It's okay to admit we don't have everything perfectly sorted out. If we had all the answers we wouldn't nbooks (or web siteed science. When it comes to the definition of energy, I want you to realize that it is important, but also to relax a little.
The fact is, no one knows what Energy is!
Really! No one knows what ENERGY is!
We only know how to describe the characteristics of its various manifestations mathmatically. The same is true of other physical phenomena, such as gravity. The "ability to do work" is more of a characteristic of energy than a definition. Don't you think? (Or what if we call it a "defining characteristic"?)
There are Two Types of Energy - in Many Forms
Despite all my nit-picking in the words above, most scientists and engineers find it acceptable and useful to talk about chemical and electrical and mechanical and magnetic energy and others. They also frequently describe internal energy as heat or "heat content" or "quantity of heat" as some of the older texts call it . But it is helpful to understand why some people say that all those other forms of energy are really types of kinetic energy or potential energy being "expressed" in different ways .
Electrical energy, for example, is the flow of charged particles called electrons or ions. When electrons are flowing through a wire or through hundreds of feet of air (an event we call lightning) it is because they are being "pushed" or forced by an electrical field. This field is caused by a difference in electrical charge. A force is exerted on the electrons and they move. Work is done on the charged particles. A force is pushing them through a distance. Actually, they are hopping from atom to atom, being pushed by an electromotive force. While the electrons are moving they contain kinetic energy. So at the itsy-bitsy atomic level electricity is a form of kinetic energy.
Mechanical energy is the useful way we sometimes refer to things like gears, engines, locomotives pulling trains, canon balls flying through the air, or other examples of energy in mechanical devices. But, of course, by now you see that all these moving parts contain kinetic energy. They are really just different modes of kinetic energy - the energy contained in a moving mass. In order to get these various objects spinning or rolling, a force has to be exerted. Work is a force acting through a distance, so the way they get moving and keep moving is by having work done on them. Work is an energy transfer process.
Chemical energy is another term we use a lot. This is more vague. We say things like, "during combustion, chemical energy is released". Hmmm. The term chemical energy refers to energy that is stored in molecular bonds, the forces that hold molecules together. So releasing chemical energy must mean the energy is finally free from its molecular bonds. In the more general sense, of course, it is potential energy. Stored energy, or energy that is "waiting to happen", or that has the "potential" to happen, or that can happen but hasn't yet, is rather sensibly called potential energy. As described in the photosynthesis section, carbohydrate molecules, used by living organisms for food (and other things), store energy in their atomic bonds. Living cells release this stored energy relatively slowly by a process called respiration. Some of the stored potential energy becomes the kinetic energy of cell processes and muscle movement and some of it becomes internal energy (often called heat). But now you know I should have said, "some of stored energy is transferred by the heat process into the internal energy of the cell. The cell is "warmed up" by increasing the average energy of the cell molecules. Eventually, of course, all of it becomes internal energy and then flows by heat transfer into the air and objects around the organism.
Enough examples. We get the idea. Maybe you can think about some other forms. Unless you are writing a thermodynamics text book it is probably okay to say there are more than two forms of energy and to use the terms heat and work as if they are a type of energy. So when you find me doing it in this web site, don't write me a nit-picky e-mail telling me heat is a process, not a form of energy. I know. I know.
Saving energy means decreasing the amount of energy used while achieving a similar outcome of end use. Using less energy has lots of benefits – you can save money and help the environment. Generating energy requires precious natural resources, for instance coal, oil or gas. Therefore, using less energy helps us to preserve these resources and make them last longer in the future.
Why is it important to save energy?
If people use less energy, there is less pressure to increase the available supply of energy, for example by constructing new power plants, or by importing energy from a different country.
What does “life-cycle” mean? What does it have to do with energy use?
Nearly all everyday products have an impact in terms of energy, especially when you consider their energy requirements across the whole life-cycle: production, use and end-of-life. In many cases the use phase is dominating. Plastics, for example, are one of the most resource-efficient materials available. In their use phase, plastics products help to save more energy than is needed to produce them: For example, when you choose a bottle of water packaged in a light weight material such as plastic, remember that lighter packaging requires less energy for transport. Thus, less fuel was used to power the truck that delivered those plastic bottles.
What can I do to save energy?
There are many sources on the web that give you ideas of what you can do to save energy. Here are a few ideas to get you started:
- Change your travel behaviour, think more in terms of public transportation, if possible, walk or ride your bicycle instead of taking the car
- Reduce your house heat by 1C, keep the windows closed while heating, dress warmly
- Choose products that come with lightweight packaging
- Turn off lights and appliances when you are not using them, use energy-saving light bulbs
- Reuse plastic bags for shopping and storage
- Use a microwave instead of a stove to reheat food
- Use rechargeable batteries instead of disposable batteries
In our daily life, we rely on many materials. Wood, metal, glass and plastics all have environmental consequences. Think about the impact of every product you use. For example, the lighter an object, the less fuel is required to transport it. A heavy suitcase in the boot of a car will require the car to consume more fuel during its journey. The same goes for all product packaging. Therefore, buying food wrapped in lightweight materials thus helps the environment.
