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Solar Power by Richard Hantula

Science and Curriculum Consultant:

Debra Voege, M.A., Science Curriculum Resource Teacher

Energy Today: Solar Power

Copyright © 2010 by Infobase Publishing

All rights reserved. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval systems, without permission in writing from the publisher. For information contact:

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Library of Congress Cataloging-in-Publication Data Hantula, Richard.

Solar power / by Richard Hantula; science and curriculum consultant, Debra Voege. p. cm. — (Energy today)

3.792’3—dc222009036864

Includes index. ISBN 978-1-60413-779-8 (hardcover) ISBN 978-1-4381-3164-1 (e-book) 1. Solar energy—Juvenile literature. I. Title. TJ810.3.H365 2010

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Photo Credits: 5: iStockphoto; 6: © Stock Connection Blue/Alamy; 10: DOE/NREL; 12: NASA; 15: Randy Montoya and Sandia National Laboratories; 17: Juan Carlos Munoz/age fotostock/Photolibrary; 18: U.S. Air Force photo/Airman

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Energy and the Sun4

CHAPTER 1:

Putting Solar Energy to Work14

CHAPTER 2:

Big Benefi ts24

CHAPTER 3:

Weak Points of Solar Power30

CHAPTER 4:

Progress, Prospects, and Dreams36
Glossary4
To Learn More46
Index47

CHAPTER 5:

Words that are defi ned in the Glossary are in bold type the fi rst time they appear in the text.

Energy makes things happen. It makes cars go and makes machines run. When you feel warm, you are feeling heat energy. When you see things, it is thanks to the energy called light.

The Sun is the biggest source of energy in our lives. The Sun gives off enormous amounts of heat and light in all directions. It has shone for billions of years. Scientists say it will continue to shine for billions of years in the future.

Earth is located very far from the Sun—about 93 million miles (150 million kilometers) away. This means that Earth gets only a small part of the energy that the Sun puts out. That energy output is so big, however, that a huge amount of light and heat reaches Earth. We call this energy solar energy, which means that it is from the Sun.

This solar energy drives the winds. It also powers the currents in the ocean (the movement of ocean waters). In fact, solar energy makes life on Earth possible. Life depends on water, and heat from the Sun causes a process called the water cycle. In this cycle, water constantly moves between Earth’s surface and the air, or atmosphere, above it. The Sun’s heat causes water to evaporate into the air. Eventually, this water falls back to the ground as rain or snow.

Solar energy makes life possible in another important way as well. Sunlight gives plants the energy they need to make

Energy and the Sun

The Sun is the biggest source of energy in our lives.

food in a process called photosynthesis. During photosynthesis, plants take in sunlight, use water, and put oxygen into the air.

Using Solar Energy in Daily Life The Sun’s heat and light have many uses. To help plants grow, some people build greenhouses, which collect solar heat. Some people rely on the Sun to dry their clothes after washing. Some people boil water or cook food using the heat of the Sun’s rays.

Sunlight is also used to produce one of our most important forms of energy: electricity. There are a couple of different methods to do this. Each method can be used in power stations, or power plants. These are large facilities that supply electricity to the public power system, which is also known as the grid.

Each method of producing electricity can also be used in smaller power-supply systems. Such smaller systems can meet some or all of the electricity needs of a machine, a small house, or another kind of building. The systems can be used by people who do not want to rely on the grid. They can also be used in places where the grid is so far away that connecting to it would cost too much or would be impossible. In addition, the systems can come in handy when it is simply not convenient to connect to the grid.

One of the methods of using sunlight to produce electricity uses the Sun’s heat to run a machine that generates electricity. The other method of using sunlight is particularly versatile. It relies on small devices called solar cells. Solar cells make electricity directly from sunlight. These cells are good power sources for small things like outdoor lights, highway signs,

Greenhouses collect the Sun’s heat. They are used to help plants grow.

and water pumps on farms. They are often used to power small electronic devices such as calculators.

