Thank-you for a most excellent article.
There are HAWTs, Savonius and Darrieus, and variations of these.
Now if you could just get everyone to stop switching the efficiency labels for the Darrieus and the American Multiblade (a low-efficiency, high-torque type of HAWT) from that 40 year old magazine article graph that keeps getting reprinted...

Excellent information. It's gotten quite annoying to see one of these "inventions" about every other week on some blog or another.

Great write-up. I am particulary skeptical of the flying kite generators. Your summary of the required easments and the obstacles they produce in a real world application puts it in perspective. What happens when the 4 KM kite descends with its carbon-fiber kite string falling across high-voltage power lines? (AT&T Austin smacks his forehead) That's right, Austin. I'm amazed that people can actually get funding for some of these projects. When you do the math on biomass energy, the entire continent could be a switchgrass farm and it still wouldnt meet our energy needs...so why fund the research? Captital Investment Analysts must be morons. 50 nuclear power plants on 50 military bases in each of the 50 states equals clean, safe and domestically generated energy...its not complicated.

Thank you, Mark, for an informative and credible article. I didn't know about the Betz limit, which must rank pretty much up there with the laws of thermodynamics.
My favorite goofy idea is the strawscraper, typical of the hot wind emitted by architects.

now i suggest you write the same article telling us off-grid wannabes without all the research data how to pick a wind generator system for 5 to 10 kw. and keeping the price low. in the spokane, wa area there is a mfg. claiming reasonable power output at lower height. how can we users tell whether their product is worth buying? thanks

it called physics and the limits to efficency ... for the most part these "new" turbine projects are simply grant or funding cons ...
if you really found a "new" way to harvest wind energy you wouldn't need tax credits or pie in the sky press releases ...

So, wondering how the Blackhawk TR-10 VAWT from BHWE (www.blackhawkwindenergy.com) stacks up to these tests. It's a variant of a Darrieus design that claims certain improvements (exhaustively delineated in this video: www.youtube.com/watch?v=C3a6LAzNsds). It all sounded logical to a lay-person like me, but maybe you have an opinion?

Great article! Finally something debunking these perennial dead ends. The one case I would disagree on is the Makani Wind flying turbines. I suspect the reduced costs and speed of installation, flexibility of changing sites and ease of scaling will help it succeed (along with Google's cash). Of course the sites for these will be in deserts and in the ocean because of the issues mentioned, but that is just fine because there are plenty of both.

Wow, best article I have ever read about wind energy, or just about any topic for that matter! Three investigative techniques really impress here.
1) The review questions is something actually new! Google has made patent searches so easy we should all be doing them.
2) The review questions whether the something is actually useful!
3) The review looks for coroborating 2nd source info for the new useful something. And if that is not available, at least compares claims back to basic public info.
Thanks so much Mike Barnard!!! Keep up the phenomenal work.

MzunguMkubwa,
Blackhawk has an excellent video. Very informative and it appears correct without exaggeration. This is a conical vertical-axis lift-type (Darrieus) wind turbine. I lived on a sailboat for eight months, so I very much liked the sailboat analogy.
A couple down sides: one is the complexity of the mechanism; can it be made at a reasonable cost? and how long will it last between maintenance? (More parts is not necessarily a bad thing. Adding parts can increase the dependability of a mechanism. But more moving parts can mean more maintenance.)
The biggest downside right now is the "Account Suspended" I get when I try to go to their web site.