The problem of energy storage, in order to save and keep the energy from supply surplus-phases, in order to be able to use it during the supply gaps, is known from the solar cell technology as well as from the windmill technology, because the sunshine as well as the wind is not constant 24/7.
Accumulators are definitely disproportionately much too expensive (even if we use only their "second life cycle"), and have also reached the end of their life after only a few years. What we need is a robust system with unlimited durability. Of course, I do not surprise anyone when I now mention the "hydrogen technology" as a well-known potential good solution.
There are corresponding projects in Europe in this field, at the moment now under the catchword "power to gas." This means, that electrical power is converted into gas (hydrogen gas) and stored in this form. The process is very simple: The water molecules are broken down (splitted) into hydrogen and oxygen by electrolysis. Typical today's modern research and development programs work with direct current electrolysis, which means that two electrodes (anode and cathode) are mounted in a container filled with water, and then the electrical energy is supplied in the form of direct current. The hydrogen gas that is formed and rises in the water, is collected.