A visualization of X-Windís vertical-axis wind turbines placed next to a road. The turbines could provide a renewable energy source to electric railways and in other places where there is limited access or restricted space. (Source: X-Wind)
Like I said, I'm an EE, so an ME or aero engineer should jump in with an explanation. Seems to me that VAWTs run on the small differences in forward vs. backward air resistance of the blades to give torque to the rotor. They have no way of aiming the air flow; but this is an advantage when you don't want the complexity of steering, or the wind is variable in angle. HAWTs rely in the inclined plane principle and most of the incident air is used in pushing on the blade. I've seen VAWT designs that use ducting or blades that feather into the wind on the return side; they increase the forward/backward resistance to give greater output, but are much more complicated or bulky. But you can put the generator on a fixed point at the bottom, a big advantage. You can't generalize and say one is better than the other. I'd expect that big turbine buyers do their calculations carefully, and for their given constraints the HAWT is the obvious answer.
vandamme, thanks for the honest answer. You said VAWTs had been studied a lot so that tells us they're not a new idea. But it also makes some of us wonder why they haven't been deployed more. You said they are less efficient than horizontal ones, so I was wondering why/how, hence my question about some comparative data between VAWTs and horizontal designs. Just because 99% of what's being used is Version A, that doesn't mean it's the best technology, only that it's the current dominating technology. It does sound like VAWTs would be worthwhile in some locations and situations and it would be interesting to know which ones.
Wind farms must be big enough so that changes in wind coming from one turbine to another can be balanced out. Beyond that, many (most?) of these farms are tied into utilities which do load balancing, just like on any other complex distributed system.
@ Nancy Golden, You are right in saying that people often jump on bandwagon without asking the right counter questions. Your horse and slaughterhouses example is not off the topic at all and points in the right direction. Euphoria of going green is all right, but it should not stop the experts from pondering over the relevant points. If someone asks critical questions, he is not necessarily against the idea. He is actually trying to raise the question so that it can be addressed before it's too late.
On paper, this idea seems flawless and all good. Potentially higher power outputs, less noise than horizontal turbines, lower costs, easy portability, less maintenance required, better returns on investments and better visibility to our 'flying friends', I wonder what else one would demand? I believe even if half of these potential qualities are true, we are up for something really useful.
Um, well no I can't, just stuff I've read in the popular press. But you notice that big turbines are all horizontal. I'm a radar engineer by trade, alternative energy enthusiast by night. VAWTs are simpler, though, because they don't need steering controls and mechanisms.
Charles after all this time you don't know the answer to that question when the wind stops? Isn't it obvious? Isn't it the same if they made too much power? What would they do?
What do they do when the train stops? Oh My!!
And the VAWT's are only 10-20% as cost effective as HAWT's as they are less eff, take 3-10x's the materials, space with many more parts. Only a fool or one who didn't have a clue would recommend them.
I've done both kinds and built some of the best ones made and no way a VAWT is worth doing for cost effective power.
Nothing even new about Railways powering with RE, mostly wind or solar has been mentioned 50+ times I can think about.
The real killer app is for the wind, solar production not to run the train as much as pay for and running it by selling power. Also pipeline, powerline and commuication lines space rentals to pay for the trains/tracks or even a profit.