[deleted]
Tidal energy is not renewable
201–210 of 350 posts
Re: Tidal energy is not renewable
#202Earlier quoted context omitted.
> The single most important assumption in this paper is that energy consumption will increase by 2% per year. There's a 2nd big assumption: That tidal energy extracted is additional Earth's rotational energy loss above what Earth does by itself. According to the paper, tidal energy is dissipated through friction between ocean water & the seafloor. This dissipated energy subtracts from Earth's rotational energy. And s…
>Author's 2nd assumption is that as tidal energy is tapped, this is extra energy that subtracts from Earth's rotation. Not so. The calculation of the 1031 years is equation 19 and assumes the decrease in rotational energy all goes to human purposes. The flaw in the OP is the assumption that human consumption keeps rising at .02 per year for 1031 years: we would probably boil the oceans away because of the waste heat…
> we would probably boil the oceans away because of the waste heat from using that much electrical power.
Which would slow the earth due to the change in angular momentum
Re: Tidal energy is not renewable
#203Earlier quoted context omitted.
More countries are now sub-2.0 replacement, China is down to 1.09 so the peak is unlikely to get much more than that.
A Google search for “china children per woman” gives me 1.705 Are you talking about something else ?
I suppose that would be replacement rate if there were 42% more women than men in China. But according to Wikipedia there actually 4.5% more men than women.
Re: Tidal energy is not renewable
#204Earlier quoted context omitted.
The UN has revised peak projections down several times; the peak is now expected at 10 billion.
Almost every human population is under strong selection pressure towards having more people. This dip in fertility cannot and will not last.
The future is Amish
Re: Tidal energy is not renewable
#205Earlier quoted context omitted.
Conversely the people who argue against growth never have any answers they want to elaborate on. They have "well we can't have endless growth" and that's where the conversation stops. They never want to examine the consequences of that thought (no growth means we're into a zero-sum game) or whether they think we're even plausibly close to the limit (instead they want to have a proxy argument about environmental damag…
I'd really like to see you point to specific instances of this. I could point to any number of examples refuting this, but really prefer you lay your cards on the table first.
I mean you're doing that right now. You seem to believe we can't have infinite growth. Okay...and? Do you have anything more to add other then a mathematical reductio ad absurdum talking about 1000 year timespans? What tangible actions and economic model do you believe this should inform in the next 5 to 10 years, which you as a citizen of a democracy have some role in choosing and advocating for?
Re: Tidal energy is not renewable
#206The comment here focus on the exponential growth of energy needs assumed. However that is besides the point, unless I am missing something. If the increase doesn’t happen in 1000, may be 10000. The main point for me is that by using the tidal energy we are slowing down the earth rotation. That just sounds intuitively wrong to me. This energy is already released because of the rotation, how can converting that impact the earth’s rotation?
Re: Tidal energy is not renewable
#207Earlier quoted context omitted.
> The single most important assumption in this paper is that energy consumption will increase by 2% per year. There's a 2nd big assumption: That tidal energy extracted is additional Earth's rotational energy loss above what Earth does by itself. According to the paper, tidal energy is dissipated through friction between ocean water & the seafloor. This dissipated energy subtracts from Earth's rotational energy. And s…
Your observation seems to make sense. Intuitively, if we extract energy from the tides, tides will be less tall and the speed of water will be smaller. Ocean currents will slow down too. What I don't know is, less friction on the seafloor means that we would actually make Earth slow down less faster than it would do if left alone?
It’s a bit odd to extrapolate to this level. It’s like thinking, yes, I can set one tree on fire and release energy, but look how crazy it is if all the trees in North America burn at once!!
And currents are also affected by the rotation of the Earth, temp differences, and salinity differences so they might not change dramatically.
Re: Tidal energy is not renewable
#208Earlier quoted context omitted.
I'd really like to see you point to specific instances of this. I could point to any number of examples refuting this, but really prefer you lay your cards on the table first.
I mean you're doing that right now. You seem to believe we can't have infinite growth. Okay...and? Do you have anything more to add other then a mathematical reductio ad absurdum talking about 1000 year timespans? What tangible actions and economic model do you believe this should inform in the next 5 to 10 years, which you as a citizen of a democracy have some role in choosing and advocating for?
https://news.ycombinator.com/item?id=37386474>
Again: I have sources. You?
I'm reading this as you don't.
Re: Tidal energy is not renewable
#209I'm not sure the author realized this, but they're actually making a statement about how crazy exponential growth is. Not about the sustainability of tidal power. This becomes obvious once you look closer at what that 2% growth rate (as assumed in the post) implies. Our global energy consumption in 2008 was estimated to be 474 exajoules. The total energy received by the earth from the sun during a year is about 5 mil…
> Our global energy consumption in 2008 was estimated to be 474 exajoules. If my maths is right, that's about 40,000 kcal per person per day, or about 15 times the energy consumption of an average adult. I'm trying to figure out if that's a lot or not. On the one hand, not: this ratio is not strictly bounded in any way, and the human energy consumption is an arbitrary denominator. Still, a very rough interpretation i…
[deleted]
Re: Tidal energy is not renewable
#210> Based on the average pace of world energy consumption over the last 50 years, if we were to extract the rotational energy just to supply 1% of the world's energy consumption, the rotation of the Earth would lock to the Moon in about 1000 years.
This is bananas. I stopped right there and closed it. I see somewhere else in this thread that they tried to do that by extrapolating an exponential growth curve through an outlier (the industrial revolution!) for a thousand years. Maybe that explains it.
But... that's not an error. That's just bananas. Absolutely insane.
Some quick googling, FWIW, gives the earth's rotational kinetic energy as a quite plausible 2.1e29 J (though a little of this will not be extractable tidally, as the earth will lock to the moon at a few percent of rotation speed), and the total world energy consumption as 22.8 TWh/year. So the back of my envelope says that at current consumption we have a hair over... two trillion years.