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Forgive me my lack of understanding of the englisch language, but I do not understand the distinction you make. Hydroelectricity: Is this power you obtain by p

Forgive me my lack of understanding of the englisch language, but I do not understand the distinction you make. Hydroelectricity: Is this power you obtain by placing turbines behind a huge concrete wall of a large river? If so, how is the scenario of building a large concrete dam in the mountains where water is pumped up a hill to covert it into kinetic energy any more better? I understand that hydroelectricity is used to supply the basic power need, say 80% and a water reservoir with turbines to cover power peak needs.

Gwypaas 4y ago
Because you're not disrupting a river's flow and natural ecosystem, you only utilize the watershed some more during the initial filling period. After that, it's a closed system separate from the river ecosystem where only evaporation causes leakage.
- roamerz 4y ago
  That ship has already sailed as most power producing dams have been around for long time. Removing them would destroy the (now natural) ecosystem they have created. Plus dams have way more benefits to us than the extremely clean energy they produce - not just store.
  - brookst 4y ago
    This is the first time I've seen a claim that dams create ecosystems that we should worry about destroying. As far as I know, they disrupt fish and animal migrations, reduce natural carbon sinks, reduce biodiversity, and block sediment from providing nutrients downstream. Is there any source saying dams create healthy natural ecosystems? A necessary evil I can kind of see, but a net positive for ecosystems? That seems doubtful.
    - whiddershins 4y ago
      I don’t know. I suspect the bias is towards the pre-dam ecosystem so it might be challenging to rationally compare them. Certainly an ecosystem will grow up around nearly any situation.
    - chasd00 4y ago
      there are many human ecosystems living below the dam though. Removing the dam means removing entire towns downstream in some cases.
      - pencilguin 4y ago
        That is not, in fact, true. Almost all dams have a river flowing below them, where it always did. A very few places use all of the inflow for irrigation.
    - roamerz 4y ago
      Yup my opinion only. To me water is life and if you let it flow to the ocean where it’s only use is to dilute saltwater you’ve wasted a precious natural resource.
      - Gwypaas 4y ago
        Dams does not save any water except the initial filling. Their inflow and outflow match over a seasonal cycle.
        jcranmer 4y ago
        Also, they tend to cost water instead: the larger surface area increases the amount "lost" to evaporation.
        roamerz 4y ago
        Perhaps. I suppose that would depend on size and depth of the reservoir and the makeup of the river. Also without a dam the water would be traveling the river mostly during the cold wet season with little evap. So yeah likely so. But in the end the cost would be lost saltwater. Probably a benefit for those that are worried about sea levels.
        roamerz 4y ago
        Yup that’s simplistically true. The difference though they do allow you to choose when it gets released. Around where I live that allows irrigation of crops during the summer months. That water does not go into the ocean. Also around here many of the municipalities draw water downstream from the dam as well. A portion of that travels through the sewer systems, gets purified then dropped back into the river.
  - azylman 4y ago
    This is not the case, removing dams still can come with huge benefits to the ecosystems those dams disrupted: https://www.mercurynews.com/2019/05/08/four-years-after-californias-largest-dam-removal-project-the-fish-are-coming-back/ https://www.mercurynews.com/2019/05/08/four-years-after-cali...
    - roamerz 4y ago
      Read the article. Sounds like in that instance it was a good choice to remove the dam and had a good outcome. Well based on the information presented anyhow. Also I’m not sure if the main justification for removal pencils out for me. Yes some fish - 123 so far - were able to reproduce further upstream by 7 miles. What would have happened if the dam was still in place? Breed just below the dam? Do the fish really care where they do the deed or lay their eggs? Can’t believe that would be very true. Heck when I was their age I was pretty happy to do the deed and wasn’t too too awful concerned where it was at either. :D
  - mullen 4y ago
    No. First off, most dams silt up, not only not of being use in storing water but also not in creating power. Second, once they silt up, whatever ecosystem there is also destroyed and artificially created ecosystems are never natural and usually are bad for local fish populations. Artificial lakes can also host a number of non-native fish and are not any benefit to the native species that should be living there. Also, dams also block the migration paths of native fish. Just think of this way, dams have a life span and for the most part, most of them in US have hit the end of their life spans and should be removed. They serve no purpose to anyone.
    - dismalpedigree 4y ago
      Right. Storing water for 50M+ people and generating enormous quantities of electricity. No use at all.
    - idiotsecant 4y ago
