The article leaves me with more than a few doubts with this strategy of storing power. One issue that concerns me is the amount of energy that will need to be spent in manufacturing all the concrete and steel drums as well as the amount of pollution this will generate. There will also be the pollution in transporting the drums onto the battery locations. I get that this isn't a unique problem and other forms of "green" power generation also suffer from this such as wind turbines or even photovoltaic panels. Once the drums are onsite there is likely minimal maintenance needed so once the cost of producing is done, there should be a way to figure out how many years or months it would take to offset that.