I mean, it’s not like concrete is scraping on the walls going up and down, it’s on a pulley system which would be efficient in terms of doing energy transfer. The article mentions round-trip efficiency above 80 percent, so I’m not sure pumping water could be much more efficient than that.
The main problem with gravitational storage is that it is incredibly weak compared to chemical, compressed air, or flywheel techniques (see the post on home energy storage options). For example, to get the amount of energy stored in a single AA battery, we would have to lift 100 kg (220 lb) 10 m (33 ft) to match it. To match the energy contained in a gallon of gasoline, we would have to lift 13 tons of water (3500 gallons) one kilometer high (3,280 feet). It is clear that the energy density of gravitational storage is severely disadvantaged.
It seems the problem is not necessarily one of conversion efficiency, but rather of scale. In order to store significant amounts of electrical energy using mechanical means, you need to move a lot of weight. Manufacturing the concrete blocks requires money and raw materials, and a pulley system robust enough to move them around wouldn’t be cheap either. The pumped storage hydroelectric systems which currently provide the vast majority of our grid energy storage partially circumvent this expense by taking advantage of natural bodies of water and advantageous topography.
That being said, it’s definitely a fascinating concept and one worth exploring. But there are well established difficulties that explain why this type of energy storage isn’t already widespread.
Well, this 80% efficiency is what they are targeting not what the system will do.
The test system Energy Vault build in a MUCH smaller form factor had a round-trip efficency of 75%
The EVx ™ system is projected to achieve an impressive round-trip efficiency exceeding 80%. Source
Only time will tell if they can reach 80% with a bigger system or at all. If they actually manage this it would be a decent alternative to Hydrodams in areas where these are just not possible since it would be a similar round-trip efficency.
Pumped storage systems have a round-trip efficiency of about 80%, which is competitive with battery storage. Source
In my opinion these systems are inferior to fly wheel energy storage (can reach up to 90% round trip efficency
Source) but might still be an option depending on price.
High friction is my guess.
I mean, it’s not like concrete is scraping on the walls going up and down, it’s on a pulley system which would be efficient in terms of doing energy transfer. The article mentions round-trip efficiency above 80 percent, so I’m not sure pumping water could be much more efficient than that.
https://dothemath.ucsd.edu/2011/11/pump-up-the-storage/
It seems the problem is not necessarily one of conversion efficiency, but rather of scale. In order to store significant amounts of electrical energy using mechanical means, you need to move a lot of weight. Manufacturing the concrete blocks requires money and raw materials, and a pulley system robust enough to move them around wouldn’t be cheap either. The pumped storage hydroelectric systems which currently provide the vast majority of our grid energy storage partially circumvent this expense by taking advantage of natural bodies of water and advantageous topography.
That being said, it’s definitely a fascinating concept and one worth exploring. But there are well established difficulties that explain why this type of energy storage isn’t already widespread.
right, it only makes sense if you do it at large scale
What about friction within the pulley?
Again, they state over 80% efficiency in the article. So, that’s your answer.
Well, this 80% efficiency is what they are targeting not what the system will do. The test system Energy Vault build in a MUCH smaller form factor had a round-trip efficency of 75%
Only time will tell if they can reach 80% with a bigger system or at all. If they actually manage this it would be a decent alternative to Hydrodams in areas where these are just not possible since it would be a similar round-trip efficency.
In my opinion these systems are inferior to fly wheel energy storage (can reach up to 90% round trip efficency Source) but might still be an option depending on price.