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What is Hydropower?

Hydropower (from hydro meaning water) is energy that comesfrom the force of moving water. The fall and movement of water is part of a continuous natural cycle called the water cycle.

Energy from the sun evaporates water in the Earth’s oceans and

rivers and draws it upward as water vapor. When the water vapor reaches the cooler air in the atmosphere, it condenses and formsclouds. The moisture eventually falls to the Earth as rain or snow,replenishing the water in the oceans and rivers. Gravity drives thewater, moving it from high ground to low ground. The force of moving water can be extremely powerful

.Hydropower is called a renewable energy source because thewater on Earth is continuously replenished by precipitation. Aslong as the water cycle continues, we won’t run out of this energysource.

Hydro Dams

It’s easier to build a hydropower plant where there is a naturalwaterfall. That’s why the first hydropower plant was built at Niagara Falls. Dams, which are artificial waterfalls, are the next best way.

Dams are built on rivers where the terrain will produce an artificiallake or reservoir above the dam. Today there are about 80,000dams in the United States, but only three percent (2,400) have power-generating hydro plants. Most dams are built for floodcontrol and irrigation, not electric power generation.

A dam serves two purposes at a hydropower plant. First, a damincreases the head, or height, of the water. Second, it controls theflow of water. Dams release water when it is needed for electricity production. Special gates called spillway gates release excesswater from the reservoir during heavy rainfall.

Hydropower Plants

The flow of water represents a huge supply of kinetic energy thatcan be put to work. Water wheels are useful for generatingmechanical energy to grind grain or saw wood, but they are not practical for generating electricity. Water wheels are too bulky andslow. Hydroelectric plants are different. They use modern turbinegenerators to produce electricity, just as thermal (coal, oil, nuclear) power plants do, except they do not produce heat to spin theturbines.

Hydropower and the Environment

Hydropower dams can cause several environmental problems,even though they burn no fuel. Damming rivers may permanenalter river systems and wildlife habitats. Fish, for one, may nolonger be able to swim upstream.

Hydro plant operations may also affect water quality by churniup dissolved metals that may have been deposited by industry lago. Hydropower operations may increase silting, change watetemperatures, and lower the levels of dissolved oxygen.

Hydropower has advantages, too. Hydropower’s fuel supply(flowing water) is clean and is renewed yearly by snow and

rainfall. Furthermore, hydro plants do not emit pollutants into tair because they burn no fuel. With growing concern over greenhouse gas emissions and increased demand for electricityhydropower may become more important in the future.

Hydropower facilities offer a range of additional benefits. Mandams are used to control flooding and regulate water supply, anreservoirs provide lakes for recreational purposes, such as boatand fishing.

Tidal Energy

The tides rise and fall in eternal cycles. The waters of the oceanare in constant motion. We can use some of the ocean’s energy

 but most of it is out of reach. The problem isn’t harnessing theenergy as much as transporting it. Generating electricity in themiddle of the ocean just doesn’t make sense—there’s no one thto use it. We can only use the energy near shore, where peopleneed it.

Tidal energy is the most promising source of ocean energy for today and the near future. Tides are changes in the level of theoceans caused by the rotation of the Earth and the gravitationa pull of the moon and sun.

Tidal energy plants capture the energy in the changing tides. Alow dam, called a barrage, is built across an inlet. The barrage hone-way gates (sluices) that allow the incoming flood tide to pinto the inlet. When the tide turns, the water flows out of the inthrough huge turbines built into the barrage, producing electric

Today, the electricity from tidal plants costs more than fromconventional power plants. It is very expensive and takes a lontime to build the barrages. Also, tidal plants produce electricityless than half of the time. On the other hand, the fuel is free andnon-polluting, and the plants are easy to maintain. Tidal powera renewable energy source. The plants do affect the environmethough they produce no air pollution.

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Wind is simply air in motion. It is caused by the uneven heating of the Earth’s surface by radiant energy from the sun. Since theEarth’s surface is made of very different types of land and water, itabsorbs the sun’s energy at different rates.

An ideal situation for the formation of local wind is an area whereland and water meet. During the day, the air above the land heatsup more quickly than the air above water. The warm air over theland expands, becomes less dense and rises.

Today, people use wind energy to make electricity. Wind is calleda renewable energy source because the wind will blow as long asthe sun shines.

Wind Direction

A weather vane, or wind vane, is used to show the direction of thewind. A wind vane points toward the source of the wind. Winddirection is reported as the direction from which the wind blows,not the direction toward which the wind moves. A north wind blows from the north toward the south.

Wind Speed

It is important in many cases to know how fast the wind is blowing. Wind speed can be measured using a wind gauge or 

anemometer.

Today’s Wind Turbines

Today’s wind turbines use blades to capture the wind’s kineticenergy. Wind turbines work because they slow down the speed of the wind. When the wind blows, it pushes against the blades of thewind turbine, making them spin. They power a generator to produce electricity.

