New wind technology
Nearly 240GW of wind-generation capacity has been installed around the world so far, mostly on-land and mostly based on conventional three-bladed horizontal-axis propeller type designs. But many new ideas and designs for wind devices are also emerging, with cost reduction for offshore projects being a key issue.
Going back to basics, there’s a two-bladed propeller-type offshore turbine design being developed for offshore use by Dutch company 2-B Energy, which has the advantage that, unlike three bladed rotors, they can be more easily transported, fully pre-assembled and pre-tested, on a ship’s deck to a wind farm construction site. www.2-benergy.com/
The Danish offshoot of China’s Envision is also developing a 3.6MW two-blade design, with the outer sections of the blades being pitch adjustable. It’s claimed that this will reduce stress loading and, since less tower and blade material is needed, could cut costs by 10%. http://www.windpowermonthly.com/news/1115270/Close—-Envisions-36MW-offshore-machine/
There have already been several designs for ducted wind turbines, with annular collars seeking to concentrate and accelerate the wind flow. In general the power augmentation is not seen as likely to outweigh the extra costs of the shroud system. But a new wind technology being developed in Japan, the Wind Lens, is claimed to be more effective. Verification experiments on a 5kW version have, it is claimed, yielded 2.5 output augmentation from devices with an annular ring compared with devices without, and according to Professor Yuji Ohya from Kyushu University, augmentation of up to three times is possible. He says ‘the merit of two- or three-fold increase in power output leads to higher cost performance’: given their efficiency, the turbines can be smaller, reducing costs. It also claimed that they can help improve safety, reduce noise pollution, therefore making the technology more accessible in urban environments. http://www.mdpi.com/1996-1073/3/4/634
Three 5kW units were put in a sea-shore park near Fukuoka city and two 100kW units have also now been built. In addition, Modern Power Systems reported that, last December, a demonstration plant was tested offshore on a floating platform in Hakata Bay in Fukuoka, 600 metres off a sandbar that links Fukuoka city with Shikanoshima Island. The tethered platform has two small ‘Wind Lens’-equipped turbines and some solar panels. At wind speeds of 10m per second, the turbines can generate 3kW of power. Modern Power System says the floating wind power system will be used for verification experiments over the next year by Kyushu University together with the Environment Ministry and the city of Fukuoka. Then a new round of testing will be carried out in the southwestern tip of the Sea of Japan using a 60m platform with a pair of 200 kW wind lens units, and thereafter the aim is to build an offshore wind farm with giant 5000 kW ‘Wind Lens’ turbines, located at ocean depths exceeding 100m.
Japan is of course now very keen to press ahead with offshore wind projects, as it attempts to move away from reliance on nuclear power, following the Fukushsma accident. For example there are plans to build floating wind turbines off the Fukushima coast, initially, six 2MW units and then possibly up to 80 by 2020 in a 1GW offshore wind farm. So new designs like the Wind Lens may be in with a chance.
In parallel, vertical axis designs are being developed for offshore use, like the UK Aerogenerator X Nova project http://vimeo.com/13654447 and the French Vertiwind. www.youtube.com/watch?v=kkqzlEqsxww&feature=player_embedded
These are H (or V) shaped devices, but EU/RISO’s Deep Wind project is a ‘eggbeater’ shaped Darrieus design. http://www.DeepWind.eu
The big advantage of vertical-axis devices is that they operate regardless of which direction the wind is coming from, and the generator is at the base, not at the top of a tower. That makes them more stable - especially helpful for floating devices. It also opens up possibilities for very novel on-land developments. For example, US company Free Wind LLC has developed a unique vertical-axis, vortex-driven wind energy conversion system, WinDynamo(tm). The rotor is located inside stationary exterior cowling, with baffles and louvers that create internal vortices from impinging wind, driving a generator, and also a flywheel and compressed-air energy-storage device, mounted at the base. That ensures a more balanced and continual power output, despite variable winds. See www.windynamo.com/
Being a vertical axis system, it is tolerant of turbulent, shifting, non-laminar air flows caused by vertical obstacles, such as buildings. So it can be located in cities and suburbs, where the electricity it makes will be used directly with lower distribution losses. In addition, since it has a stationary exterior cowling, a protective mesh can be installed around the intakes to prevent birds, bats or debris from coming in contact with the turbine, and lightning rods can be installed on top to avoid storm damage. The cowling will also contain any mechanical failure without damage to the surrounding infrastructure.
The developers also claim that the system is visually unobtrusive and silent, operating with very low friction and minimal maintenance by using low-cost permanent-magnet levitation bearings. Well it seems unlikely that any rotating device can be entirely noise free - at the very least there will be aerodynamic noise as the wind passes through the cowling and across the blades. But it looks like it could be an idea worth exploring. See Animation at: www.youtube.com/watch?v=9a3AgZ3R9Fk
However, perhaps wisely, most of the R&D effort around the world is focused on upgrading conventional horizontal-axis designs - developing larger units of up to 10MW or more, with offshore use the main focus. Some are sea-bed mounted, sometimes using tension leg designs, like the Dutch Blue H device. But fully floating devices are being tested to allow location in deep water further out to sea, like the Norwegian Hywind and Sway turbines www.sway.no
One of the most intriguing is the Swedish Hexicon design, with a series of turbines mounted on a hexagon-shaped lattice platform, which can rotate around a central axis to align with the wind direction. The Maltese government says it plans an eventual 36-turbine scheme to be located 20km off the island’s north-east coast in water depths of 100-150 metres, with a massive 460-metre-wide platform. Being further out to sea it would also be much less visible than an inshore wind farm, and the areas around the Maltese islands are considered to be too deep to allow for the economical and feasible construction of fixed monopole wind farms. www.hexicon.eu/
However, if you want really exotic ideas, there’s the Windstalk from New York design firm Atelier DN - a forest of over 1000 thin 55 meter tall, swaying poles, with embedded piezo-electric generators, using compression strains, as well as fluid pumping generators at the base, to convert the swaying motion into energy. Very much just a concept for the moment, but who knows, new ideas like this, and some of the others mentioned above, may yet prove to be winners. http://atelierdna.com/?p=144
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