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WIP-August 2011.pdf - Global Media Publishing Ltd. - Uk.com

WIP-August 2011.pdf - Global Media Publishing Ltd. - Uk.com

EDITOR’S LETTER

EDITOR’S LETTER WELCOME A warm welcome to this month’s issue of Worldwide Independent Power - as always bringing you closer to the stories and issues affecting on-site power and cogeneration around the world. For editorial comments, please do not hesitate to contact the editor. BIENVENUE Soyez le bienvenu à cette issue de Worldwide Independent Power. Comme d'habitude, nous vous apportons toujours plus près des sujets qui affectent l'énergie et la co-generation sur place autour du monde. N'hésitez pas contacter le rédacteur pour des commentaires éditoriaux. WILLKOMMEN Herzlich Willkommen zur Ausgabe dieses Monates von Worldwide Independent Power. Wie immer bringen wir Sie näher heran an die Ereignisse und Geschichten der Stromerzeugungsindustrie rund um die Welt. Für redaktionelle Kommentare und Anregungen wenden Sie sich bitte an den Autor. BIENVENIDO Bienvenido a esta edición de Worldwide Independent Power. Como siempre, acercándolo a los temas que afectan a la energía y a la cogeneración in-situ. No dude en contactar con nuestro editor para cualquier cuestión editorial. BENVENUTI Benvenuti a questa nuova edizione di Worldwide Independent Power. Come sempre cercheremo di offrirvi storie e questioni riguardanti on-site power e cogeneration a livello globale. Per commenti editoriali, si prega di contattare l'editore. Aidan Turnbull - Editor Getting in a spin with wind power According to the US-based California Institute of Technology, the power output of wind farms can be increased by an order of magnitude - by a factor of 10 - just by placing turbines on a given plot of land in a better way. Researchers at Caltech who have been conducting a unique field study at an experimental two-acre wind farm in northern Los Angeles County think this could be the way forward to get more from wind energy. Field tests conducted by John Dabiri, Caltech professor of aeronautics and bioengineering, and colleagues during the summer of 2010 have revealed that, despite improvements in the design of wind turbines which have increased their efficiency, wind farms remain relatively inefficient. Today's wind farms generally employ horizontal-axis wind turbines (HAWTs), the standard propeller-like monoliths that you might see slowly turning, all in the same direction, in the hills of Tehachapi Pass, north of Los Angeles. Dabiri's experimental farm, known as the Field Laboratory for Optimised Wind Energy (FLOWE), houses 24 10-metre-tall, 1.2-metre-wide vertical-axis wind turbines (VAWTs) which have vertical rotors. Generally, the individual turbines have to be spaced far apart. With this type of design, the wake generated by one turbine can interfere aerodynamically with neighbouring turbines, with the result that "much of the wind energy that enters a wind farm is never tapped," reports Dabiri. He compares modern farms to "sloppy eaters," wasting not just real area - and thus lowering the power output of a given plot of land - but much of the energy resources they have available to them. Designers compensate for the energy loss by making bigger blades and taller towers, to suck up more of the available wind and at heights where gusts are more powerful. "But this brings other challenges," Dabiri says, such as higher costs, more complex engineering problems, a larger environmental impact. Bigger, taller turbines, after all, mean more noise, more danger to wildlife and an even larger eyesore. The solution, claims Dabiri, is to focus instead on the design of the wind farm itself, to maximise its energy-collecting efficiency at heights closer to the ground. While winds blow far less energetically at, say, 30 feet off the ground than at 100 feet, "the global wind power available 30 feet off the ground is greater than the world's electricity usage, several times over," he says. That means that enough energy can be obtained with smaller, cheaper, less environmentally intrusive turbines, as long as they're the right turbines, arranged in the right way. VAWTs are ideal, Dabiri says, because they can be positioned very close to one another. This lets them capture nearly all of the energy of the blowing wind and even wind energy above the farm. Having every turbine turn in the opposite direction of its neighbours, the researchers found, also increases their efficiency, perhaps because the opposing spins decrease the drag on each turbine, allowing it to spin faster. The results showed that an arrangement in which all of the turbines in an array were spaced four turbine diameters apart (roughly 5 metres, or approximately 16 feet) completely eliminated the aerodynamic interference between neighbouring turbines. Pretty good, eh? [ Images and video of the field site are on: http://dabiri.caltech.edu/research/windenergy.html ] EUROPE ASIA-PACIFIC MIDDLE EAST AFRICA AMERICAS W ORLDWIDE I NDEPENDENT P OWER • AUGUST 2011 5

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