Great Walls of America 'could stop tornadoes'

[xchrom]

http://www.bbc.com/news/science-environment-26492720


More than 800 tornadoes were recorded in the US last year

Building three "Great Walls" across Tornado Alley in the US could eliminate the disasters, a physicist says.

The barriers - 300m (980ft) high and up to 100 miles long - would act like hill ranges, softening winds before twisters can form.

They would cost $16bn (£9.6bn) to build but save billions of dollars of damage each year, said Prof Rongjia Tao, of Temple University, Philadelphia.

He unveiled his idea at the American Physical Society meeting in Denver.

[Turbineguy]

1. The RW would connect

all three walls together to form a prison for climate scientists.

[GeorgeGist]

2. Tao doesn't understand metereology ...

http://www.koco.com/news/oklahomanews/norman/physicist-says-building-giant-walls-in-us-may-prevent-tornadoes-in-tornado-alley/24675402

[Demeter]

3. 30 storey walls?

I don't know, X. I think wind farms would be more useful and just as effective...but I would use Savonius-style turbines, not the standard bladed ones:

STANDARD WIND TURBINES



IMAGINE ALL THOSE BLADES SHAKING LOOSE AND SENT FLYING IN A TORNADO....


SAVONIUS ROTOR VARIATIONS:

[xchrom]

5. that is some amazing stuff.

the 1st thing that popped into my mind was - is there some way to use all that energy.

[dixiegrrrrl]

6. I had no idea there were better types of turbines

Certainly the Savonius types look safer for birds.

[Demeter]

9. Better? Maybe, Different, Certainly

The main problem with Savonius is that they top out quickly. They just can't handle as high a wind as the bladed turbines.

On the other hand, they could be made of sturdier, heavier stuff, so that more wind is needed to turn them. It's an area that needs more research.

[kristopher]

15. No more research is needed.

We have a complete understanding of the benefits and trade-offs among the different designs of turbines.
The two approaches are horizontal axis and vertical axis wind turbines.
The vertical axis wind turbines can't scale up - they are doomed by the fact that higher towers and more area being swept by the blades are the key to getting more energy out of the labor and material involved in building a turbine.

It is a settled issue. Horizontal axis turbines are superior.

[Demeter]

17. But not in this particular application

If instead of building a plain old wall, a wall of energy extractors was built....

[kristopher]

18. OK, I see your thought now.

The VAWTs are about 30 feet high. The wall proposed is about 1000ft high and 150 ft wide. I don't think that wind turbines of any sort could replace the wall; however it might alter the required size of the wall if it were topped with turbines of some sort. As you say, it would require some modeling to establish the optimum configuration.
Sorry I jumped, but the comment about HAWTs throwing blades when, in fact the VAWTs are more likely to suffer damage in high winds set a tone that seemed unreasonable on first read.

[northoftheborder]

7. Some of those Sovonius blades look like sculpture, works of art. Why haven't some of those...

....been erected in the US, or maybe they have.

[LouisvilleDem]

10. They are inefficent

The angle of attack changes as the turbine spins, so each blade generates its maximum torque at only two points on its cycle. This makes them much less efficient than conventional turbine blades (which are rotated to always face the wind and the optimal angle of attack) and also creates a pulsing output.

[northoftheborder]

11. OK, thanks for info

[caraher]

13. There's some interesting research that may revive the concept

I saw a talk by John Dabiri of Caltech this weekend that argued that wind farm design may have gone astray because of excessive attention to the performance of individual turbines (which is indeed much higher for horizontal axis designs). He argues that the figure of merit should be the performance of the wind farm as a whole, and that taking account of how each turbine affects the air flow seen by other turbines in an array we ought to be able to extract more like 25 W/m^2 rather than the 2.5 W/m^2 our best farms currently achieve (limited by the need to separate them by large distances to minimizes effects of turbulent wakes).

[kristopher]

16. The metric being used is not the most meaningful.

I haven't read the work in a couple of years, but as I recall the comparison was fuzzed quite a bit by some illegitimate assumptions. There are others but first and foremost is the fact that one of the benefits of widely spaced wind turbines is that they are widely spaced and thus have a low impact on current land use.

It's been a couple of years since I read the initial study, but I don't recall anything that made me think this approach had any significant economic advantages that would drive its adoption. Did you hear anything during Q&A to make you think it was causing a re-evaluation?

[caraher]

19. I agree that land use might have been problematic

Certainly the test arrays he showed were not compatible with your typical US midwest-style agriculture. Nobody really pressed him on the issue of other forms of land use; to the extent that he pressed an economic case it was that these are simpler to install and maintain and have a much smaller visual impact, which might help with permitting and general acceptance.

From a physics perspective it was an interesting concept, and it does appear at least to have some niche applications, such as military installations where the effects of large horizontal-axis turbines on radar might be a concern or where it's more challenging to transport, assemble and maintain conventional turbines.

I just found it intriguing because I'd always taken for granted that the vertical axis approaches were technically inferior, but this is perhaps less obvious.

[TexasProgresive]

4. What are the unintended consequences of erecting these walls?

That's just it-no way to know.

[hatrack]

8. I'd say just carry bundles of money in wheelbarrows to the burn pit . . . .

Saves time!

[Nihil]

12. Isn't it just wonderful?

People rail against wind farms for "spoiling the view" yet think that putting up
hundreds of miles of 980' high solid concrete walls would be a good move ...?!?!




The expression "What a prick!" springs to mind ...

[NickB79]

14. And they thought we could stop the Dust Bowl by paving over the Great Plains

No joke, it was seriously considered (read the famous book The Worst Hard Times for more laughs along those lines).

Just because something is scientifically feasible doesn't mean it's even remotely feasible to carry out in actuality.