system
Given the following post, respond as if you're commenting on Reddit:
human
Why aren't we using gravitational potential batteries instead of electro-chemical ones for large scale power storage?

I have heard of an idea that we could dig holes and put weights on vertically moving platforms. When there is excess power generation motors lift the weights. When the power is needed we simply let the weights descend turning electric generators. It seems to me that this way of power storage can be build on a huge scale and would be much simpler to make than enormous batteries. With power storage for cities solar panels and wind turbines can store power for cloudy windless days. Why aren't we using this technology? Is it even possible?
gpt
We do, there are many power stations with two pools, top and bottom, at night, they pump bottom to top with excess power, during peak they run top to bottom through turbines.  So these would be gravitational batteries using water as the working fluid.