Renewable Energy
Protecting Fish at Hydroelectric Plants
A great advantage of hydroelectric power is that it does not produce the air pollution of fossil fuels. But a big disadvantage is that it disrupts river ecosystems. Certain fish, most notably salmon, migrate upstream every year to spawn and reproduce. Dams serve as barriers to fish migration and lead to population declines. One way to eliminate this problem is to construct fish ladders, also called fishways or fish steps. Click each image to learn more about how fish can be protected at hydroelectric plants. pg 9
Hydrogen Fuel Vehicles
A hydrogen vehicle uses hydrogen as fuel. In a hydrogen vehicle, the hydrogen may be burned or reacted with oxygen in what is called a fuel cell. Upon reaction with oxygen in a fuel cell, the hydrogen produces water and electricity. To support hydrogen vehicles, we would need entirely new infrastructure in the U.S. We would need to build special hydrogen fuel stations for people to fuel up their cars. We would also need pipelines for transporting hydrogen from its place of production to various places all over the country.
Slide 5
A parabolic trough is the most common technology used in solar power plants. It has a reflector that receives sunlight and focuses it on a collect or. Because of its parabolic shape, the trough can concentrate sunlight from 30 to 100 times its normal intensity. A solar dish can track the sun throughout the day , moving as necessary so that the sunlight is always concentrated at the center of the dish. It can concentrate the sunlight to over 2000 times its normal intensity. A solar power tower uses hug e arrays of computer-controlled mirrors, called heliostats, to track the sun and focus sun light on central heat collection units.
Slide 2
Active solar heating involves absorbing energy from the sun and then pumping a heat-absorbing fluid through special collectors, mounted on the roof or on special racks, oriented toward the sun. Unlike passive solar heating, active solar heating relies on some sort of collector and a mechanical device to distribute the heat in the structure involved. This home has solar energy collectors on the roof. They collect heat energy , which is then pumped through the house to heat spaces and water
Advantages and Disadvantages of Geothermal Power
Advantages of Geothermal Energy - Very high energy efficiency and renewable - Lower carbon dioxide emissions - Low land use - Low land disturbance Disadvantages of Geothermal Energy - Scarcity of suitable sites - Odor pollution (the hot water often smells like rotten eggs) - Reservoirs can be depleted if used faster than renewed - High cost at less than favorable sites
Slide 6
Another small but important use of solar energy is to make solar cookers, like the one you see here. These are small homemade devices that concentrate sunlight to heat water and cook food. You can use these anywhere. Currently, they have been widely distributed to people in several developing nations. The solar cookers let them heat drinking water to cut down on infectious bacteria in the water before they drink it. The cookers also allow the people to cook their food without having to burn firewood. This prevents erosion and desertification of cut forests. The time saved in using this device also allows the family to focus on growing healthy vegetables.
Questions 1. Who leads the world in using the most wind power? U.S. Denmark Russia China 2. Which statement is most true about wind power? Its cost is steadily coming down, making it a desirable form of renewable energy. It is the world's most costly form of renewable energy. It is more polluting than fossil fuels. It is used only in Europe and has not made its way to the U.S. yet. 3. Which of the following may be harmed by wind farms? birds bats dolphins all of the above 4. To minimize their disruption to ecosystems, many wind power plants are built offshore in bird migration paths on farms all of the above 5. Which instrument measures wind speed? yaw drive wind vane anemometer turbine 6. What is the best wind speed for wind turbines? about 13 mph over 55 mph between zero and 12 mph at least 100 mph
Answers *Correct answers are indicated with an asterisk. 1. Who leads the world in using the most wind power? U.S. *Denmark 2. Which statement is most true about wind power? *Its cost is steadily coming down, making it a desirable form of renewable energy. 3. Which of the following may be harmed by wind farms? birds bats dolphins *all of the above 4. [To minimize their disruption to ecosystems, many wind power plants are built offshore in bird migration paths *on farms all of the above 5. Which instrument measures wind speed? *anemometer 6. What is the best wind speed for wind turbines? *about 13 mph
Questions 1. True or False: Hydropower is derived from burning hydrogen fuel. 2. True or False: The Three Gorges Dam in China is the world's largest hydropower operation. 3. True or False: A collection of water held behind a dam is called a reservoir. 4. True or False: Water enters through the spillways. 5. True or False: At a hydropower plant, energy from magnets makes a turbine spin. 6. True or False: Hydropower plants have the disadvantage of high air pollution. 7. True or False: Electricity is generated when magnets spin within a copper coil. 8. True or False: Magnets within the generator sp in to produce electricity at a hydropower plant. 9. True or False: Hydropower is the second l eading source of renewable energy worldwide. 10. True or False: In the U.S., hydropower is used widely in all 50 states, and accounts for much of our energy needs. 11. True or False: Even though the U.S. gets only about 7% of its electricity from hydropower, we have used almost all of our potential for hydropower. 12. True or False: Hydroelectric reservoirs can also be used for boating and irrigation. 13. True or False: Dams disrupt the natural flow of rivers and can harm wildlife. 14. True or False: Dam failure is common but rarely a serious threat of harm. 15. True or False: Fish ladders at hydroelectric pl ants give migrating fish a safe route around a dam.
