29-03-2005 07:34									#31
	Support Apolyton, pre-order Civilization IV

quote: Originally posted by KrazyHorse quote: Sea level doesn't really exist. It is a theoretic tool that enables relative comparisons Duh. Nobody ever said that every piece of the Pacific is always at the exact same level. Do you get your rocks off stating the obvious?

Were you drinking? That was very aggressive.

	29-03-2005 07:38									#32
	Support Apolyton, buy Galactic Civilizations: Deluxe Edition

quote: Originally posted by KrazyHorse Though a difference of 6 metres over ~60 km is a dumbass way to generate hydro...

Surely the fall would happen right at the turbine/dam just as in a river?

	29-03-2005 07:40									#33
	Support Apolyton buy from Amazon

quote: Originally posted by GePap IN fact, the locks are mainly to get ships high enough to traverse the Canal, which is at a higher level than either Oceans. In essence, ships come from either side, get lifted to cross the artificial lake over the highlands, get to the other set of locks, they are brought down, and the trip continues.

I like those wheel things that move ships.

	29-03-2005 07:40									#34
	Avatar Enlargement: We've got the solution

Let's blast a new canal through Nicaragua and have competition...

	29-03-2005 07:49									#35
	Support Apolyton, buy Alpha Centauri

quote: Originally posted by TCO Were you drinking? That was very aggressive.

I'm trying to be more like you.

	29-03-2005 08:40									#36
	Support Apolyton, buy GURPS/ Alpha Centauri

Wouldnt the counterclockwise spin of the earth mean that all bodies of water would be higher on their east side (in direction of spin) than west (against spin). So, of course, looking at a cross section across the Isthmus of Panama the Pacific ocean will appear higherthan the Atlantic.

	29-03-2005 08:47									#37
	Enter the AD-FREE zone

quote: Originally posted by KrazyHorse I'm trying to be more like you.

Aaah...very tongue in cheek. You were actually making a point against me rather than the person involved.

	29-03-2005 08:48									#38
	Enter the AD-FREE zone

Whyy? It's not like the earth's spin is accelerating...

	29-03-2005 08:49									#39
	Support Apolyton buy from Amazon

quote: Originally posted by TCO Surely the fall would happen right at the turbine/dam just as in a river?

Yes, but that means you have to transport all that water the 60 km across the isthmus.

	29-03-2005 08:57									#40
	Support Apolyton, buy Galactic Civilizations: Deluxe Edition

quote: Originally posted by KrazyHorse Yes, but that means you have to transport all that water the 60 km across the isthmus.

Ever seen a lake behind a dam? Seriously the head loss in the channel will not be that high. (I mean look at the TVA lakes). Of course, the whole thing assumes a clear cut.

	29-03-2005 14:27									#41
	Increase the size of your Attachments

yes, most dams have lakes behind them. The level is pretty constant. It doesn't matter if the entire elevation is constant through 59.9 km. Just the act of releasing water through a dam (via the turbines of course) would create a void allowing water to fill the space recently vacated.

So yes you could have it completely level and then drop 6 m. I'm not exactly sure how much power that would create. There isn't much potential energy. But yet, you are essentually holding back an entire ocean. .

	29-03-2005 14:31									#42
	Support Apolyton or Terrorists Win

quote: Originally posted by SpencerH Wouldnt the counterclockwise spin of the earth mean that all bodies of water would be higher on their east side (in direction of spin) than west (against spin). So, of course, looking at a cross section across the Isthmus of Panama the Pacific ocean will appear higherthan the Atlantic.

The things that gets me is the oceans are connected at the bottom. The Indian is connected to the pacific, and the pacific is connected to the atlantic on the southern tip of s. america. And the atlantic is connected to the indian ocean via the tip of s. africa. You'd think the level would even out. But I guess I could see how the level could vary near the equater.

	29-03-2005 14:39									#43
	Enter the AD-FREE zone

quote: Originally posted by TCO Ever seen a lake behind a dam? Seriously the head loss in the channel will not be that high. (I mean look at the TVA lakes). Of course, the whole thing assumes a clear cut.

Exactly. All for a 6 metre gain.

The nuber of places you could put a hydro dam which wouldn't require such massive effort for such minimal reward is very large...

