Wind turbine installation

Wind power refers to the kinetic energy stored in wind, and it's extraction using wind turbines. This article deals mainly with the intricacies of large scale deployment of wind turbines to generate electricity.

See wind turbine for more on individual turbines.

Wind Turbine

As a general rule, wind generators are practical where the average wind speed is greater than 20 km/h (5.5 m/s). Obviously, meteorology plays an important part in determining possible locations for wind parks, though it has great accuracy limitations.

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How Does Wave Energy Work?

Wave power is a method of electrical generation, where energy from waves moving in water is transferred into an electrical current; the electricity thus produced is coined asrenewable energy.
Wave power generation is not a widely employed technology with only a few experimental sites in existence. Wave power has however an advantage in comparition with many other renewable energy sources, because of it's stability in production. Where for instance the amount of wind power being produced relies heavily on how strong winds there are locally, which fluctuates heavily from day to day and from season to season, the amount of wave power being produced wouldn't fluctuate so heavily, since the amount energy stored in waves are more constant, and not so heavily dependent on the local weather conditions.

Wave power

The problems sketched is one of the heaviest barriers in making an entire area dependent on renewable energy, for instance in a country like Denmark where approximately 20 % of the power being produced originates from wind farms, when the wind is strong, however over 100 % of the consumption of the danish energy grid is being produced by wind farms, and the surplus is being sold to other nearby countries, such as Sweden and Germany at a low price (since these countries also has a high production of wind and river energy at times with wind in Denmark), when there is no wind, Denmark has to buy power from it's neighbouring countries at a much higher price. These conditions makes wind power less profitable, and many experts are of the opinion that Denmark has reached it's maximal percentage of wind power being generated, unless some sort of storage of energy is being used. Wave power could, when fully developed be another key for expanding the amount of renewable energy being produced, because of its much more stable production.

Wave power

Many different system designs are currently being developed.
• In one system, floating blocks are driven by wave action to push or pull a generator lying in the water. Water pushing through tubes will push a turbine which drives the generator.
• With another method, wave action compresses air in a tunnel which drives the vanes of the generator. The bigger the difference between wave top and wave valley, the more power potential there is.
• In yet another design, the overtopping of the waves are being led to a reservoir, the water, being pulled downwards through a tube by gravity, drives a generator.

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Water turbine - Types of Turbine

Water Turbine

Water turbine - Types of Turbine
Water is very heavy and its flow energetic. The Power available in flowing water is described by;
where:
•  Power( Joules/sec or Watts)
•  turbine efficiency
•  density of water (Kg/meter3)
•  accelaration of gravity (9.8 meters/sec2)
•  head (meters, this is the height at which still, unimpeded water starts falling from)
•  flow rate (meters3/sec)
Theory of operation
Water turbines are divided into two groups; reaction turbines and impulse turbines.
Impulse turbines change the direction of flow of the water, leaving the exit flow with diminished energy. The water's energy is converted to kinetic energy by a nozzle prior to hitting the turbine blades. No pressure change occurs at the turbine blades and the turbine doesn't require a housing for operation. Impulse turbines are more often used in high head applications.
Reaction turbines are acted on by water changing pressure as it moves through the turbine. The turbine must be cased to contain the water pressure (or fully submerged in the water flow). Reaction turbines are more often used in low head applications.
Turbine designs often combine both these concepts.
The critical speed of a water turbine is the speed at which water flows through the turbine without resistance and no energy is extracted from the water flow. The operating speed is always less than the critical speed.
Some water turbines are designed to reverse flow and turn into a pump. They can fill a high reservoir during off-peak electrical hours and revert to a turbine for power generation during peak electrical demand.

Types of turbines
Reaction turbines:
• Francis
• Propeller
• Kaplan
• Tyson
• Water Wheel
Impulse turbines:
• Pelton
• Turgo
• Banki(Crossflow)

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Solar water heating

Using the sun to heat water
A collector is placed on or forms the roof of a building, or on a wall facing the sun, or may be free-standing. The working fluid is either pumped or driven by convection through it. Active control or simple physics ensures it only moves when a net gain in heat will occur.

The collector can be a simple glass topped box with copper pipes in it, or a set of metal tubes surrounded by a evacuated (near vacuum) glass cylinder. A parabolic mirror can also be added to concentrate the sun's light on the tube.

A simple water heating system would pump cold water out to a collector to be heated, the heated water flows back to a collection tank. This type of collector can provide enough hot water for a family, for very little or no monthly cost.

Solar water heating

Heat is stored in a hot water tank. The volume of this tank will be larger with solar heating systems in order to allow for bad weather, and because the optimum final temperature for the absorber is lower than a typical immersion or combustion heater.

