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Доклад: What is energy \english\

Название: What is energy \english\
Раздел: Топики по английскому языку
Тип: доклад Добавлен 15:05:39 07 апреля 2002 Похожие работы
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What is energy.

Everything in the universe is either energy or matter. For us humans, energy is the means for doing work. Picking up a book, watching TV or launching a Space Shuttle all needs energy. Without it there would be no life, for all life uses energy.

Energy, so far as we are concerned, comes from only two sources: the Sun and the decay of radioactive elements inside the Earth. The Sun radiates its warmth out to all the planets, but ours happens to be about the right distance away to be able to support Life. In fact, Life seems to control the temperature of the planet like a thermostat.

But what about oil, gas or coal, which also come from inside the Earth? They were formed because of the energy from ancient sunshine from millions of years ago driving life on Earth. These have formed 'fossil fuels' or 'non-renewable' energy sources.

Energy is the power that we use to do things, whether it is thinking about building a ship or actually building it. Building it needs large amounts of energy to power blast furnaces to make the steel, mills to roll it and electricity to weld it to form the ship's structure. That ship, when built, has engines, which push it through the water. Most energy is not available to us in a usable form. We have to convert it into another form to make it work for us.

Here are two examples:

What is energy \english\ A fast-flowing river is full of energy we can't use. If you dam it and install turbines, you get electricity.

What is energy \english\ Coal is just black rock with one odd property ... it burns. If you burn it, you can warm your home, cook food or raise steam in a boiler - to make electricity.

Life needs energy. Life's energy is self-perpetuating only so long as there is sunshine. Plants can convert it and store it for their next generation (as in potato tubers, groundnuts, rice or peas). Animals eat the plants or each other, die and decompose, freeing nutrients for plants again. It is a sustainable cycle. For hundreds of thousands of years, humans have merely been a part of this cycle. Then we got clever and discovered that we could use energy other than from our own muscles to do work for us.

First we discovered that wind could drive our ships and water could power our mills. Later, we found that coal could make heat and steam for machinery. Then came oil and gas and nuclear power, all needed in increasingly large amounts to fuel our endless appetite for being comfortable and doing things with as little effort as possible. So we heat our homes, schools and workplaces in the winter. In the richer countries, most people have a car (or several) so that they can travel about. Transport guzzles huge amounts of energy - all so that we can have goods and services when we want them.

Kinds of energy resources.

Almost all of the energy we use comes from non-renewable sources.

All non-renewable energy sources create pollution, in part due to their extraction from the crust of our planet but mainly from their burning. Only two types exist: the fossil fuels (coal, oil and natural gas) and nuclear fuels (uranium, plutonium and, for the future, unusual types - isotopes - of hydrogen such as deuterium and tritium).

Fossil fuels are useful to us only because they liberate heat energy when we burn the carbon they contain. "Burning" - combustion - is really oxidation; making carbon and oxygen combine to liberate heat. Unfortunately for us, the principal byproduct is carbon dioxide, CO2 . Most scientists believe that this is an important contributor to global warming. The heat from coal, gas and oil we can use either directly or indirectly to raise steam in boilers and generate electricity using steam turbines to drive generators. By contrast, properly managed nuclear fuels liberate no pollution to the atmosphere at all. Accidents are rare in the nuclear power industry but when they occur, their potential for long-lasting damage is horrific. The disaster at Chernobyl on April 26, 1986 was by far the world's worst nuclear accident.

Phytoplankton are tiny floating plants called algae. The commonest are golden or brown colored diatoms and din flagellates. Zooplankton are tiny animals, which eat the phytoplankton but are themselves the main food for fish and some whales. Oil (petroleum) and natural gas formed by complex decay processes from microscopic life forms called phytoplankton (phyto=plant) which floated in the world's oceans millions of years ago. Just like today's phytoplankton, they harnessed the Sun to photosynthesis and store energy. When these myriads of tiny floating plants died, they sank to the sea floor and became mixed with muds from distant rivers, and were gradually buried. Over immense periods of time, the soft sediments became ever more deeply buried and slowly hardened into rocks. Heat from the Earth's interior and the weight of the overlying rocks gradually changed the energy-containing substances in the accumulated plants into hydrocarbon liquids and gases. Hydrocarbons are simple molecules made up of carbon and hydrogen atoms joined together in chains or in rings. These molecules, being light and mobile, migrated upwards through the rocks but eventually became trapped beneath impermeable rock structures in the Earth's crust. The oil and gas companies around the world know how to find these trapped reservoirs and release their contents by drilling holes into them. As everyone knows, crude oil and gas from these deposits form the basis for the world's largest energy industry: oil and gas. Much oil and gas production now comes from underneath the seabed. As the technology for extraction continues to advance, production becomes possible from deeper and deeper waters. This means that new oil and gas fields will continue to be found for some years yet so the early forecasts of oil running dry have proved to be wrong. But we know that the supplies are limited. We also know that every drop of oil we burn adds to the monumental environment problems we already have by pumping gases like carbon dioxide (CO2 ) into the atmosphere. Many scientists worry that this continual release of CO2 is an important cause of global warming. Coal is carbon; so is graphite (lead pencils) and diamond (a girl's best friend as well as the hardest substance known). Every living organism is made up of molecules based on carbon. Without carbon, there would be no life. Coal is the most plentiful fossil fuel and, unfortunately, the most polluting. Like oil and gas, coal started as living plants - mostly trees - in low lying swampy areas not much above sea level, tens or hundreds of millions of years ago. As the trees died, they did not decompose (as they normally would, returning the carbon locked in their tissues to the atmosphere). Because of the water logging, normal decay processes couldn't function. So thick layers of peat built up over thousands of years. These then became covered in sands or muds as the land subsided. As more material accumulated above the peat, the water was squeezed out leaving just carbon-rich plant remains. After millions of years, this slowly changed - metamorphosis - (like the oil and gas from the plankton) into coal.

