Starwind5 Modular Design : EHD vs XHD

We have been here before…

Flowind 3 blade 17m dia 30m H

Flowind Circa 1992:
SHD “Standard Height Diameter” 160kW NP on Left, EHD “Enhanced Height Diameter” 330kW NP on the Right , the latter at the time, although only two were ever made,  was one of the biggest production turbines of its time, designed to replace on same mount the 160kW system. (Altamont Pass in N. CA, USA)

SHD vs. EHD “Enhanced Height Diameter”

Yesterday’s XHD 3:1 Enhanced Height Diameter downsized

What we have learned… 400kW NP production Darrieus “Egg Beater” 3 Blade VAWT  in 1992? really? (well almost, the two early EHD/xHD examples were  de-rated to 330kW after field trials)

Going places where no wind turbine had gone before commercially, Flowind 160kW SHD VAWTs were the first (unknowingly) high density/per acre power deployment in 1984, and hardly anyone knew it. Pacific Gas and Electric was the benefactor, where Flowind alone produced 1% of all of California electricity needs with a fleet of 800+ SHD Flowind turbines. Hard to believe but really true (see Paul Gipe’s site for more info at, he was there when it all went down.) SHD was almost symmetrical about a 1.18:1  ratio. (Cape Chat Eole at 4.2MW nameplate, considered an SHD design at 1.5:1 , was de-rated to 2.5MW for a 5 year operational contract built by the Quebec division Shawinigan Engineering, now part SNC Lavalin is still the all time champ… Huge cost over runs, brake re-work, etc.., Today it still dwarfs HAWTs in size in MW NP)

Cape Chat 4_2MW NP derate to 2_5MW circa 1988

Cape Chat, Quebec Canada (built in 1988 and still standing)
@ 4.2MW NamePlate NP the all time MW NP champ of the last millenium, it was de-rated for a 5 year contract to 2.5MW NP.

What happened to  early large scale VAWTs? The HAWT  spin doctors happened, and they received more R&D dollars to leap frog NP kW power label of the Flowind systems.

Yes Flowind also made more than a few mistakes along the way in those pre-Internet times of expensive supercomputing. (more on this a bit later).

35% Taller, Double the power…

What we did learn from studying the Sandia National Labs web site on “Historic” or “Old VAWT Technology” information is that Flowind did indeed more than double power output with a modest 35% increase in height, and a reduction of about 15% in the working diameter (which raised the rpm 42% from 38rpm on average to 54 rpm, where the designed called for constant rpm to drive the transduction generations directly to the grid)

Flowind called the new height to diameter relationship “EHD” or Enhanced Height Diameter, which in effect was a 3:1 Height Diameter ratio of about 17m  working diameter and 51m in height which you see in the picture above. Originally the EHD  design was  rated at 400kW NP, however real life performance was disappointing versus the simulated expectations of the time, and the EHD was de-rated to 330kW NP. Even still an excellent advance.

What was important in the EHD ratio of the time was the increase in the vertical size of the effective working diameter, nearly tripling the effective working zone, and even though the working equator diameter was reduced 12%, the net result was a doubling of power through a 2X increase in torque and 42% higher rpm.

All for Not… repetitive Aerodynamic Stall and Aeroelastic Flutter = Cracked Connectors

Alas it was all for not when G.W. Bush came to office and immediately cancelled the Federal Wind Credit in 1997, causing Flowind, the only commercial VAWT dealer of the time to shutter it’s doors, along with Carter, AWI and Zond (Later an asset buy by GE), completely wiping out the large US Wind turbine industry in a single stroke in favour of more oil and gas industry (and coal and nuclear industry) subsidies.

Flowind had its own technical problems with the first fleet of 800 systems, as they had to all come down for maintenance as cracks appeared at the rotor connector joints and needed to be repaired after only 6-7 years of operation, an unpredicted and costly repair, costs which contributed to Flowind’s financial duress and eventual bankruptcy.

