Comment by startupfounder | Hacker News Reader

Comment by startupfounder | Hacker News Reader

I have repelled (using Industrial Rope Access) off hundreds of multi-megawatt Wind Turbines on $1B+ wind farms around the world to inspect and repair the 13+ ton fiberglass blades and wanted to give my 2 cents. [A clarification: Wind Turbines generate electricity, Wind Mills mill flour. It's a small but important detail.]

Operation & Maintenance expense is my biggest issue with new technology. I have met many design engineers that have never been inside of a nacelle or even visited a wind farm. In the real world generators and blades break, hurricanes, lightning, shit happens. Cranes are extremely expensive and a 2MW "mast" that can compete with today's technology is going to be crazy tall. How to repair a lightning cable? Cranes are over $10k per day and cables take a few days to fix.

Today there is a 26 story ladder in the interior of the support tower that people climb up to fix hardware in the nacelle. To inspect the blades we then rig our anchors to the generator, pop out the top hatch and repel over the nose cone and down onto a blade in the "down" position. The only specialized hardware needed is anchors, carabiners, ropes, harness and helmet.

Vortex Bladeless would be impossible to inspect and repair using this method, yes drones are great for inspection, but what about repairing a stress crack on the tip? You would need a crazy tall crane that is even more expensive and with cranes the wind speeds need to be a fraction that of Industrial Rope Access. This means your available repair days are even less and the turbine has to be shut down for longer for the fix to occur.

I am all for new technology and crowd financing, but there are many practical obstacles this team needs to overcome in the design phase to build a product that can actually scale in the real world.

Also, feel free to AMA if you have specific wind turbine questions.

It is certainly a valid point that maintenance costs are a huge burden on wind farms, that said, you cannot really jump to the conclusion that 2MW of generation capability would be deployed as one giant tower. From the web site it seems it would be 2x 1MW towers but it could easily be 10 separate 200kW towers or even 100 20kW towers. The density of a this with respect to wind turbines seems a bit higher.[1]

That said, their web site makes them out to be idealistic dreamers (I know that sounds judgemental but it is the impression I got from it). If Google were still running the RE<C initiative I'd suggest they put a couple of test units next to the data center at The Dalles (its on the Columbia River and was always windy whenever I visited there). If they can build a 4 - 10kW one and its something you can stick in your backyard, I would expect that they can build a small business out of that to develop the expertise to build the big ones. I worry that if they try to do too much too soon they will become overwhelmed.

[1] Caveat the amount of energy you can pull out of a moving mass of air at STP is finite.

Most wind farms are on leased land and the fee is based on the MWh generated. Farmers want to maximize revenue from wind harvesting while minimizing crop harvest revenue loss. Remember roads are built between turbines for big cranes and trailers to deliver and install the turbines and there is parking underneath the turbine for maintenance workers.

Having 500 4kw systems cuts into harvest revenues as do 10 20kw systems as the equivalent square footage lost to generate 1MWh is an order of magnitude larger.

Also, wind turbines blades in colder climates tend to accumulate ice in the winter and thus are permitted to be located away from populated areas. Some big chunks of ice have been flung hundreds of meters. The larger the blade the further the distance you need to put your structure for safety reasons. These masts shouldn't be put on buildings (vibration) or near populations (ice).

It sounds like you are attributing the same space usage for these types of generators as wind turbines, when it appears they could be much more closely packed. I wouldn't expect ten of these to use ten times the square footage as the wind turbines. Additionally, I wouldn't expect ice to be flung as far (but I'm not sure what the oscillation is really like), but from the design, maybe ice poses other challenges to these.

MWh/sq.ft.

I am attributing larger footprint usage to trying to generate a similar power output given current wind mast technology. 10 wind masts alone don't take up the same space as 10 classic turbines, but the the number of wind masts necessary to generate the equivalent output of 10 classic turbines is greater that 1:1 due to wind swept area per turbine.

I try not to be pedantic, but I was really confused for a minute- I believe you mean "rappel".

(Or if you want to sound fancy, "abseil")

You are correct! My right hand pinky finger doesn't have the dexterity it used to. I can crank out words with one "P" in them, but when I have to do the double tap of the "P" it becomes a real issue.

I actually slip up and omit a "p" from time to time, but it's really the "e" - "rapel" vs "repel" - that threw me :)

And I suck at spelling :)

In this case, why bring the worker to the repair site when you can bring the repair site to the worker? This new technology is in the form of a cantilevered mast. It would be a basic engineering problem to design the structure to be raised and lowered when repair is needed.

The primitive model is a tabernacled mast on a sailboat.[1]

[1] http://imgur.com/XwMCxbv

> It would be a basic engineering problem to design the structure to be raised and lowered when repair is needed.

I'm a big sailer too. I used to crew on racing boats and classic schooners.

Let's say we have a cantilevered mast and can swap it out "quickly". For 2MW worth of generation that would be a massive engineering feat and would mean that you have inventory not being utilized stored in the warehouse. Not just a generator or blade, but an entire system unutilized sitting around! Also most sailing masts are fairly light (aluminium) and short (30'). A 2MW wind mast would be 10x a sailing mast and hold all of the generator and electronics, not just a hollow tube that needs to be structurally sound. also masts are designed to be rigid and are held in place using shrouds and stays. A wind mast designed to move can not be held in place using guy-wires as that defeats the purpose of the dynamic wind mast.

Workers on these wind farms are making between $10 and $25 each and every hour. Some specialized workers are making double that at times, but let's keep the average of $20/hr.

It doesn't make economical sense even if you didn't need a crane to swap it out. And yes you would need a crane as this would be a multi-ton structure.

> 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

It would be really cool if the mast could retract, either using some kind of collapsing structure or a hole dug out underneath the structure. Great for repairs, also would allow a farm to retract for extreme weather events.

Yeah, until the retraction mechanism breaks.

No problem, just put the retraction mechanism in a lifting mechanism to lift it out of the ground for maintenance!

Reply on news.ycombinator.com