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> draining everyone downstream to 0% I don't see how that follows. Hydroelectric power use doesn't destroy water. Minus some evaporation, all water upstream ma

by gnode 8y ago

> draining everyone downstream to 0% I don't see how that follows. Hydroelectric power use doesn't destroy water. Minus some evaporation, all water upstream makes its way downstream whether the gravitational potential energy is converted to electricity or wasted like normal. When building a dam, there's a temporary and arbitrarily small reduction in downstream flow as the reservoir is accumulated, but the more significant issue is usually permanent upstream flooding. Regardless, my understanding is that Idaho is planning to increase its use of solar to make its way to 100%, with hydro being used to balance the supply-demand discrepancy. I would expect any hydro capacity to already be fully utilised on a long term basis.

thaumasiotes 8y ago
It doesn't destroy the water, but it does destroy the flow. More hydroelectric power generation upstream means less use of the river downstream, because it's been pacified into a long pond. This is an area of serious contention in many places, particularly where rivers cross national boundaries. > wasted like normal But the river flow is not normally wasted. Everyone along a river uses it. In particular, if you're willing to assume (correctly) that generating hydroelectric power in Idaho drains gravitational potential energy out of the river -- in Idaho -- then it immediately follows that the people downstream won't be able to generate hydroelectric power from the river, because the energy was all drained out in Idaho. Which is what I said in the first place.
- ethbro 8y ago
  You're conflating a few issues. (1) River flow is an ecological issue, as underflowing or surge flowing a river has devastating consequences to everything living in it. This is usually what's fought over (example: TN-GA-AL-FL legal battles). (2) Gravitational potential energy is not something that can be depleted in the way you're talking about. If Idaho is at 3,000 ft above sea level, whether or not they build a hydro dam doesn't impact the ability of Washington or Oregon to build hydro dams at lower elevations.
  - thaumasiotes 8y ago
    > Gravitational potential energy is not something that can be depleted in the way you're talking about. If Idaho is at 3,000 ft above sea level, whether or not they build a hydro dam doesn't impact the ability of Washington or Oregon to build hydro dams at lower elevations. Gravitational potential energy is depleted when anything's elevation lowers. In rivers as in everything else, it is converted to other forms of energy. In rivers, that is kinetic energy. This is depleted in the normal way by harvesting it as "hydroelectric power". Building a hydroelectric dam at 3,000 feet won't impact the ability of Oregon to build one at 0 feet and get 3,000 feet worth of river energy. But rivers flowing through Idaho started out with more than 0 energy (they're flowing!), which would also have been available for Oregon to use. Idaho's gain is Oregon's loss. They can't drain Oregon to literally 0 energy extractible from the river, but they can come close.
    - zaroth 8y ago
      Idaho is not sending the water into Oregon at any lower elevation because they added a dam and a hydro-plant upstream! Hydro plants don’t harvest the ambient kinetic energy because the terminal velocity of the water is quite low! You can’t build a hydro plant at 0ft elevation, even if that water just flowed down a 10,000ft mountain. A hydro plant takes a specific localized elevation drop and turns that drop into power by harvesting the gravitational mass of the water to rotate turbines installed along the way. The water at the top entrance to the hydro plant is sitting perfectly still in a reservoir built to feed the plant. If you tried to put a turbine at the bottom of a fast flowing river it wouldn’t work. You need the weight (mass) of millions of tons of water pushing directly down on your turbines to generate the necessary power. Now here’s a fun thought. All that potential energy in the water at the top of the mountain, that potential energy got into the water when it evaporated from the surface and raised up into the atmosphere. So really it’s all just another form of solar power.
      - thaumasiotes 8y ago
        Which hypothetical river contains more energy when it reaches Oregon? - A river that came from 8,000 feet - A river that came from 3,000 feet Oregon potentially has access to energy that Idaho cannot extract from the river, by virtue of Idaho's higher elevation. But any and all energy that Idaho does extract from the river is energy that would otherwise have been available downstream. Again, all gains to Idaho are losses to Oregon. The reverse is not true: Oregon enjoys some minor gains which are not losses to Idaho.
- kortilla 8y ago
  Gravitational potential isn’t something magic in the water. It loses the same amount of potential going from 3000ft to 2000ft whether there are 0 dams or 10 dams generating in the middle.
  - thaumasiotes 8y ago
    This is a sensible phrasing to use, but in that case you shouldn't say the dam harvests gravitational potential energy; you should say it harvests kinetic energy. The kinetic energy is just gravitational potential energy from somewhere else.

