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What is energy - Реферат

Energy resources year 10 06.12.2010

Alexey Ardalin

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:

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

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.