Wind power surges ahead!

..or at least the technology does. Whilst Greece struggles to reach its obligations to increase dramatically renewable energy resources, wind turbine technology moves forward at gale force. It is estimated wind could provide up to 20% of the global energy market by 2030 (3% in 2015).

‘Traditional’ wind turbine technology is being overtaken by new designs aiming to reduce production, maintenance and installation costs and minimise environmental impacts such as the effect on migratory birds and road building needed to transport turbines to a site.

The problems with the current wind turbine technology include:-
-- effect of rotating blades on birds,
-- top heavy,
-- generators and gearboxes sitting on top of support towers 100 metres above the ground which can weigh more than 100 tons,
-- as weight and height of turbines increases the material and maintenance costs for components also increases,
-- access - need wide straight roads to transport turbines and support towers to the site.

Here are examples of three alternative wind turbine technologies, Vortex, Energy kites and Vertical Access Wind Turbines (VAWT).

Vortex



Vortex, which has been attracting a lot of publicity and funding.

Vortex  is a vertical turbine where wind shears down one side of the cylinder in a spinning whirlpool or vortex which exerts force on the cylinder causing it to vibrate. The kinetic energy of the oscillating cylinder generates electricity through a linear generator at the base similar to those used in wave energy systems.

They claim that it is more efficient, cost effective and environmentally friendly because:
-- no gears or blades reducing manufacturing costs by 53%,
-- no moving parts in contact avoiding fatigue and wear,
-- no friction therefore no need for lubrication and no spare parts/ replacements required,
-- reduction in maintenance costs by 80%,
-- reduction in operating costs by 51%
-- lower environmental impact.
A key advantage is that these turbines are less likely to affect birdlife and that shorter turbines can be equally effective.

The main criticisms are:
-- unproven on a large scale,
-- each turbine has less energy efficiency than a conventional turbine,
-- potential stability in turbulent conditions making it difficult to optimise energy efficiency,
-- potential noise.
Vortex are currently working on several small scale projects and plan to deploy their largest turbine, 150 metres high with a 1MW generating capacity, by 2018.   vortex bladeless

Energy kites

Energy kites or ‘flying windmills’, airborne wind turbines.
Makani Power now owned by Google’s semi secret research facility (Google X) plan to begin tests of a full scale 600 KW kite. The principle is to use series of energy kites like a flying windmill flying high in the sky.

As illustrated in the photograph above, the ‘kite’ has rotors on the wings rather like helicopter blades that help to propel the kite into the air paddling like a kite, the 26 foot wing span traces circles 250 feet overhead. Thus the propellers become generators and electricity flows down the that tether restraining the kite. The designers claim that this technology is less expensive and will be able to harvest energy more efficiently. Conventional turbines ‘top-out’ at 300 feet (blade tips reach 500 feet). A tethered ring of kites can fly much higher making more efficient use of the wind and using fewer lighter materials consequently generating lower cost electricity.

As with Vortex, ground based maintenance would reduce costs. They can also be installed where access to install conventional turbines is limited, but these kites may not be so good for bird life.  makani

Vertical Access Wind Turbines (VAWTs)

A ‘wind tree’ from French company (L’Arbre a Vent) which is a type of VAWT. These turbines have a main rotor shaft set transversely to the wind (not necessarily vertical), the main components (like Vortex) are housed in the base of the turbine easing maintenance. They do not need to be pointed into the wind removing the need for wind sensing mechanisms. John Dabiri at Caltech has found that turbines placed close to each other could produce more energy than those far apart. This has influenced the he design concept behind VAWT where ‘forests’ of low level turbines can be ‘planted’ in more urban environments. Placing supply closer to demand.

These turbines tend to be much lower than conventional turbines capturing wind speeds of less than 8 kilometres per hour (kph) whereas conventional turbines are capturing winds at 35 kph or greater. The wind trees are 9 metres tall and 7 metres wide containing 54 green leaf turbines generating 5.4 KW equating to 2,400 kWh per annum. A solar array delivering the same capacity would require a roof space of 131 square metres. The trees plastic leaves turn silently in the wind. There are already a number of wind trees installed in Paris and they are installed at the Roland Garros tennis stadium which in 2016 used 100% renewable energy. Impact on bird life? Maybe such trees would augment the life of birds rather than endanger them! :  newwind

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