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Grid storage is different from powering EVs though. You don’t provide a week of grid backup via battery. You do stuff like pump 100 million gallons of water int

Grid storage is different from powering EVs though. You don’t provide a week of grid backup via battery. You do stuff like pump 100 million gallons of water into a dam with a hydro plant ready. I think water is more efficient then hydrogen even.

DanHulton 5y ago
Sure, but it's very dependant on geography, if you want to do it at scale. We're definitely going to have to adopt a mixed approach, so I'd say it still makes sense to keep the research into hydrogen, batteries, all of it.
maxerickson 5y ago
That's 3 minutes of maximum generation at https://en.wikipedia.org/wiki/Ludington_Pumped_Storage_Power_Plant https://en.wikipedia.org/wiki/Ludington_Pumped_Storage_Power... I guess that plant doesn't have an extreme amount of head or a particularly large reservoir. It's about 7 minutes at https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Station https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Sta... , which has a lot more head. So you need a lot more pumped storage if you want to start talking about days of backup, and we already used quite a few of the best sites.
turbinerneiter 5y ago
Hydrogen is not very efficient, hydro is very efficient. But the energy density for hydro is lower than people think. m * g * h -> you either need lots of water or lots of height. Best is to have both. You only get that in the Alps and you need some special geoprgaphic features to make it work. Europe is also densely populated and the nature we have left, we want to preserve, so we can't flood all of it. Do the math, figure out how big of damn we would need to store 3TWh. My result: at 1000m pump height, you would need 3000 billion liters, which is cube of water with a length 1.5km. Double check this tough, I'm not sure if I did all the conversion correctly
- japanuspus 5y ago
  I am not sure there is a universal value for "what people think" about pumped hydro energy density, but your numbers are quite far of: 3TWh at 1000m pump height would require 3e6Wh3600s/h/(1000m1000kg/m3*9.8m/s2) = 1.1e6m3, so a waist-high lake of one square kilometer would do. For what it is worth, in Europe, Switzerland is doing a lot of pumped hydro powered by surplus French nuclear power in the summer time. Norway has huge amounts of hydro and only pumps a little, but it doesn't matter much: The Scandinavian grid is so well connected, that hydro will ramp down when power is available elsewhere, in effect providing on-demand provider for the whole region.

DanHulton 5y ago

Sure, but it's very dependant on geography, if you want to do it at scale. We're definitely going to have to adopt a mixed approach, so I'd say it still makes sense to keep the research into hydrogen, batteries, all of it.

maxerickson 5y ago

That's 3 minutes of maximum generation at https://en.wikipedia.org/wiki/Ludington_Pumped_Storage_Power_Plant https://en.wikipedia.org/wiki/Ludington_Pumped_Storage_Power... I guess that plant doesn't have an extreme amount of head or a particularly large reservoir. It's about 7 minutes at https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Station https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Sta... , which has a lot more head. So you need a lot more pumped storage if you want to start talking about days of backup, and we already used quite a few of the best sites.

turbinerneiter 5y ago

Hydrogen is not very efficient, hydro is very efficient. But the energy density for hydro is lower than people think. m * g * h -> you either need lots of water or lots of height. Best is to have both. You only get that in the Alps and you need some special geoprgaphic features to make it work. Europe is also densely populated and the nature we have left, we want to preserve, so we can't flood all of it. Do the math, figure out how big of damn we would need to store 3TWh. My result: at 1000m pump height, you would need 3000 billion liters, which is cube of water with a length 1.5km. Double check this tough, I'm not sure if I did all the conversion correctly

japanuspus 5y ago
I am not sure there is a universal value for "what people think" about pumped hydro energy density, but your numbers are quite far of: 3TWh at 1000m pump height would require 3e6Wh3600s/h/(1000m1000kg/m3*9.8m/s2) = 1.1e6m3, so a waist-high lake of one square kilometer would do. For what it is worth, in Europe, Switzerland is doing a lot of pumped hydro powered by surplus French nuclear power in the summer time. Norway has huge amounts of hydro and only pumps a little, but it doesn't matter much: The Scandinavian grid is so well connected, that hydro will ramp down when power is available elsewhere, in effect providing on-demand provider for the whole region.