Answers 1. False Feedback: Hydropower is derived from the energy of moving or flowing water. 2. True Feedback: The Three Gorges Dam in China is the world's largest hydropower operation. 3. True Feedback: A collection of water held behind a dam is called a reservoir. 4. False Feedback: Water enters through the penstock. 5. False Feedback: Energy from moving water makes the turbine spin. 6. False Feedback: Hydroelectricity produces very little air pollution. 7. True Feedback: Electricity is generated when magnets spin within a copper coil. 8. True Feedback: Magnets within the generator spin to produce electricity at a hydropower plant. 9. False Feedback: Hydropower is the leading s ource of renewable energy worldwide . 10. False Feedback: Hydropower accounts for only about 7% of our electricity, and is used mostly in the Pacific Northwest where rivers are suitable. 11. True Feedback: Even though the U.S. gets only about 7% of its electricity from hydropower, we have used almost all of our potential for hydropower. 12. True Feedback: Hydroelectric reservoirs can also be used for boating and irrigation. 13. True Feedback: Dams disrupt the natural flow of rivers and can harm wildlife. 14. False Feedback: Dam failure is rare but can be very deadly. 15. True Feedback: Fish ladders at hydroelectric plants give migrating fish a safe route around a dam.
Geothermal Power Plants
At a geothermal power plant, hot water is withdrawn from deep inside Earth through a production well. The water is hot and under great amounts of pressure. Through a process called flashing, the pressurized water is converted to steam. The steam turns a turbine and generates electricity production at a generator. After the steam is used, it cools, is collected in a cooling tower, and then gets pumped back down into the ground to replenish the water that was initially withdrawn. This way no water is wasted and the supply of hot underground water does not run out.
Advantages and Disadvantages of Hydropower
Clearly hydropower produces very little air pollution and it has no harmful waste products that have to be disposed of. Alternatively, can you think of any disadvantages of hydropower? Think about what probably happens to fish trying to make their way downstream. How might a hydroelectric dam affect their efforts? Click through the images to learn more about this and other pros and cons of using hydropower. pg 8
The Environmental Impacts of Wind Power
Compared to fossil fuels, wind power has few environmental impacts. It consumes no fuel and emits no air pollution. Constructing wind turbines does require the use of another energy source. This means that fossil fuels are usually burned to transport and construct new wind turbines, thus emitting carbon dioxide to the atmosphere during the construction phase. Scientists estimate, however, that the carbon dioxide emitted during construction is "paid back" within nine months of wind power use. That is, once the wind turbine is in place, it creates energy that will only cut back on the future need for fossil fuels. Click each image to learn more about some disadvantages of wind power. pg 20
Wind Power
Did you ever blow bubbles as a kid? You use moving air—your breath—to create the energy to blow the bubbles. This same idea can also provide us with clean renewable energy just by using the wind. Wind power generates electricity with moving air. The blades on a windmill turn when struck by the wind. The turning of the blades cause a turbine to spin and generate electricity. Roll over the image below to learn more about the blades, generator and yaw drive of a modern wind turbine.
