# Another windmill question - why vertical instead of horizontal? **URL:** \ **Category:** Factual Questions\ **Created:** [June 30, 2008, 8:25pm UTC](https://boards.straightdope.com/t/another-windmill-question-why-vertical-instead-of-horizontal/454812 "2008-06-30T20:25:47Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Defensive\_Indifference](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/defensive_indifference/32/6502_2.png) [@Defensive\_Indifference](https://boards.straightdope.com/u/Defensive_Indifference)\ **Post date:** [June 30, 2008, 8:25pm UTC](https://boards.straightdope.com/t/another-windmill-question-why-vertical-instead-of-horizontal/454812/1 "2008-06-30T20:25:47Z")
Inspired by **Tom Tildrum’s** [question](http://boards.straightdope.com/sdmb/showthread.php?t=473764)… You know those windspeed sensors (like [this](http://www.sciencescope.co.uk/images/anemometer.jpg) one)? Could a much larger device of a similar design be used to generate electricity? Of course, I am not an engineer, and I imagine that the engineers who desgined those giant propeller-style generators picked that design for a reason. I would think, though, that the Giant-Anemometer design would have the same output for any wind direction (I presume the giant propellers’ speed varies with wind direction), and if you clustered them, with the arms at different heights, you could cram more in the same land area. What painfully obvious thing am I overlooking? ---
**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\ **Post date:** [June 30, 2008, 8:31pm UTC](https://boards.straightdope.com/t/another-windmill-question-why-vertical-instead-of-horizontal/454812/2 "2008-06-30T20:31:23Z")
[QUOTE=Bayard] What painfully obvious thing am I overlooking? [/QUOTE] The buckets on one side of the device are moving INTO the wind. No matter how streamlined they are, they will experience significant drag. This also means that the entire structure experiences uneven stresses and has to be made stronger (and heavier) to compensate, further reducing efficiency. With a normal propellor-style windmill the load is symmetrical and blades are delivering power-generating force through their entire rotation. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [June 30, 2008, 8:33pm UTC](https://boards.straightdope.com/t/another-windmill-question-why-vertical-instead-of-horizontal/454812/3 "2008-06-30T20:33:48Z")
Forward surface area. A vertical windmill has 100% of its forward surface area against the wind, whereas a horizontal one has less than 50%, and some of the rear surface area works against the rest (for example, the back of the LH cup in that picture). Remember too that windmills rotate to face the wind. ---
**Author:** ![GorillaMan](https://avatars.discourse-cdn.com/v4/letter/g/50afbb/32.png) [@GorillaMan](https://boards.straightdope.com/u/GorillaMan)\ **Post date:** [June 30, 2008, 8:34pm UTC](https://boards.straightdope.com/t/another-windmill-question-why-vertical-instead-of-horizontal/454812/4 "2008-06-30T20:34:21Z")
They do exist: [Wind turbine - Wikipedia](http://en.wikipedia.org/wiki/Wind_turbine#Vertical_axis) ---
**Author:** ![Defensive\_Indifference](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/defensive_indifference/32/6502_2.png) [@Defensive\_Indifference](https://boards.straightdope.com/u/Defensive_Indifference)\ **Post date:** [June 30, 2008, 8:42pm UTC](https://boards.straightdope.com/t/another-windmill-question-why-vertical-instead-of-horizontal/454812/5 "2008-06-30T20:42:00Z")
[QUOTE=Quartz] Remember too that windmills rotate to face the wind. [/QUOTE] Huh. I didn’t know that. :smack: > [@Gorilla Man](#): > > They do exist: [Wind turbine - Wikipedia](http://en.wikipedia.org/wiki/Wind_turbine#Vertical_axis) That makes me feel better, though. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [June 30, 2008, 8:45pm UTC](https://boards.straightdope.com/t/another-windmill-question-why-vertical-instead-of-horizontal/454812/6 "2008-06-30T20:45:35Z")
On edit: nevermind ---
**Author:** ![garygnu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garygnu/32/2924_2.png) [@garygnu](https://boards.straightdope.com/u/garygnu)\ **Post date:** [July 1, 2008, 2:23am UTC](https://boards.straightdope.com/t/another-windmill-question-why-vertical-instead-of-horizontal/454812/7 "2008-07-01T02:23:39Z")
[Here](http://www.nextenergynews.com/news1/nextnews7.30a.html) is a proposed magnetically-levitated turbine that will use a vertical axis. If it ever gets built it’ll be a sight to see just on how big it is. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [July 1, 2008, 3:22am UTC](https://boards.straightdope.com/t/another-windmill-question-why-vertical-instead-of-horizontal/454812/8 "2008-07-01T03:22:02Z")
They exist, but there are reasons they aren’t common. From that same Wiki page. > [@](#): > > VAWT disadvantages > Most VAWTs produce energy at only 50% of the efficiency of HAWTs in large part because of the additional drag that they have as their blades rotate into the wind. This can be overcome by using structures to funnel more and align the wind into the rotor (e.g. “stators” on early Windstar turbines) or the “vortex” effect of placing straight bladed VAWTs closely together (e.g. Patent # 6784566).