Groups of solar cells—which are called solar arrays—are used where larger amounts of power are needed. Solar arrays are sometimes used to make electricity in large power stations. Solar arrays (and sometimes smaller numbers of solar cells) can be a good source of electricity for remote villages that are located far from any grid. Solar arrays are also a common power source on spacecraft and space stations.

Top Fuels Most of the energy people use today comes from fuels like coal, oil, and natural gas. These are examples of fossil fuels. For a long time, burning fossil fuels has been a common way to keep buildings warm. Fossil fuels are also used to power vehicles. Imagine how much gasoline and diesel fuel is used every year!

Energy and Power

When people say “solar power,” they usually mean electricity made from solar energy. Scientists, however, tend to use the words energy and power to mean certain specifi c things. For them, power is the rate at which work is done. It is measured in units such as watts and megawatts (one million watts). In contrast, energy is the ability to do work. It is measured in units such as kilowatt-hours and British thermal units (BTUs). One BTU is the amount of heat needed to raise the temperature of a pound (0.45 kilograms) of water by 1º Fahrenheit (0.56º Celsius).

Did You Know?

Gasoline and diesel fuel are the most popular fuels for cars, buses, and trucks. Both are made from oil—which makes them fossil fuels.

Fossil fuels are also the most common energy source for producing electricity. They are burned to make heat, which is used to make water boil and turn into steam. The steam runs a machine called a turbine that produces a turning action, which causes a generator to produce electricity.

Nuclear power is another key energy source today, providing about 6 percent of the world’s energy. Nuclear power is an important way of generating electricity in countries such as France and the United States. It is also used to power certain kinds of ships.

Fossil fuels have many advantages. Currently, they are abundant—there is enough coal, oil, and natural gas to meet the world’s needs. They work well, are easy to use, and are cheap

Making Electricity

To produce electricity, most power plants burn fossil fuels to boil water. When the water boils, it produces steam. The steam is then heated further so that it has enough pressure to turn the blades on a turbine. The hot steam pushes against the blades, causing the turbine to spin. The turbine is attached to one end of a long pole, or rod. The other end of the rod is connected to a generator. There are large magnets and metal coils inside the generator. When the rod turns, the magnets spin, producing electricity inside the coils. The electric current that is produced then makes its way along transmission lines to homes, offi ce buildings, and wherever it is needed.

Did You Know? enough for general use. They also have serious drawbacks, however. For one thing, they will not last forever. Earth has only a limited supply of fossil fuels, and once they are used, they are gone forever. In other words, they are not renewable. Another problem is that burning fossil fuels puts gases and other substances into the air that make the air dirty, or polluted. Scientists say that some of the gases may even change Earth’s climate. Land and water may also be polluted by gases and dust from burning fossil fuels. They may be harmed as well by accidents involving fossil fuels, such as oil spills.

Nuclear power has some advantages. It does not cause the pollution that fossil fuels do. Also, there will probably be plenty of fuel for nuclear power plants in the future. Uranium is the main fuel currently used in nuclear plants. Earth’s supply of uranium may run low at some point in the future, but other types of fuel for use in nuclear plants can be made easily.

Like fossil fuels, nuclear power has serious drawbacks.

The chief one is that materials like uranium give off harmful radiation—radioactivity—that can cause sickness or death.

Where Does the Sun Get Its Energy?

The Sun’s energy comes from nuclear fusion. This process is quite different from the one used to produce nuclear power on Earth. Nuclear power plants use a process called fi ssion. In fi ssion, heavy atoms are split apart, creating smaller atoms plus radioactivity and energy— what we call nuclear energy. In fusion, light atoms—such as hydrogen—combine, or fuse. This process creates new, heavier atoms. It also releases a great deal of energy.

Did You Know?

Today’s nuclear power plants have safeguards to keep radiation from leaking out. A serious accident or a terrorist attack, however, might still release dangerous radiation. Another problem is finding ways to dispose of radioactive waste. A permanent storage place has not yet been built for the most dangerous waste.