Hydroelectric Power Plants
Electricity is generated in a hydroelectric power plant. Notice that it has many of the same parts as a fossil fuel-burning electrical plant or a nuclear energy reactor. That is because many of the same concepts are at work here. A dam is built across a river to hold back water in a collection area, called a reservoir. The water is kept behind the intake opening, and so it is under pressure. When the intake is opened, water rushes through a tube, called the penstock. Energy from the moving water then turns the turbine blades. The spinning turbine makes magnets spin in the generator. Magnets spinning within a copper wire in the generator produce electricity. That electricity is then sent out from the power plant through various transmission lines. The water returns to the river through a device, called a spillway. Nothing is burned and no air pollution is given off.
Under what circumstances would the production of hydrogen fuel be the least polluting?
Electricity is required to produce hydrogen fuel. So we have to use fossil fuels in electrical power plants to create hydrogen, which means creating the pollution that comes with burning fossil fuels. But if we can use clean renewable sources to produce the electricity to make hydrogen fuel, then there is less pollution
Slide 3
Energy from the sun can also be converted to electrical energy. Photovoltaic cells, called solar cells or just PV cells for short, are heat conductors. They are thin wafers of silicon with very small amounts of metals. When sunlight strikes the cells , they emit electrons and create electrical current. Because each cell produces only a small amount of electricity, many cells are wired together in a panel. Panels can be big enough to power whole buildings or small enough to power a watch. PV cells have the potential to provide electricity for millions of people worldwide, who live in remote rural areas and do not have access to electricity from traditional power plants. Because manufacturing these cells is extremely ex pensive, we need new technology to make it a more cost effective source.
Modern Wind Power
Europe uses the most wind power. Denmark, Germany, and Spain have thousands of wind turbines. Check out this newscast from NBC News to see how wind power is used in Denmark. Be on the look out for how wind power has become so successful in Denmark. Notice how wind power is helpful to the people both economically and environmentally.
Solar Radiation
Every year, enough solar radiation reaches the Earth to provide about twice as much energy as will ever be obtained by all of Earth's non-renewable energy sources (fossil fuels and nuclear power) combined. Insolation, which is a measure of the amount of solar radiation that reaches a given area, varies throughout the world. It is highest near the equator and lowest near the poles. This is because Earth is tilted on its axis. The poles are tilted away from the sun during various times of the year. The equator gets more direct sunlight.
Hydropower
For centuries, water mills, like Mabry's Mill, have been used to grind grains into flour or to saw timber. Small water mills like this are in sharp contrast to modern hydropower stations. Hydropower or hydraulic power comes from the energy of moving or flowing water. Today, the world's largest hydropower operation is the Three Gorges Dam on the Yangtze River in China. Click through the tabs to learn more about hydropower.
What is the relationship between the availability of geothermal power and plate tectonics?
Geothermal power has been limited to areas that are tectonic plate boundaries. Remember that the boundaries are places where magma is likely to be rising to the surface and where geothermally-heated water is found. Today, technology allows us use geothermal power in some other areas, but it is still mostly limited to tectonic boundaries.
Where Geothermal Power is Used
Geothermally-heated water is closer to Earth's surface in some places than it is in others. Countries that have the best access to geothermal energy are Iceland, Chile, the U.S., the Philippines, Italy, and New Zealand. In the U.S., geothermal electricity is generated in five states: Alaska, California, Hawaii, Nevada, and Utah. As of 2007, there were plans to build new geothermal power plants in seven other states with suitable geologic features, mostly in the western part of the country. The Energy Policy Act of 2005 makes geothermal plants eligible for federal tax benefits, giving a boost to geothermal energy in the U.S. The United States generates an average of 15 billion kilowatt hours of geothermal power per year. This is comparable to burning some 25 million barrels of oil or six million short tons of coal per year. Six million Americans get their electricity from geothermal energy. In 1999, Santa Monica, California became the first city in the U.S. to get all its electricity from geothermal sources.
