There are a lot of extra acres on wind farms.
That, in part, is the idea behind Wind Harvest International, which says it can double to power output of large wind farms by strategically placing its vertical wind turbines between the large, multi-megawatt horizontal turbines that stand in them now.
In fact, the company's "I am the spare arms of Robby the Robot" turbines might even be able to increase the power output of the existing, multi-megawatt, multimillion-dollar turbines already in the ground.
"We can put a megawatt of turbines between two horizontal megawatt turbines," said Kevin Wolf, the company's chief operating officer. "We can double the power output and maybe increase the power of the other turbines."
Although one of the most mature and capital-intensive segments in alternative energy, wind has enjoyed a surge of popularity with venture capitalists. Among the companies percolating to the surface are Nordic WindPower (two-bladed turbines), FloDesign Wind and Boulder WindPower. (On the other hand, Makani Power has been struggling, say sources.)
While Wind Harvest's wind turbines differ in many respects from vertical turbines from Mariah Power and others on the market, the fundamental secret sauce lies in how and where the turbines get planted in the ground. In short, the company places three or more counter-rotating turbines next to each other to create a vortex. The small-scale cyclone that results effectively increases the available amount of harvestable energy.
Vortexes might sound a bit New-Agey: Stonehenge and the Great Pyramids are alleged to be massive energy vortexes. But companies such as Watreco in Sweden and the Palo Alto Research Center are similarly trying to harness the physical forces generated of water vortexes to reduce the cost of desalination, water purification, and/or producing algae fuels. Vortexes also explain why fish can stay stable in onrushing currents and bicyclists or animals can travel in packs with less effort.
The economic implications of Wind Harvest's strategy -- assuming the science works out in practice and wind farms adopt it -- are significant. With more turbines on the same plot of ground, the millions spent to connect and balance the power generated at wind farms could be paid off more rapidly and the real estate, of course, would becomes less expensive as a function of power production.
Boosting the performance of existing turbines would further help ameliorate wind's chronic problem: unpredictability, resulting in wind turbines that only generate power about 30 percent of the time. By increasing the power output when the wind blows, the capacity factor could creep up. Reliability could also potentially increase: in high wind conditions, wind farm owners could shut off their horizontal turbines but still harvest power from the vertical ones.
The company wants to sell a version to power 25-kilowatt generators, a 75-kilowatt version and a 75-kilowatt device for low-wind conditions. Working prototypes churn away outside Palm Springs and the company hopes to start selling some commercially in 2011.
Horizontal vs. Vertical
In ordinary situations, the familiar three- (and sometimes two-) bladed wind turbines arranged on a horizontal axis are inherently more efficient than vertical ones, which look like lawnmower rotors stood on one end, admits Wolf. Why? Some of the blades in conventional vertical turbines are always pushing against the wind. If the turbine turns clockwise, power is generated by blades in the 1 through 5 o'clock positions while blades at the 7 through 11 o'clock positions. Horizontal turbines don't have this problem.
Wind Harvest ameliorates this by placing three or more turbines in close proximity to each other -- the blades swing as close as a meter apart -- rotating in alternating directions. A vortex is generated in the passage between turbines that accelerates localized wind speed to 1.75 times the ambient wind speed. The velocity on rotors on the downwind side accordingly jumps too. In the end, this results in more torque and lift and hence greater energy production.
"It is only effective in a three turbine array or more," Wolf said, adding that Sandia National Labs has conducted several simulations on the coupled vortex effect in wind.
Wind Harvest, he added, has a patent for placing vertical turbines in an efficient manner to create vortexes. Finding patent infringers could be easy: vertical wind arrays can often be detected via satellite photos.
Vertical turbines strategically placed would exploit winds that are out of reach of mega-turbines. And how would verticals potentially help horizontals? If a vertical turbine converts wind power into another form of energy, the wind has less energy at that spot. In theory, this could draw higher winds to the horizontal turbines, he says, adding that it's an 'if' on the performance characteristics.
Wind Harvest has also tweaked its vertical turbine so that there is less stress on the blades and bearings to improve longevity. "The bearings don't bear weight," Wolf emphasized.
The first markets will likely be the United Kingdom and Italy, which just passed generous feed-in tariffs in the 30 to 40 cent per kilowatt hour range. The UK also ruled that wind turbines 15 meters or shorter are exempt from local planning objections. Wind Harvest's 25-kilowatt turbine stands 15 meters. The turbines work in on- and off-shore environments.
Calling Wind Harvest a startup is a bit of a stretch. CEO Bob Thomas, who advised then-governor Jerry Brown about alternative energy in the 70s, has been tinkering with the concept for years. The company is currently raising funds.
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