this post was submitted on 29 Jul 2023
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Caveat: I'm pro wind if it gets us off fossil fuels. It's better than doing nothing and perfect cannot be the enemy of good enough (for now).
That said: in the late 1890s and early 1900s, scientists already knew about fossil fuels and greenhouse gasses and they didn't speak up loud enough.
Take the idea of wind energy and project it's growth a hundred years. From a pure physics perspective, when harvesting wind energy, you must steal kinetic energy from the wind. What happens when we're harvesting say, 1% of all the kinetic energy of the atmosphere. Or 10%. Surely that will have major weather and climate effects. Or some far future anime sci fi outcome where we've captured 100% of the kinetic energy of the atmosphere and no air is moving except through turbines...
This turbine is very cool. What else should we be doing to prevent wind power from turning into the next generation's climate disaster?
Stop making assumptions, don't jump to conclusions. Do the science, gather data, apply math.
Until then, we can at least appreciate global warming means an increase in atmospheric energy or wind speed and availability. We should rather be worried about storms damaging turbines.
Is it really stealing any more wind than say, a tall building though?
*than
Thank you
A tall building does not stop the wind. The wind moves around it. Think about it from a conservation of energy perspective: if the building stole the energy from the wind, that energy has to end up somewhere. The building isn't converting that much of the energy into some other form (electricity, heat, etc.) so the energy must still be present in the wind. (Some small amount is converted to heat through friction when the wind hits the building, but it is tiny.)
It also transfers a non trivial amount of energy into the ground which I guess is kind of it's job if you think about it.
In effect, it's turning the energy it stole back into heat somewhere too, when the energy is used. Thermodynamics always wins.
A portion of it yes as the material flexes. But it's not transforming it all to heat, most of it gets transferred through the structure and the building foundations into the ground. That's my understanding at least, I'm not really sure how converting all the energy to heat would work but maybe I'm not understanding your point.
So, conservation of energy requires that if kinetic energy is removed from the wind, it must be converted to another form. If a building removes energy from the wind (through friction, flexing, transferring vibrations into the ground, etc.), that energy total must be equal to the kinetic energy lost by the wind. Thermodynamics says that any conversion of energy from one form to another results in some of that energy being converted to heat. So there's some direct heating caused by the process of the wind hitting a building. That heat is largely heating of the air itself. After all, all those molecules had to collide with one another when they ran into the building.
The noise, vibrations, and other forms of energy conversion will all also end up as heat eventually, as they're absorbed by the materials. So some indirect heating as well. In the ground, this is basically vibrations due a shuddering building being dampened by the material and turned into heat.
Now clearly on a windy day a building does not start significantly self-heating due to the wind hitting it. So the total amount of energy absorbed by a building cannot be that substantial. So, if one side of the equation (energy absorbed by building and converted into heat) is very small, then the energy removed from the wind must also be very small. Mostly the wind just changes direction to move around it.
Close, but not quite. One cubic meter of air at atmospheric conditions is about 40 moles, or 575 grams. Let's say 600 g to be generous.
Wind moving at 250 km/h (cat. 5 hurricane) contains about 1.5 kJ of kinetic energy per cubic meter.
If all that energy is used to heat the same air, it's temperature is increased by roughly... 3.5 K.
Now consider the fact that kinetic energy scales as the square of velocity: for a normal windy (say 15 m/s wind), we only get a temperature increase of 0.16 K, which is practically immeasurable.
For these calculations I didn't even consider the building, which has a massive specific heat capacity compared to air.
In summary: Because the thermal energy required to increase temperatures appreciably is of a completely different order of magnitude than the amount of kinetic energy in the wind, the fact that a building isn't heating up is not a solid argument that only a small portion of the kinetic energy in the wind is being lost when it hits the building. In fact, even if all the energy was lost, you wouldn't even notice the temperature change, unless you were in a cat. 5 hurricane, in which case the building is probably already gone.
There is a whole lot of sky, my dude. I don’t think it’s plausible that we could capture even 1% of the kinetic energy of wind currents if we wanted to.
But also, wind is ultimately solar energy: the sun heats up parts of the planet at a time, the temperature differences cause pressure differences, and pressure flows from high to low. If we could somehow capture most of that kinetic energy, the result would be that areas which heat up stay warmer, and areas which don’t heat up as much stay cooler.
