Chapter 28. Chapter 28: Sun, Wind, and Water Energy

How do wind and solar power technologies capture energy?

Why You Should Care

We have already learned that energy cannot be created or destroyed, but it can be transferred and transformed. Solar energy reaches earth as electromagnetic radiation; part of this radiation we can detect, or see, as light, but other wavelengths include infrared, or radiant heat, and different forms of ionizing radiation like ultraviolet. We can capture the heat from solar energy passively through designing buildings to be warmed by the Sun or actively through solar water heaters. Photovoltaic cells, or solar panels, use the photons in light to create an electric current. The heat from solar energy creates convective currents in the atmosphere, or wind, and we can harness this kinetic energy from the wind by using windmills. Traditionally, windmills were used to provide kinetic energy, but now we are using them widely to create electricity.

Although solar and wind power are much cleaner to use than fossil fuels, they aren’t without drawbacks. Some people object to the look of windmills on the horizon or solar panels on roofs. Neither solar or wind power are constant, so there has to be a way to store energy or a backup energy source for nights, cloudy days, and days with little wind. Probably the biggest deterrent to adopting solar and wind power is cost. The startup costs for installing personal or public solar or wind energy systems are high, prohibitively so for many people. But, if one figures in all of the hidden costs associated with using fossil fuels—acid precipitation, smog, global climate change, and groundwater pollution are just a few—it’s definitely worth using sustainable energy sources.

Question 28.4

For each of the components of a wind turbine listed below, write a short description of what it does in the process of producing electricity. Make sure to think about how energy is transformed in the process.

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999

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1) The blades capture the kinetic energy of the wind and use it to spin the shaft.

2) The shaft transfers the kinetic energy of the blades to the gear box.

3) The gear box increases the rotation speed of the shaft.

4) The generator uses the increased speed from the gears to convert kinetic energy into electricity.

The following questions refer to the labeled parts of the diagram above:

Question 28.10

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999

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Correct.

Incorrect.

Question 28.11

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*Note that this question refers to placement in the Northern Hemisphere; the answer would be the opposite direction for houses built in the Southern Hemisphere.

999

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Correct.

Incorrect.

Question 28.12

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999

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Correct.

Incorrect.

Question 28.13

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999

Try again.

Correct.

Incorrect.

Question 28.14

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999

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Solar thermal systems use the Sun to heat water or other fluids in a series of tubes that is used to heat water for use in the house or to heat the house with radiators or similar systems. (If you've ever felt water coming out of a garden hose on a sunny summer day, you know how this works!) Photovoltaic systems use solar energy to create electricity that is used by the home or sold back to the power company. Thermal systems are usually somewhat less expensive to install and therefore usually have a quicker payback time than PV systems.