Published on April 24th, 2014 | by Mike Barnard23
UGE Vertical Axis Certification: Behind The Hype
April 24th, 2014 by Mike Barnard
UGE has taken an excellent and necessary step, one most small wind turbine manufacturers never do: they have had independent certification of one of their devices performed. A wholly praising article was published in CleanTechnica on April 22, 2014, just a couple of days before this article.
The article, as with most press on the subject, made several positive points about the UGE, some accurate, some slightly less so, but any actual analysis of comparative output of generation and implications for lifecycle costs of electricity was conspicuously missing. This is a fairly critical point when considering wind generation technologies.
Let’s make one thing clear: I like UGE as a company. They sell complete renewable energy solutions including solar, wind, and inverters at a not unreasonable price with packages for residential and industrial settings. The UGE VAWT is an attractive device and some people will be willing to pay a premium for aesthetic values as our previous article points out. I have no problem with people who have lots of money spending it on good-looking objects that generate reasonable amounts of electricity. Personally, I’ve paid a premium based on aesthetic reasons for consumer electronics, vehicles, clothes, furniture, and a number of other things, so people basing part of their decision on that factor is completely reasonable. UGE services a specific subset of the renewables market. It has a solid track record of growth and a partner model which extends its reach. It’s a good business model and the helical vertical axis wind turbine is part of their chosen differentiation.
But feeding the vertical axis wind turbine hype mill as these articles tended to do is a bit more problematic, as it makes it seem as if certification implies equivalence to horizontal axis wind turbines, which isn’t the case. And pretending that this will make a significant difference to wind generation is also problematic.
The UGE certified device appears to be the VisionAir5. It has a published power curve, although it’s unstated whether it is the same one provided by and certified by Intertek. It’s labeled as 5, which implies something in this space, as more often than not numbers in the name of devices denote the nameplate capacity rating in kilowatts or megawatts. However, the VisionAir5 has a listed power output of 3.2 KW in the table of specifications. Even there, some inflation appears to be occurring, as the actual power curve shows an average power of 2.5 KW.
It’s worth comparing this to a power curve for a similarly rated HAWT, but it’s a bit tough as the VA5 is rated at 3.2 KW, which is an unconventional number. However, let’s take the Bergey Excel 10 KW device as a comparison. I would have used the 6 KW Bergey device but the link to the certification report was broken at the time of analysis. At least right now, Bergey publishes their certification report, while UGE doesn’t.
I’ve scaled the power curves to be easily comparable along the horizontal axis. Something that leaps out is that the Excel 10 actually has a peak power output of 12.5 KW but is labelled a 10 KW device, while the UGE has a maximum 3.2 KW output and that is the referenced output. An apples-to-apples comparison at the same 11.5 m/s wind speed shows that the UGE is actually comparable — by that simple and reductive measure — to a 1.8 KW device, not a 3.2 KW device. UGE claims an average power of 2.5 KW in their power curve material if not their other documentation, which is likely the number that is most comparable.
It’s worth looking at swept area and comparable production as well. While VAWTs tend to be mounted lower with most of UGE’s home material showing very low mounting on rooftops and the like, let’s ignore the mast height for now, assuming if you were serious about wind generation you would put the device as high as possible. The Bergey 10 KW device for example is specified usually with a 30 meter (100 ft) mast. I’ve created equivalent Bergey scaling for swept area assuming lowered power ratings, knowing that power output is linear with swept area all else being equal.
It’s pretty obvious from the table that at the maximum UGE power output, the Bergey would require only 74% of the swept area to achieve similar output at its nameplate capacity, an already unfair comparison as this isn’t Bergey’s maximum output but its 11.5 m/s output. The comparison just gets more and more in favour of the Bergey as more realistic comparisons are made at 2.5 KW and 1.8 KW, with a Bergey device only requiring 58% or 52% of the swept area to achieve similar output. VAWTs already require substantially more material — a key factor in cost of manufactured objects — than HAWTs for the same swept area.
Paul Gipe has done this analysis already in his comments on the UGE announcement, so I will quote him.
Worse, UGE’s data confirms the fundamental disadvantage of most VAWTs, they are much more material intensive than conventional wind turbines. The relative mass of a wind turbine—a measure of its material intensity that includes the rotor and nacelle—is often used as a shorthand for its expected cost. The more the relative mass of a turbine, the more its likely cost. The specific mass of UGE’s VisionAIR is four times more than Bergey’s Excel 6.
However, beyond relative mass for the same swept area, the analysis shows that for equivalent power output, much more swept area is also required, so the additional cost of materials is then further multiplied by a factor of almost two. Mr. Gipe’s analysis of relative mass shows that it’s over four times more.
These pretty basic comparisons show the reason why the lifecycle cost of electricity (LCOE) for horizontal axis wind turbines is always better than the LCOE for vertical axis wind turbines. They have to sweep twice the area with four times the material to achieve the same capacity. Added to this is that they are so often sited in very poor wind resources with masts that are too short because of their ‘advantage’ of being able to catch turbulent air, and the capacity factor drops tremendously.
This is something our previous article got backwards when put in relative terms. “The vertical system is far more compact than the now-familiar horizontal axis wind turbines,” that article stated. It’s true the UGE 3.2 KW device is much, much smaller than utility scale wind turbines, but if it were scaled up it would have to be twice as big and four times as heavy, with a correspondingly more robust tower. The Bergey 10 KW device is also much smaller than a utility-scale wind turbine, but if scaled up would be roughly the same size.
Our previous article had it right that the certification raises the bar for the also-ran category of vertical axis wind turbines, making it even harder for this lesser technology to get a foothold. That’s probably a good thing, but it also is a double-edged sword for UGE as they try to convince people that their obviously inferior certified results are still worth investing in.
On the noise issue as well, it’s important to not buy the hype over the substance. UGE makes the claim of being extremely quiet, but what do the numbers say? Well, their published numbers state 38 dBA as the noise of the VisionAir5 device. The Bergey Excel 10 is rated at 42.9 dBA, and the rated 4.9 dBA is an audible difference to human ears although not an enormous one. But that additional 4.9 dBA comes with three to four times the electrical power generation. UGE claims that their uncertified UGE 9M device is <38 dBA at 12 m/s, which is interesting as they scaled it up by a factor of roughly four yet assert lower noise; this is unlikely and certification would clarify this. It is possible of course, as VAWTs just can’t spin as fast due to inefficient capture of airflow, but it’s unlikely.
This only becomes important in a minor way if you were to put this device on the roof of a house over a bedroom, which UGE implies is reasonable but Bergey doesn’t begin to think is reasonable. The Bergey device with its 30 m mast would see attenuation of noise down to about 40.5 dBA at the base of the mast, which is close to World Health Organization noise recommendations for nighttime noise already, and even then Bergey devices aren’t put right beside homes typically but where the air is cleanest in a paddock. The only real value that the UGE statement of quietness brings is that with a really small, low output device you can put it on top of homes where the wind resource is poor without disturbing peoples’ sleep. This isn’t necessarily a great tradeoff as it takes an inefficient device and reduces its effectiveness further.
It’s great that UGE went the extra mile and became certified. But it isn’t particularly transformative. What will be transformative for the distributed small wind market is the new United Wind offer combining excellent analytics of output and fiscals with Bergey and other certified horizontal axis wind turbines, allowing guaranteed returns and a no-money down lease. But that article is still brewing after my conversation with the CEO this week.
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