Most wind turbines have the same basic parts: blades, shafts,gears, a generator, and a cable. (Some turbines do not havegearboxes.) These parts work together to convert the wind’senergy into electricity.

1) The wind blows and pushes against the blades on top of thetower, making them spin.

2) The turbine blades are connected to a low-speed drive shaft.When the blades spin, the shaft turns. The shaft is connected to agearbox. The gears in the gearbox increase the speed of thespinning motion on a high-speed drive shaft.

3) The high-speed drive shaft is connected to a generator. As theshaft turns inside the generator, it produces electricity.

4) The electricity is sent through a cable down the turbine tower toa transmission line.

The amount of electricity that a turbine produces depends on itssize and the speed of the wind. Wind turbines come in manydifferent sizes. A small turbine may power one home. Large wind

turbines can produce enough electricity to power up to 1,000homes. Large turbines are sometimes grouped together to provide power to the electricity grid. The grid is the network of power lines connected together across the entire country.

Wind Power Plants

Wind power plants, or wind farms, are clusters of wind turbineused to produce electricity. A wind farm usually has dozens of wind turbines scattered over a large area.

Choosing the location of a wind farm is known as siting a windfarm. The wind speed and direction must be studied to determinwhere to put the turbines. As a rule, wind speed increases withheight, as well as over open areas with no windbreaks.

Turbines are usually built in rows facing into the prevailing wiPlacing turbines too far apart wastes space. If turbines are tooclose together, they block each other’s wind.

The site must have strong, steady winds. The best sites for winfarms are on hilltops, on the open plains, through mountain pasand near the coasts of oceans or large lakes.

What is Biomass?

Biomass is any organic matter—wood, crops, seaweed, animalwastes— that can be used as an energy source. Biomass is probably our oldest source of energy after the sun. For thousanof years, people have burned wood to heat their homes and cootheir food.

Biomass gets its energy from the sun. All organic matter contaistored energy from the sun. During a process called photosynthesis, sunlight gives plants the energy they need toconvert water and carbon dioxide into oxygen and sugars. Thessugars, called carbohydrates, supply plants and the animals tha plants with energy. Foods rich in carbohydrates are a good sourof energy for the human body!

Biomass is a renewable energy source because its supplies are nlimited. We can always grow trees and crops, and waste willalways exist.

Reporter:

Elvie Venus M. Eslabon

IV-9 AB/BSE Literature

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References:

http://www.need.org/needpdf/infobook_activities/SecInfo/HydroS.pdf 

http://www.need.org/needpdf/infobook_activities/IntInfo/WindI.pdf 

http://www.need.org/needpdf/infobook_activities/SecInfo/BiomassS.pdf 

 Types of Biomass

We use four types of biomass today—wood and agricultural products, solid waste, landfill gas and biogas, and alcohol fuels.

Wood and Agricultural Products

Most biomass used today is home grown energy. Wood—logs,chips, bark, and sawdust—accounts for about 49 percent of  biomass energy. But any organic matter can produce biomassenergy. Other biomass sources include agricultural waste productslike fruit pits and corncobs.

Wood and wood waste, along with agricultural waste, are used togenerate electricity. Much of the electricity is used by theindustries making the waste; it is not distributed by utilities, it iscogenerated. Paper mills and saw mills use much of their waste

 products to generate steam and electricity for their use.

Solid Waste

Burning trash turns waste into a usable form of energy. One ton(2,000 pounds) of garbage contains about as much heat energy as500 pounds of coal. Garbage is not all biomass; perhaps half of itsenergy content comes from plastics, which are made from petroleum and natural gas.

Making electricity from garbage costs more than making it fromcoal and other energy sources. The main advantage of burningsolid waste is that it reduces the amount of garbage dumped inlandfills by 60 to 90 percent, which in turn reduces the cost of landfill disposal. It also makes use of the energy in the garbage,rather than burying it in a landfill, where it remains unused.

Landfill Gas

Bacteria and fungi are not picky eaters. They eat dead plants andanimals, causing them to rot or decay. A fungus on a rotting log isconverting cellulose to sugars to feed itself. Although this process

is slowed in a landfill, a substance called methane gas is still produced as the waste decays.

Methane gas is colorless and odorless, but it is not harmless. Thegas can cause fires or explosions if it seeps into nearby homes andis ignited. Landfills can collect the methane gas, purify it, and useit as fuel.

Biomass and the Environment

Environmentally, biomass has some advantages over fossil fuesuch as coal and petroleum. Biomass contains little sulfur andnitrogen, so it does not produce the pollutants that can cause acrain. Growing plants for use as biomass fuels may also help keecarbon dioxide levels balanced. Plants remove carbon dioxide—one of the greenhouse gases —from the atmosphere when theygrow.