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SAFE-T Wind Systems: Wind Power Innovation Through Iterative Design

SAFE-T Wind Systems Rethinks Wind Power with Spherical Turbines

Today’s most visible wind turbines stand as tall as skyscrapers. Energy utilities must make heavy investments not only to build them, but also to route the electricity they produce from remote locations to the cities that need the energy. But imagine instead a small, safe, inexpensive wind turbine — the size of a large beach ball — that could be installed on most any flat surface. Put a few dozen of them on the roof of a warehouse and you would be able to offset some of the power that building uses from the grid, all at a fixed cost per kilowatt hour for a long period of time.


That’s the vision of Charles Valenza, co-founder of Sacramento-based SAFE-T Wind Systems. SAFE-T is the acronym for Spherical Air Foil Energy Turbine, which accurately describes the product that Valenza and his colleagues are working to prototype and bring to market.


Hardware Innovation through Iterative Design

Any hardware startup in the trenches of development work can expect to go through many design iterations as it translates an initial idea into a finished design, a viable product, and ultimately a self-sustaining business. Although Valenza has no prior background in wind energy or aerodynamics, he has a broad background in business and a passion for creative thinking. The seed of SAFE-T Wind’s product stemmed from two simple questions he had: why are all the wind turbines so big? And why are they located so far away from where the ultimate users are?


Answering that question means putting small, economical turbines right where the energy is needed — an outcome that will be reached only through that process of design iteration. The SAFE-T Wind team, including Valenza (CEO), co-founder Kevin Goldstein (CTO), and Brett Sargent (COO), have already built a couple of simplified prototypes that they are using to test their design and prove that it will perform as expected. The work is made easier because many of the turbine components, including the hub generators, micro and system inverters, and turbine slip rings, use currently available technology. But then there’s the airfoil design . . .


turbine stage 2b-LFpersp [full shroud].jpg


The Unique Design Challenge of a Spherical Turbine

The real breakthrough in SAFE-T Wind’s product is its spherical shaped turbine. Instead of the straight propeller-type blades of traditional windmills, the SAFE-T Wind design incorporates a set of highly swept, and highly twisted airfoils that together form a spherical shape. The shape, configuration, and detailed design of the airfoil is all-new, so it is still being developed and refined by the team.


This is a particularly difficult design problem because the rotation of the spherical shape results in each airfoil “seeing” clean and turbulent air flow. In the terms of aerodynamic flow, each airfoil encounters a leading-edge flow, a trailing-edge flow, and a high-angle-of-attack flow at different points during each rotation of a blade. Also, the flow is faster across the airfoil’s middle section in comparison to the end sections where it attaches to the axis of the turbine. On top of that, each turbine will likely see disturbed air flow from other turbines located upstream from it.


Designing the airfoil shape to address these varying airflow conditions has been a substantial challenge. The elements of each airfoil that can be modified include the airfoil sweep (forward or aft sweep), twist, thickness, and trailing edge contour. For example, testing revealed that an initial forward sweep transitioning to a traditional aft sweep led to improved performance for the turbine.


Accelerating Hardware Development with 3D Design Software

Initially, the SAFE-T Wind design team used 2D drawing software as well as a lot of pencil and paper to iterate and refine the complex elements of the airfoil shape. Then the company became a semifinalist in the Western Region CleanTech Open, which meant they were awarded a license to use Fusion 360. The team got up to speed quickly with the software, and found that it enabled them to make much faster progress with their design iterations. Using the software, they can now rapidly alter specific elements of the airfoil design, such as twist or sweep in 3D, and then quickly visualize the results of their changes.


Within a short period, SAFE-T was able to create and refine several detailed prototypes. Design modifications that previously would have taken days to visualize and create could now be created and refined within a couple of hours. As they move closer to a finished product, the SAFE-T team anticipates that digital files created in Fusion 360 will also simplify fabrication of their airfoil designs through 3D printing.


Although the process of design iteration can sometimes seem endless while it’s underway, it’s a small price to pay to bring a brand-new technology to market — especially for a company that is passionate about changing an entire industry.



Development Plans and Investment Strategies

As noted, the SAFE-T Wind team is continuing their design and manufacturing efforts, and expect to be able to test two of their prototypes during the first quarter of 2015.  Intentions are to be able to put at least one of their designs through some wind tunnel testing, and then, with funding, build out a small pilot site of 10 turbines for further testing and certification.


SAFE-T Wind is currently seeking investment from a variety of sources, including Angel groups, SBIR grants, and possibly through strategic partnerships with one or more energy service companies.


It looks like 2015 will be a busy and windy time for SAFE-T Wind. Stay tuned for more!


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