5 ms·

Still one of the most efficient energy storage systems is to pump water up a hill. There are losses in evaporation and conversion but these losses are low when

Still one of the most efficient energy storage systems is to pump water up a hill. There are losses in evaporation and conversion but these losses are low when compared to batteries. A system where we used solar power to pump sea water up into a man made reservoir would be very interesting.

epistasis 11y ago
Round trip efficiency of pumped hydro is 70%-80%, maybe up to 87% according to some people: https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit... A standard lithium ion batter is at 87% in the worst case, when it's AC-DC-storage-DC-AC. Going direct from solar panels to storage would save one trip: http://www.catalyticengineering.com/top-ten-facts-about-teslas-350kwh-powerwall-battery/ http://www.catalyticengineering.com/top-ten-facts-about-tesl... In any case, the efficiency of storage is only one aspect; it limits how cheap the storage can potentially be, but electricity lost due to inefficiency is not the primary driver of storage cost with any of the currently used technologies.
- dv_dt 11y ago
  What's fascinating is some of the research around combined solar & battery designs which to merge the two functions on a materials level.
  - epistasis 11y ago
    I haven't heard of this, do you have any suggested reading material?
    - dv_dt 11y ago
      I was mostly thinking of this research at Ohio State https://www.sciencedaily.com/releases/2015/08/150801082647.htm https://www.sciencedaily.com/releases/2015/08/150801082647.h... But I think there may be other areas that I'm not finding specifically right now... ("solar battery" is a poor search term for this research...)
      - epistasis 11y ago
        This sounds fantastic: - a redox flow battery coupled directly to solar charging - super high specific energy, ~0.33kWh/kg which is right on par with traditional solid lithium ion batteries My remaining questions are: - Compared to PV solar + lithium ion battery, how much insolation is required to store a kWh? - What is the cost/kWh of the lithium iodide? - What is the cost/kW of the solar charger, discharger? - Can the anode and cathode be used to charge the battery from standard electricity, in addition to the (more efficient) solar method? Thanks for this pointer, this gives me even greater optimism about the future of storage!
      - ZenoArrow 11y ago
        You might find this video interesting: http://youtu.be/rsuB-6-n-MM http://youtu.be/rsuB-6-n-MM
- Gibbon1 11y ago
  The efficiency of pumped heat electrical storage is a little worse than pumped hydro. Short description you use use a compressor to compress and heat gas. Use the hot compressed gas to heat rocks. Later recover the energy using a turbine. The advantages over pumped hydro are, The power density is much higher, 100000 joules/kg vs 300-500 joules/kg. You can locate storage facilities pretty much anywhere that's out of shrapnel range. In case the big tank of gas and rocks blows up. Doesn't have the environmental impact of dams. And rocks are significantly less precious than huge amounts of water.
skc 11y ago
Pumped hydro is always brought up, which is bizarre to me because it's highly dependent on your geography, unlike battery storage.
- __jal 11y ago
  Why is it bizarre? It is a dead-simple, relatively efficient storage mechanism that could potentially coexist with municipal-scale reservoir systems (thus gaining cost efficiencies). Sure, Kansas, US is not the first place one would look to build one. But most of the world is not Kansas. To flip that around, there exist applications where battery storage isn't reasonable. Is it thus also bizarre to bring batteries?
  - toomuchtodo 11y ago
    I can drop cargo containers full of Tesla Powerpacks anywhere in the world. I cannot build hydro pumped storage just anywhere.
    - __jal 11y ago
      ...And? You're not answering: > To flip that around, there exist applications where battery storage isn't reasonable. Is it thus also bizarre to bring batteries? The post I was replying to called talking about hydro storage "bizarre". I was pointing out that it isn't. The logic here seems analogous to saying that compact cars suck because you can't use them as a dump truck.
      - toomuchtodo 11y ago
        My argument is that battery storage will slowly become better than all other energy storage methods as the price comes down. Its also helpful that it can be transported and colocated anywhere necessary.
  - ghshephard 11y ago
    I'm curious - can you name a scenario in which battery storage isn't reasonable? It seems to me that once we hit the cost/price/weight/density points, they are a solution to pretty much any problem of power storage.
aaronwidd 11y ago
A system that uses solar to desalinate seawater and pump it to a reservoir by day, then used for hydro power at night and again for crop irrigation, would certainly be one of the most exciting green engineering projects out there
- jcoffland 11y ago
  Yes. Unfortunately water desalination requires a ton of energy but you can use the sun directly.
kartickv 11y ago
Does it work with seawater? Some countries have a frightful shortage of freshwater, so rather than risking loss due to evaporation, could you pump seawater uphill?
- techdragon 10y ago
  In theory seawater would work but it's important to consider the increased expenses and operating troubles from seawater. Corrosion, bio-fouling, increased need for filters and filter maintenance, etc...

