The Wind at Work: An Activity Guide to Windmillsby Gretchen Woelfle
Explaining how the wind works, what windmills have contributed to the past, and why they offer environmental promise today as a source of clean, renewable energy, this revised and updated edition offers a glimpse into all the current and historical uses for wind power. Featuring new information on wind energy technology and wind farms, new photographs, and 24… See more details below
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Explaining how the wind works, what windmills have contributed to the past, and why they offer environmental promise today as a source of clean, renewable energy, this revised and updated edition offers a glimpse into all the current and historical uses for wind power. Featuring new information on wind energy technology and wind farms, new photographs, and 24 wind-related activities—from keeping track of household energy use and conducting science experiments to cooking traditional meals and creating arts and crafts—this handy resource offers kids interested in the science of energy and green technologies an engaging, interactive, and contemporary overview of wind power.
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Read an Excerpt
The Wind at Work
An Activity Guide to Windmills
By Gretchen Woelfle
Chicago Review Press IncorporatedCopyright © 2012 Gretchen Woelfle
All rights reserved.
Harnessing Wind Power Through Time
* * *
Night fell on the flatlands of Holland. The wind howled, rain slashed to earth, and waves broke higher and higher on the beach. Flashes of lightning revealed a high wall of earth built to hold back the sea. Waves crashed against this dike, throwing water to the fields beyond and washing away parts of the dike itself.
The Dutch called the sea the Waterwolf, and tonight the Waterwolf was on the prowl, trying to steal their lands. All night long flickering lanterns moved along the top of the dike as villagers kept watch. If the dikes broke, the Waterwolf would swallow their farms and homes.
By morning, the rain subsided and the wind dropped. The storm was over. The dikes had held. Tired Dutchmen stumbled home to bed.
But there was no rest for the windmillers. All night they had worked the windmills to pump water from the overflowing canals back out to sea. Now they had to drain the flooded fields to save the crops. For days and nights, giant windmill sails would turn, pumping and pumping until the fields were dry. The wind that nearly destroyed the land would now help to save it.
The History of Wind Power
Wind is created by the sun as it warms the earth unevenly. Warm air expands and rises. Cool air rushes in to take its place. This air movement is what we call the wind.
For more than a thousand years people have harnessed the wind with windmills. People used the wind to propel sailboats on the water long before they built windmills on land. Billowing sails filling with wind replaced the hard work of men rowing and paddling. Eventually, wind-powered machines moved on land and saved a lot of heavy labor. The wind-filled windmill sails then turned a shaft, wheels, gears, and finally, millstones, water pumps, or other machines. Before the invention of windmills and water mills, men or animals turned heavy millstones by trudging around and around in a circle, hour after hour, day after day, crushing grain to make flour. It was mind-numbing, body-breaking work.
The wind is not a perfect source of energy. It can be steady or gusty. It can change direction in a few seconds. It can grow to the force of a hurricane or die completely. Scientists can predict daily and seasonal wind patterns, but these patterns won't tell if or how much the wind will blow tomorrow afternoon. Even so, the wind has been reliable enough for many uses through the centuries.
Like the wind itself, windmills have come and gone. From AD 1200 to 1900, windmills were the most powerful machines in Europe. They ground grain, pumped water, pressed oil, sawed wood, and performed many other tasks. In the 1800s windmills were replaced by steam engines. Today about 900 Dutch windmills remain out of 10,000 that stood 200 years ago. In America, six million windmills pumped water on the dry Western plains until the 1940s, when electric and gasoline engines did away with most of them. Today a new kind of windmill turns in the wind.
Many people think of Dutch models when they think of windmills, but windmills come in many shapes and sizes. Ancient Persian-style mills looked like revolving doors. Modern wind turbines look like giant airplane propellers. All of them can harness a powerful energy source to work for us.
Wind Power Today
Thousands of wind turbines stand in the hills and plains of the United States today. Thousands more are scattered across Canada, Europe, China, and the rest of the world. They are new versions of an old idea.
From far away, wind turbines look like toy pinwheels that catch the sunlight as they spin. Up close, these pinwheel giants stand on 300-foot towers with whirling blades up to 300 feet in diameter. A generator behind the blades converts wind energy to electricity. Underground cables carry electric currents to power lines that feed the electricity to nearby towns and cities.
Clean, Renewable Energy Source
Wind power is a renewable source of energy, so we will never run out of it. It's clean, safe, and free for all to use.
Currently, most of the energy we use comes from burning coal, oil, and natural gas. These are called fossil fuels. When these fuels burn, gases such as carbon dioxide, nitrogen oxides, and sulfur compounds escape into the air. The gases react with sunlight to create smog. They also trap heat in our atmosphere and cause global warming. All these conditions are harmful to forests, crops, wildlife, and humans.
