I came across an online report about "Uranium Storage Battery." I would like to summarize and share some of the interesting points here. Uranium has been considered as having the potential to be used as an active material for batteries due to its chemical features. Japan Atomic Energy Agency has developed the Uranium Storage Battery, which is the world's first and uses chemical characteristics of uranium, for commercial purposes. They also confirmed the performance of its discharging and charging capabilities. Depleted uranium is a waste byproduct created when fuel is produced in the nuclear power plant. However, current nuclear power plants can't use it as fuel and they have to stowed as waste. Currently, there are 16,000 tons of depleted uranium in Japan. That's why we can reuse it as an available resource for storage batteries. Renewable electricity output is unstable because solar power and wind turbines are strong affected by the weather. So, we need energy storing devices like storage batteries for stable power supply. Hence, new energy storing technology has been attracting a lot of attention lately. There is about 1.6 million tons of depleted uranium stored across the world. Hence, they will contribute to making the decarbonized society a reality if this technology is available in the near future. I guess it is very useful for countries, which have very limited resources, like Japan. Note that "saving energy" does not mean storing energy. It means using less energy like turning of electrical equipment or using more efficient equipment etc. "Storing energy" is what you described in your post. Like storing excess energy to be used later when needed.