storage of energy.
-
3:17 - 3:20The efficiency of the cell itself
is a challenge, too. -
3:20 - 3:23If sunlight is reflected
instead of absorbed, -
3:23 - 3:28or if dislodged electrons fall back into
a hole before going through the circuit, -
3:28 - 3:31that photon's energy is lost.
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3:31 - 3:33The most efficient solar cell yet
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3:33 - 3:39still only converts 46% of
the available sunlight to electricity, -
3:39 - 3:44and most commercial systems are currently
15-20% efficient. -
3:44 - 3:46In spite of these limitations,
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3:46 - 3:47it actually would be possible
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3:47 - 3:51to power the entire world
with today's solar technology. -
3:51 - 3:53We'd need the funding
to build the infrastructure -
3:53 - 3:55and a good deal of space.
-
3:55 - 3:59Estimates range from tens
to hundreds of thousands of square miles, -
3:59 - 4:01which seems like a lot,
-
4:01 - 4:06but the Sahara Desert alone is over
3 million square miles in area. -
4:06 - 4:09Meanwhile, solar cells are getting
better, cheaper, -
4:09 - 4:12and are competing
with electricity from the grid. -
4:12 - 4:17And innovations, like floating solar farms,
may change the landscape entirely. -
4:17 - 4:19Thought experiments aside,
-
4:19 - 4:21there's the fact
that over a billion people -
4:21 - 4:24don't have access
to a reliable electric grid, -
4:24 - 4:27especially in developing countries,
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4:27 - 4:29many of which are sunny.
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4:29 - 4:30So in places like that,
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4:30 - 4:35solar energy is already much cheaper
and safer than available alternatives, -
4:35 - 4:37like kerosene.
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4:37 - 4:39For say, Finland or Seattle, though,
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4:39 - 4:42effective solar energy
may still be a little way off.
- Title:
- How do solar panels work? - Richard Komp
- Description:
-
View full lesson: https://ed.ted.com/lessons/how-do-solar-panels-work-richard-komp
The Earth intercepts a lot of solar power: 173,000 terawatts. That’s 10,000 times more power than the planet’s population uses. So is it possible that one day the world could be completely reliant on solar energy? Richard Komp examines how solar panels convert solar energy to electrical energy.
Lesson by Richard Komp, animation by Globizco.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 04:59
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