Модуль 4 - Modal Verbs (1096808), страница 6

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Here, in the heatexchanger, it heats another set of pipes filled withwater to make steam. The steam in this second setof pipes turns a turbine to generate electricity.Below is a cross section of the inside of a typicalnuclear power plant.Nuclear FusionAnother form of nuclear energy is called fusion. Fusion means joining smaller nuclei (the plural ofnucleus) to make a larger nucleus. The sun uses nuclear fusion of hydrogen atoms into heliumatoms. This gives off heat and light and other radiation.In the picture to the right, two types of hydrogen atoms, deuterium and tritium, combine to make ahelium atom and an extra particle called a neutron.Also given off in this fusion reaction is energy! Thanks to the University of California, Berkeley forthe picture.Scientists have been working on controlling nuclear fusion for a long time, trying to make a fusionreactor to produce electricity.

But they have been having trouble learning how to control thereaction in a contained space.What's better about nuclear fusion is that it creates less radioactive material than fission, and itssupply of fuel can last longer than the sun.4. Ocean Energy22The world's ocean may eventually provide us with energy to power our homes and businesses.Right now, there are very few ocean energy power plants and most are fairly small. But how canwe get energy from the ocean?There are three basic ways to tap the ocean for its energy. We can use the ocean's waves, we canuse the ocean's high and low tides, or we can use temperature differences in the water. Let's take alook at each.Wave EnergyKinetic energy (movement) exists in the moving waves of the ocean.

That energy can be used topower a turbine. In this simple example, to the right, the wave rises into a chamber. The risingwater forces the air out of the chamber. The moving air spins a turbine which can turn a generator.When the wave goes down, air flows through the turbine and back into the chamber through doorsthat are normally closed.This is only one type of wave-energy system. Others actually use the up and down motion of thewave to power a piston that moves up and down inside a cylinder. That piston can also turn agenerator.Most wave-energy systems are very small.

But, they can be used to power a warning buoy or asmall light house.Tidal EnergyAnother form of ocean energy is called tidal energy. When tides comes into the shore, they can betrapped in reservoirs behind dams. Then when the tide drops, the water behind the dam can be letout just like in a regular hydroelectric power plant.Tidal energy has been used since about the 11th Century, when small dams were built along oceanestuaries and small streams.

the tidal water behind these dams was used to turn water wheels tomill grains.In order for tidal energy to work well, you need large increases in tides. An increase of at least 16feet between low tide to high tide is needed. There are only a few places where this tide changeoccurs around the earth. Some power plants are already operating using this idea. One plant inFrance makes enough energy from tides (240 megawatts) to power 240,000 homes.23This facility is called the La Rance Station in France. It began making electricity in 1966. Itproduces about one fifth of a regular nuclear or coal-fired power plant.

It is more than 10 times thepower of the next largest tidal station in the world, the 17 megawatt Canadian Annapolis station.Ocean Thermal Energy Conversion (OTEC)The idea is not new. Using the temperature of water to make energy actually dates back to 1881when a French Engineer by the name of Jacques D'Arsonval first thought of OTEC.

The finalocean energy idea uses temperature differences in the ocean. If you ever went swimming in theocean and dove deep below the surface, you would have noticed that the water gets colder thedeeper you go. It's warmer on the surface because sunlight warms the water. But below thesurface, the ocean gets very cold.

That's why scuba divers wear wet suits when they dive downdeep. Their wet suits trapped their body heat to keep them warm.Power plants can be built that use this difference in temperature to make energy. A difference of atleast 38 degrees Fahrenheit is needed between the warmer surface water and the colder deep oceanwater.Using this type of energy source is called Ocean Thermal Energy Conversion or OTEC.

It is beingdemonstrated in Hawaii.24.

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