> We aren't really in any kind of a place to grasp the enormity of the numbers. Numbers that big really do become meaningless.
If that's true, that's all the more reason not to comment.
You're saying we can't grasp the numbers, but apparently you think you can grasp them well enough to conclude that humans won't have a significant effect.
If we really can't grasp the numbers, then the only conclusion we can come to is that we don't know. I think "I don't know" is something that we need to say more often if we're being honest with ourselves.
> For instance, in BTUs, about 80 million british quads of the energy that the sun gives earth will make it to the surface in a year. (I know the sun delivers more than 80 million british quads, but I'm not counting the 30% that gets reflected). Now I'll be nice, and say an additional 10-20% of that is absorbed by biomass. (It's not, it's way closer to 10%, but I'm being nice.) And an average American home uses what? say 50 million BTUs a year, (About 12 - 15 thousand kWh), if they're being profligate?
> So the wind is coming from the interplay of the solar energy absorbed by different areas of the ocean and different areas on land. (Another caveat, our atmosphere can trap some of the energy, which will add to new energy sent by the sun, and kind of spiral in that fashion. This is what happened to Venus, which is why they have like 500 mile an hour winds there.) In any case, ignoring the climate warming, we'd have to find some way to harness enough wind to make an impact against, say, 20 million british quads of BTUs.
Back-of-napkin math is pretty unconvincing. For example, you made no mathematical connection whatsoever between the energy from the sun numbers you were throwing around, and the amount of that that gets converted into wind energy. You said that 80 million quads of energy hit's the earth from the sun, so your "20 million British quads of BTUs" is arbitrarily choosing to say that 1/4 of the sun's energy is converted to wind?
So let's sanity check that. quads is a unit of energy E, and E = 1/2 x m x v^2
Now let's convert our numbers into reasonable units and plug them into the equation. 20 million quads = 2 x 10^7 quads. 1 quad = 1.055 x 10^18 joules[1], so that's 2.11 x 10^25 joules. The mass of the earth's atmosphere is 5.15 x 10^18 kg[2]. Plugging these numbers into E and m in the equation, we get:
E = 1/2 x m x v^2
2.11 x 10^25 = 1 / 2 x 5.15 x 10^18 x v^2
2.11 x 10^7 = 1 / 2 x 5.15 x v^2
4.22 x 10^7 = 5.15 x v^2
2.1733 x 10^8 = v^2
14700 = v
Just to be clear, joules is kg x m^2 / s^2 and our mass was in kg, so this velocity is 14700 m/s. You guessed that 20 million quads of the sun's energy was being converted into wind, but if that were true, the average velocity of the earth's atmosphere would be 14700 m/s. To be clear, that's the average velocity, and we know that wind isn't uniform throughout the atmosphere, so some parts would be faster. For comparison, the speed of sound in air is 343 m/s.
So yeah, the numbers you are using are incomprehensibly large because they are wrong, wrong, wrong by a few orders of magnitude.
To be clear, this isn't a criticism of wind power. It's obvious that the clear and present danger of global warming is a much more pressing concern than unknown effects of wind power. It's a criticism of people answering questions they don't know anything about.
While I was calling you out for essentially making up numbers, I noticed that my [1] link above contains the global energy consumed in 2004. I decided to look for more recent numbers, and on this page[1] found that estimated world energy consumption was 5.67 x 10^20 joules.
Let's convert that to wind speed:
E = 1/2 m x v^2
5.67 x 10^20 = 1 / 2 x 5.15 x 10^18 x v^2
5.67 x 10^2 = 1/ 2 x 5.15 x v^2
1.134 x 10^3 = 5.15 x v^2
2.2 x 10 ^ 2 = v^2
14.8 = v
So we'd expect that if all the world's energy came from wind, it would reduce wind speed in the world by an average of 14.8 m/s.
For comparison, average wind speed in Chicago, the windy city, from 2010 to present was 9.9 miles/hour[2] = 4.43 m/s.
Before you lose your calm, and conclude that wind power is evil, let me reiterate, back of napkin math STILL shouldn't convince anyone of anything. I'm merely posting this to show that back of napkin math can be used to calculate much different results.
I think that you missed a time term somewhere. You're looking at global energy use for an entire year. Don't you want to normalize that to joules used per time period (i.e. power) before determining how it affects instantaneous-average wind speeds?
The lowest published estimate I have seen for extractable global wind power [1] is as little as 18 terawatts in the paper by Miller, Gans, and Kleidon:
"Estimating maximum global land surface wind power extractability and associated climatic consequences"
18 terawatts happens to be exactly equivalent to an annual energy output of 5.67 x 10^20 joules.
18 terawatts is the low end of the estimated range in this paper; the upper end is 68 terawatts.
[1] The authors only considered wind farms placed on land, perhaps because offshore wind was so much more expensive in 2011. Their lowest estimate is too low, even if you stick with the rest of their methodology, after adding offshore wind.
> I think that you missed a time term somewhere. You're looking at global energy use for an entire year. Don't you want to normalize that to joules used per time period (i.e. power) before determining how it affects instantaneous-average wind speeds?
