Bergey 15 Installed in Tehachapi—New Era for Bergey

By Paul Gipe

Bruce Hatchett of Pacific Solar & Wind gave me a call a few weeks ago to tell me they were installing a Bergey 15 kW wind turbine in Tehachapi, wondering if I wanted to get some photos of it. “I don’t do that anymore,” I whined to Hatchett. “I have a full agenda playing with electric cars.”

Not one to be deterred by an aging wind nerd, Hatchett added that the Bergey 15 was replacing a Bergey 10 kW that I’d photographed before. I’d used the photo on the cover of one of my books. “Really?” I asked. I was racking my brain trying to think of it when I looked up from my computer and the photo was staring me in the face.

I’d framed that cover and put it on the wall right in front of my desk. It was one of my better shots showing small wind in action and I’d used it on the cover of my 1993 book Wind Power for Home & Business. And I’d been using that photo off and on ever since.

1993! That was a long time ago. I would have had to photograph that turbine in the early 1990s, suggesting that the turbine had been spinning above the Tehachapi skyline for nearly three decades.

Hatchett had piqued my curiosity.

The wind bug is like a virus. Once it’s in your system it just won’t go away. All it takes is a little nudge and it’s again coursing through your body.

Now, I was hooked. I had to go up there despite the drive, the wind, and the cold.

Hatchett greeted me warmly and then I saw Brent Scheibel on the Bobcat they were using to move stuff around. Scheibel knows his way around wind turbines and heavy equipment. He had also been a good neighbor when I operated the Wulf Test Field for two decades. We bumped elbows, this being Covid times. It was like old home week for wind nerds.

They introduced me to Alejandro Martinez. He was the third person on the team and a wind technician in training. Martinez represents the next generation. Hatchett’s been a Bergey dealer since 1982 and you can’t do this kind of work forever.

Disclosure: I was a Bergey dealer in the early 1980s and sold a few—very few—machines before I moved to California. I know Mike Bergey and I knew his dad Karl. I’ve been a fan of Bergey turbines for nearly four decades.

Bergey Country

Tehachapi and the adjoining High Desert is Bergey Country. I counted three operating Bergeys from the installation site and I know there are more than what were visible. And they were all operating—typical of a Bergey. You seldom find one down—or at least stopped.


I’ve used a series of photos illustrating the installation of a 10 kW guyed Bergey in my last two books from a site in Tehachapi. I don’t know if that machine is still there but there have been a lot more installed since then. There’s a Bergey just about everywhere you look in Tehachapi.

Tehachapi is a good windy place for Bergey.

The small wind industry needs new sales so there are people around like Hatchett and Martinez to service the machines that are still operating—like those in Tehachapi.

That’s good I thought to myself, I am glad Bergey’s selling wind turbines in Tehachapi again. The small wind turbine market has been in the doldrums for several years now so it’s good to see one going up. No, that doesn’t quite capture the situation. Cheap solar PV has killed the market. It’s been a bloodbath. Bergey is about the only company left in North America and that’s largely due to the stubbornness of Mike Bergey—and the fact that he makes wind turbines that last.

Radical Departure–Trademark Furling Gone

Bergey’s new machine carries the Bergey mantra of “keep it simple” to the ultimate extreme. While other wind turbine designers developed ever cleverer mechanisms for feathering the blades in high winds, Bergey continued paring down their drive trains to the bare minimum using the force of the wind itself to furl the rotor about its axis at the top of the tower toward a hinged tail vain. This became the tried and true hallmark of Bergey’s rugged design and probably one of the reasons they’re still in business and everyone else isn’t.

In a radical departure, the Bergey 15 has gone a step further. It doesn’t use furling at all. Nope. It uses dynamic braking—and only dynamic braking. It’s also dispensed with the pultruded fiberglass blades that were another feature of Bergey turbines. Blades on the new machine are fully contoured on both surfaces and don’t twist longitudinally like the old Bergey Blades.

And if all that wasn’t shocking enough, the thing was painted gray—not the Bergey yellow that I’ve known for more than four decades. Is nothing sacred?

The gray is a sign of the times. We want small wind turbines accepted in the community and if that means dropping bright yellow for dull gray, so be it.

Dynamic Braking & Stall

The first thing you notice about the Bergey 15 is the heating elements protruding from the back of the main frame that supports the generator. These resistive heaters and sophisticated design of the new airfoil enable Bergey to stall the rotor in high winds rather than furling the rotor to control overspeed. That’s the theory anyway.

The powerful permanent magnets in the generator can bring the rotor to a halt in normal conditions. In strong winds, there’s a lot of power that needs to be dissipated quickly and that’s where the heating elements, or dump load, come in. Bergey can program how much load is dumped to the heating elements to put the rotor into stall and then bring the rotor under control.

That Bergey put the dump load at the top of the tower shows that Bergey knows small wind. Putting the dump load down on the ground introduces numerous paths to failure. The load needs to be on the rotor at the top of the tower and that’s just where Bergey put it.

It’s a bold move on Bergey’s part.

Others have taken this path. I was a critical of Southwest Windpower when they chose this strategy for the Skystream. I expected to hear reports of hundreds of Skystreams losing their 3.7-meter diameter rotors in storms. They didn’t. I heard a rumor of maybe one turbine losing a rotor this way. Southwest Windpower’s David Calley tried to convince me that the powerful Neodymium magnets they used were strong enough to bring the rotor to a halt. He might have been right. The company failed for other reasons.

