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Is 90% efficiency really feasible for electrical -> mechanical -> electrical?
[1] https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...
So how many joules can it contain? I mean, technically I can get a super cap the size of jam jar to kick out 1 kw, just not for very long. A watt is a unit of how much energy is expended in a second, not how much energy is stored. There is a reason why hydrostations in wales use lakes to store energy, because you need a lot of mass at great height to be of any use.
Numbers not looking reasonable for this concept.
The principle however of storing energy by raising a weight could also be used anywhere with a steep enough hill/cliff/montain and the weight could in theory be on a rail not just suspended.
Efficiency would potentially not be on par, however linked into solar/wind systems this is less about efficiency and more about creating a 1MW long term battery with a lifetime of 50+ years.
Guessing cost of digging and maintaining a hole compared to installing a guide rail is significantly higher.
If you can build one of these cheaply, and the running costs are trivial, then it's worth doing.
How many of them would you need to smooth out the energy of a wind farm, for instance?
The energy density for gravity is just immensely small, that's why you need dams holding back rivers to use them to generate electricity. For a 1km hole (that's in the middle of their 500m - 1500m range) you have an energy density of 10kJ/kg of the weight that stores the energy. The energy stored in a Tesla roadster battery pack is around 50kWh which is 180MJ. This means that you need a 18,000kg weight in a 1km deep…
That's why companies like Ambri are looking at using other materials in the batteries they're developing for grid energy storage.
What determines the depth of the whole? I mean, since E = mgh, you can get the same energy storage capacity with a less deep hole if you use a heavier weight. And you can get a heavier weight either by using more expensive material (why use a cheap one? it's not like it's going to wear or anything), or a larger hole. I'm not sure what determines the cost of digging a whole, but I suspect depth matters more than area.…
I suspect they plan on recovering the power with a generator. So the input shaft to the generator has to rotate. With a deeper hole, you get more 'clicks' on the generator so you can produce power for a longer period of time before having to pull the weight back up.
You should be able to get millions of rotations from a single centimetre hole, given that the mass is large enough and you have a good gear ratio..
What determines the depth of the whole? I mean, since E = mgh, you can get the same energy storage capacity with a less deep hole if you use a heavier weight. And you can get a heavier weight either by using more expensive material (why use a cheap one? it's not like it's going to wear or anything), or a larger hole. I'm not sure what determines the cost of digging a whole, but I suspect depth matters more than area.…
Nevertheless, the density of Lead is 11.35 g/cm3 (the density of water is 1 g/cm3). The densest element in this table is Osmium with 22.6. So replacing if you replace a Lead weight with a more expensive weight you only gain x2.