Nope. I may have messed up my calculations somewhere, but I'm quite confident in my equation (kinetic energy E = 1/2 x m x v^2).
That paper looks pretty interesting, but I'm going to follow my own advice and admit I don't know: I don't have the background to evaluate the validity of their atmospheric model. The conclusion[1] is pretty important if it's true.
[1] "Furthermore, we show with the general circulation model simulations that some climatic effects at maximum wind power extraction are similar in magnitude to those associated with a doubling of atmospheric CO2. "
> You've calculated that a year of energy consumption is equivalent to the kinetic energy of the atmosphere moving at 14m/s.
> This says nothing about how energy flows through the system, which is what will determine the impact on wind speeds.
shrug
I'm not gonna teach you guys high school physics. You can look up E = (1/2)mv^2 in any Physics textbook or your favorite search engine.
Before you disagree further, try calculating this yourself. Look up how to calculate the final speed of an object from kinetic energy. Make sure you plug energy units (i.e. joules) into E and power units (i.e. watts) into P. This isn't hard math, and the necessary equations are all over the internet.
> The value you plugged in was a year of energy consumption. Why not a day, or a century?
...because when I pulled the number from wikipedia it said it was the energy consumption for a year, not for a day or a century.
> You're not using the equations incorrectly, but they're not telling you what you think they are.
> They are telling you - if we store up all the power use of humanity for this length of time, then use it to blow the air, how fast will it go.
...no, it's telling me if we collect the energy used by humanity during this length of time, then use it to blow the air, how fast will it go. You cannot use "energy" and "power" as if they were interchangeable, they are not.
What you may be missing is that these physics equations go both directions. If we take the blowing of the air and use it to produce the energy used by humanity during this length of time, we'd expect to see the same decrease in speed.
There's nothing wrong with my sentence. It might be a bit informal, but "power use for a length of time" is a quantity of energy.
The decrease in speed you're describing is one time, not continuous. This is the issue both parent and I are pointing out. It's a shame to me that you aren't willing to see your error and instead resort to nitpicking, but I'm not going to try to explain a third time.
If that's true, that's all the more reason not to comment.
You're saying we can't grasp the numbers, but apparently you think you can grasp them well enough to conclude that humans won't have a significant effect.
If we really can't grasp the numbers, then the only conclusion we can come to is that we don't know. I think "I don't know" is something that we need to say more often if we're being honest with ourselves.
> For instance, in BTUs, about 80 million british quads of the energy that the sun gives earth will make it to the surface in a year. (I know the sun delivers more than 80 million british quads, but I'm not counting the 30% that gets reflected). Now I'll be nice, and say an additional 10-20% of that is absorbed by biomass. (It's not, it's way closer to 10%, but I'm being nice.) And an average American home uses what? say 50 million BTUs a year, (About 12 - 15 thousand kWh), if they're being profligate?
> So the wind is coming from the interplay of the solar energy absorbed by different areas of the ocean and different areas on land. (Another caveat, our atmosphere can trap some of the energy, which will add to new energy sent by the sun, and kind of spiral in that fashion. This is what happened to Venus, which is why they have like 500 mile an hour winds there.) In any case, ignoring the climate warming, we'd have to find some way to harness enough wind to make an impact against, say, 20 million british quads of BTUs.
Back-of-napkin math is pretty unconvincing. For example, you made no mathematical connection whatsoever between the energy from the sun numbers you were throwing around, and the amount of that that gets converted into wind energy. You said that 80 million quads of energy hit's the earth from the sun, so your "20 million British quads of BTUs" is arbitrarily choosing to say that 1/4 of the sun's energy is converted to wind?
So let's sanity check that. quads is a unit of energy E, and E = 1/2 x m x v^2
Now let's convert our numbers into reasonable units and plug them into the equation. 20 million quads = 2 x 10^7 quads. 1 quad = 1.055 x 10^18 joules[1], so that's 2.11 x 10^25 joules. The mass of the earth's atmosphere is 5.15 x 10^18 kg[2]. Plugging these numbers into E and m in the equation, we get:
Just to be clear, joules is kg x m^2 / s^2 and our mass was in kg, so this velocity is 14700 m/s. You guessed that 20 million quads of the sun's energy was being converted into wind, but if that were true, the average velocity of the earth's atmosphere would be 14700 m/s. To be clear, that's the average velocity, and we know that wind isn't uniform throughout the atmosphere, so some parts would be faster. For comparison, the speed of sound in air is 343 m/s.So yeah, the numbers you are using are incomprehensibly large because they are wrong, wrong, wrong by a few orders of magnitude.
To be clear, this isn't a criticism of wind power. It's obvious that the clear and present danger of global warming is a much more pressing concern than unknown effects of wind power. It's a criticism of people answering questions they don't know anything about.
[1] https://en.wikipedia.org/wiki/Quad_(unit)
[2] https://en.wikipedia.org/wiki/Atmosphere_of_Earth