The answer exists and has existed ever since they built hydroelectric dams in series. Use the excess power generated during the day to pump water from the lowest lake to the highest lake. Let the water flow down at night and generate power. been doing it for many years. solar power converted into potential energy. 1st year physics.
That’s a good idea as well or underground heat sinks that give off heat over the course of the night as well.
You need huge, economical energy storage systems which do not exist and won’t ever exist. Dams filled with water. problem solved. Except they don’t want to solve the problem.