wind
How much land and wind are required? Will my town let me install a turbine? Installers re commend sites with average wind speeds of at least 12 mph, but specific land requirements vary from place to place. Zoning codes sometimes impose a minimum requirement on lot size or on the distance a turbine may be placed from a property line, and may vary depending on the height of the proposed turbine. Also, it is essential to have a site with unobstructed access to winds, which most often requires higher towers, larger land lots, and non - urban locations . Currently, less than 1% of all small wind t urbines are used in urban applications partly due to zoning restrictions, but mostly because wind quality is much poorer in densely built environments. Contact your turbine factory dealer or see AWEA small - wind permitting guide at www.awea.org/smallwind for help navigating the permitting process. How does the rated capacity of a small wind system compare to its actual performance? Rated capacity indicat es the electric power (kilowatts) at a given wind speed, so the answer depends on wind speed - and the turbine. A more accurate indicator of energy prod uction, however, is swept area . A 5 - kW turbine (average residential size, 18ft. ro tor diameter) produces around 8 ,000 kWh per year in 12 - mph average winds, whi ch is about 100% of what an average U.S. home requires. At the larger end of the spectrum, a 100 - kW turbine (60ft. diameter) in these co nditions will generate around 20 0,000 kWh per year. Are batteries or other storage needed? There are two types of syst ems: those connected to the electricity grid ("on - gr id") and those used off - grid (for battery charging ) or backup power. Many systems sold today are off - grid, but demand is rising for on - grid systems which essentially use the grid as a "battery": when the wind blows, the owner uses electricity from the turbine; when winds are low and consumption is high, the owner us es electricity from the grid. The smallest wind turbines are used in conjunction with solar photovol taic technology . How are small wind syst ems maintained? Routine inspections should be performed once a year of a turbine's 20+ - year lifespan. A professional installer or trained technician (usually the manufacturer or dealer that sold the turbine) maintains the turbine and tower through physica l inspections, though some turbines can be monitored remotely from a home computer. How can I advocate for good policies? AWEA, our members, and our allies actively engage state and federal lawmakers to promote good policies for small wind, such as tax c redits, streamlined zoning and permitting, net metering, and standardized grid interconnection rules. Grassroots activism is a key component of our efforts. To join, visit the following link : http://www.awea.org/issues/grassroots/index.cfm Where can I go for more information? The America n Wind Energy Association has a toolbox of information on its Web site for people interested in installing a small wind system at www.awea.org/smallwind . On this site, you can find advice from an expert, some state - specific information abou t buying and installing a small wind turbine, success stories, technical information, and much more
Small Wind
How would you like a wind turbine in your backyard? Small wind refers to small-scale wind power that individual homes or businesses can use. They can even be installed on a roof and supply up to 25 percent of a home's electricity. In the U.S., a home wind turbine will cost about $12,000 to $50,000 to install, but there are government incentive programs that may rebate as much as a 50 percent of the cost to homeowners who install wind systems. And some states offer government grants to cover almost all the expenses involved. Small wind systems will also begin to pay for themselves after about five to 10 years in electricity savings. This fact sheet from the American Wind Energy Association gives you all the info you need to find out about installing a windmill on your property. Find out if small wind is feasible for you!
Why must special care be taken when storing and transporting hydrogen fuel?
Hydrogen is a gas and it can explode when storing and transporting it
How We Make Hydrogen Fuel
Hydrogen produces very little pollution and it's made from readily available water, so why is it not used more than fossil fuels? Hydrogen does not exist by itself in nature. We have to extract the hydrogen from hydrogen-bearing compounds like water (H2O). In order to extract the hydrogen from something else, we have to use electricity. So we have to use energy to get energy, and that's like spending money to get money. One way around this would be if the electricity used to extract hydrogen came from a non-polluting renewable source of energy, like solar power. However, it would take huge amounts of solar cells to produce the electricity we need to produce enough hydrogen for every car in America. The first column of the diagram shows various materials from which hydrogen can be obtained. The second column shows various methods used to extract the hydrogen. Each of those requires the use of some other energy source. The bottom line is that hydrogen is not an energy source like coal or oil. It is a fuel produced by using energy and thus its energy yield will always be low.
Worldwide Trends in Hydropower
Hydropower is the worldwide leading renewable energy source. The small pie chart in the bottom of the picture shows you all sources of worldwide energy. Fossil fuels account for a large percentage. The top pie chart shows you the main sources of renewable energy. Hydropower, in light blue, is the main source of renewable energy on a worldwide basis. In the U.S., hydroelectric power supplies about seven percent of our energy needs nationwide. But it supplies nearly 50 percent of the electricity used on the west coast, because of the high occurrence of suitable rivers. In the U.S., we have created dams and reservoirs along about 98% of the rivers that can generate hydropower. Therefore, there is little room to expand hydropower in the U.S. On a worldwide basis, however, humans have only tapped about 13 percent of our hydropower potential. China, India, South America, and Africa can still use much more hydropower. The World Energy Council estimates that Africa uses only seven percent of its potential hydropower; that Asia uses only 22 percent of its potential, and South America uses only 33 percent.
