There isn’t any doubt in my mind that wind power will play a larger role in the United States in the years ahead; so when I had a chance to set up a tour of a large wind turbine installation for SBE Chapter 14, the Connecticut Valley Chapter, I jumped at the chance.
In July I was driving out to do routine transmitter maintenance on WAPJ(FM) in Torrington, Conn., a community-based, noncommercial station with which I have been involved since its inception in 1999.
Like most broadcast engineers I look at towers as I drive around. On this day, much to my surprise, I spotted a strange new structure on a hill on the west side of Torrington. It was a self-supporting tower with a wide face and what looked like a platform on the top. It dwarfed nearby farm silos; I estimated that it had to be close to 200 feet tall.
Fig. 1: Artist’ conception of a single-level 50 kW wind turbine. It had a uniform cross section, unlike most self-supported towers, which are tapered at least to some extent. It looked like a few radar installations I had seen; however it was not at the top of the hill but on the side. Our area is well covered by FAA and weather radars, so I couldn’t image why anyone would put radar in Torrington.
Clearly this wasn’t a broadcast or cellular tower; it was too low for the former and too wide for the latter. The idea that it might be a wind turbine crossed my mind, but this was unlike any wind installation I had seen.
It only took a few minutes to find the tower, which is located on a working farm. As I drove up I spotted two small wind turbines at the base, turbines that would later be hoisted to the top of the structure. Clearly this was a work in progress. Carpenters working nearby gave me the name of the company that was putting up the wind turbine.
Mid-sized
When I got back to the office that day I found the website and sent an e-mail inquiring about the installation. The next day I heard back from Dave Hurwitt, vice president of marketing.
Fig. 2: Arist’s conception of a six-level, 300 kW turbine. He told me that Optiwind was founded in 2007 by Russ Marvin, an engineer with a background in fuel cells and fan technology. In examining the wind market, he found vibrant supplier markets for large turbine applications like wind farms and small turbine applications for residential use, but little technology customized for the midsized market.
These customers — schools, manufacturing plants, retailers, water treatment plants, etc. — have different needs and locations than wind farms. Marvin felt that the products serving this market were too expensive and didn’t meet its needs because they essentially were reduced-scale industrial turbines.
He raised venture capital funding in 2008 and now has a company of 26 people based in Torrington manufacturing a new style of turbine. They hope to launch commercially beginning in 2011; the structure I’d encountered was a prototype.
The company expects to fill a market need for wind turbines in the 100 kW to 1 MW range. It claims several unique features including multiple small turbines in place of a single large unit and a supporting structure that actually accelerates the wind into the fan blades.
Significant installation savings are promised with their design, which eliminates the need for an expensive crane; the tower is assembled horizontally on the ground and then raised to the vertical position using hydraulic jacks!
Another significant expense of large turbine installations is the concrete used in the base. Instead of using massive amounts of concrete to support the tower, Optiwind uses pilings that go down 50 feet or more and are filled with concrete, saving in concrete costs. This method also allows the design be installed in locations where it is difficult to bring in large quantities of concrete.
The users for whom Optiwind hopes to install its turbines generally will experience much lower wind speeds than you find on open-prairie wind farms.
As such, Optiwind says it has uses a system that accelerates wind into a series of smaller, quieter fans that are safer and require less maintenance. By using fixed pitch blades, permanent magnet direct drive generators and sealed bearings, they reduce maintenance and ownership cost.
Fig. 3: System under construction with two, 25 kW direct-driven wind turbines installed at the top of the tower. When completed, there will be a total of three levels with a capacity of 150 kW. Also, the turbine reportedly does not cause the interference issues of conventional turbines because they don’t require lightning protection in the blades. The blades are not the highest point and thus don’t requiring lightning rods in them. Protection is at the top of the tower instead.
Prototype
Our meeting started at the Optiwind facility in an old factory building formerly used by the Torrington Company. After being treated to pizza we sat down for an informative PowerPoint presentation by Dave Hurwitt.
He covered economies of wind generation and said that large, single-blade wind turbines are fine for generating large amounts of power, for instance greater than a megawatt, but that they are very expensive. Optiwind’s economical design would allow the turbine to be located where the power is needed, such as adjacent to a factory, high school or government building or perhaps even a broadcast facility.
The design uses a tower that is 199 feet tall to avoid the need for FAA obstruction lights in most areas. That height can support six levels or rings, with each ring supporting two, 25 kW AC alternators for a total capacity of 300 kW. The Torrington installation will be a 150 kW installation with dual five-blade driven generators at three levels.
Then we drove up to their installation on Klug Hill Road in Torrington.
As you can see in the pictures, things had changed since my visit a month earlier. The first of three rings had been hoisted to the top of the structure and the five-blade fans had been connected to the two 25 kW AC turbines.
Fig. 4: First level being installed on the ground prior to being hoisted up to the top of the 200-foot tower. This is what I saw when I first visited the tower in July. The entire ring assembly rotates around the tower so that it is always facing into the wind. The cylindrical housing between the turbines is designed to increase wind speed by 1.7 times, increasing efficiency significantly.
As you can imagine, maintenance on a traditional wind turbine with a blade 100 feet or more in length is problematic. Any work requires a large, expensive crane; swapping out a generator or fan blade can take weeks, during which the system is offline.
Optiwind says it designed its system for ease of maintenance. The structure has a built-in hoist system eliminating the need for a crane; individual components such as the fan blades and generators can be swapped out relatively quickly. The failure of a single generator or even a group does not take the entire unit offline.
Other advantages include elimination of low-frequency acoustic noise and of interference to VHF and UHF signals caused when conventional designs are placed near transmitting antennas.
The Optiwind design starts producing power with wind speeds as low as 4 mph and is capable of operating up to 40 mph.
I’m going to stay in touch with the folks at Optiwind. Perhaps someday I’ll be able to specify one of their wind power systems for one of my broadcast clients?
John Ramsey is chief technical officer with Marlin Broadcasting and president of Ramsey Communications Services. He is chairman of SBE Chapter 14 in Connecticut.
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