	29-03-2005 14:42									#44
	Support Apolyton, buy Alpha Centauri

quote: Originally posted by Dissident yes, most dams have lakes behind them. The level is pretty constant. It doesn't matter if the entire elevation is constant through 59.9 km. Just the act of releasing water through a dam (via the turbines of course) would create a void allowing water to fill the space recently vacated. So yes you could have it completely level and then drop 6 m. I'm not exactly sure how much power that would create. There isn't much potential energy. But yet, you are essentually holding back an entire ocean. .

Ocean or no ocean the water will only flow through at a rate which is proportional to the cross-sectional area of the narrowest point of the channel.

most hydro dams use a drop of something like 50 metres or more, and they don't involve tunnelling 60 km through a mountain range to do it.

	29-03-2005 15:00									#45
	Support Apolyton buy from Amazon

Roughing out a few figures, even assuming no loss from interaction with walls of canal (assuming the water was accelerated instantaneously to its final velocity and that it managed to travel from one side of panama to the other without loss), if we kept the width and depth of the canal as it stands today, we would generate a maximum (assuming 100% efficiency of turbines) of 400 MW. For comparison purposes, the amount of hydro power generated by Niagara falls is something like 5000 MW

	29-03-2005 15:05									#46
	Put an end to popups!

So we'd have to make the Canal a straight shot across panama and increase its cross-sectional area 13-fold to match Niagara falls. This is assuming the most ideal situation; in fact, most turbines run at around 30% efficiency, so now we're talking 40 times the current area. Add in the hydrodynamics and you're probably talking 200+ times the current area...

	29-03-2005 15:06									#47
	Increase the size of your Attachments

we all know it's useless and impractical. We're just discussing if it can be done.

As I said before. Cutting through mountains isn't as easy as games like civ2 would have you believe.

A dam would be useless anyways. How would the ships traverse? You could have a bypass, but that would have to use locks again.

	29-03-2005 15:08									#48
	Help yourself to an AD-FREE life

I know you don't think we should do it. I'm just presenting the available power and the limiting factors as rough estimates as a general thought exercise.

	29-03-2005 19:54									#49
	Browse Apolyton AD-FREE

quote: Originally posted by KrazyHorse Whyy? It's not like the earth's spin is accelerating...

Its evidence that the earths rotation is slowing

Heres the answer. It involves the rotation but not in the way I was (incorrectly) thinking.

quote: You were taught correctly. The Pacific and Atlantic Oceans have different heights with the highest sea surface in the Western Pacific. But don't worry about all that Pacific water rushing into the Atlantic and flooding the Texas coast. As far as equalizing levels, this has occurred but introduces an idea that many people find hard to imagine. The difference in heights is a result of a "dynamic equilibrium". Dynamic means changing, but equilibrium means balance, which we usually think of as no change. How can this be? Think of an unchanging balance as one like you can find on a scale where you place the same weight on both sides and it will balance -- always and forever. There is no new weight added or removed, no energy added or removed. This is Static equilibrium, an unchanging balance. A dynamic equilibrium involves the balance of changes. Imagine on your scale that you have cups instead of weights. Each cup the same size and is being dripped into and overflows but it will still balance if the fluid dripping in and out balances on both sides. Here there is a dynamic equilibrium with changes in mass or weight. If we want to imagine an equilibrium that also includes energy, let's have one side of the scale have a smaller cup than the other. Water drips in and overflows, but the two sides can never balance because the two cups can never hold the same amount of water. This gets a little complicated, so hang in there. The cups can't balance each other with weight alone. The lighter cup will go up and the heavy cup will go down. You can make a dynamic equilibrium by pushing down on the lighter cup. Now you have two cups with different amounts of water that balance. Hmmm? This can only happen with the addition of energy. This is similar to how the sea surface heights can be different -- there is a dynamic equilibrium. It is indeed affected by the rotation of the Earth which is where some of the energy used to maintain the balance comes from. More comes from the Sun and its heat. The energy acts through winds on the sea surface and currents which tend to cause water to "pile up" where currents are swift. Imagine the surface of your morning juice in its cup. If you swirl that juice, the surface is no longer 'level' but slanted (and the slant rotates with the swirl). This slant is maintained as long as you continue to swirl the cup. You have an equilibrium that requires energy. The moment you stop adding energy by swirling, the surface of the juice levels out. It is now a static system with a static equilibrium that is simple to understand. There is a huge science project (yes, scientists do science projects too) called TOPEX/Poseidon that looks at the sea surface (and other ocean information) from orbiting satellites. And there are oceanographers who specialize in studying the sea surface and what causes it to be different from flat. Some of this information is available on the Internet including really cool pictures made from satellite information. You can start looking at these locations:

http://www.madsci.org/posts/archive...67100.Es.r.html

	29-03-2005 20:24									#50
	Support Apolyton, buy Civilization: The Boardgame

quote: Originally posted by Docfeelgood So which is heavier? 100 pounds of lead or 100lbs of feathers? Hundred pounds is a hundred pounds such as sealevel is sealevel. All the oceans that are at sealevel are the same height.