America is in a desperate need to change its ways when it comes to energy. With the war in the Middle East and the United States dependant on their oil, America finds itself in a tough spot when it comes to energy. Being dependent on another country, especially one that is at war with can the country, be extremely unsettling when it comes to the well being of a country. But America has one energy source that is completely renewable, not dependent of other countries, and extremely cheap. Energy Efficiency, reducing how much energy one uses. Technology has made tremendous strides in created household goods, cars and homes that use half of the energy old items used to. The amount of energy saved can reduce drastically the rate of greenhouse gases surrounding our planet. Although being energy efficient is a necessity for the well being of our planet, the causes of the deterioration of earth are so minute that society does not realize how easy and simple it would be to undo the effects of wasting energy.
Energy efficiency is the act of reducing the amount of energy being used in daily life.
Renewable sources of energy
Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides and geothermal heat, which are renewable (naturally replenished). About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomas, which is mainly used for heating, and 3.4% from hydorelectricity. New renewables (small hydro, modern biomass, wind, solar, geothermal, and biofuels) accounted for another 3% and are growing very rapidly.
Renewable energy replaces conventional fuels in four distinct areas: electricity generation, hot water/space heating, motor fuels and rural (off-grid) energy servicesRenewable energy is derived from natural processes that are replenished constantly. In its various forms, it derives directly from the sun, or from heat generated deep within the earth. Included in the definition is electricity and heat generated from solar, wind, ocean, hydropower, biomass, geothermal resources, and biofuels and hydrogen derived from renewable resources.
- Power generation. Renewable energy provides 19% of electricity generation worldwide. Renewable power generators are spread across many countries, and wind power alone already provides a significant share of electricity in some areas: for example, 14% in the U.S. state of Iowa, 40% in the northern German state of Schleswig-Holstein, and 20% in Denmark. Some countries get most of their power from renewables, including Iceland and Paraguay (100%), Norway (98%), Brazil (86%), Austria (62%), New Zealand (65%), and Sweden (54%).
- Heating. Solar hot water makes an important contribution to renewable heat in many countries, most notably in China, which now has 70% of the global total (180 GWth). Most of these systems are installed on multi-family apartment buildings and meet a portion of the hot water needs of an estimated 50–60 million households in China. Worldwide, total installed solar water heating systems meet a portion of the water heating needs of over 70 million households. The use of biomass for heating continues to grow as well. In Sweden, national use of biomass energy has surpassed that of oil. Direct geothermal for heating is also growing rapidly.
- Transport fuels. Renewable biofuels have contributed to a significant decline in oil consumption in the United States since 2006. The 93 billion liters of biofuels produced worldwide in 2009 displaced the equivalent of an estimated 68 billion liters of gasoline, equal to about 5% of world gasoline production.
Mainstream forms of renewable energy
A wind farm located in Manjil, Iran. Airflows can be used to run wind turbines. Modern wind turbines range from around 600 kW to 5 MW of rated power, although turbines with rated output of 1.5–3 MW have become the most common for commercial use; the power output of a turbine is a function of the cube of the wind speed, so as wind speed increases, power output increases dramatically. Areas where winds are stronger and more constant, such as offshore and high altitude sites, are preferred locations for wind farms. Typical capacity factors are 20-40%, with values at the upper end of the range in particularly favourable sites.Globally, the long-term technical potential of wind energy is believed to be five times total current global energy production, or 40 times current electricity demand. This could require wind turbines to be installed over large areas, particularly in areas of higher wind resources. Offshore resources experience average wind speeds of ~90% greater than that of land, so offshore resources could contribute substantially more energy.
Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air.
BiomassBiomass (plant material) is a renewable energy source because the energy it contains comes from the sun. Through the process of photosynthesis, plants capture the sun's energy. When the plants are burnt, they release the sun's energy they contain. In this way, biomass functions as a sort of natural battery for storing solar energy. As long as biomass is produced sustainably, with only as much used as is grown, the battery will last indefinitely.
In general there are two main approaches to using plants for energy production: growing plants specifically for energy use (known as first and third-generation biomass), and using the residues (known as second-generation biomass) from plants that are used for other things. The best approaches vary from region to region according to climate, soils and geography.
Bioethanol is an alcohol made by fermenting the sugar components of plant materials and it is made mostly from sugar and starch crops. With advanced technology being developed, cellulosic biomass, such as trees and grasses, are also used as feedstocks for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form, but it is usually used as a gasoline additive to increase octane and improve vehicle emissions. Bioethanol is widely used in the USA and in Brazil.
Biodiesel is made from vegetable oils, animal fats or recycled greases. Biodiesel can be used as a fuel for vehicles in its pure form, but it is usually used as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered vehicles. Biodiesel is produced from oils or fats using transesterification and is the most common biofuel in Europe.
Biofuels provided 2.7% of the world's transport fuel in 2010.
Geothermal energyGeothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet (20%) and from radioactive decay of minerals (80%). The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface. The adjective geothermal originates from the Greek roots geo, meaning earth, and thermos, meaning heat.
The heat that is used for geothermal energy can be stored deep within the Earth, all the way down to Earth’s core – 4,000 miles down. At the core, temperatures may reach over 9,000 degrees Fahrenheit. Heat conducts from the core to surrounding rock. Extremely high temperature and pressure cause some rock to melt, which is commonly known as magma. Magma convects upward since it is lighter than the solid rock. This magma then heats rock and water in the crust, sometimes up to 700 degrees Fahrenheit
From hot springs, geothermal energy has been used for bathing since Paleolithic times and for space heating since ancient Roman times, but it is now better known for electricity generation.
BY BELLA ZAHID