Impacts of Terrain on Wind Favor VAWTs

The influence of terrain to enhance and enable future wind energy

Harry Valentine | Nov 04, 2015   writes  for

The future cost competitiveness of wind turbines would include the ability to convert the kinetic energy of high-speed wind to electrical power. Over the next decade, economic constraints would require governments to reduce direct and indirect subsidies to various segments of the energy sector. As a result, alternative wind energy technologies such as airborne turbines and terrain enabled wind power technologies with superior cost performance and higher availability, would likely emerge.”

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We know at Harvistor through our own experience in field testing and supplemental simulations on QBlade (TU Berlin) Starwind5 proves Mr. Valentine correct in his prognosis for the wind industry in general


Most Turbines Today are  RPM limited through expensive braking mechanisms to avoid generator burnout somewhere between 13 and 15 m/s depending on the make model and wind turbine type.

So what happens to the kinetic power in the wind above 15m/s?

This extra wind power  is wasted. “Left on the table” so to speak. Ignored, by all of today’s wind turbine vendors, except Starwind5. (We expect next gen wind turbine design competitors to address Mr. Valentine’s salient points, in fact we welcome it as do investors of under performing wind assets (which is most of them), but so far no challenger which can operate subsidy free has arrived on the scene as of the writing of this post)

The classic legacy wind vendor argument  is as follows: the wind  percent occurrence as told by the wind site’s Weibull curve is “not worth it” with no explanation provided other than that wind range is too minimal in occurrence. We at Harvistor, like Mr. Valentine beg to differ, as most sites with only 3% occurrence of the wind above 15m/s will actually add 8%  and as much as 15% to the AEP Annual Energy Production depending on the quality of the site and accurate placement of the wind turbine.

The real reason  ” it isn’t worth chasing wind over 15 m/s” for those legacy wind turbine  vendors because their designs, today’s HAWTs and VAWTs are incorporating expensive electro-mechanical braking systems of antiquated Aerodynamic rotor designs in order to avoid narrow band and top speed limited rpm generator burnout.

Starwind5 delivers new aerodynamics to the rotor to improve startup an deliver better gust capture conversion to electricity while employing wide band rpm generator sets to allow electricity generation between 15 m/s and 24 m/s  efficiently at lower  25% lower tip speeds with lower bearing wear and  therefore much better price/performance and reliability, for a 35% better LCOE “Levelized Cost of Energy”.


What exactly is “TERRAIN ENABLED WIND POWER? Simply said, at Harvistor it means the installed wind turbine should be able to perform and thrive in semi turbulent wind made up of  ever changing wind angles of attack and wind changes of direction and also changes of wind speed (handling accelerations and slow downs equally well to maximize power output). VAWTS of all types inherently address rapid changes in wind direction. Few  VAWTS today address the rest of the requirements of wind angle of attack, rapid changes in wind speed and heaven forbid, swirling, twisting turbulent wind. None, VAWT or HAWT, embrace both Terrain enabled wind power and high speed wind operation save one, Harvistor’s Starwind5.

The “take home” point to remember is not all VAWTS are created equal, “phi” or “Eggbeater” Darrieus VAWTs can and do address the former and latter challenges to be excellent terrain enabled wind powered generators of electricity, Straight blade “Gyromill” VAWTS address only rapid changes in wind direction, and actual slow down when wind angle of attack varies frequently due to irregular surrounding terrain, which is everywhere, unless the site happens to be bald faces prairie “flat as pee on a plate” or calm waters (means no wind). HAWTS, big and small today address neither of Mr. Valentine’s well targeted requirements for future wind turbine improvements.

Wind Power users and prospective buyers need more articles like Mr. Valentine’s article. These pointed articles on what is needed in wind turbine design clearly shed light on what we need to do as wind turbine designers to get wind of all sizes out of the subsidy game, which is 100% controlled by state and federal and even county governments with the use of your tax dollars. It’s time for change in wind turbine design, the key to any bankable design.

Which brings up a more important point regarding debt and loan financing by banks. Bankers should also demand from Wind developers that they incorporate wind turbine technology which does capture high wind and can operate efficiently at low and medium speeds in uneven terrain. These requirements must be mandatory for bankers before they extend credit to protect their own investors and their depositors.

Wind Powered Facility developers, owners and prospective buyers and investors  need to get brave (instead of doing the me too thing) and vote for change in the wind industry (and get off subsidies) by placing their capital & investment dollars with projects that incorporate  wind turbine designs able to capture high speed wind and terrain enabled wind, the exact sources of energy which will put their investments into the “black” and generate investment returns quickly.

It’s time for Starwind5 Low Mount Wind Turbines. Commercial “phi” or “Eggbeater” VAWTs worked in mass with Flowind in the 1980s as Low Mount Wind Turbines in semi turbulent wind, and they will work again, this time with much lower LCOE and much higher reliability due to much better designs like Starwind5.

As for Airborne wind turbines flying as birds or rotating as paddle wheels high in the air in  search of high speed wind as Mr. Valentine suggests, we at Harvistor think the verdict on such high flying designs is still out.., while they may work (we can certainly adapt Starwind5 to do the same) , we believe that siting can a be a  safety problem (planes, birds, etc..,)  not easily overcome (local, state and country safety laws/regulations)  and the transmission cable length costs can be much more expensive, and, have any of you post readers really ever seen a kite operate in extreme wind?