Thats an inane answer.
As many ppl have posted (see post above for example) oceans are not always at "sea level".
And thats what the original poster asked...

	29-03-2005 21:26									#51
	Support Apolyton, buy Civilization 2

The acceleration (for a typical dam/hydro turbine) does happen almost completely at the nozzle/turbine and thus there is little headloss from flow thorugh the lake behind the dam. Is 30% efficiency reasonable for a water turbine? Steam turbines have efficiencies in the high 90's, but of course there is a larger pressure drop.

I agree with you that 18 feet of head is not worth drilling through 40 miles of mountains for...

	29-03-2005 21:33									#52
	Support Apolyton, buy Call to Power 2

Kitty, were you thinking of a heat cycle efficiency with the 30%? The water turbine is just a mechanical energy conversion device. Here is some Googled info:

http://www.tev.ntnu.no/vk/publikasj...le/chapter1.pdf

http://www.azsolarcenter.com/otherre/hydro1.html

	30-03-2005 01:41									#53
	Support Apolyton, buy Civilization III: Complete

quote: Originally posted by SpencerH Its evidence that the earths rotation is slowing

With a timescale of a billion years or so?

That's a bad joke...

As for the link it simply states that large scale meteorological and geological (but not astronomical) forces are to blame. The reason is not obvious from a physics point of view...

	30-03-2005 01:46									#54
	Support Apolyton, buy GURPS/ Alpha Centauri

quote: Originally posted by TCO Kitty, were you thinking of a heat cycle efficiency with the 30%? The water turbine is just a mechanical energy conversion device. Here is some Googled info: http://www.tev.ntnu.no/vk/publikasj...le/chapter1.pdf http://www.azsolarcenter.com/otherre/hydro1.html

No. I know the difference between a heat engine and a turbine.

I did a quck google search on it and my hit gave an efficiency of 0.30. Either they were in error or I misread. I was slightly surprised at how low the efficiency was, actually, but decided to take what I thought was their word since I am but a theorist...

	30-03-2005 01:48									#55
	Support Apolyton, buy Civilization III: Complete

quote: Originally posted by TCO The acceleration (for a typical dam/hydro turbine) does happen almost completely at the nozzle/turbine and thus there is little headloss from flow thorugh the lake behind the dam.

However this means that the flowrate is much lower than the flowrate I used (the maximum possible value of ~8 m/s). A reasonable flowrate for a path which does not slope too much would have to be more like 1 m/s, so take the power I gave you and divide by 8...

	30-03-2005 01:59									#56
	Support Apolyton

quote: Originally posted by KrazyHorse However this means that the flowrate is much lower than the flowrate I used (the maximum possible value of ~8 m/s). A reasonable flowrate for a path which does not slope too much would have to be more like 1 m/s, so take the power I gave you and divide by 8...

I'm struggling to understand your thought process. Where did 8m/second come from? I tend to think in terms of volumetric flow rates versus velocities for a system with changing cross-sectional area. What's the velocity of water "accross the lake" behind Hoover dam?

	30-03-2005 02:06									#57
	Full PM-box? Change here!

How about we use nuke bombs to clear the channel? There are some ones that are designed for this kind of work...

	30-03-2005 02:09									#58
	Inflate your Upload Space

also, just because the step change is only 18 feet does not mean the supply (and exhaust) channels are limited to this depth. They could be deeper, which will minimize head loss from friction with the channel walls.

	30-03-2005 02:10									#59
	Increase the size of your Attachments

Need to extend these channels off shore a little bit, too...

	30-03-2005 02:12									#60
	Increase the size of your Attachments

I like it better than the laser launching system which requires a beam that stays on target (and does not spread) over 1000 bounces and planetary distances or whatever...)