I'm super sceptical of these types of approaches, to the point that I often question some of the weird financial incentives that can cause money to be put into stuff like this in the first place.
Simple physics says that gravity is actually a pretty poor energy storage mechanism (see other fanciful ideas about stacking heavy blocks). Pumped water storage is about the only form that actually makes sense from a cost/energy storage perspective because (a) in nearly all those cases the reservoirs already exist, and (b) you're pumping a lot more than a couple Olympic-swimming pools worth of water. And even then the costs can be giant - LA was looking into a $3 billion project to use pumped storage behind the Hoover Dam a few years ago, not sure what happened with that.
There is just so much "green washing" going on these days, I think it's more important to focus on things we know will work, or improvements to ideas that already work.
People don’t understand the grid energy storage market. Some think it’s only about storing as much energy as possible over as much time as possible. That’s not the full picture. Response time and ability to handle several cycles a day is also very important for many grid energy storage applications.
The stacking of heavy blocks you mention is actually a very decent idea. No, it’s not going to compete with pumped hydro for seasonal storage. But that was never the point. It’s about shifting load a few hours a couple of times every day. Perhaps with some spare capacity to help with a day or two with less power.
We need both solutions. Pumped hydro is not that great for cycling often and rapid response and it’s much harder to find good sites to build it. Big water reservoirs are extremely damaging to the environment. They obviously destroy all land based life on the land they claim, and the constant cycling up and down of the water lever means the conditions for life in the water is atrocious as well.
A fun fact is that for hydro power plants it’s becoming viable to install battery energy storage on site. Wouldn’t think that makes sense would you? By putting some of the power regulation loads on the battery they can run the hydro power plant production more evenly, reducing pressure variations that causes more wear and tear, which increases long term maintenance costs.
Don’t watch those YouTube “debunkers” for insight into these kinds of topic. They rarely do more than 10 min of research. (I know one of them did a video on Energy Vault that always gets shared in these conversations, despite the fact that there’s not a single valid point in the video)
Many hydroelectric plants with a reservoir are already energy storage systems. They can adjust their power output up and down. They can, for short periods, drain the reservoir faster than it is being filled. The seasonal patterns of rainfall, and energy demand, influence how much power a plant can output in terms of peak and average, both short and long-term.
At Niagara Falls, the falls can be diverted through the plants, nearly shutting the falls off. It isn't normally done, for both ecological and sightseeing reasons, but when power was needed after the 2003 blackout, the falls were reduced to about 15% flow: https://www.theglobeandmail.com/news/national/how-the-power-...
The total energy stored is relatively tiny, but devices want a smooth electrical signal not just energy from a wire.
Ideally you want an instant response time and GWh of energy storage on the cheap, but that instead grid operators use many different systems to simulate that.
Simple physics says that gravity is actually a pretty poor energy storage mechanism (see other fanciful ideas about stacking heavy blocks). Pumped water storage is about the only form that actually makes sense from a cost/energy storage perspective because (a) in nearly all those cases the reservoirs already exist, and (b) you're pumping a lot more than a couple Olympic-swimming pools worth of water. And even then the costs can be giant - LA was looking into a $3 billion project to use pumped storage behind the Hoover Dam a few years ago, not sure what happened with that.
There is just so much "green washing" going on these days, I think it's more important to focus on things we know will work, or improvements to ideas that already work.