Why no use of "wind channels" to direct more wind at wind turbines?

Use two large walls to form a V shape, leaving a narrow gap where the pointy end of the V is. Place the wind turbine in the narrow gap.

Seems to me you could get a lot more power this way. Why do I never see it?

They sort of do. Wind farms are put in areas where they have previously determined by use of equipment that get alot of natural wind tunnel effect do to the topography.

I don’t think many of the ones I’ve seen (and there are a lot around) are like that. There are many offshore, where it’s obviously windy, but there’s no wind tunnel effect. Others are on hills or flat areas, not in valleys, etc.

It seems to me to be impractical.

If the tunnel is stationary then its shielding the blades when the wind direction isn’t exactly correct.

Its impractical to make the tunnel rotate…

Also, the wind coming from the wind tunnel may be turbulent, - turbulent wind behaviour is bad news to turbines

As has been mentioned, this is only good when the wind blows into the V shape. Even then it accomplishes little more than putting up a few more windmills, and requires a waaaaaay more intrusive and heavy duty construction. People get pretty NIMBY about the slender towers, imagine how they’d feel about an even taller solid wall.

All those wind towers rotate to face the wind. Besides that, it just wouldn’t work. Air flowing on a scale as large as that is not like water flowing down a babbling brook. It’s emmensely more complex and unpredictable. The fastest super computers always have to be used to predict things like weather or airflow across a potential aircraft design. No offense, but this is an example of what I call ‘Wyle E. Coyote’ engineering, In the real world, the numbers just don’t add up.

Wind channels are being used … just not the sort you are thinking of.

Air flowing on a scale as large as that is complex but not unpredictable - channeling is achieving by consideration of optimizing the ability to capture the energy from adjacent wakes.

The focusing the energy bit is being done with some solar cells btw, either by mirrors on a large scale, or in individual cells by inexpensive lenses.

I have seen some designs for small-scale wind channels, so people are trying it out. I don’t know if it ever actually works out to be practical, though.

I know of one wind farm located at the top of a ridge at the head of a steep valley. The prevailing wind funnels up the valley and right into the face of the windmills.

Artificial structures are probably more intrusive and costly than the wind-farm itself.
Funnelling as you describe does depend on the regularity of the wind direction. Any funnelling structures will be rendered useless if the wind comes from some other direction.

The first thing I thought of when I read the thread title was reenforced by your post.

Decades ago there was a proposal to bore tunnels in the mountains surrounding the L.A. Basin, and to use giant fans in them to remove the smog and blow it into the desert. I’m sure the residents of the Antelope Valley would not have been pleased.

you’re talking about a vertical axis wind turbine such as this. Focusing the wind on it would absolutely increase it’s power capacity just as has been done with water turbines since the beginning of time.

It wouldn’t be hard to build a structure to funnel more air into it but we already have that naturally in cities. Tall buildings create artificial canyons and these types of turbines are already taking advantage of the effect. Here’s aboxed structure atop a building. Not an angled funnel but the structure takes advantage of prevailing winds but allows for crosswinds. Here’s a view of a conventional horizontal wind farm using anatural canyon.

I think we’ll see exactly what the op is talking about using cities as natural canyons rather than spend money to create the same thing. If I were building a vertical wind generator and had a large out building I’d put it at a corner of the building and put up a fence next to it. It’s all about cost.

As I read this thread I kept thinking about the strong winds in the concrete canyons in our larger cities. Here is a parking garage that takes advantage of this. Of course this type of thing is only feasible for new construction. What I was thinking of was a horizontal version of this. Just turn that turbine (or whatever design is most efficient) on its side and "string them between existing building every 5 or 10 stories. This could be done for existing buildings and would surely pay for itself pretty quickly. I’m sure that New York’s new liberal mayor would go for this big time.

The OP has obviously never driven the 10 from LA to Palm Springs. Why spend a billion dollars on walls that won’t work (snerk!) when Mother Nature does it for you?

Walls and a V-shape? It would be immense and horribly impractical to move to follow the wind.

The large black rectangle in the bottom left is an air intake to one of the wind tunnels at Ames Research Center. It’s not a power generator, but there is a fan at the narrow end of the funnel.

Another view from ground level. There’s a car next to it at the far end for a size comparison, and this still isn’t nearly tall enough to be useful for a typical wind turbine.

Wasn’t that one of Jethro’s crazy ideas from The Beverly Hillbillies?

Here’s a map of wind farms,

and one of wind

but it doesn’t really do justice to the concept. I’ve seen dynamic/moving pictures of air flow that work much better. There are a couple of wind channels that are lined with wind farms, and on a moving picture you can see a lot of wind going through,

That was the creepy lunatic mayoral(?) candidate Eileen Anderson(?), who sang her platform proposals:

Wouldn’t you know it? There’s a (short) thread on smog tunnels. And apparently they did mention it on The Beverly Hillbillies:

But it actually was proposed, as shown in this list.

I think cheap land out in the middle of nowhere is a big part of it; even though West Texas doesn’t seem to be ideal for wind energy, there are a lot of wind farms out there, because if there’s not oil under the land, it’s not good for much else. So even though the wind isn’t all that awesome, they can put up a lot of turbines to make up for it and the whole thing would be cost effective.

By that same token, Cape Cod looks like it would be an awesome place for a wind farm according to that wind map, but it’s really unlikely you’ll see any serious wind farms on land there.