Wind power is a clean, economical energy source that can help reduce environmental pollution. Wind turbines could generate 20 percent of America's electrical power by the year 2030. This would reduce carbon emissions by an amount equal to what 140 million cars produce each year. Wind power is a clean, renewable energy that we will never use up. Some people discovered this a thousand years ago. Others don't know about it yet. But whether you've heard it or not, there's good news in the wind.CHAPTER 2
Ancient Wind Machines
* * *
Before people invented windmills they found other ways to harness the wind. Sails on boats carried mariners faster and farther than before. Four thousand years ago men in large sailing canoes explored the South Pacific. They found their way by watching the wind, stars, and ocean currents as they sailed from one small island to another across hundreds of miles of open ocean. In Egypt, graceful dhows have sailed down the Nile River for 5,000 years. By 450 BC Phoenician sailors had traveled beyond the Mediterranean, north to Britain and south along the west coast of Africa.
Kites in the Wind
Kites are another way that the wind has been used for exploration. More than 2,000 years ago, the Chinese began flying kites. They flew them in battle to signal their troops. On Kite Day they sent kites aloft, asking the sky gods to send good fortune in the coming year.
Benjamin Franklin began experimenting with kites as a boy. One day he floated on his back while his kite pulled him more than a mile across a lake. Since his kite would not carry him back against the wind, he paid a smaller boy a few pennies to tote his clothes from one shore to another.
In 1752 Franklin flew a kite during a thunderstorm to prove that lightning contained electricity. He tied a key to the end of a silk kite string before sending it aloft. When lightning did strike his kite, he felt a slight electrical shock. He was lucky that his kite string remained fairly dry or his experiment would have been much more shocking. A Russian professor was killed a year later when he repeated Franklin's experiment with a wet kite string.
Scientists continued to use kites into the 1900s. Wilbur and Orville Wright designed and flew giant box kites. These experiments helped them invent the first successful airplane in 1903. From 1898 to 1933, the US Weather Service sent kites aloft to record temperature, humidity, and wind speed.
Archaeologists in the early 1990s found evidence to suggest that people living in Sri Lanka in the AD 700s used the wind to smelt (separate) metal from rock ore in an unexpected way. Traditionally, smelting furnaces are tall, narrow structures. People fan the furnace with a bellows to make the fire burn very hot — hot enough to melt metal. But in Sri Lanka they dug large crescents near the top of steep mountainsides. Each July and August monsoon winds blew across the Indian Ocean, up the slopes, and into these crescent-shaped furnaces. Winds of 25 to 30 mph rushed into the furnaces and created a mini-tornado. Charcoal fires inside the furnace reached at least 2200ºF (1200ºC), hot enough to smelt iron or steel.
Professor Gill Juleff, the British archaeologist in charge of the excavations, says, "These furnaces break all the rules about smelting furnaces, yet we're sure they were used for making iron, and perhaps steel." Muslim armies invaded Sri Lanka during that time, and iron and steel were probably used for weapons as well as farming tools.
We first hear of windmills from traveling Arab geographers around AD 950. They visited the high desert plains of Seistan in ancient Persia, near the present Iran-Afghanistan border. There, a hot gale force wind blew from June through September. It was called "the wind of 120 days, the wind that killed cows."
People in Seistan built vertical axis windmills that resembled modern revolving doors enclosed on two sides. The wind entered on one side, twirled the doors around, and exited on the other side. Attached to millstones, the windmills ground corn into meal. Connected to a pump, they raised water from underground wells to irrigate the parched land. The advantage of this windmill was that it worked no matter which way the wind blew. However, the wind only pushed against one door at a time, so only one-fourth of the windmill was using the wind at any given moment.
Windmills on the Move
Legend has it that in the 1200s the Mongolian armies of Genghis Khan captured Persian windmill builders and took them to China to build irrigation windmills. Persian-style windmills also spread westward through the Middle East. In Egypt they were used to grind sugar cane.
Centuries later, European settlers in the West Indies hired Egyptians to plant sugar cane and build windmills to grind it. It was in this way that a few ancient Persian-style windmills reached the New World.CHAPTER 3
Windmills in Europe Across the Centuries
* * *
On the windy plains of Suffolk, along the east coast of England, a strange sight appeared one day in AD 1191. Dean Herbert, an old priest from the local church, built a windmill with two heavy millstones to grind wheat into flour for the people of the parish.
Abbot Samson, the head of the nearby monastery, heard about the new machine and ordered his workmen to tear it down. The abbot owned the only water mill in the region. Every farmer came to his mill to grind grain into flour to make his bread, and each of them gave the abbot a share of their flour as payment. A curious mill like Herbert's windmill was bound to attract a lot of customers. This would not do.
When poor Herbert learned of the abbot's objection and realized there was no way to change his mind, Herbert ordered his own workers to take the mill apart so that he could at least save the lumber. The abbot's men were shocked when they arrived at the location of Herbert's mill and found nothing but the wind.