Solar Power
Imagine if you could charge all of your digital gizmos with just the energy from the Sun. Maybe someday solar energy will power all our cameras and phones, much like solar calculators that run off the energy from the Sun without being plugged in to anything. Because the Sun shines everywhere, it is completely free and renewable. It can be used on a small scale (pocket calculators) or on a large scale (houses, even towns).
Geothermal Power
Remember the sidewalks of Klamath, Oregon? They are warm on snowy days. Their source of warmth is geothermal power. Geothermal power (from "geo" for earth and "thermal" for heat) consists of energy stored in soil, underground rocks, and fluids in Earth's mantle. In general, rock temperatures increase as you move downward through Earth's interior. The rate of this temperature increase the further you go down is known as the geothermal gradient. Just 300 to 400 feet down, the temperature becomes quite warm. Once you get about 10,000 feet below Earth's surface, the temperature is hot enough to boil water. Sometimes water makes its way close to the hot rocks and magma below Earth's surface. The hot magma can heat the water to boiling and that water makes its way back up to Earth's surface through openings in the Earth's crust. In parts of the world where geological conditions are right to produce this type of activity, the heated water can be withdrawn and used to turn a turbine, just like in coal-burning power plants. Except, in these cases, no fuel is burned because the water is already hot. Click through the tabs to learn more about geothermal power
Summing Up Hydrogen
So what are the pros and cons of hydrogen fuel? On the plus side, hydrogen fuel produces no air pollution and would be completely renewable. On the negative side, the production of hydrogen requires the use of electricity, and that electricity often comes from fossil fuel-burning power plants. The production of hydrogen can cause just as much pollution as the burning of gasoline in cars. The only way around this dilemma would be to use renewable, non-polluting energy sources to produce the electricity used to produce the hydrogen. Is that feasible in light of the fact that renewable energy sources currently account for just two percent of the electricity generation in the U.S.? Iceland has become the first nation to say they will transition their hydrocarbon economy to a hydrogen economy and has vowed to do so completely with clean renewable energy. Should the U.S. do the same?
The Advantages and Disadvantages of Solar Power
Solar energy has very little impact on the environment. It produces no pollution and no waste by-product. It does not require mining and does not disrupt the land. But like all other forms of renewable energy, solar energy is underused. It accounts for less than one percent of energy consumption in the U.S. However, states like California and Florida are beginning to use it more. The big drawback to solar power is that the equipment needed to generate it is very expensive. Most analysts believe solar energy will not be used extensively until it becomes cheaper. As long as fossil fuels remain accessible, and relatively cheap, there is little public interest in developing the more expensive solar energy. Global governments are beginning to offer tax breaks and other incentives to try to encourage business and individuals to use more solar energy because of the environmental benefits that it offers. One successful example of this is the Indian Solar Loan Program, which provides monetary support to builders of solar-powered homes in India. It has brought electricity to thousands of people there who otherwise do not have access to it, while also encouraging a movement away from using fossil fuels.
Consider three important renewable energy sources: solar power, hydropower, and wind power. How are all three of these dependent on the sun?
Solar power is derived from radiant energy from the Sun. Hydropower relies on water supplies in the water cycle, which is in turn driven by energy from the Sun. Likewise, the wind blows because of temperature and pressure differences caused by the Sun.
Slide 4
Solar power plants work in the same way as other power plants that we have learned about. The sun heats water, which is brought to a boil to produce steam. The steam then turns a turbine and powers a generator. Because high temperatures are needed to heat the water to boiling, solar power plants concentrate the energy from the sun into one location. These systems are used most commonly in desert areas with ample sunlight. Most have natural gas turbines that can provide backup electricity on cloudy days or at night.