But we’re talking about gravity-bound gases, here. If we tried to capture too much, the gases would just find an easier route to equalize, such as going above our turbine network.
Not feasible now. Project a hundred or four hundred years. What if some future Elon is building fully AI controlled factories that do nothing but push out wind turbines that are getting increasingly taller to find moving air.
See also: the ocean is too big to pollute.
How high are you right meow?
When I was in grad school for planetary sciences, my fellow grad students decided I was naturally high. Is looking at the big picture being high? If so, meow.
Feasibility aside, it’d be a lot more practical to get cracking on that Dyson swarm. Photovoltaics are a much more efficient way to capture solar energy, or even direct solar thermal (ie mirrors and steam turbines)
Dyson swarm is great, but only if it isn't beaming power back to the earth. If it's beaming back energy to earth, we're effectively pointing mirrors at the earth so it captures more energy from the sun. That's sort of the opposite of what we're trying to achieve.
But if we've got a Dyson swarm then we've got the power needed to do really intense weather modification, we could build a big facility in the south pole to refreeze it and beam the excess heat to Mars or one of the more distant space bases
You’re getting shit on for asking questions, but these articles seem to bring out the worst in armchair engineers.
It’s worth remembering that wind is the result of solar flux adding energy to our atmosphere. From a practical perspective, we can’t deplete the energy as it gets added constantly no matter what we do. Putting big turbines in the wind does alter local flow profiles but, again from a practical perspective, the mass fraction of air flow modified is minuscule. Further, part if the design of wind farms includes making sure that the turbines stay out of each other’s wake, sort of like keeping solar panels on a solar farm from being in the shadow of another panel.
To bring solar into it again, the concern about stopping the wind is like the concern for overheating the planet by putting up to many solar panels. You see, solar panels have a higher albedo (absorption) of solar radiation than the planet, on average. It’s like pavement vs a gravel road - the pavement is going to heat up more. If you run the numbers, though, the effect is negligible, more like adding 1 dark rock out of every 1000 to the gravel road.
We use, worldwide, something like 1/10,000th of the solar energy that falls on earth. It’s often worthwhile to ask questions like yours, even if only to offer a vehicle for explaining why and how engineers and scientists have had the same questions and found the answers.
Stay curious, friend.
Fair enough, but if humanity had geared up for renewable electricity generation, there would have been more motivation to fund and perform research on battery tech.
Why are you trying to blame "scientists for not speaking up loud enough" and not the ruling class and politicians who have time and time again worked against the interest of people and the stability of Earth's climate in the name of quarterly profits and claiming lower taxes.
And then you're suggesting that the climate impact of wind turbines is going to cause more changes versus what we're already doing.
Do you not think trees? Buildings? Cars? Other mega structures? Are not already changing the way wind is moving? Look at the physical profile of a wind turbine, how much space does it take up at once? Now compare that to the face of a building. How many tens, hundreds of blades could fit in that space? Compare that to Earths entire atmosphere. And you're out here suggesting somehow we'd be at 10% coverage? Even 1% is completely outlandish.
You claim to be pro wind and then just offer absolutely absurd arguments against it. And you're acting like we're doing enough with our current climate crisis to run into another disaster in the future. Wishful thinking, honestly we'll be lucky if we can get far enough to have the issues you're imagining.
There is no one solution, that's how we got ourselves into this mess.
Diversify energy production and reduce energy use, make more efficient houses, cars, machines, work places, more energy efficient living.
Wright's Law applies to solar panels, wind turbines, and more. Basically, as production capacity increases, the cost of production decreases by approximately the ratio of 18% for each doubling of production capacity. This equation will continue to drive the total energy production capacity up while driving energy costs down. With abundant cheap energy, we will keep finding things to use it for.
On an individual level, this looks like: you installed LEDs, so now you have budget available to run the giant TV.
Basically, even though we become more efficient in our daily lives with regard to energy use as individuals, the more energy we produce and use as a civilization. Cheap energy enables progress. Yes, the CPU in your cell phone is very energy efficient, but the energy it took to manufacture it isn't included in your calculations. The more advanced our stuff becomes, the more energy it takes to make it, and run civilization itself.
There is very little you can do as an individual to change the trajectory of global energy production and consumption, but we can at least try to choose better energy sources. The only thing we can do as a civilization in the very long term would be to move production off planet. Or, you know, revert to a stone age civilization where everyone ceases to exist.