[–] Grospoliner ago
Too bad.
It's a balance between engineering economy and performance. You might be able to design and ship a product which never breaks and meets performance, but the production cost may be astronomical and any return on the product will be non-existent. Either way, when the cost exceeds the benefits of the product, it isn't viable.
In reality though all mechanical parts will wear down over time simply because that's how mechanical interaction works. Maintenance, preventative or reactive, will still be needed for any machine.
Breakdown from 2010 on turbines says there is an average of 6 incidents for every ten machine-years of use. That results in about 30-40% of the operating cost of the turbine (6 to 10 USD or so per megawatt-hour).
So if they break down a bit more then once every two years, preventative maintenance is what every 6 months? I understand it is nice to have the work be easy to do, but if downtime is 1% and uptime is 99% it seems logical to make the uptime a bit more efficient (2 blades) rather then shortening the downtime (time to stop with the brakes) by a small amount. Especially if the main advantage of the single blade design is in wear on the brakes as that accounted for 0.6 days worth of downtime per year according to your site, where as efficiency in the blades would add to the power output offsetting that cost.
[–] ZYX321 ago (edited ago)
The tower is a huge part of the expense (relative to the cost of a braking system or the blades themselves)... I can't imagine putting something that provides less power output up on the tower would be attractive. A balanced single blade system just couldn't have appreciably less intertia. Braking (as far "I need to stop NOW or SOON"), you don't generally care about braking from a "deceleration" standpoint, you care about braking to prevent acceleration into dangerous speeds, right? You're not taking a heavy intertial mass and trying to slow it down, you're just keeping it from speeding up in heavy winds, in which case the intertia is a help.
IANAP, but... these are "common sense" things in my own head which I might be wrong about... as with most common sense.
[–] Grospoliner 1 point -1 points 0 points (+0|-1) ago
Individual blades can run into the hundreds of thousands of dollars and the surface area each turbine is optimized for faces diminishing returns on power generation efficiency. This system is probably just built for a specific power range and cost, and it didn't make sense to add onto that cost by adding a second blade.
From classical mechanics, inertia helps prevent change in acceleration in either magnitude, increasing or decreasing, so it can be both detrimental and beneficial. It's certainly not the only reason they designed the tower like this (and in all honestly probably isn't the main one), but it will be a factor in it given how angular momentum and acceleration behave.
[–] ZYX321 ago (edited ago)
The graphs there are $/MW. It seems like they list the of a typical U.S. wind turbine blade, 50 meters, at $55K. But their cost per MW for 50 meters is much higher... The graphs confuse me, but the charts seem straight forward. Even their larger 70 meter blade (which would be a huuuuuuuuuuuuuuge wind turbine on a huge tower) isn't hundreds of thousands of dollars though.
But would it make more sense to just have a smaller turbine?
But you don't regularly use the brake for slowing it down, you use the brakes for preventing it from going too fast. Inertia isn't really a factor that hurts you there. When trying to stop the blade entirely for maintenance, inertia keeps you from doing that so fast, but that's not really a "QUICK DO IT NOW!" type operation.
There is some decent write up on Wikipedia on this though that might sort of hint at the answers to most of our questions.