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The use of wind power to produce mechanical energy dates around the Middle Ages and in 1900 appears the first machine equipped with an electrical generator. From the 30s and even early 50s machines became popular small-sized (up to 3kW) in rural areas, where there was still no electrification network system to cover large areas. But the technological problems and the low prices of the fuel made it difficult, if not impossible, for wind energy to compete.
The energy crisis of the 70s, which caused a sharp rise in oil prices and its derivatives, promoted the search of alternatives to satisfy the energetic needs of some countries really dependents on oil products. So those countries started thinking about saving and storing energy and also on not conventional energies, appearing energy wind as an economic solution. This encourages new technologies with reliable and powerful equipment.
Nowadays wind energy is mostly used to obtain electrical supply. Itâ€™s a really powerful energy and its improvement means a vast advance for sustainable development.
Following data will help to realize how important and extent wind energy is becoming:
On 2010 and 2011 9,648 MW and 9,616 MW respectively of wind power capacity was installed in the EU
On 2011 21.4% of the power capacity installations was wind power (71.3% was renewable power installations)
Since 2000 28.2% of new capacity installed was wind power concerning a total of 47.8% for renewable energies
Wind power increased an annual average market of 15.6%
Moreover, wind power has not stopped its growth. As an inexhaustible source lots of expectations are put on it.
The following information includes wind energy needs to run, its applications and present and future development. The goal is to obtain a global framework that can serve as a guide for future researches.
This section embraces the most important wind energy technologies and for each one the necessary equipment.
Device used to convert kinetic wind energy into electricity. Wind turbines consist of the following elements (EWEA; WWEA, 2006):
Foundation: Its aim is to fix the wind generator into the soil. There are different types of foundations depending on the stability of this ground:
Shallow: This type is the most used. The footing for the Wind Turbine consists of a large reinforced concrete plate under the soil.
Pile: commonly used for weak subsoil. The foundation plate is fixed into the subsoil thanks to the piles
Offshore Wind Turbine foundations depend on the seabed:
Figure E.2.1. Different types of offshore foundations, from left to right: monopile, tripod, jacket and gravity base. Source: http://www.theengineer.co.uk
Monopile: the foundation is fixed into the sea floor around 10 to 20 metres deep. It is composed by a single pile with a diameter of approximately 4 metres.
Tripod: Three piles are fixed around 10 to 20 metres deep in the sea floor. It also has a steel frame to distribute the loads along the tripod.
Jacket: the structure is fixed deep in the sea floor. It looks like an electricity pylon that supports the loads.
Gravity Base: Placed on the sea floor and made of concrete, has enough strength and stability to no longer need fixing.
Tower: Its mission is to support the loads of the structure situated at the top and stabilize the whole structure against wind static loads. There are different types of towers: steel and concrete towers, pre-cast concrete towers, steel lattice towers, hybrid towers etc.
Blades: Here is where energy creation starts. The wind speed creates an impulse that moves and spins the rotor blades (just like an aircraft wing). It is common to have three blades made of synthetics reinforced with fiberglass and carbon fibers.
Nacelle: It is a frame which houses the machinery. Inside the nacelle we can find:
Low-speed shaft: the spin of the blades makes this shaft moved around 30-60 rotates per minute.
Gearbox: The gears in this box connect both shafts.
Figure E.2.2. Wind turbine elements. Source: Rowe, J., April 2002.High-speed shaft: This shaft moves around 1000-1800 times per minute. This shaft is connected to the generator activating it to produce electric power.
Generator: leads this power to a transformer that converts it into the right voltage for the larger electricity grid.
Device used to pump water, converting kinetic energy of the wind into mechanical energy. They started to be used thousands of years ago and its design has not changed. Their conservation and maintenance is minor. They are commonly used for small amounts of water and low pumping heights. Windmills consist of the following elements:
Tower: made of galvanized steel and around 4 to 12 metres high.
Blades: made of galvanized steel and around 1.8 to 5 metres long.
Pump: is directly driven by the rotor.
Regulating Reservoir: for covering consumption peaks and periods of wind calm.
THE ZERO-BLADE TECHNOLOGY
Figure E.2.3. Zero blade wind turbine Source: Shapon energy.The wind energy without blades. This device creates energy with a sail that follows a non-rotation spin and forth motion. This movement permits obtaining mechanical energy and then it allows its conversion into a hydraulic pressure that could be stored. Also electrical energy could be obtained with a hydraulic motor and a generator.
Figure E.2.4. Wind stalks. Source: Markham, D., April 2012.The wind energy through stalks instead of blades. This device generates electricity thanks to piezoelectric ceramic discs with electrodes between them located inside each pole. The wind speed moves the discs and compresses them, generating a current through the electrodes.
Figure E.2.5. Wind lens. Source: Markham, D., April 2012.The wind energy, whose blades are joined with a circle around. Its efficiency can be three times better than conventional wind turbines based on the same principles.
The wind energy with vertical axis. Already used in farms in United States for covering peak season and without creating environmental noise impact.