No one knows how windmills found their way to Europe. The Crusaders, European soldiers who tried to capture Palestine from the Turks, probably saw Persian-style windmills in the Middle East. However, the windmills that appeared in Europe were nothing like the Persian ones. Perhaps they were reinvented in Europe.
These earliest European windmills are called postmills. These mills resemble a type of water mill found in Europe around 1200. Some historians believe that a clever person turned a water mill upside down, enlarged its paddles to catch the wind, and invented the first postmill.
Millwrights built postmills out of wood, with a few iron fastenings. The mill had to be light enough for the miller to turn, yet strong enough to withstand the fiercest storms and constant vibrations caused by spinning sails and grinding gears. The mill had to be perfectly balanced so that the millstones remained level no matter which way the mill was turned. If the stones weren't level, grain would not grind evenly. Many postmills lasted for centuries, thanks to the superb engineering skills of medieval millwrights.
During the 1300s, one millwright realized that he didn't need to turn the entire postmill when the wind changed direction; he only needed to turn the sails. The sails, attached to the roof or cap of the mill, could revolve on an outdoor track. The miller turned only the cap to face the sails into the wind. The rest of the building remained fixed to the ground. This meant the mill could be bigger, heavier, and stronger. These mills reminded people of the long shirts, or smocks, that farmers wore, so they called them smock mills.
Windmills in Southern Europe
In the 1500s people in Spain, Greece, and the Mediterranean islands began to build small stone tower windmills. In these drier countries, windmills were used to pump water to irrigate fields as well as to grind grain. There are 10 restored tower windmills in Campo de Critana, La Mancha, Spain, that are now Cultural Heritage Sites.
Draining the Netherlands
"God created the world, but the Dutch created Holland," says an old Dutch proverb. The official name of the country is the Netherlands, which means "low lands," for much of the country is near or below sea level. For thousands of years the Dutch built sea walls, or dikes, to hold back the sea, their fierce Waterwolf.
In the 1600s the Dutch began to reclaim land that was below sea level. Using dikes and drainage windmills, they pumped water out of the lakes and marshes. As the new land dried, they dug canals to channel rainwater and groundwater for the new farms and villages they built. These new lands were called polders. With the help of windmills and dikes, the Dutch were able to hold back the Waterwolf and create a country that is twice as big as before.
Draining the English Fens
The English also tried to drain their marshes and create new farmland. In 1588 a drainage windmill began work in the fens (marshes) of Lincolnshire. Adventurers with money to spend hired drainers to do the work for them. But the fiercely independent slodgers, who lived by hunting and fishing in the fens, liked the land as it was. As soon as the drainers would build a dike and windmill, the slodgers tore it down. Nature was on the slodgers' side, for winter storms helped to destroy the dikes and flood the land again. The battle over the fens went on for centuries. It wasn't until the mid-1800s that the drainers finally won.
What Windmills Can Do
Windmills sprouted all over Europe and made many jobs easier and faster. By the early 1700s the Netherlands and England each had about 10,000 windmills. Thousands more worked in France, Germany, Denmark, and Eastern Europe.
Grist mills ground grain, but they also ground cocoa, gunpowder, malt, and mustard. Paint mills ground pigments for paint as well as herbs and chemicals to make medicines and poisons. Oil mills pressed the oil from seeds, and millers sold the leftover seedcakes for cattle feed. Glue mills processed cow hides and animal bones. Hulling mills removed the outer layer of rice and barley kernels. Fulling mills pounded woolen cloth into felt. The Dutch called these "stink mills," because rancid butter and aged urine were used in the process. Miners used windmills to blow fresh air into deep mine shafts. Windmills also provided power to make paper and to saw lumber.
Windmills came in all sizes. Sawmills with a crane, hoists, gears, and saws might be 80 feet tall with sails 100 feet in diameter. Large saw frames cut giant logs, and smaller saws cut beams and boards. Leftover scraps of lumber were sent to a small, 25-foot windmill that cut them into strips and slats. Many farms had even smaller mills, about five feet tall, to pump water from the fields.
Sawmills and paper mills grew so large — housing saws and pulp vats, storage and drying sheds — that they "split the seams" of their smock and became rectangular factories with windmills on top.
Not everyone welcomed the new inventions. Dutch guilds — somewhat like our modern trade unions — protested against early industrial windmills, so the millers formed a guild of their own to promote their trade. In the 1600s English sawyers who were afraid of losing their jobs destroyed the first wind sawmill built in Dept-ford (near London).
Excerpted from The Wind at Work by Gretchen Woelfle. Copyright © 2012 Gretchen Woelfle. Excerpted by permission of Chicago Review Press Incorporated.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Meet the Author
Gretchen Woelfle is an award-winning author of picture books, short stories, and environmental nonfiction. She has written for Cicada, Cricket, and Spider magazines and the anthology series Stories from Where We Live.
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