Cylindrical Towers are the Secret to Capturing More Wind

A classical image of fluid flowing around a cylinder shows it speeding up at the sides and slowing or stagnating at the front and back. This let Majid Rashidi, Professor of Mechanical Engineering at Cleveland State University, realize that placing wind turbines in the naturally forming high-speed areas at the sides would let them generate more power than if the turbines were free standing. To test his hypothesis, Rashidi applied for a two-year grant from the Dept. of Energy and NREL, won it, and built a 25-ft diameter cylindrical tower on the roof of a CSU building. His idea mounts a pivoted truss across the top of a cylindrical tower to extend beyond its circumference. Arms extend down from the end of the truss to hold four 2-m diameter turbines (two on each side). The turbines are the off-the-shelf Swift design from Cascade Renewable Energy Solutions, Grand Rapids, Mich. Each is rated for about 2 kW at max wind speed.

Controls and monitors nearby show what each turbine is producing. During my visit, an almost calm morning, the control turbine some 150 ft away was barely turning in the light breeze while those by Rashidi’s cylinder were spinning much faster. And when the wind picked up, the turbines made no discernable noise, partially because the circular rim prevents vortex shedding at the blade tip, a noise source. The existing design uses a time averaged control to turn the device into the wind. But Rachidi plans on testing a passive less expensive directional fin, like a weather vane, for the same function.

The CSU professor says his design improves power capture by three to four fold. In addition, the design would be ideal for retrofitting existing round structures such as silos or water towers that adorn many rooftops in large cities. Rashidi says the school owns the technology and is still in the proof of concept stage. Commercialization would be a next step.

Two to build wind towers

To serve North American markets, Martifer Energy Systems and Hirschfeld Wind Energy Solutions say they will form a joint venture to manufacture wind towers and related components in the U.S. The joint venture, Martifer-Hirschfeld Energy Systems LLC, will be equally held by each party. The company will develop a factory in San Angelo, Texas, to build steel towers for wind turbines. The investment until now was developed solely by Portugal-based Martifer Energy Systems, and represents about $40 million which generated 225 jobs. The companies plan two stages, with the first representing an investment of about $30 million and completion expected for Q2 2010. The factory is expected to reach a capacity of 400 towers/yr by 2013.

This venture joins the expertise of Martifer Group for manufacturing wind-power components along with Hirschfeld’s local footprint and experience in infrastructure fabrication. Martifer Energy Systems produces towers, coverings, and gearboxes for wind turbines.  Through a joint venture with REpower Systems AG of Germany, Martifer designs and manufactures wind turbines, and it assembles REpower wind turbines in Portugal. The company also builds wind farms for third parties.

Where to place wind towers wins $10,000 prize

A clever idea from a French team of engineers and architects is to build vertical-axis wind turbines into existing towers that carry high-voltage power lines. The idea was good enough to win a $10,000 Metropolis Next Generation Design Prize.

Judges say Wind-it, winner of the Metropolis Next Generation Design Prize, solves the problem of linking energy generation and transmission by mounting vertical-axis wind turbines inside transmission towers.

The team, Julien Choppin, 31, and Nicola Delon, 31, are partners in Paris architectural firm. Also sharing the prize is Raphaël Ménard, director of a 20-person design firm.
The concept behind the winning design, called Wind-it, answers one challenge to developing wind power: where to site turbines. The idea uses existing infrastructure, the towers and pylons that carry more than 157,000 miles of high voltage lines in the U.S. The proposed turbines can be stacked within already sited towers. No design details are available as to weight, cost, or efficiency of the proposed turbines.