Navigant Research Blog

The Return of Vertical Axis Wind Turbines

Dexter Gauntlett — May 21, 2013

Vertical axis wind turbines (VAWTs) appear to be making a comeback after a few dormant decades, but it’s unclear how much legs the somewhat maligned technology will have in the market.  VAWTs are most commonly known in the United States from their days during the 1970s to the early 1990s in California, when Sandia National Laboratories and several private companies worked together to design and deploy a number of 500 kW-600 kW utility-scale VAWTs in California.  The units worked fairly well, even if not as well as expected, for a number of years.  But they ultimately ran into mechanical problems that stifled their commercial viability.  By that time, interest had largely shifted to today’s more common three-bladed horizontal axis wind turbine (HAWT) designs, and the industry has never looked back.

VAWTs do potentially offer advantages over HAWTs, including producing power with less wind so they can be located closer together and closer to the ground for easier maintenance and installation.  There are at least 28 active VAWT manufacturers in the world today, primarily producing less than 10 kW units intended for use in urban and building-integrated settings.  Yet, many companies in this sector, such as Helix Windpower and Windspire, have faced significant financial challenges.  Small wind turbines in general have faced increased scrutiny, as there are many cases of both VAWTs and HAWTs not performing as advertised in the urban environment.  The establishment of the Small Wind Certification Council has been a major step forward for a small wind industry that is looking to regain credibility.  Still, only five small wind turbines are currently certified by the council – all HAWTs.

These challenges did not, however, prevent the largest building-integrated VAWT installation in the United States from coming online in June 2012.  It uses 18 4.5 kW Venger Wind V2 turbines on the roof of the Oklahoma Medical Research Foundation.  The V2 wind turbines are 18.5 feet tall and are designed to start producing electricity at winds of 8.9 mph, well below Oklahoma City’s annual wind speed average, according to Venger Wind.

Packing Them In

Making inroads in the utility-scale market is a challenging task for VAWTs, given the formidable competition from incumbent manufacturers that have a long history of commercial viability and strong technical performance.  There is strong, though relatively limited, potential in the medium wind turbine market segment (100 kW-900 kW range) related to rural areas, islands, community wind, schools, and other distributed wind applications.  No known commercially available VAWT product currently exists in that power range – Italy’s Ropatec offers the largest known VAWT unit at 20 kW.  But a number of universities and companies are taking a closer look at VAWT technology and applications and are seeking to learn from others’ successes and failures.

A Caltech study that analyzed the performance of six VAWTs more tightly packed together found that they produced 21 to 47 watts of power per square meter of land area, compared to just 2 to 3 watts per square meter from a similarly sized HAWT farm.  Shanghai Aeolus Windpower Technology (SAWT) currently offers less than 10 kW VAWTs, but has stated plans to develop 50 kW and 1 MW units.  Sandia National Labs received a $4.1 million grant in June 2012 to reevaluate VAWTs, including their potential for offshore applications – an opportunity that Japanese, Korean, and Chinese researchers and companies are also examining.

Finally, high-profile projects at Adobe and the Lincoln Financial Field (home of the NFL’s Philadelphia Eagles) continue to drive interest in VAWTs.  But only actual performance details over time will determine if the resurgence of VAWT interest is based on concrete technical improvements or hype.

One Response to “The Return of Vertical Axis Wind Turbines”

  1. Robert Reive says:

    First thanks for your article on creating awareness that VAWTs are indeed back. VAWTs in the past have been plagued with poor aerodynamic performance and higher build costs than HAWTS, the latter because of the necessary additional materials and labor required to build the VAWT form, the former because many of today’s designs are recycled experimental designs from the 1970s and 80s using airfoils from NACA research performed in the 1930s and 1940s. Modern HAWT design by comparison uses advanced RANS Computational Fluid Dynamics “CFD” solvers to arrive at their final design form for rotor blades and supporting structures. As far as I know only Harvistor has really solved the VAWT with supercomputer driven custom RANS CFD solvers in the same “HAWT” fashion, in our case using over 512 CPU nodes to support an 8 million 3D prism air mesh, where the compute job (using Openflow Clusters) spanned over 2 days to generate 25 seconds of valuable data in 500 GBytes plus worth of storage for each run. The effort was then validated with Field testing, not wind tunnel testing, just like the Big HAWTs. The results have allowed Harvistor to mount lower (offsetting micro HAWT capital costs advantages for the turbine itself with mast capital and operating cost savings) and also run at 25% lower tip speed ratios (TSRs) to improve the life of the system with 15-35% more power output given the mount height reduction. Move importantly we at Harvistor Canada have improved on past Sandia/Flowind and Canadian NRC performance for the VAWT with purpose built CFD RANS designed airfoils (just like HAWTs) which yield a 25% advantage in COE, at a minimum. Yes VAWTs are back and it is a small group of companies you can count on one hand leading the way with cutting edge R&D and the latest in RANS CFD solvers running on Supercomputer Infrastructure. It’s expensive (compute time, analysis,etc..) and it has meant throwing out 25 years of research from Sandia and others regarding past generation VAWTs, (even Modern Sandia realizes this..), but it has been really worth it as the VAWT is back!

    Thanks for writing this article, it’s important your readers know that of the 48 VAWT vendors out there only 1 in 10 are legitimate, and surprisingly none of them are the older established VAWT companies.

    Sincerely

    Robert Reive
    CEO, President
    Harvistor Canada
    robert.reive@harvistor.com

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