Wind energy - Different types of wind turbines

There seem to be three main types of wind turbine. And they really should be called wind turbines. Windmills are mills. ie. they grind flour or something.

These three main types of wind turbine, like most lists of three things, seem to have good points and bad points about them.

One type of wind turbine is an Horizontal Axis Wind Turbine, or HAWT.
This is the kind of turbine that  most people I know would think of as a windmill. It looks a bit like a fan. It can spin very rapidly depending on how many blades it has. Because it can be made to spin rapidly it's great for generating electricity. Its pretty complicated to build, and you are faced with having to come up with some way to get whatever we harvest at the top down to the ground, where it can be useful. We might harvest the energy as mechanical rotatey stuff, say for grinding flour, but that would be at a shaft sticking out of the back of the windmill. We have to get that rotatey stuff down to the ground by using a gearbox or something to change its direction, so we can bring it down the shaft to grind our flour on the ground, where flour grinding is best done.

Similarly if we stick a generator up there behind the wind turbine, we need to get the electricity down to the ground. The problem is the entire wind turbine constantly requires pointing in different directions to track the wind, so any wires you run down the pole it's sitting on can end up getting wrapped around and around it, until it either gets stuck or something breaks. There are ways around this, but it's an extra complication.

Another type of wind turbine is a VAWT or, you guessed it, a Vertical Axis Wind Turbine. This is the kind of wind turbine that is made of scoops. It spins around a shaft sticking up from the ground. It's often the kind a weather station might use on a very small scale to determine wind speed. It's probably the simplest of the designs mentioned here, but is the least efficient. It also wont spin very fast. I believe this kind is correctly called a Savonius VAWT.

And the third is a funkier modern version of the VAWT with blades instead of scoops. Its called a Darrieus VAWT, and takes a few different forms, but basically it is thin blades that rotate around some distance away from the central shaft.

Picture this. Get the blades from a three bladed windmill, and snap them off. Magic them to the outside of a 44 gallon drum, running from top to bottom and spaced out evenly around the drum. Stick a shaft through the centre of the drum so it can spin around that shaft. Now remove the drum but keep the blades magically in place. Now rebuild the whole thing so it looks the same but with struts to connect the blades to the shaft, no magic, and no barrel.

Or this slightly different version...

Snap off two or three 10 metre helicopter blades (land first) attach them to an 8 metre pole. To do this you need to bend them so they bow out from the shaft. Make them look a bit like a giant egg whisk. Weld it all together and you're done.

The advantage of the VAWT forms is that the power take off can be done at the bottom of the shaft that the whole thing spins around, rather than 40 foot up in the air. The shaft that is stuck into your generator is right at your feet, and the wires coming from it don't need to spin around. They are simple to build, because they don't need to track the wind. They work well in gusty conditions for the same reason. Wherever the wind comes from is just fine by them.

I cant see how you might furl one, so perhaps you need some kind of electronic breaking system or something. Its also possible they are self limiting due to the blades having to track through their buddy's turbulence. Who knows. I'll find out if it's important.

But they are slow, and not very efficient because half the device is coming the wrong way, back into the wind at any time. They get away with this because their blades, or scoops, catch more wind one way then the other. As I understand it, an ice cream scoop shape, for instance, catches more than three times as much air when the air is hitting the open bit where the ice cream sits, compared to the back of scoop. So if you built a parachute with the scoop shape upside down, unkind expert observers might point at you with derision as you plummet to earth on test day.