      This is a pretty incomplete understanding of the issue, there are plenty of dams where silting is not an issue at all and will serve their purpose for centuries if properly maintained. There are also dams where silting is a regular problem. A so called 'sediment bypass' is often a feature of these dams, where water is pulled from the base of the dam through a bypass to clear out silting. It all depends on the natural hydraulic dynamics of the dam - some are better placed than others.
  - pencilguin 4y ago
    We are, in fact, demolishing dams at an increasing rate. Dams very commonly destroy fisheries worth far more than any value the dam can deliver.
BurningFrog 4y ago
I think the idea is to start pumping up water at existing hydroelectric power plants. If you do this using wind or solar power the dam becomes a giant battery you charge.
- sidewndr46 4y ago
  Where does this extra water come from?
  - whiddershins 4y ago
    It’s just borrowed
  - BurningFrog 4y ago
    Hydro power work by water flowing down turbines from a higher body of water to a lower. So you can typically pump the lower water back up, using wind or solar power.
    - sidewndr46 4y ago
      Wouldn't this mean the downstream would have no water flowing through it?
      - pfdietz 4y ago
        Pumped hydro can be built entirely off rivers. There's a plan to put a reservoir for one on top of a mesa in the desert in Arizona, for example.
        sidewndr46 4y ago
        What does the location of the reservoir matter? If you're taking a river and pumping it up on top of somewhere (a mesa in your example) aren't you going to cause the river to basically run dry everywhere downstream of where your pump is?
ethbr0 4y ago
Pumped hydro is burning energy to pump energy into a (usually artificial) reservoir. Then, later, allowing that filled reservoir to drain through a hydroelectric plant and generate electricity. This solves 2 major problems, compared to alternatives. 1) The scaling costs (with respect to energy storage capacity / volume) are extremely low. E.g. instead of building twice as much battery, you're just consuming additional empty space behind the dam. 2) There is no time-cost to storing energy in pumped hydro, which affords great flexibility in when it's stored and when it's extracted. E.g. stored on a bright day when the wind is blowing, extracted at night when there's no wind. In essence, it turns spikey supply and demand patterns into more constant ones, which are cheaper and more efficient to service.
tialaramex 4y ago
> I understand that hydroelectricity is used to supply the basic power need, say 80% and a water reservoir with turbines to cover power peak needs This seems like you either didn't understand what pumped storage is, or you've confused several related technologies. A typical pumped storage scheme goes like this: We find a mountain with a high lake and a low lake. We dam the high lake so that its natural outflow (perhaps to the low lake) ceases. We dig tunnels between the lakes, and we put an electric pump/ turbine in the tunnels. When we put electricity into the pump, water from the low lake is pumped up to the high lake (until it gets too full and we stop). This stores energy. When we let the water down the pipe through the turbine instead, the same water flows from the high lake down to the low lake, giving slightly less electricity via the turbine. Unlike the conventional hydro electric power plant this is not really producing electricity, it is storing it, hence the words "pumped storage". We can use this to move electricity in time, which otherwise has to be done very expensively with batteries. For example, when it's windy in the middle of the night in the UK, the French and Belgians buy some of our cheap electricity, and the stored power hydro facilities in Wales and Scotland also use that electricity to pump water up to their top lakes. The next afternoon, when peak electricity usage occurs as the sun goes down and people begin cooking evening meals, the pumped storage releases the water, making electricity it can sell at peak prices. In the UK the pumped storage plants are privately owned, so they benefit financially from this arbitrage.
- didgetmaster 4y ago
  Do you know the efficiency of using pumped storage? In other words, for every MW of electricity used to pump the water up the hill, how much do you get back in power generation when the water flows back down through a turbine? You will lose a bit of water to evaporation during this process, but it should be fairly negligible. Also all reservoirs lose some water by leakage into the ground. How does the efficiency compare to various battery storage techniques?
  - WJW 4y ago
    Batteries can get up to 95%+ efficiency, pumped hydro up to 85% efficiency so batteries win out in pure energy efficiency. However, when you take into account the economic efficiency then pumped hydro usually comes out very favorable. Battery prices have been falling rapidly over the last few decades, but simply damming up a mid-sized valley can store such a ginormous amount of water that is it hard to compete.
gwbas1c 4y ago
Think of pumped storage like a battery: In areas with a lot of solar, pumped storage runs when there is a lot of daylight to store the energy for nighttime use. Pumps run when the sun is out, turbines run at night.
- b4je7d7wb 4y ago
  Or the opposite in areas with wind/nuclear. Pump it up during the night when demand and prices are low, then run turbines during day when demand and prices are higher. Arbitrage.

