Many of our energy sources are unpredictable, sun and wind being the obvious ones. Some of our energy sources are very predictable, but their demand is not. We end up selling power, sometimes at negative prices, when we are making more than we can use and cannot easily scale back a nuclear reactor’s output, as an example.
Storage seems to be the obvious answer. There are projects out there to do energy storage; one uses a large reservoir and pumps water up when there is extra power. The pumps are the same turbines used when the water flow is reversed, to generate electricity. Apparently some 60% of the energy can be recovered. That’s a lot better than giving it away for less than nothing.
Batteries don’t seem to be big enough to make a large dent in the power grid, at least not in today’s technology. But there are other possibilities. Heat could be stored, for instance. Chemical reactions could be driven (charging a battery is one special case, there must be others).
Nevertheless there does not seem to be much research into this problem / opportunity.
One weird thing I recall is the compression of nitrogen. Under heat and pressure, nitrogen can enter a state where the atoms are so close together, in a sense they do not know which atom is bound to which. At this point the N-N triple bond (one of the most energetic chemical bonds knows) is effectively broken and a new state of matter is achieved. Heat is absorbed.
If the compressed nitrogen is allowed to expand, the energy is restored. The product is hot nitrogen. While you can suffocate in pure nitrogen, it is about 78% of ordinary air by volume. If dispersed, it is harmless. It can run a heat engine – pistons or turbines.
No doubt there are some engineers out there who can come up with a better energy storage scheme. Any ideas? We need to solve this problem, especially as we try to move to renewable energy sources that are not constant.