Nuclear power taps the ultimate source of energy, which powers the universe, and its myriads of stars like our Sun. It exploits the famous E=mc2 [e1] equation, which shows that matter, can change into energy. Nuclear engineers deliberately arrange to "split" certain atoms - this is called nuclear fission. When this happens, some matter gets destroyed - liberating huge amounts of energy. This energy mostly ends up as heat from which you can make steam to drive turbines and generators, and make electricity in power stations. In the Sun, atoms of hydrogen fuse to create helium and liberate the seemingly endless stream of energy we call sunlight. Without this solar fusion reactor 150 million kilometers away, our home planet would be a frigid lifeless world. Scientists hope to reproduce this fusion reaction in a controlled way to yield almost unlimited energy supplies with far fewer radioactive waste problems. So far, they've only managed the uncontrolled reactions ... hydrogen bombs. The discovery of nuclear reactions is a wonderful example of the neutrality or indifference of science. Like so many other discoveries, humans for good or for ill could exploit nuclear reactions. The pressures of war caused the ill to be developed first but out of that development came an industry, which now provides 22% of electricity supply in the OECD countries. In France, it provides 73%; in the UK 23% and 17% in the USA. And whilst it's true that the two nuclear bombs used in anger on Japan killed and maimed hundreds of thousands, they have some way to go to catch up with the hundreds of millions of people who've lost their lives because of ordinary bombs, high-explosive shells, bullets and mines. Many claim that the very existence of nuclear weapons has prevented major conflict since World War 2. But what really scares people - and rightly so - is that modern nuclear weapons could destroy the entire planet ... if they're ever used in anger again. So now, there are forces -like the World Court Project - afoot to make their possession and use illegal throughout the world. On the other hand, many countries view with disgust the idea that the nuclear "haves" should keep their weapons whilst making sure that the "have nots" don't get any; a kind of nuclear imperialism. This is a good reason for making all such weapons illegal. Otherwise, proliferation is a worry, particularly since the break-up of the Soviet Union, which has inadvertently made weapons-grade materials available on the international black market. Sooner or later, extremists will accumulate enough of this to build a crude device, which could easily be carried by a vehicle, driven into a major city and detonated. The prospects are frightening. As in any industry, accidents happen. Serious accidents can mean the spreading of dangerous radioactivity into the environment. Several serious accidents have occurred, as everyone knows. Several other less well-known accidents associated with the race to build nuclear weapons occurred in the former Soviet Union, causing the contamination of hundreds of square kilometers of land. Renewable sources - Renewable energy sources have long been energy's Cinderella. Today, wind power is finally coming into its own. Denmark, already employing 12,000 people in its wind industry, intends wind power to produce half its total electricity needs by 2030. Several major wave power projects are now underway and solar energy is booming in Germany, the western USA and, in a smaller way, in remoter parts of the South. Equally important in cold climates is the design of buildings to capture 'passive' energy and retain it through insulation. Other minor renewables include geothermal power in volcanically active countries like Iceland, while tidal barrages remain a possibility in the UK and eastern Canada.

People use some kinds of renewable sources.

At first, it is wind energy. We have been harnessing the wind's energy for hundreds of years. From old Holland to farms in the United States, windmills have been used for pumping water or grinding grain. Today, the windmill's modern equivalent – a wind turbine – can use the wind's energy to generate electricity. Wind turbines, like windmills, are mounted on a tower to capture the most energy. At 100 feet (30 meters) or more aboveground, they can take advantage of the faster and less turbulent wind. Turbines catch the wind's energy with their propeller-like blades. Usually, two or three blades are mounted on a shaft to form a rotor. A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity. Wind turbines can be used as stand-alone applications, or they can be connected to a utility power grid or even combined with a photovoltaic (solar cell) system. Stand-alone wind turbines are typically used for water pumping or communications. However, homeowners or farmers in windy areas can also use wind turbines as a way to cut their electric bills. For utility-scale sources of wind energy, a large number of wind turbines are usually built close together to form a wind plant. Several electricity providers today use wind plants to supply power to their customers.

