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There are a myriad of energy sources available to humans, from the most basic forms of harnessing our natural environment, to cutting-edge technological forms, able to generate immense amounts of energy. Different energy sources are preferable for different reasons, ranging from environmental concerns, to economy of cost, to what is available in a given area. What follow are some of the most common energy sources used in the modern world.
The most common energy sources on the planet in modern times are those which use fossil fuels to generate their energy. More than 85% of all primary energy on earth comes from fossil fuels, and although this percentage is being reduced slowly, total energy consumption continues to increase. Basic fossil fuels have been used to generate energy dates back earlier than recorded history, with coal used as a fuel for thousands and thousands of years.
In the modern world, fossil fuels power nearly everything. Coal and natural gas power plants generate massive amounts of electricity, distributed through countries by national power grids. Gasoline and diesel are used as the primary energy sources for cars and trucks. Ships, planes, rockets, motorcycles, and virtually everything else that moves uses some form of fossil fuel.
The supply of fossil fuels on the planet is, however, a finite resource, and is rapidly dwindling, causing serious concerns about controlling steady supplies. At the same time, environmental concerns about fossil fuels are growing steadily. It is estimated that some 21.3 billion tons of carbon dioxide are generated by fossil fuels each year, with only about half of that absorbed by natural processes. This is thought to be contributing to global warming, and people are suggesting alternatives as a way to move away from such pollutive fuel sources.
One such alternative is nuclear fission, commonly just referred to as nuclear power. Nuclear power plants stimulate a nuclear reaction in uranium-235, which causes its atoms to split, releasing enormous amounts of energy. This energy heats up water, which then transforms into steam, which is used to turn turbines. These turbines create electricity, which can then be moved around the country. One of the major hurdles to mainstream adoption of nuclear power is a public perception of its dangers, and the difficulty of disposing of nuclear waste.
Hydroelectric energy is one of the less popular renewable energy sources available, but is still widely used, especially in certain countries. Hydroelectric generation concentrates the power held in a river’s slow descent, by building a dam or other way to regulate water flow, and then using that regulated flow to turn turbines, which in turn generate electricity. Basic hydropower is one of the older forms of renewable energy, making use of simple water wheels placed at strategic locations in rivers to do things like grind grains. Although hydroelectric power is renewable, there are environmental concerns over damming rivers.
The two most popular forms of renewable energy, and the forms where the most attention is currently focused, are solar power and wind power. Solar power makes use of photovoltaic cells to convert the sun’s energy to electricity, or passively lets sunlight heat air or water. Wind power uses massive turbines, which are moved directly by the wind, to generate electricity. Wind power is a very clean power source, and in certain regions, such as the United States, it is being seriously considered as a major contributor to national energy needs in the future.
Although fossil fuels are the most commonly used sources of energy, they are still a form of solar energy. Almost all the energy humans use is directly or indirectly derived from the sun, or the earth's interior energy. Fossil fuels are simply stored solar energy from millions of years ago. All of the organisms that decayed and became fossil fuels got their energy by converting solar energy.
Even most alternative energy sources of energy are indirect forms of solar energy or direct forms of the earth's internal energy. This article did a great job of breaking up energy into different categories, I just wanted to add a perspective often overlooked.
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