Renewable Energy
Suppose you have a one-year subscription to your favorite magazine. At the end of the year, you do not want to miss a single upcoming issue. Fortunately, most magazine publishers have very easy ways for you to renew your subscriptions and never miss a single issue. As long as you keep renewing the subscription, you will never stop receiving your favorite magazine. Energy sources are like your subscription—you definitely do not want them to run out. But, there is a major difference—only some energy sources can be renewed. If we can replenish our supply of energy after we use it, we never run out. One example is hydropower. Electricity from hydropower comes from running water. Since the water cycle always replenishes our water supplies through precipitation, we can always rely on hydropower. This is a renewable energy source. In contrast, a non-renewable energy source eventually runs out. Like a magazine whose publisher decides to stop making the magazine—it cannot be renewed. Once we use up all our fossil fuels and uranium supplies, they are gone for good. We cannot replenish them.
What provides the energy in these two images?
That's right—water.
How can the extraction of geothermal water affect aquifers?
The extraction of water can lead to land subsidence if aquifer reservoirs are depleted faster than they are filled back up.
What is the major disadvantage of using hydrogen fuel?
The major disadvantage is that hydrogen does not exist by itself in nature. It must be extracted from other substances, and this requires additional energy. It is like spending money to get money
Storing Hydrogen Fuel
The oil-derived gasoline we use in our cars now is a liquid. Because hydrogen is a gas, it occupies a much larger volume of space than liquid gasoline. Therefore, storing hydrogen requires some special technology and specialized infrastructure to keep it safe and prevent explosions.
Hydrogen Fuel
The world pretty much runs on a hydrocarbon fuel economy. Hydrocarbon fossil fuels are the dominant sources for the fuel that we use for our motor vehicles. But, as you have learned, fossil fuels produce all kinds of pollution when used, and their supplies are limited. Using alternative sources of energy, such as wind, water, and the Sun, we can decrease our use of fossil fuels. But these alternative energy sources really only help us to produce heat and electricity for homes and businesses. What about an alternative fuel source for our transportation needs? Hydrogen is an alternative fuel that can be used to power motor vehicles (cars, trucks, airplanes, etc.). Using hydrogen instead of fossil fuels would eliminate almost all the air pollution we have today. Also, its only byproduct after combustion is water vapor, which is completely non-polluting. Hydrogen is obtained from readily-available water and is thus completely renewable. In light of all of these, some people have argued for a transition from a hydrocarbon economy to a hydrogen economy. Click through the tabs to learn more about hydrogen fuel.
The Uses of Solar Energy
There are two ways to convert solar energy to heat so that it can be used in homes and buildings, and to heat water. The first way is passive solar heating. A passive solar heating system absorbs the heat from the sun and stores the heat within a structure. It does not rely on any mechanical device to distribute the heat. Basically , passive solar heating is what happens in your car when it sits in the sun. Passive solar heating relies on orienting buildings and windows within buildings toward the sun to take advantage of incoming solar energy in the most efficient way.
Why are fossil fuels and uranium considered non-renewable?
These take nature millions and millions of years to make. They are definitely not renewable on human time scales.
View of a Hydroelectric Turbine
This diagram is an up-close view of a turbine and generator in a hydroelectric power plant. Again, you can see how water pushes on the blades of the turbine, which then spins and makes parts of the generator spin to produce electricity. Watch this video to see how this happens. pg 6
wind
What size turbine is needed to power an entire home? On average, a typical American home would require a small turbine with a 5 - kilowatt (kW) generating capacit y to meet all its electricity needs. A machine of this size has a diameter of approximately 18 feet. The exact size needed to power a home, however, can range from 2 kW to 10 kW (12 - 25 ft. diameter) based on a home's energy use, average wind speeds, and the turbine's height above ground (which affects its productivity). How tall are they? T he average height of a small wind turbine (of any capacity) is about 80ft. (about twice the height of a neighborhood telephone pole), with a range of 30 - 140 ft. Gene rator size and tower height are not generally related; a 5 - kW turbine could be on a tower anywhere from 30 - 140 ft. in height, for example. What is the average payback period ? The length of the payback period depends on the turbine, the quality of wind at the installation site, prevailing electricity rates , and available financing and incentives. Depending on these and other factors, the time it takes to fully recover the cost of a small wind turbine can take anywhere from 6 to 30 years. How much do they cost? The purchase and installation of a system large enough to power an entire home costs, on average, $30,000, but the price can range from $10,000 to $70,000 depending on system size, height, and installation expenses. The purchase and installation o f very small (<1 kW) off - grid turbines generally cost $4,000 to $9,000, and a 100 - kW turbine can cost $350,000. The federal government and m any states have rebate or tax credit programs in place to encourage investment in small wind (see http://dsireusa.org ). W hat happens when the wind does no t blow? For grid - connected systems, the user will not notice a difference when the wind is not blowing. The utility provides electricity when the wind does not blow, and any ext ra electricity the turbine generates is sent back to the utility system to be used by a neighbor. Off - grid turbines store power in batteries for on - demand use and are often complemented by solar electric panels to provide more consistent generation. Do I need to take wind measurements ? Taking detailed measurements to gau ge your wind resource is often unnecessary. Experienced installers/dealers or manufacturers can determine whether your property is suitable for a system by inspecting the surrounding are a
wind power
Wind power accounts for about one percent of global electricity, but some countries use a greater percentage than others. Denmark leads the world in wind energy, getting about 20 percent of its electricity from the wind.
