6 ms·

I did a bit of scratch math with the notion this might be more suited for individual, home power storage rather than grid supply - You need something in the ord

I did a bit of scratch math with the notion this might be more suited for individual, home power storage rather than grid supply - You need something in the order of a 5m tall tower bearing 73 tonnes to store 1 kilowatt hour (even then, ignoring conversion losses). So that's the weight of ~ten class-4 fully laden heavy trucks. Once you can get it up in the air then the higher you can go you're doubling your storage in a linear fashion. Hoist one of those trucks to 50 meters (perhaps you have a handy cliff in your backyard) and you've stored as much as the ten trucks did at 5 meters. So yeah scale seems hard, but the low technology/materials requirements and potential for gradual scale-up make this worthy of deep investigation. I think there's a lot of wandering off into dead-ends as far as limitations go though - Solutions that depend on a lot of concrete pouring, for example, are a no-go if the end goal is reducing atmospheric carbon.

chris_engel 5y ago
Hm, you also need to consider that 5 trucks can have a much higher combined output than the 1 truck 5 times as high. The storage might scale this way but not the output when demand is high.
- rsa25519 5y ago
  > Hm, you also need to consider that 5 trucks can have a much higher combined output than the 1 truck 5 times as high. How so?
- SagelyGuru 5y ago
  You can make that one truck descend five times faster, giving the same output.
  - randallsquared 5y ago
    "...for a given drop rate" seems implied. There will be a maximum drop rate that is supported by the machinery being built, and it seems reasonable, though not mandatory, that a 5x weight system will be designed to handle more generation than whatever it's 5x of.
  - rakoo 5y ago
    The total available energy in such a system is defined by m * g * z where m is the mass and z is the elevation difference. It doesn't depend on the speed at which it goes down
berkes 5y ago
I can imagine this tech all packed up in a standard 40ft shipping container and dropped on premise. This would be rather simple tech, that can supplement solar and wind on your farm, lodge, campsite or island. Another piece in the puzzle for smaller scale independence. Not to replace metropolis-scale energy demands, as grandparent implies, but to smooth out fluctuations on hourly, household scale.
- marcosdumay 5y ago
  I imagine chemical batteries would be easier to ship and install, and require less maintenance. I really can't imagine any mechanical system that involves plugging and unplugging a load (or anything more complex than that) to be useful at small scales.
arbitrage 5y ago
I think you are drastically underestimating the density of bulk metal. Trucks, while impressive as an illustration, are not quite dense enough to be practical or applicable in an energy-storage scenario.
- FooHentai 5y ago
  Absolutely, useful just to illustrate the scale we're talking about for a given amount of energy stored as a real-world analog easy to recall. Assuming you used cast iron as weights that has a density of ~7800kg/m³ at regular temperatures, so you're looking at about 10 cubic meters for that 1kWh of potential energy storage using an abundantly available, non-toxic material that will endure.
tekstar 5y ago
This exists at least in one place, with trains on a hill in Nevada. https://aresnorthamerica.com https://aresnorthamerica.com "ADVANCED RAIL ENERGY STORAGE"
- FooHentai 5y ago
  That's awesome, thanks for the link
jodrellblank 5y ago
> "a 5m tall tower bearing 73 tonnes to store 1 kilowatt hour" By comparison, a pint of gasoline stores about 4 kilowatt hours.
- BenjiWiebe 5y ago
  Too bad we can't just synthesize gasoline with electricity at a decent efficiency.
  - jodrellblank 5y ago
    There is a tree which produces a biodiesel substance at a rate of 40 litres/tree/year. https://www.smh.com.au/national/farmer-planning-diesel-tree-biofuel-20060920-gdof98.html https://www.smh.com.au/national/farmer-planning-diesel-tree-...
- FooHentai 5y ago
  Yes, but only once. This is energy storage not energy source for the purpose of human utility. The ability to pull that 1kw of potential energy back up (with some renewable source eg wind turbine) to be output over again is where the comparison breaks down. A fairer comparison is current battery tech, you can pack something like 40kwh in 200kg of batteries (rough guess based on leaf ev battery modules). So vastly more in the same space/weight. But those are complex and energy intensive to manufacture, and have limited lifespans before further energy investment is required to recycle/replace them. The relative simplicity and long lifespan of gravity storage seems like it has potential. Not to mention the potential for owner/operator to self install, which could be great for developing nations.