The Bottom line with Flowind is they did not have the aeronautical understanding required to fly their system correctly, which any keen observer at air shows will understand when an airplane does the 360 degree loop, it creates lift on the wings by changing the airfoil shape with the ailerons so lift is towards the center, not away from it, the common mistake of all early VAWT efforts still committed today by many small VAWT vendors. Flying away from the shaft together with “fly away” centripetal forces needs stronger and thicker materials to keep the VAWT structure together and adds weight, all not good for start-up, bearing life and over speed control (a larger more expensive and regularly used and replaced brake is required), the three biggest O&M and Capex Cost failings of earlier VAWTs.

Add in the fact their EHD was really a 3:1 eXtreme Height Diameter , made the whole cable and stay tie down method too costly to erect and service

XHD 3:1 resized to EHD 2:1… a bit of secret sauce (and ROP, install/maintain savings)

“What we have found in the new Starwind5 is we can do away with the expensive to install and maintain cables and stays used by Flowind and others in favour of using 2:1 EHD ratio which makes it easy to lower and erect with standard G/N “Gravity Neutral” poles and a low cost winch, in minutes rather than costly hours. Add this to the fact the Starwind5 five rotor blades fly towards the shaft to create an even stronger structure at high rpm and you have a real winner!”

Robert Reive Managing Director Starwind5, February 2016.

Enter Starwind5… Lighter, More Responsive, Lower Cost, Stronger and now EHD


Starwind5 Happy Earth Day Background ScreenShot

Like Flowind, Starwind5 has travelled a very long road to get to commercial reality in 2016. Starwind5 has been 8 years in the making come December 2008, where it can be said Flowind also took 8 years to get to commercialization, where Flowind really started back in 1976. Many in the know would say they collaboratively hijacked the Canadian NRC National research Council efforts by Raj Rangi and Peter South (started in 1966) at the Canadian Ministry of Natural resources. Flowind therefore really started by proxy in 1976 via Sandia, if you trace early Sandia National Labs (USA) collaborative involvement with the Canadian NRC , as Rangi and South tried to breathe modern engineering into the 1925 Georges Jean Marie Darrieus (France) Egg-Beater VAWT design using modern wind tunnel testing techniques in Ottawa Canada over an almost 20 year period. Unfortunately Flowind’s lack of sound aeronautic and aero-elastic design engineering advice was the root cause of vibrations and harmonics which ultimately caused the rotor cracks in the first place. Peter South went on to try with Addecon in Pincher Creek, Alberta with TV Tripod VAWT suspension and four blades, a design also fraught with vibration that ultimately failed.

A Past Reflection with different vibrations.., another lesson learned: Addecon

P South Addeccon Pincher Creek AB 

4 Blades, 3 Towers = 6 Vibrations per rotation…. hmm

Pincher Creek AB, circa 2004, P. South Addecon (Formerly MNR w/ R. Rangi)
A “Tweenie” at 1.5:1 Height to Diameter between SHD and EHD…


Starwind5 has learned from Flowind (and Sandia’s) past mistakes, and also has really good sound aeronautics advice, experience and expertise that reaches back to the  1940s, where we have combined all this know how into a sound aero-dynamic and aero-elastic design with little vibration and even torque distribution to extend bearing life and ease rotor connector wear to hit a 20 year usable life and really take the Darrieus design to new levels, combined with new EHD driven performance, new material strength and reliable geometry and telemetry, all of which is required to make your power generation project bankable.

It goes without saying that controlling harmonics means less vibration which equals longer bearing life without much maintenance if any, and together with flying toward the shaft means very little if any rotor end connector wear, a lesson learned from Addecon. (Thanks)

EHD the last word in VAWT design…

Starwind5 EHD in 2:1 Form…

It’s an old adage, one we take seriously at Starwind5, “we stand on the shoulders of giants” to see and create the future, and those that went before us like Flowind, Sandia and Addecon have helped every step of the way.

Starwind5’s EHD “Enhanced Height Diameter” option and the use of five fast blades with a rotor system having over 20% greater solidity then in the past 3 blade Flowind design, as well as flying toward the shaft, makes  Starwind5 a strong reliable design with minimal vibration and excellent performance, 35% more in fact that previous Flowind designs, and a definite world beater in 2016.

Kudos to Georges Jean Marie Darrieus circa 1925 🙂

GJM Darrieus Patent 1925 FranceGJMD Portrait