What is energy english
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.
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.
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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?
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.