Alternative Fuels Because of the drawbacks of fossil fuels and nuclear power, people have been looking for alternatives. The ideal source of energy would be cheap, abundant, and clean. It would also be renewable. Several alternative energy sources are in use today. Each has strong points and weak points.

Water power is an important energy source in some parts of the world. The force of falling water is used to drive turbines to generate electricity. Usually, dams are built for this purpose.

These students are collecting solar thermal energy to cook eggs.

Water power is a renewable source. Dams, however, can be built only where there is a suitable stream of water. Also, dams and the reservoirs they create can damage the environment. Dams can stop fi sh from traveling upstream to produce their eggs. In addition, when a reservoir forms, it fl oods the land. This can destroy plants and kill or push out wildlife that lived in the area.

Wind, like water, is a renewable energy source. It is clean and found around the world. Some areas have less wind than others, though, and there is practically no place where the wind is always blowing. Because of this, wind cannot serve as a continuous supply of power.

Tidal power and geothermal energy are two alternative energies that are less commonly used. Tidal power relies on the movement of the tides to generate electricity. Suitable tides, however, occur only in certain parts of the world. Geothermal power relies on underground heat. It, too, can be used only in certain areas.

The Sun Does It All

The Sun is responsible for most forms of energy used in the world today. Fossil fuels were formed from the remains of living things, which needed the Sun in order to live and grow. Wood—another common energy source— comes from trees, whose existence depends on sunlight. Modern biofuels are commonly made from crops like corn, sugarcane, or switchgrass, which also depend on the Sun. Wind power, water power, and tidal power are all a result of processes driven by the Sun.

Did You Know?

Biofuels—fuels made from materials coming from plants or animals—are yet another alternative. Ethanol made from plants is an example. Since new plants can always be grown, biofuels are renewable. Biofuels, however, must be burned in order to produce energy. This releases gases into the air that may be harmful. Another drawback is

In Their

Own Words

“We...should be using Nature’s inexhaustible sources of energy—sun, wind and tide. I’d put my money on the sun and solar energy. What a source of power! I hope we don’t have to wait until oil and coal run out before we tackle that.”

Inventor Thomas Edison, 1931The International Space Station has giant solar arrays that provide power.

Solar Power 1% Water Power 36%

Geothermal Energy 5%

Biofuels 53%

Wind Power 5%

Oil (Petroleum) 40%

Renewable Energy

Coal 2%Natural Gas 23%

Nuclear

Power 8%Renewable Energy 7%

Sources of Energy Used in the United States

Note: Figures are for the year 2007. No information is included for hydrogen fuel because it was not yet being used in large enough quantities. Source: U.S. Energy Information Administration that growing the plants uses a lot of land. That land cannot be used for other purposes, such as growing food crops.

That leaves solar energy. Solar energy is extremely abundant and almost completely renewable: The Sun’s power will last almost forever. Currently, however, solar energy makes up only a tiny portion of the energy used in the United States. In 2007, renewable energy made up just 7 percent of U.S. energy consumption. Solar energy accounted for only 1 percent of that renewable energy. In the foreseeable future, solar energy may not produce major amounts of the world’s power supply. Nevertheless, as the use of solar energy grows in the United States and the world, solar energy may well play an important role in the world’s energy future.

There are many ways solar energy can be put to work. Some are known as active methods. Others are called passive methods. An active method for putting solar energy to work makes use of electrical or mechanical equipment—for example, a pump. Passive methods use little or no electrical or mechanical help. A greenhouse is an example of a passive method, since it collects the Sun’s heat without any type of equipment.

There are also two basic ways to make electricity from solar energy. One uses solar cells, which convert sunlight directly into electricity. This approach is called photovoltaic. (Photo means “light,” and voltaic refers to electricity.) Solar cells are often called photovoltaic cells, or PV cells, for short. The other approach to making electricity is called thermal. (Thermal comes from a Greek word meaning “heat.”) Solar thermal power systems use the Sun’s heat to run a machine that generates electricity.

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