Comment by kbenson | Hacker News Reader

Comment by kbenson | Hacker News Reader

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> a 2MW "mast" that can compete with today's technology is going to be crazy tall

I wonder about how the power generated scales as the size increases. It's 100W at 9', and 4kW at 40'. At ~4.5x the height there's 40x the power generated. It's foolish to assume the same exponential gains apply continuously, but given the reduced footprint, is it possible that laying out five of the 40' units is sufficient for 2MW (edit: wait, I totally fudged that math, so this point doesn't really make sense), and at that size, you might be able to just use a bucket truck for maintenance?

We shouldn't assume just because it's a new technology that the same problems don't need to be addressed, but we also shouldn't assume the same problems need to be addressed in the same manner. This article doesn't do a lot to explain the details, and as you've explained I've heard that maintenance of wind turbines is where a lot of the money to run wind farms goes, so it's interesting to look at new designs from the standpoint of how it may radically change maintenance, not just scale with the current methods.

That said, you obviously have more experience with this than me, so hopefully you'll be able to provide some more perspective on the ideas here.

P.S. Something that occurs to me is that I have no idea how they stop the oscillation caused by the wind for maintenance on those. You can lock the turbine blades, but I'm not sure how you prevent something made to oscillate naturally in the wind from doing so, easily.

P.P.S I totally messed up my math because I wasn't thinking straight, 5x4kW is not even close to 2MW. I'll leave this here for historical purpose, but much of my point lacks any weight now...

> I wonder about how the power generated scales as the size increases.

Yes, there are two factors, wind speed and blade swept area.

Height: "Energy in the wind is not linear. Double the wind speed and the energy increases not by double but by a factor of 8. As speed increases the power is increased by a cube factor."[0] You want to capture that higher elevation wind to maximize power output while also factoring in the cost of the tower heigh and stability. Most 2MW turbines have a tower height of between 60 and 100 meters depending on the local wind profile.

Blade Swept Area: "Energy captured by the rotor is linear. If you double the swept area, you double the amount of energy it can capture."[0] If you can double the length of a classic wind turbine the swept area increases by a factor of 4!

This is where the problem lies. Even if there was the cost efficient method of building a 2MW Mast turbine the swept area would only be a fraction that of a classic wind turbine, say only 45 degrees in each direction. This makes the height necessary just unrealistic. Just thinking about an entire farm of these these wobbling back and forth makes me giggle.

> we also shouldn't assume the same problems need to be addressed in the same manner.

Totally agreed! But these fiberglass "Masts" are still in the outdoor environment. They still get struck by lightning, they still need generators replaced, they still have electronics, etc. This is why I have moved away from my believe system that wind energy will make up a huge factor of our energy production needs and have become very bullish on solar. Mechanical electricity generation requires maintenance and moving parts increase complexity exponentially. Wind energy is no longer a technical problem to be solved, we have already done that with three bladed turbines, it's a financial and incremental improvement problem.

[0] http://www.power-talk.net/swept-area.html

Thanks for the references on how this would function. I wasn't really assuming a 45 degree oscillation, I wonder what oscillation they they are assuming in their projections. I imagine a single "blade" would be moved less by the same amount of wind, but there are probably plenty of factors I'm not considering. I imagine scaling these up you have some pretty crazy engineering problems to overcome, like how to deal with the repeated strain at the base.

In the end, it may be that the better use for these is indeed the 40' 4kW version for the back yard. I could see that pairing with a bunch of chained Tesla powerwall units to good effect.

> I imagine a single "blade" would be moved less by the same amount of wind, but there are probably plenty of factors I'm not considering.

Modern wind turbines have a cut in wind speed of maybe 3.5m/s and my guess is that these wind masts don't have a cut-in speed. So in low wind resource regions they may be effective at capturing market share because they can produce electricity with only a slight breeze.

> I imagine scaling these up you have some pretty crazy engineering problems to overcome, like how to deal with the repeated strain at the base.

Modern turbines have plenty of vibrations that the tower and foundation have to deal with. I was in the nacelle of a wind turbine when a surprise small tornado came to town, we were full on rodeo mode with the tower swaying back and forth. That being said on a day to day basis most of the forces are countered with the rotating mass (someone else can explain this better than I) so the turbine doesn't transfer much horizontal load to the foundation.

With the wind mast there would be most horizontal load on the foundation as there is not another blade or two to counteract the motion and thus it would require a larger foundation.

If you want to buy a 4kw turbine you can find one used for under $7k which is much less than this new technology. As better 3 bladed tech comes online there will be a larger second market for used turbines and thus might be a better economic option then buying unproven new wind mast technology. Pairing used or new wind tech to batteries can really benefit the offtaker depending on the marketplace.

About maintenance of wind turbines: but when you compare the actual costs of O&M on wind turbines they are actually still pretty cheap compared to traditional energy sources, and it will likely get cheaper as the tech matures and common problems are addressed through improved manufacturing and better tools.

But I agree that for places on earth close enough to the equator to have plentiful solar irradiance, also in the winter, solar looks like it is going to win hands down.

> it will likely get cheaper as the tech matures and common problems are addressed through improved manufacturing and better tools.

Yes! They are very cheap compared to coal fired power plants. During University I helped prepare one of the first wind turbines (call the wind furnace[0]) ever built to be shipped to the Smithsonian. This initial prototype turbine was built in 1972. Now 43 years later we have massive adoption of the technology and we are still ironing out the bugs. Big O&M cost are blade repair, gearbox and generator swapout and yes they are getting cheaper, but most of the these costs are the cost of the crane coming in.

Modern turbines are fairly new to the market and we are still collecting data on how the components last over time. Most manufacturers, Siemens, GE, Gamesa, etc provide a 3-5 year warranty. Their incentive is to produce as many cheap components as possible that last the 3-5 years so they don't have to replace the parts under warranty.

Wind turbines are very complex feats of engineering, solar panels on the other hand are simpler to make than sheetrock and as we scale that technology and come up with creative financing options that guarantee savings market penetration is going to be even greater than wind even in regions far away from the equatorial region.

creative finance is the key to clean energy scale and adoption, not technology.

[0] http://www.umass.edu/windenergy/about/history/furnace

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