Still, I am an old-timer. We learned the hard way that the Danish design admonition that all wind turbines must have some aerodynamic means to control the rotor under emergency conditions grew out of painful experience. And that meant some mechanical device whether it is furling, as on the earlier Bergeys, or pitchable blade tips on the Danish machines of the 1980s.

Forty years ago stall was simply not enough with the technology then available.

Stall using today’s powerful permanent magnets coupled with modern electronics may work reliably. Time will tell. It worked for Skystream. But the rotor on the Bergey 15 sweeps seven times more area than the old Skystream.

And that may be part of the reasoning behind the Bergey 15. It’s nearly twice the size of the Bergey 10. The Bergey 15 uses a rotor 9.6 meters in diameter. That’s nearly as big as the Carter 25 machine of the early 1980s. At that size maybe furling just doesn’t work well and you need to do something different.

If there’s a wind engineer out there that can make dynamic stall work in a machine nearly 10 meters in diameter, Mike Bergey’s the man.

Repurposing Carter Towers

Jay Carter installed 300 of his two-bladed, downwind machines in California, including Tehachapi, and he installed them on tilt-up tubular towers. While his turbines are long gone, his towers are still around. They’ve been used as light standards for football fields in Bakersfield and they’ve been repurposed for, you guessed it, Bergey wind turbines in Tehachapi.

That turbine I photographed long ago was mounted on an old Carter tower. And the new Bergey 15 that replaced it was being installed on the same tower.

They’re a good match. The Carter 25 used a 10-meter rotor and the Bergey 15 is almost the same size. If that Carter tower can take a two-blade, downwind turbine with all it’s twisting and thumping, it can surely handle a smoother running three-blade, upwind Bergey.

Hatchett and his crew adapted the mounting plate for the new Bergey to fit the old Carter tower and with Scheibel’s skillful use of the Bobcat they mounted the generator and main frame carefully onto the tube. The Bergey 15 main frame is not something you can easily manhandle. It’s a hunk of steel and magnets. Moving it takes equipment.

I left before they raised the machine, but they got it up and running that same day.

Specific Area Much the Same

The trend in the wind industry is to design machines for sites with ever lower average wind speeds as we begin to exhaust the windiest sites. These are referred to as Class III machines. For example, large commercial machines were being installed in the Midwest in the last decade with Specific Areas of 4.8 to 4.9 m²/kW of rated capacity.

Essentially, these machines use a very large rotor for a relatively low generator capacity in what French engineer Bernard Chabot called the “silent wind revolution.” This contrasts markedly with the Carter 25 of the early 1980s. The Carter had a Specific Area of 3.1 m²/kW. Much worse than the Carter 25 was the Fayette 95. The Fayette 95 claimed it could generate 95 kW with an 11-meter diameter rotor, giving it a Specific Area of 1.0 m²/kW.

When Southwest Windpower introduced its Skystream, they bucked the trend in small wind turbines of inflating the generating capacity. They targeted broad areas of the country with a fairly short tower and rated their turbine accordingly.  Their small turbine was advertised to deliver a Specific Area of 5.7 m²/kW.

This is still a far cry from the approach advocated by one of the founding fathers of wind energy, Ulrich Hütter, in 1958. He designed his famous turbine at the University of Stuttgart with a Specific Area of 9.1 m²/kW.

Eocycle, the Quebec manufacturer of small wind turbines, comes closest today to Hütter’s approach. Their Class III machine, the Eocycle 25, has a Specific Area of 8.7 m²/kW.

The Bergey 15 sweeps nearly twice the area of its predecessor, the Excel 10. Yet Bergey doesn’t label the machine the Bergey 20. Instead Bergey opts for de-emphasizing generator size and. As a result, Bergey’s design delivers a better Specific Area than the Bergey 10 of 4.6 m²/kW versus 4.3 m²/kW.

In contrast to Eocycle, Bergey’s are designed for windier Class II sites that would be unsuitable for the Canadian turbine.

The Great Gray Hope

For the remaining small wind turbine dealers like Hatchett, the Bergey 15 is the great gray hope. According to Hatchett, it’s the first time in more than a decade that wind is a better buy than solar in the windy high desert of California.

This is in part due to Bergey simplifying the turbine further and nearly doubling the rotor area. It’s also in part to subsidies that still exist for small wind in California.

I’d thought all state subsidies had been eliminated years ago after a major scandal involving a fly-by-night small wind company that was promising outlandish returns. Indeed, that program was eliminated.

However, another program, promoting what the state calls “self generation.” California’s Self-Generation Incentive Program (SGIP) pays a substantial chunk of change—upfront—for small wind based on performance at a wind speed of 30 mph (13.4 m/s).

Hatchett says that the Bergey 15 I saw being installed qualified for a whopping $19,000 in cash subsidies from the state.

And the recent Covid-19 stimulus packages that have passed Congress have extended the small wind tax credit as well.

With the SGIP, federal tax credits, and the Bergey 15’s much greater generation than its predecessor, small wind is again looking up in windy places like Tehachapi.