epistasis 11y ago

Round trip efficiency of pumped hydro is 70%-80%, maybe up to 87% according to some people: https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit... A standard lithium ion batter is at 87% in the worst case, when it's AC-DC-storage-DC-AC. Going direct from solar panels to storage would save one trip: http://www.catalyticengineering.com/top-ten-facts-about-teslas-350kwh-powerwall-battery/ http://www.catalyticengineering.com/top-ten-facts-about-tesl... In any case, the efficiency of storage is only one aspect; it limits how cheap the storage can potentially be, but electricity lost due to inefficiency is not the primary driver of storage cost with any of the currently used technologies.

dv_dt 11y ago
What's fascinating is some of the research around combined solar & battery designs which to merge the two functions on a materials level.
- epistasis 11y ago
  I haven't heard of this, do you have any suggested reading material?
  - dv_dt 11y ago
    I was mostly thinking of this research at Ohio State https://www.sciencedaily.com/releases/2015/08/150801082647.htm https://www.sciencedaily.com/releases/2015/08/150801082647.h... But I think there may be other areas that I'm not finding specifically right now... ("solar battery" is a poor search term for this research...)
    - epistasis 11y ago
      This sounds fantastic: - a redox flow battery coupled directly to solar charging - super high specific energy, ~0.33kWh/kg which is right on par with traditional solid lithium ion batteries My remaining questions are: - Compared to PV solar + lithium ion battery, how much insolation is required to store a kWh? - What is the cost/kWh of the lithium iodide? - What is the cost/kW of the solar charger, discharger? - Can the anode and cathode be used to charge the battery from standard electricity, in addition to the (more efficient) solar method? Thanks for this pointer, this gives me even greater optimism about the future of storage!
    - ZenoArrow 11y ago
      You might find this video interesting: http://youtu.be/rsuB-6-n-MM http://youtu.be/rsuB-6-n-MM
Gibbon1 11y ago
The efficiency of pumped heat electrical storage is a little worse than pumped hydro. Short description you use use a compressor to compress and heat gas. Use the hot compressed gas to heat rocks. Later recover the energy using a turbine. The advantages over pumped hydro are, The power density is much higher, 100000 joules/kg vs 300-500 joules/kg. You can locate storage facilities pretty much anywhere that's out of shrapnel range. In case the big tank of gas and rocks blows up. Doesn't have the environmental impact of dams. And rocks are significantly less precious than huge amounts of water.

skc 11y ago

Pumped hydro is always brought up, which is bizarre to me because it's highly dependent on your geography, unlike battery storage.

__jal 11y ago
Why is it bizarre? It is a dead-simple, relatively efficient storage mechanism that could potentially coexist with municipal-scale reservoir systems (thus gaining cost efficiencies). Sure, Kansas, US is not the first place one would look to build one. But most of the world is not Kansas. To flip that around, there exist applications where battery storage isn't reasonable. Is it thus also bizarre to bring batteries?
- toomuchtodo 11y ago
  I can drop cargo containers full of Tesla Powerpacks anywhere in the world. I cannot build hydro pumped storage just anywhere.
  - __jal 11y ago
    ...And? You're not answering: > To flip that around, there exist applications where battery storage isn't reasonable. Is it thus also bizarre to bring batteries? The post I was replying to called talking about hydro storage "bizarre". I was pointing out that it isn't. The logic here seems analogous to saying that compact cars suck because you can't use them as a dump truck.
    - toomuchtodo 11y ago
      My argument is that battery storage will slowly become better than all other energy storage methods as the price comes down. Its also helpful that it can be transported and colocated anywhere necessary.
- ghshephard 11y ago
  I'm curious - can you name a scenario in which battery storage isn't reasonable? It seems to me that once we hit the cost/price/weight/density points, they are a solution to pretty much any problem of power storage.

aaronwidd 11y ago

A system that uses solar to desalinate seawater and pump it to a reservoir by day, then used for hydro power at night and again for crop irrigation, would certainly be one of the most exciting green engineering projects out there

jcoffland 11y ago
Yes. Unfortunately water desalination requires a ton of energy but you can use the sun directly.

kartickv 11y ago

Does it work with seawater? Some countries have a frightful shortage of freshwater, so rather than risking loss due to evaporation, could you pump seawater uphill?

techdragon 10y ago
In theory seawater would work but it's important to consider the increased expenses and operating troubles from seawater. Corrosion, bio-fouling, increased need for filters and filter maintenance, etc...