Dam The Thermodynamics!
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I saw this NY Times article The $3 Billion Plan to Turn Hoover Dam Into a Giant Battery[^] Is it just me, or is this about the stupidest $3 billion boondoggle ever? Rather than pumping water that you've just released through the dam, back into the reservoir behind the dam, why not just let less water flow through the dam and supplement the shortfall with the solar energy? You'd be thermodynamically ahead.
I live in Oregon, and I'm an engineer.
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I saw this NY Times article The $3 Billion Plan to Turn Hoover Dam Into a Giant Battery[^] Is it just me, or is this about the stupidest $3 billion boondoggle ever? Rather than pumping water that you've just released through the dam, back into the reservoir behind the dam, why not just let less water flow through the dam and supplement the shortfall with the solar energy? You'd be thermodynamically ahead.
I live in Oregon, and I'm an engineer.
It seems storage of bulk power is still an issue so if they have an oversupply of say solar energy they turn it off. Pumping water uphill would use that over supply instead of turning it off and the water at the top of the dam basically act as a storage device. What happens to unused electricity on the National Grid? | Science Focus[^] justifying 3bn expenditure is another matter :(
Never underestimate the power of human stupidity RAH
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It seems storage of bulk power is still an issue so if they have an oversupply of say solar energy they turn it off. Pumping water uphill would use that over supply instead of turning it off and the water at the top of the dam basically act as a storage device. What happens to unused electricity on the National Grid? | Science Focus[^] justifying 3bn expenditure is another matter :(
Never underestimate the power of human stupidity RAH
I understand the concept of pumping water uphill into a reservoir as energy storage. And yes, a hydroelectric dam is what you use for this kind of energy storage. The part I don't get, is where one uses a large dam like Hoover Dam for this. The thing's on a river. You can't pump more water upstream than you're letting flow downstream through the dam. The best you can do, is to pump all the water you let through back up. If you've got that much solar energy that you can do that, then you have more than enough to replace all of the electricity you get by letting any water through the dam. In fact, because of losses, you actually have more than enough energy. Unless they're getting water from somewhere else, and the article doesn't say they're doing that, then this make absolutely no thermodynamic sense.
I live in Oregon, and I'm an engineer.
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I understand the concept of pumping water uphill into a reservoir as energy storage. And yes, a hydroelectric dam is what you use for this kind of energy storage. The part I don't get, is where one uses a large dam like Hoover Dam for this. The thing's on a river. You can't pump more water upstream than you're letting flow downstream through the dam. The best you can do, is to pump all the water you let through back up. If you've got that much solar energy that you can do that, then you have more than enough to replace all of the electricity you get by letting any water through the dam. In fact, because of losses, you actually have more than enough energy. Unless they're getting water from somewhere else, and the article doesn't say they're doing that, then this make absolutely no thermodynamic sense.
I live in Oregon, and I'm an engineer.
The important issue is does it make economic sense? This kind of thing is done near Yosemite at Shaver Reservoir. Water is pumped uphill during the night when demand is much lower and power much cheaper. It flows downhill during the day to generate power during the time of highest demand and most expensive power. Economically this is a win, largely because of the very high cost of power in the area.
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The important issue is does it make economic sense? This kind of thing is done near Yosemite at Shaver Reservoir. Water is pumped uphill during the night when demand is much lower and power much cheaper. It flows downhill during the day to generate power during the time of highest demand and most expensive power. Economically this is a win, largely because of the very high cost of power in the area.
Still doesn't cover the OP question, why not use less water when demand low. dunno about US hydro plants but visited some in NZ medium sized plants they typically have 4 - 6 inlets, they can fully or jusr partially close any of these. when consumer draw is low close the valves, and let the solar/wind run the consumer draw. rather then feed consumer draw from the dam and have wind/solar pump water uphill, (which as OP mentioned is simply way less efficient then slowing the water.) what's next? - build huge fans to spin the windmills on sunny windless days? - build powerful UV lights to make solar when the wind blows at night? - why not charge drone batteries so they can fly up and seed rain clouds above dams. combine all these ideas (incl the water pumps) and many more to create endless ways to consume excess power rather than just turn the damm plants down!
This internet thing is amazing! Letting people use it: worst idea ever!
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I saw this NY Times article The $3 Billion Plan to Turn Hoover Dam Into a Giant Battery[^] Is it just me, or is this about the stupidest $3 billion boondoggle ever? Rather than pumping water that you've just released through the dam, back into the reservoir behind the dam, why not just let less water flow through the dam and supplement the shortfall with the solar energy? You'd be thermodynamically ahead.
I live in Oregon, and I'm an engineer.
'Water up mountains' has been a preferred energy store for a long time, and very effective it is too. Plenty of weight in water, plenty of PE. So when you have an excess of any energy, solar, wind, whatever, or just a limited supply of 24/7 energy, you use it to pump water up hill. Then when you get a surge in demand, you open the taps and run the turbines. Simple engineering, effective solution.
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'Water up mountains' has been a preferred energy store for a long time, and very effective it is too. Plenty of weight in water, plenty of PE. So when you have an excess of any energy, solar, wind, whatever, or just a limited supply of 24/7 energy, you use it to pump water up hill. Then when you get a surge in demand, you open the taps and run the turbines. Simple engineering, effective solution.
Munchies_Matt wrote:
Water up mountains' has been a preferred energy store for a long time, and very effective it is too.
Viz. the Dinorwic pumped storage scheme, with which I was intimately and rather dangerously associated - as a one time photogrammetrist I was 'volunteered' to go into the old mineshafts around the planned tunnel with a pair of calibrated survey cameras on a sledge and photograph long abandoned shafts that were deemed too dangerous to send a surveyor down, and subsequently pull the plates up on a stereo-comparator to see if there were any side shafts. The this was in the mid seventies, and the Dinorwic scheme is still working successfully today.
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Munchies_Matt wrote:
Water up mountains' has been a preferred energy store for a long time, and very effective it is too.
Viz. the Dinorwic pumped storage scheme, with which I was intimately and rather dangerously associated - as a one time photogrammetrist I was 'volunteered' to go into the old mineshafts around the planned tunnel with a pair of calibrated survey cameras on a sledge and photograph long abandoned shafts that were deemed too dangerous to send a surveyor down, and subsequently pull the plates up on a stereo-comparator to see if there were any side shafts. The this was in the mid seventies, and the Dinorwic scheme is still working successfully today.
The one in South Wales?
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The one in South Wales?
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Still doesn't cover the OP question, why not use less water when demand low. dunno about US hydro plants but visited some in NZ medium sized plants they typically have 4 - 6 inlets, they can fully or jusr partially close any of these. when consumer draw is low close the valves, and let the solar/wind run the consumer draw. rather then feed consumer draw from the dam and have wind/solar pump water uphill, (which as OP mentioned is simply way less efficient then slowing the water.) what's next? - build huge fans to spin the windmills on sunny windless days? - build powerful UV lights to make solar when the wind blows at night? - why not charge drone batteries so they can fly up and seed rain clouds above dams. combine all these ideas (incl the water pumps) and many more to create endless ways to consume excess power rather than just turn the damm plants down!
This internet thing is amazing! Letting people use it: worst idea ever!
There is probably some sort of legislation that prevents them from closing off the minimum flow. There may also be environmental or mechanical reasons to keep the flow going. Oz is looking at doing the same thing in the snowy mountain scheme, I know that close off all the flow into Jindabyne the level drops by about 10m in summer.
Never underestimate the power of human stupidity RAH
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OK. I thought there was one in the south too, but could be mistaken. Makes sense up north though, more mountainous.