Hydrogen fuel cells begin to show off in the world of competitive racing

[kristopher]

26. What is the specific problem you want storage to solve?

You first need to answer that question before you start looking at the best way to solve it. The goal of being carbon neutral is good, but that is a characteristic you want to incorporate into your solution, it doesn't define the problem.

Is the problem meeting home heating needs in Maine during the month of January?

Do you want to provide power for your automobile?

Does a hospital need to have emergency power available no matter what?

The list you presented is a start but trying to incorporate the pros and cons into it is premature without a specific application in mind. What might be the best solution for a large agricultural operation will require a degree of energy portability that supplying an office complex wouldn't, so the solutions would probably be different.

Also, I'd suggest that neither heat storage nor battery storage are characterized by "noxious by-products". There are some technologies in these categories that you might say that about, but not-so-much for most of them (lithium, zinc and NIMH (chemical) ice or rock batteries (thermal).