I don't truly understand this "problem". I understand storing the energy in batteries is currently very expensive economically and materially.
However I believe there are plenty of "goods" (irrespective of if they are bulk materials, or partially processed products) which have a high processing energy per volume ratio (this does not need to be recoverable stored energy).
Allow me to give an example: currently we have a drought in Belgium (or at least Flanders). We are not landlocked, there is plenty of water in the sea. Desalination is energy intensive. Instead of only looking at energy storage, why can't we increase the processing capacity (more desalination sites capable of working in parallel), and desalinate say sea water during the energy flood? I don't expect this to be an ideal real world example, only a pattern for identifying such examples: any product (could be composite parts, or bulk material) which is relatively compact and has some high energy per product volume processinng step. Just do the process (desalination, welding some part to another part...) when the sun shines, and store them for later.
Products with very high step energy density are good candidates for storing, and could help flatten daily variations, and perhaps even seasonal variations!
Now some companies would prefer avoiding risk if they don't have guaranteed orders far enough into the future, then perhaps there should be a market for insurance or loans, so that the company is encouraged to take the risk, instead of wasting the cheap energy...