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  An Introduction to Energy Sources Life on Earth began and survived millions of years because of favorable climate conditions. Climate can be viewed as the renewable resource with Sun's energy as a energy component and oceans as water reservoirs (material components). Energy of the Sun supports circling of water on the Earth, therefore making life on Earth possible. Where there is no water, there is no quality life, like for instance in deserts. Earth's climate changes have reached the level of climate crisis. Solution how to get out of this crisis is very simple: return to less harmful energy sources. However, lobbies that support use of fossil fuels are too strong on energy market and at this moment there is no sign of slowing down in the usage of dirty energy sources. Such approach could very easy endanger the future climate conditions, making the life of ecology sensible  plants and animals almost impossible, and since all species live in natural balance that would affect all life on earth. To avoid this grim prediction of Earth's future, some countries started stimulating energy saving programs and transition to clean energy sources. Globally, there is no major improvement because amount of energy gained from these clean energy sources is negligible to amount of energy that is gained from fossil fuels. This picture shows the world energy consumption from year 1850 to year 2000. We can see that energy consumption in the first half of the 20th century has doubled, and after this period, in the second half of the 20th century world came to considerably higher energy consumption. Consumption of energy is ten times  bigger than it was in beginning of the 20th century. Major energy sources of 20th century were nonrenewable energy sources. These are:    coal    oil    natural gas    nuclear energy Coal, oil and natural gas are also called fossil fuels. Two main problems of non-renewable energy sources are limited quantity and environment pollution. Combustion of fossil fuels emits large quantities of CO 2  which is a greenhouse gas. This is probably the main reason of global temperature increase in last decades. Nuclear power plants are not dangerous for the atmosphere, but substances created as the result of nuclear reaction remain radioactive for years, and should be stored in special chambers. Renewable energy sources do not suffer of similar problems. Most significant renewable energy sources are: World energy consumption between year 1850 and 2000 compared to world  population increase in same period. Energy consumption is increasing much faster than population.     wind energy    Sun energy     bioenergy    water energy Renewable energy sources do not pollute environment in the same amount as non-renewable do,  but they are also not completely clean. This primarily affects to the energy gained from biomass which has the same effect as fossil fuels, and that is CO 2  emissions when combusting, but carbon circle is at least closed in that case. Biggest problems of  renewable energy sources (water energy excluded) are price and small amount of gained energy. Renewable energy sources have huge  potential, but at this moment our current technology development does not allow us to rely strictly upon them. GREENHOUSE EFFECT This picture shows the Greenhouse Effect . Part of reflected sun radiation is reflected back to Earth by greenhouse gases (CO 2 , N 2 O, CH 4 , HFC, PFC, and SF6), and that effect is responsible for temperatures on the Earth. If greenhouse effect would not exist Earth's temperatures would be about 30°C lower than they are now. Since the concentration of the carbon dioxide has grown  during the last century, greenhouse effect is stronger than it used to be. That has consequence in the global increase of the average temperatures on the Earth. Consequences of global warming are ice melting, rise of the sea level, agriculture influence and etc. Major sources of CO 2  are wood and biomass combustion, deforestation and fossil fuels combustion. In 1997 Kyoto  protocol was signed to decrease emission of C0 2  into the atmosphere. Countries that signed this  protocol obliged themselves to decrease the emission of CO 2  into the atmosphere. Every country has its own determined goal percentage in decreasing emission of CO 2 , and it all relates to decreasing it until year 2012 compared to year 1990. Average planned decrease is 5.2% until year 2012. Major issues concerning the Kyoto protocol are the fact that USA has not ratified it yet, and large costs of replacing current dirty energy sources with clean energy sources. Term dirty energy sources applies to biomass and fossil fuels, while clean energy sources are nuclear power plants and renewable sources without a biomass. ACTUAL RELATION OF ENERGY SOURCES Fossil fuels are the main energy source used for supplying the actual mankind needs. Vast majority of energy gained from renewable sources relates to the water energy. Other renewable sources are momentarily energetically negligible. Since in the future we will be forced to satisfy our energy needs from renewable sources, we have to think of the way to transform renewable sources to an usable energy. The main problems are expensive and long researches, with most transformations relating just to the production of electrical energy. Factor that contributes to higher research costs is also variety of renewable energy sources. Energy Consumption as a Measure of Prosperity Energy is one single important entity that determines a countries economy and the per capita energy consumption, which is closely linked to the per capita income or the per capita energy consumption is a measure of the prosperity of the nation. For example, the per capita income of USA is about 50 times more than that of India and also the per capita energy consumption is 8000kWh per year, whereas the per capita energy consumption in India is 150kWh. India with nearly 20% of world population consumes only about 1% of world’s energy consumption. These figures justify the fact that energy consumption is an indication of the prosperity of a country. The energy sources are broadly classified as commercial and noncommercial. The commercial sources include the fossil fuels (coal, oil and natural gas), hydro electric power and nuclear  power while the non-commercial sources include wood, animal waste and agricultural wastes. While the developed countries get most of the energy from commercial sources, the developing countries like India, the use of commercial and non-commercial sources are about equal.  ENERGY SOURCES Introduction to energy The energy of a body is its capacity to do work. It is measured the total amount of work that the  body can do. Energy is the primary and most universal measure of all kinds work by human  beings and nature. Every thing what happens the world is the expression of flow of energy in one of its forms. Different forms of energy The different forms of energy are: 1. Mechanical energy (kinetic and potential) 2. Thermal (or) Heat energy 3. Chemical energy 4. Electrical energy 5. Nuclear energy 6. Electromagnetic energy 7. Gravitational energy The S.I unit of energy is Joule or KJ or Watt.h. Primary Energy Sources Primary energy sources can be defined as sources which provide a net supply of energy Coal, Oil, Uranium etc., are examples of this type. The energy required to obtain these fuels is much use than what they can produce by combustion or nuclear reaction. The supply of primary fuels is limited. It becomes very essential to use these fuels sparingly. Examples Coal, natural gas, oil and nuclear energy. Secondary Energy sources Secondary fuels produce no net energy. Though it may by necessary for the economy, these may not yield net energy. Secondary sources are like sun, wind, water (tides), etc. Solar energy can by used through plants, solar cells, solar heaters and solar collectors. Energy Consumption as a Measure of Prosperity Energy is one single important entity that determines a countries economy and the per capita energy consumption, which is closely linked to the per capita income or the per capita energy consumption is a measure of the prosperity of the nation. For example, the per capita income of USA is about 50 times more than that of India and also the per capita energy consumption is 8000kWh per year, whereas the per capita energy consumption in India is 150kWh. India with
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