At second, it is bio energy. We have used bio energy – the energy from biomass (organic matter) – for thousands of years, ever since people started burning wood to cook food or to keep warm. And today, wood is still our largest biomass resource for bio energy. But many other sources of biomass can now be used for bio energy, including plants, residues from agriculture or forestry, and the organic component of municipal and industrial wastes. Even the fumes from landfills can be used as an energy source.

The use of bio energy has the potential to greatly reduce our greenhouse gas emissions. Bio energy generates about the same amount of carbon dioxide as fossil fuels, but every time a new plant grows, carbon dioxide is actually removed from the atmosphere. The net emission of carbon dioxide will be zero as long as plants continue to be replenished for bio energy purposes. These energy crops, such as fast-growing trees and grasses, are called bio energy feedstocks. The use of bio energy feedstocks can also help increase profits for the agricultural industry.

I think, that it is very important to use sun energy. The Sun is the center of our solar system and the source of life on the planet earth. Moreover, as petroleum continues to pollute and destroy the earth, what better way than to look to the Sun for a solution?

The earth and either being used or simply bouncing off are always capturing the heat from the Sun. Solar technology utilizes this heat energy and converts it to electrical energy, which is then fed into the power grid for users. That, albeit, is not all. One of the benefits of solar energy is its ability to be used widely and in specialized situations. For instance, "Small systems can be installed on the roofs of homes to heat water for domestic use. Moderate-size systems can supply hot water, steam, and hot air to schools, hospitals, businesses, and industries. Large solar thermal electric installations can generate electricity in quantities comparable to those generated in intermediate-size utility generating plants (that is, 100 to 200 megawatts [MW] of electricity)."

One myth about solar power is that it requires large areas of land in order to be deemed useful. One example of this falsity is "Solar collectors covering less than half of Nevada could supply all of the United States' energy needs." While that seems like a lot of land, that area divided my 50 states and spread out could almost go unnoticed. One of solar powers biggest advantages is cost. For 1% of the construction cost on a building, solar panels installed could save up to 50% on heating bills. In addition, at a more consumer level, a resident of a home could save almost $500 within just the first year of installation. As an added bonus, the savings are likely to increase over the years due largely to increase in electrical bills. Thus, a solar heating system is capable of paying for itself in less than 10 years. The answer to the energy crisis the world is seeing could be to simply return to that with we depends on already, the Sun.

Flowing water creates energy that can be captured and turned into electricity. This is called hydropower. The most common type of hydropower plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. But hydropower doesn't necessarily require a large dam. Some hydropower plants just use a small canal to channel the river water through a turbine. Another type of hydropower plant – called a pumped storage plant – can even store power. The power is sent from a power grid into the electric generators. The generators then spin the turbines backward, which causes the turbines to pump water from a river or lower reservoir to an upper reservoir, where the power is stored. To use the power, the water is released from the upper reservoir back down into the river or lower reservoir. This spins the turbines forward, activating the generators to produce electricity.

The ocean can produce two types of energy: thermal energy from the sun's heat, and mechanical energy from the tides and waves. Oceans cover more than 70% of Earth's surface, making them the world's largest solar collectors. The sun's heat warms the surface water a lot more than the deep ocean water, and this temperature difference creates thermal energy. Just a small portion of the heat trapped in the ocean could power the world. Ocean thermal energy is used for many applications, including electricity generation. Ocean mechanical energy is quite different from ocean thermal energy. Even though the sun affects all ocean activity, tides are driven primarily by the gravitational pull of the moon, and waves are driven primarily by the winds. As a result, tides and waves are intermittent sources of energy, while ocean thermal energy is fairly constant. Also, unlike thermal energy, the electricity conversion of both tidal and wave energy usually involves mechanical devices. A barrage (dam) is typically used to convert tidal energy into electricity by forcing the water through turbines, activating a generator. For wave energy conversion, there are three basic systems: channel systems that funnel the waves into reservoirs; float systems that drive hydraulic pumps; and oscillating water column systems that use the waves to compress air within a container. The mechanical power created from these systems either directly activates a generator or transfers to a working fluid, water, or air, which then drives a turbine/generator.

Conclusion.

Thus, humanity uses many kinds of energy: renewable and non-renewable. To make sure we have plenty of energy in the future, it's up to all of us to use energy wisely. We must all conserve energy and use it efficiently. It also up to those of you who will want to create the new energy technologies of the future. One of you might be another Albert Einstein and find a new source of energy. It's up to all of us. The future is ours but we need energy to get there.

The world has changed dramatically over the last 200 years, thanks largely to fossil fuels – coal, oil and natural gas. These have provided us with cheap and convenient energy, which we use to heat and cool our homes and to run our cars, appliances and industries. But there has been a cost. No city in the world is immune from the polluting effects of fossil fuels, and they contribute vast quantities of greenhouse gases to the atmosphere, something that many scientists believe causes global warming. So, in the last few decades, scientists have been looking for ways to produce energy without adverse side effects. Promising renewable energy sources such as wind, direct solar and biomass are dealt with in other Nova topics (see links at the end of this page). Now we'll have a look at hot dry rocks, waves and hydrogen. It may be some years before these energy sources make a big impact but they illustrate the diversity of options that are available.

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