Gwypaas 4y ago

Because you're not disrupting a river's flow and natural ecosystem, you only utilize the watershed some more during the initial filling period. After that, it's a closed system separate from the river ecosystem where only evaporation causes leakage.

roamerz 4y ago
That ship has already sailed as most power producing dams have been around for long time. Removing them would destroy the (now natural) ecosystem they have created. Plus dams have way more benefits to us than the extremely clean energy they produce - not just store.
- brookst 4y ago
  This is the first time I've seen a claim that dams create ecosystems that we should worry about destroying. As far as I know, they disrupt fish and animal migrations, reduce natural carbon sinks, reduce biodiversity, and block sediment from providing nutrients downstream. Is there any source saying dams create healthy natural ecosystems? A necessary evil I can kind of see, but a net positive for ecosystems? That seems doubtful.
  - whiddershins 4y ago
    I don’t know. I suspect the bias is towards the pre-dam ecosystem so it might be challenging to rationally compare them. Certainly an ecosystem will grow up around nearly any situation.
  - chasd00 4y ago
    there are many human ecosystems living below the dam though. Removing the dam means removing entire towns downstream in some cases.
    - pencilguin 4y ago
      That is not, in fact, true. Almost all dams have a river flowing below them, where it always did. A very few places use all of the inflow for irrigation.
  - roamerz 4y ago
    Yup my opinion only. To me water is life and if you let it flow to the ocean where it’s only use is to dilute saltwater you’ve wasted a precious natural resource.
    - Gwypaas 4y ago
      Dams does not save any water except the initial filling. Their inflow and outflow match over a seasonal cycle.
      - jcranmer 4y ago
        Also, they tend to cost water instead: the larger surface area increases the amount "lost" to evaporation.
        roamerz 4y ago
        Perhaps. I suppose that would depend on size and depth of the reservoir and the makeup of the river. Also without a dam the water would be traveling the river mostly during the cold wet season with little evap. So yeah likely so. But in the end the cost would be lost saltwater. Probably a benefit for those that are worried about sea levels.
      - roamerz 4y ago
        Yup that’s simplistically true. The difference though they do allow you to choose when it gets released. Around where I live that allows irrigation of crops during the summer months. That water does not go into the ocean. Also around here many of the municipalities draw water downstream from the dam as well. A portion of that travels through the sewer systems, gets purified then dropped back into the river.
- azylman 4y ago
  This is not the case, removing dams still can come with huge benefits to the ecosystems those dams disrupted: https://www.mercurynews.com/2019/05/08/four-years-after-californias-largest-dam-removal-project-the-fish-are-coming-back/ https://www.mercurynews.com/2019/05/08/four-years-after-cali...
  - roamerz 4y ago
    Read the article. Sounds like in that instance it was a good choice to remove the dam and had a good outcome. Well based on the information presented anyhow. Also I’m not sure if the main justification for removal pencils out for me. Yes some fish - 123 so far - were able to reproduce further upstream by 7 miles. What would have happened if the dam was still in place? Breed just below the dam? Do the fish really care where they do the deed or lay their eggs? Can’t believe that would be very true. Heck when I was their age I was pretty happy to do the deed and wasn’t too too awful concerned where it was at either. :D
- mullen 4y ago
  No. First off, most dams silt up, not only not of being use in storing water but also not in creating power. Second, once they silt up, whatever ecosystem there is also destroyed and artificially created ecosystems are never natural and usually are bad for local fish populations. Artificial lakes can also host a number of non-native fish and are not any benefit to the native species that should be living there. Also, dams also block the migration paths of native fish. Just think of this way, dams have a life span and for the most part, most of them in US have hit the end of their life spans and should be removed. They serve no purpose to anyone.
  - dismalpedigree 4y ago
    Right. Storing water for 50M+ people and generating enormous quantities of electricity. No use at all.
  - idiotsecant 4y ago
    This is a pretty incomplete understanding of the issue, there are plenty of dams where silting is not an issue at all and will serve their purpose for centuries if properly maintained. There are also dams where silting is a regular problem. A so called 'sediment bypass' is often a feature of these dams, where water is pulled from the base of the dam through a bypass to clear out silting. It all depends on the natural hydraulic dynamics of the dam - some are better placed than others.
- pencilguin 4y ago
  We are, in fact, demolishing dams at an increasing rate. Dams very commonly destroy fisheries worth far more than any value the dam can deliver.

