A sailor’s look at wind turbines

Growing up around sailboats, I have always been intrigued with wind as a source of power.  Learning that you can sail relatively close to the direction from which the wind is blowing meant to me that there was more involved than simply letting sailcloth capture the breeze to push the boat downwind.

I was thrilled to learn that by sailing at different relative wind angles, or angles of attack, your boat can sail faster than the airstream by adding the boat-speed vector to the wind-speed vector.  What could be better than, in effect, making more breeze?  Many factors – like the hull’s shape, the sails’ shape and rigging’s effects on sail shape, landforms, cloud cover, and adjacent boats – all impact the potential of this fickle source of power.  The more I learned about these variables, the better use I made of the wind’s free power.

Finding myself on land, in the middle of a twelve-month restoration of a 1968 Olympic class 5.5-meter sailboat, I felt I had been giving the wind a free pass for far too long in other areas.  After all, it was good for more than just sailing around.  So when I was presented with the opportunity to lead a team on a renewable energy project for Quinnipiac University, I felt it was a fitting assignment.  The university wanted York Hill, its new residential campus in Hamden, Connecticut to incorporate a range of sustainable approaches, and wind would be very much in the mix.  I was charged with finding the right wind generator, one that could be clustered as a “farm” in the heart of the busy campus.  It would be green infrastructure serving as a park-like destination, as sculpture even, a campus conversation piece.

There are many different types of wind generators, or turbines, which are commercially available.  We limited our pool of candidates to those considered “small wind” with capacities of 100 kilowatts or less.  Capacity is defined as the instantaneous rate of electricity generation at a given wind speed, not the amount of electricity a turbine produces over time.  Smaller turbines were also appropriate to our design concept, creating a Wind Terrace where the turbines could be experienced as an art installation, rather than as potentially overwhelming pieces of machinery.  Turbines in the “large wind” category are certainly impressive, very efficient, and may be appropriate for a future project.

There are two basic groups of turbines: Horizontal Axis Wind Turbines (HAWTs), and Vertical Axis Wind Turbines (VAWTs).  The propeller type, utility-scale wind farms of the Midwest, or Cape Wind’s proposal for Nantucket Sound, are HAWTs, requiring a pointing mechanism to allow the blades to face the wind and often a starting mechanism to get the blades spinning.  On the other hand, VAWTs are like wind scoops on an anemometer, functioning without respect to wind direction.  They are generally self-starting, simple, and reliable.

After studying wind patterns over the course of a year at York Hill, our team determined that, while there was plenty of wind, landforms and building orientation resulted in wind direction and pressures that were not consistent.  Although there is little question that HAWTs are more efficient as power generators, our site variables, along with concerns over initial cost and reliability, suggested that we should focus on VAWTs.

There are two VAWTs types, Savonius and Darrieus, named after their respective inventors.  Savonius turbines are drag-type devices using scoops on a vertical rotor, and some are similar to roof-top ventilators.  Of the two, they are simpler by design, similar to the sails on a sailboat going downwind, and therefore they lack the potential to move faster than the wind.  Darrieus turbines use aero-foils mounted to a framework on the vertical rotor and generate lift like an airplane wing or the sails of a sailboat going to windward.  The speed vector of the rotating foils is added to the airflow across the foils to create a better angle of attack, effectively making more breeze – something I have spent the better part of my leisure trying to perfect in my sailboat.  Not surprisingly, I quickly determined that Georges Jean Marie Darrieus was our man.

How the Darrieus wind turbine works

Our team’s selection process was not entirely scientific; we are architects, after all.  Heavy consideration was given to aesthetics, but a few beautiful turbines were crossed off the list due to the high cost per kilowatt, attributable either to limitations of their availability within the United States or inefficiency of design.  Our list of candidates had already been whittled down to those that had long-design life spans, were efficient, and were readily available.  The Windspire produced by Mariah Power of Reno Nevada was selected for its beautiful aesthetic.  A demo turbine was place at York Hill for six months to prove the manufacturer’s claim of silent operation, and to confirm that the scale of the turbine was in keeping with our design goals.

Next time you are in the vicinity of Quinnipiac University’s York Hill Campus, visit the Wind Terrace.  Sit yourself right underneath the turbines in one of the convenient Adirondack chairs along the busy student pathway and enjoy the view.  I think you will be pleasantly surprised at how breathtaking generating electricity can be.

Brian S. Krafjack, AIA, received his Bachelor of Architecture degree from Syracuse University in 1986.  An accomplished sailor, he is a U.S. Merchant Marine Officer and a member of the Stonington Borough Planning and Zoning Commission.  He is an Associate at Centerbrook Architects.

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