The working fluid for the absorber may be the hot water from the tank, but more usually at least in pumped systems will be a separate loop of fluid contining anti-freeze and a corrosion inhibitor which delivers heat to the tank through a heat exchanger - a coil of copper tubing within the tank.
If a central heating system is also present and heats water then either the solar heat will be concentrated in a pre-heating tank that feeds into the tank heated by the central heating, or the solar heat exchanger will be lower in the tank than the hotter one.

The water from the collector can reach very high temperatures in good sunshine, or if the pump fails. Designs should allow for relief of pressure.

The collector can be a simple glass topped box with copper pipes in it, or a set of metal tubes surrounded by a evacuated (near vacuum) glass cylinder. A parabolic mirror can also be added to concentrate the sun's light on the tube. A simple water heating system would pump cold water out to a collector to be heated, the heated water flows back to a collection tank. There are even ways to do this without a pump, using natural convection. This type of collector can easily provide enough hot water for a family, for very little or no monthly cost. Temperature regulators are required to mix the hot water from the tank with cold water because at peek times the water from the collector can reach very high temperatures. Using some of the more advanced collectors, it is possible to get much higher temperatures (well above the boiling point of water) therefor a medium with a boiling point over the operating temperature is required, and many are available. This heated fluid would, by way of a heat exchanger, heat water.

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What is sea level rise?

Sea level rise, a phenomena sometimes held to be caused by global warming and thus evidence supporting the Global Warming Theory.

Rising atmosphere temperature theoretically is causing the ice caps to melt and the oceans to expand (heat does cause ice to melt and water to expand). On the other hand, heat also causes water to evaporate, so it is not known what effect global warming will have on sea level.

Some researchers believe that rising average sea levels are proof of the global warming theory and that likely further global warming will cause additional sea level rise, possibly wiping out shore-based communities.

Other researchers believe that rising average sea levels are unrelated to global warming and that any global warming thot occurs will likely result in lower average sea levels.

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Renewable energy

Renewable energy is any type of energy generation that isn't dependent on a limited resource like fossil fuels. Renewable energy may be used directly, such as solar ovens, geothermal heat pumps, or windmills. Other forms of renewable energy sources generate electricity, such as solar power cells, wind generators, tidal waves and hydroelectricpower. Still other forms generate fuels, such as vegetable oils generated from biomass.

Most renewable energy can trace their root to solar energy, perhaps with the exception of geothermal and tidal wave power. For example, wind is caused by the density difference of the air when the sun heats various parts of the earth unevenly. Hydroelectric power can be ultimately traced to the sun too. When the sun evaporates water in the ocean, the vapor forms clouds which later falls on mountains as rain which runs through turbines to generate electrity. The transformation goes from solar energy to potential energy to kinetic energy to electric energy.

Most renewable energy sources have no emissions, with the exception of biomass fuels. Even for biomass, however, the generation of new plantlife consumes the same elements from the atmosphere that it emits when burned.

Iceland is a world leader in renewable energy due to its abundant hydro and geothermal energy sources. Over 99% of the country's electricity is from renewable sources and most of its urban household heating is geothermal. Israel is also notably as much of its household hot water is heated by solar means. These countries' successes are at least partly based on their geographical advantages.

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Photovoltaic energy systems definition

Photovoltaics is the direct conversion of radiant energy such as sunlight into electricity through quantum mechanical processes. Photovoltaics is also known as 'solar electric power' or 'solar power', though the latter term fails to adequately distinguish photovoltaics from other technologies that make use of solar energy, such as solar hot water, or solar thermal electricity generation.
The photovoltaic effect - the process by which sunlight is converted to electricity - was first noted by Edmund Becquerel in 1839.
The principle component of a photovoltaic system is the photovoltaic cell, or solar cell. Commercial solar cells are typically made from silicon, though other materials such as gallium arsenide, and even more exotic combinations are also used, particularly in high efficiency laboratory devices, or cells meant for satellite and space applications, where capital cost is small compared to the cost of sending material into orbit. The common feature of the materials that can be used to make a solar cell is that they are semiconductors.
Semiconductors can have a high electrical resistance, but be put into a lower resistance mode when under the correct conditions. Another way of describing this is that there are not many free electrons in a semiconductor, but a small amount of energy can release the electrons from the atoms they are bonded to.

Photovoltaic energy

Photovoltaics research institutes
There are many research institutions and departments at universities around the world who are active in the field of photovoltaic. Countries which are particularly active in the field of photovoltaics are Germany, Japan, Australia, China, and the USA.
Some universities and institutes which have a photovoltaics research department.
• Centre for Photovoltaic Engineering at The University of New South Wales
• Institut für Solare Energiesysteme ISE at the Fraunhofer Institute
• Centre for Sustainable Energy Systems at the Australian National University
• National Renewable Energy Laboratory NREL
• Advanced Energy Systems at Helsinki University of Technology

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