The concept is quite obvious and has been proposed several times in the past. The key question is, what are the costs? Even if the costs for drilling the hole are written off over a very long time span, the wires that hold the weight and the machinery have constant operation costs. It probably can't compete with pumped storage, but pumped storage isn't viable without at least some hills. This concept could be deployed in many regions, also wouldn't take much surface space, you could deploy it even in densely populated regions. The question is: how does it compete with e.g. batteries?