First published in Cleantech magazine 2011 Issue 5. Copyright Cleantech Investor Ltd
By Mr Andrey Kotler and Dr Rami Masri
Smart Wind was established by Andrey Kotler on May 2009 in the L.N. Green Technological Incubator in Haifa, Israel. Since then the company has focused on the development of an innovative small vertical axis wind turbine (VAWT) for residential settings. Smart Wind’s proprietary technology is based on a specific use of active flow control (AFC) technology, which is used to improve the aerodynamic performance of aircraft wings. The company has deployed this technology in a VAWT, resulting in improved aerodynamic performance of the rotor blades.
During preliminary experiments between 2004 and 2006 on a wing model in the subsonic wind tunnel at the Faculty of Aerospace Engineering Technion, I.I.T., by Andrey Kotler and Prof. Tanchum Weller, compressed air was injected on the wing at different angles of attack and flow velocities. The experiments (which pre-dated the establishment of Smart Wind) assessed the differences in the lift coefficient, drag coefficient, and pitch moment coefficient while applying the injected jet stream and with the jet stream off(1). The lift coefficient was found to increase by about 10%-30% at the angles of attack 5° and 7.5° for different flow velocities, with a smaller change in the drag coefficient. These results were the motivation to apply injections of air on wind turbine rotor blades in order to increase the power production of a VAWT.
Smart Wind’s intellectual property includes a pending patent (12/898,182, US filing date: October 5, 2010) that covers a rotor in regard to a specific use of the AFC technology. The company is now in the process of filing a PCT application. Figure 1 demonstrates the basic idea behind the innovative technology.
Smart Wind created five test model configurations which were evaluated at the company’s wind turbine test site at the Technion, I.I.T. Three test model configurations are shown in photos 1, 2 and 3. The different configurations were tested against two conventional small wind turbines, one with a horizontal axis of rotation (HAWT) and the other a Savonius type wind turbine (photos 4 and 5 - see bottom of article)
Comparisons between Smart Wind’s fifth configuration and the conventional wind turbines demonstrated that the company’s test model produced more energy per rotor swept area than the two conventional wind turbines, as detailed in the Experiments Results(2).
All of the experiments to date have found that the AFC technology enhances a turbine's power production and hence enables better performance in smaller rotor dimensions. Smart Wind's increased efficiency – for greater electricity production – will translate into a relatively rapid ROI.
Smart Wind’s market strategy is to develop small wind turbines, initially focusing on efficient, cost-effective wind power solution for residential settings. Following penetration into these markets, the company will approach the commercial and urban sectors for small wind turbines and explore opportunities for applying its technology to larger wind turbines.
Principle of Action
Experiment results in Graph 1 present the power per rotor swept area produced by each wind turbine in Watts/m^2 as a function of time in minutes. The division of the power by the swept area eliminates differences in the swept area of the rotors, facilitating comparisons between the performances of the three wind turbines. The blue line represents the results of the company’s fifth test model configuration, demonstrating that Smart Wind’s test model produced more power per rotor swept area than the two conventional wind turbines. In order to compare the energy (integration of power along time) per rotor swept area for a large range of average wind speeds, especially for relatively high values, this measure produced by each turbine during short periods of time (but not less than five minutes) was calculated when the average wind speeds were relatively high.
In Graph 2 the ratio between the energy per rotor swept area produced by Smart Wind’s test model against the same measure of the conventional HAWT is shown as a function of the average wind speed. In all the experiments the company’s test model was connected to a load of 140 ohm, while the HAWT was connected to 140 ohm (red squares) and 50 ohm (blue circles). Graph 2 indicates that, beyond an average wind speed of 6 metres per second, Smart Wind’s test model produced more energy per rotor swept area. Furthermore, it appears that the ratio increases with the increase in the average wind speed to over two for average wind speeds above 8 metres per second.
Similar results are shown in Graph 3, where the ratio between the energy per rotor swept area produced by the company’s test model against the same measure of the Savonius type VAWT is shown as a function of the average wind speed. In all the experiments Smart Wind’s test model was connected to a load of 140 ohm, while the Savonius type wind turbine was connected to 140 ohm (red squares) and 80 ohm (blue circles). The results seen in Graph 3 indicate that the company’s test model produced more than twice the energy per rotor swept area, and it seems that the ratio increases with the increase in the average wind speed.
Smart Wind did not perform measurements for noise and vibration levels, but the experiments clearly demonstrated that the HAWT rotor vibrated most and generated most noise. No visible vibrations were observed in Smart Wind’s rotor and its spin was fairly silent.
In February of this year Smart Wind presented at the Eilat-Eilot Renewable conference & Exhibition in Israel(3), where a first meeting took place with Jacek Banach, the President and CEO of EXPOM, a company based in Kurzetnik (Warmia & Mazury province), Poland. During the 15th annual Cleantech International Conference & Exhibition in Tel Aviv in July 2011 Smart Wind signed a letter of intent with EXPOM(4). More recently, in September, Andrey Kotler and Jacek Banach discussed the strategic cooperation between the two companies in production, sales, installation, public relations and marketing throughout Europe.
(1) Kotler.A. and Weller.T. "Stream Jet Interaction in a Wing Wake", Technion, Haifa, Israel April 2006 - Internal Report
(2) Kotler.A. and Masri.R. "Summary report of comparison experiments", Smart Wind Ltd, Haifa, Israel, May 2011 - Internal Report
(3) Kotler. A., Weller.T. and Masri.R. "NEW GENERATION OF WIND TURBINES", Eilat-Eilot Renewable Conference & Exhibition, Eilat, Israel, February 2011
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