Windmills or Fans on top of the HK Electric Building in Wanchai?

[zerocred]

Are the windmill-looking things on the HK Electric building north of Gloucester Road in Wanchai (near SHK Centre) actually windmills? or fans?

There are two, one always seems to be spinning - quite fast even , though there appears no breeze to move the bushes on the same rooftop or trees at street level.

Or is it really a clever advert?

[DanielV]

Yes, those are demonstration wind machines producing electric power. You'll see a few others scattered around Hong Kong on tops of buildings and out on Park Island's Ma Wan Park (you can see it from the Tsing Ma Bridge when you are heading toward the airport). And of course, there is the big wind machine out on Lamma Island (I assume you know about that): http://tinyurl.com/LammaWind

If you live in a windy area you can even put up your own wind machine and be green!

Dan...

[MovingIn07]

If you want to know more, this is the firm that makes them:

MotorWave

They do wave as well. Run by a guy who is clearly brilliant if somewhat eccentric. Their wind turbines run at much lower wind speeds than the "conventional" ones and are heaps cheaper (basically made of plastic). It's a fascinating concept.

[M Khan]

I think it was in HK magazine a month or two back that I saw a short article about those two wind turbines. As I recall the article was highly critical of such roof-top power generation and suggested that of the turbines in question one spins but produces very little electricity, while the other is actually hooked-up to an electric motor! While HK magazine has never struck me as being a leading scientific or engineering journal, this last comment nevertheless struck me as being particularly dim-witted. Surely EVERY wind turbine is hooked-up to an electric motor? What is a wind turbine if not an electric motor working in reverse? Almost as bad as when I read a comment from a scientist on the BBC website that, at the start of the universe, the speed of light had been "nearly infinite". I tried to image a superscript '7' lying on its side.

[MovingIn07]

The Motorwind units are normally in large arrays - the generator (not really a motor) is attached to one end of each row, but the wheels are all connected together by cogs so that they spin together and generate the force that generates the power on the end. I wonder if that's what was meant?

[zerocred]

The 'windmills' I refer to aren't the Motorwind, those are nearer Admiralty.

I find it hard to believe the one that moves is powered by the wind - its blades are too 'flat'.

Maybe they have wired it up wrong, and it's sucking power out the grid...

[Raccon]

I think it was in HK magazine a month or two back that I saw a short article about those two wind turbines. As I recall the article was highly critical of such roof-top power generation and suggested that of the turbines in question one spins but produces very little electricity, while the other is actually hooked-up to an electric motor! While HK magazine has never struck me as being a leading scientific or engineering journal, this last comment nevertheless struck me as being particularly dim-witted.

I am not a native English speaker but in context I would say that they meant it was powered by an electric motor. Though I can't say if that claim is true or not.

Surely EVERY wind turbine is hooked-up to an electric motor? What is a wind turbine if not an electric motor working in reverse?

In which case it's called a generator, not a motor.

[Raccon]

The 'windmills' I refer to aren't the Motorwind, those are nearer Admiralty.

I find it hard to believe the one that moves is powered by the wind - its blades are too 'flat'.

Do you have a picture of it? Those things work well, even the blades are flat.

[zerocred]

I'll try to get a photo.
They are both traditional windmill configuration and the blades are not aerofoils and the angle of attack is, well, close to zero - so easy to spin with a motor. Not easy to spin due to a breeze.

[M Khan]

In which case it's called a generator, not a motor.

Well I didn't really want to dance the merry dance around the names we give to things. A rose by any other name, and all that. Whether you call it a generator or a motor, at the heart of the thing there is practically no difference (ref. Electric motors and generators ).

The article in HK magazine did seem to imply that the motor was causing the blades to turn, although as I recall it didn't go so far as to actually say so in as many words. It beggars belief that anyone would actually hook up such a windmill to a motor in order to make it turn, so I had to assume that the writer in HK magazine had erred in his interpretation of the facts. He had, perhaps, heard about this electrical/mechanical energy conversion set-up and, in his hurry to write-off the project as a failure and a sham, had made the assumption that rotation was being induced by the application of an electrical current, rather than the other way around.

Whether one or other of the windmills really is being driven by a motor I cannot definitively say. I struggle, however, to imagine any reason for such a thing.