Or, possibly, that Golden Eagles migrate.
Some migrate, but most remain in a territory. Golden eagle - Wikipedia
From your link:
and if any by coincidence came to the Altamont Pass, they had to keep moving because the range is occupied the entire year around by full time inhabitants. An eagle that took more than a hour to move through the area at less than can’t be seen by human altitude is going to find a territorial fight on its hands.
I see a lot of birds of prey dead at the bottom of electrical utility poles. Not around wind mills.
Take a look at the map on the article. Virtually no goldens are California part time residents.
1970’s called. Higher altitude winds are increasingly accessible and that’s most of the planet, not “a few places.”
Germany is sunny all the time? Who knew? I lived there and never noticed.
Yes quite right and my bad. :smack:
I was thinking about tidal currents going through straits which could be used for generating electricity. There are not many places around the globe where the flow is strong and consistent enough and close to population centers.
From the point of view of the birds, slower blades are easier to spot & dodge, as indicated by The Second Stone. Also, with the axis higher off the ground (and above the bird’s cruise altitude), the blades spend more time in air that won’t affect the birds.
Moving is what migrants do. You surely aren’t saying they can’t pass through areas where year-round birds are found, are you?
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Not really - here’s a single-blade wind turbine.
Probably impossible, in any practical sense. Most wind turbines operate with tip speed ratios under 10 (i.e. tip speed is less than 10 times wind speed) - and of course they must feather when wind gets really strong.
Here’s a link to a list of common industrial wind turbines. Max blade tip speeds range from 138 to 232 mph. I’d guess that the blades of every one of these would destroy themselves at less than 1.5 times max speed. (It would make no sense to incur the cost of producing a blade able to operate far outside its turbine’s design limits).
While a one-blade turbine might be possible, it sounds like a lose-lose proposition to me. You still need some sort of counterweight, and that counterweight is going to be adding moment of inertia and drag without adding any collection area to make up for it.
Rotor blades are not only designed to balance the “rigid body” (non-flexing) moments of inertia, but also balance the modal (flexing) modes to reduce fatigue stress and unbalanced torsional modes. In other words, a single blade is going to flap like a flag as it rotates with the torque at the root being only resisted by the geometric section of the pylon. With two or more evenly spaced blades and appropriate aerofoil design the parasitic and potentially destructive modes can be minimized by making the rotational center also the inflection point for the primary modes. It is possible to design a balanced single blade rotor as show, but it compromises maximal energy recovery for other benefits (lower parts count, less effective mass, et cetera).
Stranger
I guess one big drawback to vertical axis turbines is that they are a little less than 50% effective, as the part that captures the wind force must move upwind on the back side. Horizontal axis turbines are capturing wind power more or less evenly for the full cycle of each blade.
In the case of the single-blade turbine mentioned above, this issue is neatly handled by means of a “teetering” hub - the blade is free to fold in or out as the airflow dictates, so forces on the pylon are low.
As the pictures show, this also allows for passive ‘feathering’ in strong wind.
The counterweight looks plenty small enough that the drag would not be a big deal. And additional moment of inertia probably isn’t a big problem in a device that is typically trying to operate at a constant rpm.
Offsetting these issues are the cost savings of a single blade and the fact that it gets to operate in air that hasn’t been disturbed other blades.
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If they are not seen, yes. Goldens are highly territorial and they will fight each other. Golden eagles were used in Asia to fight wolves. Everything else in the sky backs off when they assert dominance. If they wish to pass through, they had best be quick about it and not seen and have a long head start and altitude if they are seen “passing through”. Sedentary golden eagles are in pairs that mate for life, so there is at least one ally nearby.
Okay, that’s good to know… however, the number of dead golden eagles found at Altamount has dropped since they stopped using the older, shorter, faster turbines. Are you saying that all the migrating eagles got killed by locals and the reports that they’re migrating are wrong?
They will if they perceive a valid threat - e.g. another eagle hanging around, poaching prey or looking to encroach on their territory. But it would be of less than no value to pick fights with birds that are moving through anyway, posing no threat.
The article you linked makes it clear that plenty of migration passes through areas where some golden eagles are resident.
Back to blade design - why do some blades have a “dip” in the face of the blade towards the tip? I don’t know how else to describe it. I couldn’t find an image that shows it well but it pretty obvious on the turbines near me.
Not disagreeing with what engineer_comp_geek said, just expanding on it. It’s a question of solidity, which is the ratio of the total area of the blades compared to the area swept by the blades. A high solidity turbine, think of the old Dutch windmill, spins slowly with high torque. Very useful for applications like pumping water where high torque is needed. Low solidity turbines spin rapidly with less torque which is what you want for generating electricity.
I suppose you could use a slow speed high torque arrangement and a gearbox, but that introduces extra expense and inefficiencies in power transmission.
Something like the raked wingtips on the Boeing 787? For aircraft, it reduces inefficiencies associated with tip vortices, and iincreases lift without increasing span (causing a smaller increase in wing bending loads than one would observe with a simple increase in wingspan). Presumable the same is true for wind turbines: reduced tip-vortex losses, and increased rotor torque without the bending loads that would be associated with using just a larger-diameter turbine.