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Mon Nov 26th, 2007 at 05:24:13 PM EST
This concept of Wind turbines look quite promising and is going to be build in China this year. perhaps Jerome has more information /debunk on this.
Maglev wind turbines have several advantages over conventional wind turbines. For instance, they're able to use winds with starting speeds as low as 1.5 meters per second (m/s). Also, they could operate in winds exceeding 40 m/s. Currently, the largest conventional wind turbines in the world produce only five megawatts of power. However, one large maglev wind turbine could generate one gigawatt of clean power, enough to supply energy to 750,000 homes. It would also increase generation capacity by 20% over conventional wind turbines and decrease operational costs by 50%. If that isn't enough, the maglev wind turbines will be operational for about 500 years!
Inhabitat » THE MAGLEV: The Super-powered Magnetic Wind Turbine
Construction began on the world's largest production site for maglev wind turbines in central China on November 5, 2007. Zhongke Hengyuan Energy Technology has invested 400 million yuan in building this facility, which will produce maglev wind turbines with capacities ranging from 400 to 5,000 watts
I also agree that vertical designs have certain advantages, low-wind-speed start-up and some value as a "flywheel".
I've seen an interesting development of a spade-shaped turbine (in the conventional sense of turbine) design for rooftops that purports to use the dynamics of 'ground effect' flow efficiently. So far, they're only letting contractors/distributors sign up for a unit. Supposed to be light enough to not cause damage to roof integrity. We shall see, maybe.
Energy from the Wind - Practical Answers
This means that the power density in the wind will range from 10W/m² at 2.5m/s (a light breeze) to 41,000W/m² at 40m/s (a hurricane).
so assuming 100% eficiency from this design, and hurricane speed winds you're talking 24,400 square metres of blade area.
(take into account that this is ultimate bodge physics and I really have no idea what I'm talking about, these are numbers I pulled off a random page on the internet)
Any idiot can face a crisis - it's day to day living that wears you out.
Also, there is no such thing as capturing 100% of wind energy. To do that, you would have to slow the wind down to 0 speed after your turbine, but then there would be no wind going through your turbine. If I remember correctly the theoretical max is something like 60%, and real-life turbines have a maximum of 25-30%, because they lose energy by rotating the flow. If I am not mistaken, vertical-axis machines perform even less good, 20% max. Remember, this is without friction losses or anything, just the energy you can extract from the wind while keeping it flowing.
Furthermore, it is absolutely pointless to design a turbine for huricane speeds. It would mean that you install an electric generator that will hardly ever perform at more than 15% of its capaciy, while still costing you 100% of its price.
Most wind turbines have a generator that will reach maximum capacity at 15m/s or so. At higher wind speeds, the blades are rotated to be less efficient, so that captured power stays constant (otherwise the generator fails). Somewhere between 20m/s and 25 m/s, the blades are switched to capture no wind at all, to diminish the loads on the structure.
These economics still hold for vertical axis machines, so it is save to say that a gigawatt turbine has to reach this power at no more than 20m/s, otherwise its gigawatt generator is a waste of money.
So: power at 20m/s is roughly 5000W/m2. Times 20% efficiency(ignoring friction losses etc.) is 1000 W/m2.
For a gigawatt, this means a capturing area (side view) of a million m2. Let's say the machine is 300 m high. Then it should have a diameter of 3 kilometers. Good luck with your maglev bearings to lift that.
I googled a bit around, and a think there are two stories mixed-up. The Chinese have indeed made a maglev turbine, for small scale operations. This is not as futuristic as it sounds, frictionless magnetic bearings are already quite common in high-performance electric engines. This is definetly an interesting idea, but far from proven in real life.
The gigawatt story however is put out by a very unreliable company from Arizona that is using the real Chinese invention to make their own pie-in-the-sky idea sound believable; I suspect these are simply conmen trying to lure investors.
They were expanding very fast, with clearly a lot of govenment money behind them. However, their main goal was to get closer to the level of western manufacturers, not making new concepts (how hiring unexperienced western students was going to help that goal, I do not know, but I suspect they just wanted name recognition in western academia).
From this I deduce that even the Chinese are not thinking their maglev turbines will be succesful in the short term, or they would put their money elsewhere.
By the way I found the site of the company developing the maglev turbine:
At the moment they are making small (300kW) horizontal (regular) turbines using magnetic bearings that would be especially good for low-wind conditions. Apparently they are used to power street lights.
Their R&D plans include a 200kW and later 2000kW vertical turbine, using maglev, but currently they only have a 20kW turbine. If they can build the 2000kW, and the technology is sound, they could become serious players.
you are the media you consume.
The main problem it faces however, is that wind speed vary with altitude. Hence wind speed differences at the top and bottom will result in huge structural stress. Not good. Regular turbines don't have this problem, or at least it's several orders of magnitude less, and therefore easilty countered.
A 'centrist' is someone who's neither on the left, nor on the left.
It doesn't really matter that a VAWT (Vertical Axis Wind Turbine) can work at lower wind speeds, for there's little energy to be captured there. Besides, modern VAWTs usually need startup power to get spinning, to overcome the drag "from the other side." A modern HAWT (horizontal axis wind turbine) can also begin spinning at around 4 meters per second, but a 2.5 MW turbine only produces around 200 kW or less. (With a proportionately larger rotor diameter, one gets more power at lower winds, but needs to cut out sooner.) VAWTs work great when simple shaft power is needed, and they can be cheap to build when small.
If i wanted to rate my turbine power at 40/mps, i'd design something which could be dropped into hurricanes.
"Life shrinks or expands in proportion to one's courage." - Ana´s Nin
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