The next hot thing (pun intended) is geothermal. The tech to drill deep enough opens up the possibility of extracting geothermal energy in most of the world. The tech exists and is deployed. Scaling is not yet proven but is very plausible. Geothermal runs 24/7 and can be clean base load power.
It’s not just drilling deep enough, it’s whether they can keep the wells open and flowing long enough to make the whole thing economic.
Some deep geothermal projects have failed because the wells wouldn’t stay open. Maybe this generation of companies have solved this problem; let’s wait and see.