BurningFrog 4y ago

I think the idea is to start pumping up water at existing hydroelectric power plants. If you do this using wind or solar power the dam becomes a giant battery you charge.

sidewndr46 4y ago
Where does this extra water come from?
- whiddershins 4y ago
  It’s just borrowed
- BurningFrog 4y ago
  Hydro power work by water flowing down turbines from a higher body of water to a lower. So you can typically pump the lower water back up, using wind or solar power.
  - sidewndr46 4y ago
    Wouldn't this mean the downstream would have no water flowing through it?
    - pfdietz 4y ago
      Pumped hydro can be built entirely off rivers. There's a plan to put a reservoir for one on top of a mesa in the desert in Arizona, for example.
      - sidewndr46 4y ago
        What does the location of the reservoir matter? If you're taking a river and pumping it up on top of somewhere (a mesa in your example) aren't you going to cause the river to basically run dry everywhere downstream of where your pump is?

ethbr0 4y ago

Pumped hydro is burning energy to pump energy into a (usually artificial) reservoir. Then, later, allowing that filled reservoir to drain through a hydroelectric plant and generate electricity. This solves 2 major problems, compared to alternatives. 1) The scaling costs (with respect to energy storage capacity / volume) are extremely low. E.g. instead of building twice as much battery, you're just consuming additional empty space behind the dam. 2) There is no time-cost to storing energy in pumped hydro, which affords great flexibility in when it's stored and when it's extracted. E.g. stored on a bright day when the wind is blowing, extracted at night when there's no wind. In essence, it turns spikey supply and demand patterns into more constant ones, which are cheaper and more efficient to service.

tialaramex 4y ago

> I understand that hydroelectricity is used to supply the basic power need, say 80% and a water reservoir with turbines to cover power peak needs This seems like you either didn't understand what pumped storage is, or you've confused several related technologies. A typical pumped storage scheme goes like this: We find a mountain with a high lake and a low lake. We dam the high lake so that its natural outflow (perhaps to the low lake) ceases. We dig tunnels between the lakes, and we put an electric pump/ turbine in the tunnels. When we put electricity into the pump, water from the low lake is pumped up to the high lake (until it gets too full and we stop). This stores energy. When we let the water down the pipe through the turbine instead, the same water flows from the high lake down to the low lake, giving slightly less electricity via the turbine. Unlike the conventional hydro electric power plant this is not really producing electricity, it is storing it, hence the words "pumped storage". We can use this to move electricity in time, which otherwise has to be done very expensively with batteries. For example, when it's windy in the middle of the night in the UK, the French and Belgians buy some of our cheap electricity, and the stored power hydro facilities in Wales and Scotland also use that electricity to pump water up to their top lakes. The next afternoon, when peak electricity usage occurs as the sun goes down and people begin cooking evening meals, the pumped storage releases the water, making electricity it can sell at peak prices. In the UK the pumped storage plants are privately owned, so they benefit financially from this arbitrage.

didgetmaster 4y ago
Do you know the efficiency of using pumped storage? In other words, for every MW of electricity used to pump the water up the hill, how much do you get back in power generation when the water flows back down through a turbine? You will lose a bit of water to evaporation during this process, but it should be fairly negligible. Also all reservoirs lose some water by leakage into the ground. How does the efficiency compare to various battery storage techniques?
- WJW 4y ago
  Batteries can get up to 95%+ efficiency, pumped hydro up to 85% efficiency so batteries win out in pure energy efficiency. However, when you take into account the economic efficiency then pumped hydro usually comes out very favorable. Battery prices have been falling rapidly over the last few decades, but simply damming up a mid-sized valley can store such a ginormous amount of water that is it hard to compete.

gwbas1c 4y ago

Think of pumped storage like a battery: In areas with a lot of solar, pumped storage runs when there is a lot of daylight to store the energy for nighttime use. Pumps run when the sun is out, turbines run at night.

b4je7d7wb 4y ago
Or the opposite in areas with wind/nuclear. Pump it up during the night when demand and prices are low, then run turbines during day when demand and prices are higher. Arbitrage.