The National Academies: What You Need To Know About Energy

The National Academies

What You Need To Know About Energy

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The Sun

We consume energy in dozens of forms. Yet virtually all of the energy we use originates in the power of the atom. Nuclear reactions energize stars, including our Sun. The energy we capture for use on Earth comes largely from the Sun or from nuclear forces local to our own planet.

Solar radiation reaches Earth with more than enough energy in a single square meter to illuminate five 60-watt lightbulbs if all the sunlight could be captured and converted to electricity.

Sunlight is by far the predominant source, and it contains a surprisingly large amount of energy. On average, even after passing through hundreds of kilometers of air on a clear day, solar radiation reaches Earth with more than enough energy in a single square meter to illuminate five 60-watt lightbulbs if all the sunlight could be captured and converted to electricity.

The Sun’s energy warms the planet’s surface, powering titanic transfers of heat and pressure in weather patterns and ocean currents. The resulting air currents drive wind turbines. Solar energy also evaporates water that falls as rain and builds up behind dams, where its motion is used to generate electricity via hydropower.

Most Americans, however, use solar energy in its secondhand form: fossil fuels. When sunlight strikes a plant, some of the energy is trapped through photosynthesis and is stored in chemical bonds as the plant grows. We can recover that energy months or years later by burning wood, which breaks the bonds and releases energy as heat and light. More often, though, we use the stored energy in the much more concentrated forms that result when organic matter, after millions of years of geological and chemical activity underground, turns into fossil fuels, such as coal, oil, or natural gas. Either way, we’re reclaiming the power of sunlight.

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Energy Hands-on

What do you know about energy?

In the United States, which economic sector releases the most CO2?

  • Sorry, that’s incorrect.

    In the United States, the transportation sector releases the most CO2. In 2006, the transportation sector released nearly 2 billion metric tons of carbon dioxide, nearly all of which was from oil.

  • Sorry, that’s incorrect.

    In the United States, the transportation sector releases the most CO2. In 2006, the transportation sector released nearly 2 billion metric tons of carbon dioxide, nearly all of which was from oil.

  • Correct!

    In the United States, the transportation sector releases the most CO2. In 2006, the transportation sector released nearly 2 billion metric tons of carbon dioxide, nearly all of which was from oil.

  • Sorry, that’s incorrect.

    In the United States, the transportation sector releases the most CO2. In 2006, the transportation sector released nearly 2 billion metric tons of carbon dioxide, nearly all of which was from oil.

Energy Defined

Energy

The capacity for doing work; usable power (as heat or electricity); the resources for producing such power.

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