The Economics of Wind Power
Wind power is one of the fastest growing sources of renewable energy in the world. In 2006, wind power cost just one-fifth of what it did in the 1980s. Remember how high cost is a big drawback for solar power? With wind power, the costs keep coming down, making it one of the most attractive sources of fossil fuel alternatives. One factor that must be considered is that many sites with lots of wind are far from demand centers. In other words, the places best suited for lots of wind turbines are not necessarily where people live. So constructing roads, transmission lines, and substations would have to be built. But after construction, wind energy has virtually no cost associated with it, since it requires no purchase of fuel. In many parts of the world, and in some U.S. states, governments offer tax breaks, subsidies and other financial incentives to people and businesses to use wind power.
Wind Farms
Wind power plants are commonly called wind farms. They have clusters of dozens of wind turbines scattered over a large area of land. Check out these facts about wind farms: - Wind turbines work best in steady winds of about six meters/second (13 mph). So wind farms must be situated in locations that have generally steady wind at about the right speed. - Wind farms may be located on land or at sea. Those at sea are called offshore wind farms. - The largest wind farm in the world is the Horse Hollow Wind Energy Center in Texas. It has 421 turbines and can power 220,000 homes. - Wind farms generate electricity in 28 U.S. states. The top wind power states are Texas, California, Iowa, Minnesota, and Oklahoma. - In 2006, U.S. wind farms produced enough electricity to power 4.9 million homes. - Most wind farms are not owned by power utility companies. Instead, they are owned by private investors that sell the electricity to electric utilities.
Renewable Energy: Introduction
Would the thought of icy sidewalks make you think twice about walking around in a city? If you live in Klamath, Oregon, the sidewalks are always warm and clear even on the coldest, snowiest days. That's because Klamath has something really hot going on. Klamath relies on the warmth of magma-heated water just below Earth's surface to heat its city streets and to provide heating services to buildings and homes. The city pumps the water up and distributes it to wherever heat is needed. In just a few places on Earth, this "geothermal" water is close enough to the surface that its warmth can be harnessed as an energy source. Klamath is lucky enough to be one of those places. Not only does it save money, but it also reduces the pollution associated with burning fossil fuels for heat. Relying on this underground heat does not burn anything and has no wasteful byproducts. Maybe you do not have geothermally-heated water, but maybe you do have lots of sunshine, or wind, or rivers. All of these provide sources of alternative energy.
equator
measure of solar radiation striking a given area
Variations in Insolation
nsolation also varies by season, time of day, and weather conditions. This map shows average global insolation values. Note how values are highest (orange and red) near the equator. The small black dots indicate the amount of land area necessary to replace the total world energy demand with solar electricity. That is, all the energy that people demand now (in heat, electricity, fossil fuels, etc.), could be met by solar energy in the areas the size of those dots. Variations in insolation in different areas of the world do not necessarily mean that solar energy is limited to only certain climates. As long as there is sunshine, solar energy can be used. However, some areas are better suited than others.
PV cells
part of Earth where insolation is highest
Interactive: Wind Power Directions: Review the parts of the diagram below
pg 16
passive
the main disadvantage of solar energy
active
thin wafers of silicon that conduct heat
insolation
type of solar heating system that distributes heat throughout a building
high cost
type of solar heating system that does not distributes heat
solar power plant
use the Sun to heat water and produce steam