by gnode 8y ago

thaumasiotes 8y ago

It doesn't destroy the water, but it does destroy the flow. More hydroelectric power generation upstream means less use of the river downstream, because it's been pacified into a long pond. This is an area of serious contention in many places, particularly where rivers cross national boundaries. > wasted like normal But the river flow is not normally wasted. Everyone along a river uses it. In particular, if you're willing to assume (correctly) that generating hydroelectric power in Idaho drains gravitational potential energy out of the river -- in Idaho -- then it immediately follows that the people downstream won't be able to generate hydroelectric power from the river, because the energy was all drained out in Idaho. Which is what I said in the first place.

ethbro 8y ago
You're conflating a few issues. (1) River flow is an ecological issue, as underflowing or surge flowing a river has devastating consequences to everything living in it. This is usually what's fought over (example: TN-GA-AL-FL legal battles). (2) Gravitational potential energy is not something that can be depleted in the way you're talking about. If Idaho is at 3,000 ft above sea level, whether or not they build a hydro dam doesn't impact the ability of Washington or Oregon to build hydro dams at lower elevations.
- thaumasiotes 8y ago
  > Gravitational potential energy is not something that can be depleted in the way you're talking about. If Idaho is at 3,000 ft above sea level, whether or not they build a hydro dam doesn't impact the ability of Washington or Oregon to build hydro dams at lower elevations. Gravitational potential energy is depleted when anything's elevation lowers. In rivers as in everything else, it is converted to other forms of energy. In rivers, that is kinetic energy. This is depleted in the normal way by harvesting it as "hydroelectric power". Building a hydroelectric dam at 3,000 feet won't impact the ability of Oregon to build one at 0 feet and get 3,000 feet worth of river energy. But rivers flowing through Idaho started out with more than 0 energy (they're flowing!), which would also have been available for Oregon to use. Idaho's gain is Oregon's loss. They can't drain Oregon to literally 0 energy extractible from the river, but they can come close.
  - zaroth 8y ago
    Idaho is not sending the water into Oregon at any lower elevation because they added a dam and a hydro-plant upstream! Hydro plants don’t harvest the ambient kinetic energy because the terminal velocity of the water is quite low! You can’t build a hydro plant at 0ft elevation, even if that water just flowed down a 10,000ft mountain. A hydro plant takes a specific localized elevation drop and turns that drop into power by harvesting the gravitational mass of the water to rotate turbines installed along the way. The water at the top entrance to the hydro plant is sitting perfectly still in a reservoir built to feed the plant. If you tried to put a turbine at the bottom of a fast flowing river it wouldn’t work. You need the weight (mass) of millions of tons of water pushing directly down on your turbines to generate the necessary power. Now here’s a fun thought. All that potential energy in the water at the top of the mountain, that potential energy got into the water when it evaporated from the surface and raised up into the atmosphere. So really it’s all just another form of solar power.
    - thaumasiotes 8y ago
      Which hypothetical river contains more energy when it reaches Oregon? - A river that came from 8,000 feet - A river that came from 3,000 feet Oregon potentially has access to energy that Idaho cannot extract from the river, by virtue of Idaho's higher elevation. But any and all energy that Idaho does extract from the river is energy that would otherwise have been available downstream. Again, all gains to Idaho are losses to Oregon. The reverse is not true: Oregon enjoys some minor gains which are not losses to Idaho.
kortilla 8y ago
Gravitational potential isn’t something magic in the water. It loses the same amount of potential going from 3000ft to 2000ft whether there are 0 dams or 10 dams generating in the middle.
- thaumasiotes 8y ago
  This is a sensible phrasing to use, but in that case you shouldn't say the dam harvests gravitational potential energy; you should say it harvests kinetic energy. The kinetic energy is just gravitational potential energy from somewhere else.