chris_engel 5y ago

Hm, you also need to consider that 5 trucks can have a much higher combined output than the 1 truck 5 times as high. The storage might scale this way but not the output when demand is high.

rsa25519 5y ago
> Hm, you also need to consider that 5 trucks can have a much higher combined output than the 1 truck 5 times as high. How so?
SagelyGuru 5y ago
You can make that one truck descend five times faster, giving the same output.
- randallsquared 5y ago
  "...for a given drop rate" seems implied. There will be a maximum drop rate that is supported by the machinery being built, and it seems reasonable, though not mandatory, that a 5x weight system will be designed to handle more generation than whatever it's 5x of.
- rakoo 5y ago
  The total available energy in such a system is defined by m * g * z where m is the mass and z is the elevation difference. It doesn't depend on the speed at which it goes down

berkes 5y ago

I can imagine this tech all packed up in a standard 40ft shipping container and dropped on premise. This would be rather simple tech, that can supplement solar and wind on your farm, lodge, campsite or island. Another piece in the puzzle for smaller scale independence. Not to replace metropolis-scale energy demands, as grandparent implies, but to smooth out fluctuations on hourly, household scale.

marcosdumay 5y ago
I imagine chemical batteries would be easier to ship and install, and require less maintenance. I really can't imagine any mechanical system that involves plugging and unplugging a load (or anything more complex than that) to be useful at small scales.

arbitrage 5y ago

I think you are drastically underestimating the density of bulk metal. Trucks, while impressive as an illustration, are not quite dense enough to be practical or applicable in an energy-storage scenario.

FooHentai 5y ago
Absolutely, useful just to illustrate the scale we're talking about for a given amount of energy stored as a real-world analog easy to recall. Assuming you used cast iron as weights that has a density of ~7800kg/m³ at regular temperatures, so you're looking at about 10 cubic meters for that 1kWh of potential energy storage using an abundantly available, non-toxic material that will endure.

tekstar 5y ago

This exists at least in one place, with trains on a hill in Nevada. https://aresnorthamerica.com https://aresnorthamerica.com "ADVANCED RAIL ENERGY STORAGE"

FooHentai 5y ago
That's awesome, thanks for the link

jodrellblank 5y ago

> "a 5m tall tower bearing 73 tonnes to store 1 kilowatt hour" By comparison, a pint of gasoline stores about 4 kilowatt hours.

BenjiWiebe 5y ago
Too bad we can't just synthesize gasoline with electricity at a decent efficiency.
- jodrellblank 5y ago
  There is a tree which produces a biodiesel substance at a rate of 40 litres/tree/year. https://www.smh.com.au/national/farmer-planning-diesel-tree-biofuel-20060920-gdof98.html https://www.smh.com.au/national/farmer-planning-diesel-tree-...
FooHentai 5y ago
Yes, but only once. This is energy storage not energy source for the purpose of human utility. The ability to pull that 1kw of potential energy back up (with some renewable source eg wind turbine) to be output over again is where the comparison breaks down. A fairer comparison is current battery tech, you can pack something like 40kwh in 200kg of batteries (rough guess based on leaf ev battery modules). So vastly more in the same space/weight. But those are complex and energy intensive to manufacture, and have limited lifespans before further energy investment is required to recycle/replace them. The relative simplicity and long lifespan of gravity storage seems like it has potential. Not to mention the potential for owner/operator to self install, which could be great for developing nations.