The Future of Wind Turbines: No Blades (opens in new tab)

OK, so: Betz's Law says that the maximum energy that any wind turbine can extract is 16/27 of the kinetic energy contained in the wind that it blocks. Modern three-blade wind turbines reach 75-80% of the theoretical maximum, across the entire area their rotors sweep out.[1]

That's why the classic windmill design is so classic: its efficiency scales with the square of the length of the rotors. The energy extracted by a windmill is (very roughly):

    wind_speed * 16/27 * 0.8 * π * rotor_length^2

But then the wind speed also increases with height.[2] So the game to design an efficient windmill is to sweep out as much cross-sectional area as possible, as high up in the air as possible, and that's how we get the iconic windmills we have.

I don't know anything about anything -- I just read this stuff on Wikipedia. But until a third-party engineer says otherwise, I'm super skeptical that a device like this with minimal high-altitude cross-section is anywhere in the game.

[1] http://en.wikipedia.org/wiki/Betz%27s_law [2] http://en.wikipedia.org/wiki/Wind_profile_power_law

I personally like the idea of wind turbines being tethered high-altitude blimps.

I assume the high-altitude ones could be higher than birds fly.

They could even be used as in-flight recharge stations for drones.

Substantial discussion of the concept and technology over here:

https://news.ycombinator.com/item?id=9523877

I followed the debate about renewables for quite some time and I heared stories like this before. A new design for wind energy with so obvious advantages. And you can read pretty similar stories for new solar or water power tech also pretty regularly.

I remember that already in the 90s I heared people saying that future wind turbines will have a funnel to focus the energy. Later kite-like flying turbines or turbines in donut-shaped balloons became a thing.

But wind turbines still basically look very similar than they used to be all the time, the biggest change is that they became much bigger. There's a reason for that: The design worked well and has been improved in details over the years. It's much easier to improve in small steps than to reinvent a completely new tech, which will have many downsides that the enthusiasts inventing them don't want to see.

That's not saying that it's entirely impossible that a completely new design of wind turbines will some day emerge. But I don't think it's very likely. And before I believe it I want to see them built at scale for a reasonable price. (Because one of the biggest advantages of the existing wind turbines - appart from them being environmentally friendly - is that their price dropped rapidly in the past years.)

Similar to the windbelt:

http://www.instructables.com/id/Windbelt-Redux--21st-Century...

Fluids tend to move as vortices so often reciprocating motion can be at least as efficient as rotary motion. For example it is (currently) difficult to replicate the efficiency of birds and fish with propellers.

Potentially (ahem) it's possible to extract work from ions in a flow, and if it's laminar there would be no vortex losses. Just for fun, here is an electrostatic turbine, which works a bit like an electrohydrodynamic (EHD) drive but in reverse. From what I understand, it's difficult to extract more work than it takes to ionize the fluid, so this cheats a bit by using liquid droplets:

http://www.wired.co.uk/news/archive/2013-04/3/bladeless-wind...

I find myself thinking of a grassy field swaying in the wind.

I wonder if they should try painting them deep green or something.