​​In steam turbine power stations, the fuel source (B) is ignited in the boiler (C) where water is pumped into (A), and converted to steam. This steam drives a steam turbine (D, pictured during assembly on the right) which turns a generator at E which generates electrical power. The steam is then again condensed into water and pumped back into the system. This is known as the Rankine Cycle. Depending on the complexity of the power station, more heating and cooling cycles may be added to improve overall efficiency or to increase overall power output.

Industrial power generating gas turbines does not have such a cycle and instead work very similar to that of how jet engines work, except they are built with much stronger materials. Air is fed into the turbine, where liquid fuel or gas is fed and combusted, which then turns the turbine and generator.​

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Source (left): Wikimedia Commons/CC-BY-SA-3.0

Source (right): Wikimedia Commons/CC-BY-SA-3.0​

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Coal, fuel oils, natural gas, nuclear power, oil shale, and peat are considered unsustainable sources of energy due to two main reasons.

The first reason being that these fuel sources will not last over a reasonable period of time in the near to medium-term future, due to rapidly depleting global reserves (this does not apply to newer nuclear technology, which is explained further below). For example, according to the CIA World Factbook, the current confirmed oil reserves (excluding any estimates or doubted reserves) may by completely depleted in 148 years, if the present consumption rates continue.

The second reason being that continuing to utilize these resources over the short to medium term would mean releasing large amounts of pollutants and greenhouse gases into the atmosphere, threatening to cause various more problems, as explained briefly earlier.

Although current nuclear sources and technologies pose high risks, and leaves behind highly radioactive waste, newer fusion reactors and Generation-4 nuclear reactors is an exception when it comes to sustainability. The main issue with current nuclear technology is that, apart from high operating and maintenance risks, it leaves behind highly radioactive material that cannot be disposed naturally. Presently, nuclear waste is being stockpiled, while some are planned to be buried deep underground. Nuclear waste stay harmful for tens to hundreds of thousands of years, and hence such burial poses great risks in case of any naturally created leaks.

Generation-4 reactors are being designed to reduce operation and maintenance risks, while reducing radioactive waste. Whereas fuel from newer nuclear technologies like Nuclear Fusion could last hundreds of thousands to billions of years, with very little to no radioactive waste, and minimal operation and maintenance risks. Due to newer nuclear technologies being far from commercially application and still under early development, and hence far from being considered completely sustainable, nuclear power is entirely omitted from this website as a potential solution to the current world energy issues like energy poverty.

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Sustainable sources: Biofuels, geothermal, hydropower, ocean power, solar power, and wind power
 

Sustainable energy sources include all biofuels, geothermal energy, hydropower, energy obtained from the ocean like tidal and wave power, solar power, and wind power. How these sources work, their dependability, suitable locations, and various other facts are elaborated further in this website.
Although most biofuel sources like biomass also produce considerable amounts of greenhouse gases, its fuel source include crop waste, sustainably grown crops, and other less scarce and abundantly available sources. Hence most biofuel variants are not suitable to take over as a significant power source, but instead more suitable in places where such fuel sources are frequently available.

Geothermal power is the utilization of earth’s deep subsurface heat to convert water into pressurized steam, which is then used to run a steam turbine generator. This source is only available in certain geographic conditions where access to geological heat is possible.

Hydropower can be generated using three basic techniques; the conventional dam-type facilities, pumped-storage facilities, and run-of-the-river facilities. Hydropower development potential is limited to those regions where the right geographic and water resources are available. The basic principle of hydropower generation is to release water from a pressurized source (such as behind a conventional or run-of-the-river dam) or a higher elevation (known as hydraulic head) through a water turbine, which spins and generates power as the water passes through.

Ocean power is a relatively new subject in renewable energy. This source consists of three main types, tidal power, ocean wave power, ocean thermal energy. Tidal power is utilized by the natural oceanic flow of water during tide shifting by capturing water during high tides, and releasing through turbines during low tide, and functions similar to that of hydropower facilities. Although still a relatively young technology, tidal power also includes the installing of wind turbine-like structures to capture energy during moving tides. Other forms also include ocean wave power which utilizes ocean surface waves to generate power, and ocean thermal energy power which utilizes the temperature differences between deep and shallow water to generate steam via elements with low boiling points. Both of the latter forms are under early stages of development and nor yet applied into the open energy market.

Solar power technology is available in three basic commercially-viable forms, with more under development. The most common form used in residential and commercial power generation is the flat-panel photovoltaic units, which convert sunlight directly into electricity. To improve efficiency, these panels sometimes use concentrators to focus more sunlight onto its solar cells. These concentrated photovoltaics are the second type of solar power generation. The third type, known as concentrated solar thermal energy, simply concentrates large amounts of sunlight onto a surface to heat and convert water to steam, which is then used to run steam turbines. The third type is mostly used in commercial-scale solar power generation. All three of these forms have their own subtypes, which are explained in latter parts of this website.

Wind power, with is the next most popular form of renewable energy source after solar energy, basically includes placing large commercial-scale wind turbines in series called wind farms, to harness the essentially unlimited power of the wind. Wind turbines come in two basic forms, namely Horizontal-Axis Wind Turbines (HAWT) or Vertical-Axis Wind Turbines (VAWT), with the earlier being the most common.

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References:

http://www.howstuffworks.com/environmental/energy/power.htm

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http://www.iea.org/textbase/nppdf/free/2011/key_world_energy_stats.pdf
http://www.think-energy.net/KWvsKWH.htm

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http://science.howstuffworks.com/steam-technology8.htm
http://www.energyquest.ca.gov/story/chapter06.html
http://www.massengineers.com/Documents/howgasturbinework.htm
https://www.cia.gov/library/publications/the-world-factbook/rankorder/2178rank.html
https://www.cia.gov/library/publications/the-world-factbook/rankorder/2174rank.html
http://www.firstscience.com/home/articles/big-theories/nuclear-fusion-energy-for-the-future_17006.html
http://science.howstuffworks.com/fusion-reactor.htm

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http://www.britannica.com/EBchecked/topic/967492/biofuel
http://www.eere.energy.gov/basics/renewable_energy/geothermal_electricity.html
http://geo-energy.org/basics.aspx
http://www.renewableenergyworld.com/rea/tech/hydropower
http://www.alternativeenergyprimer.com/Run-of-River-Hydro.html
http://environment.about.com/od/offbeatenergysources/a/ocean_power.htm
http://science.howstuffworks.com/environmental/green-tech/energy-production/ocean-power1.htm
http://www.powerfromthesun.net/Book/chapter01/chapter01.html
http://centurionenergy.net/types-of-wind-turbines

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