These are not open problems in the sciences, just some ideas for useful technological breakthroughs that should be within reach, but haven’t been done yet. There may be obvious reasons they can’t be done, but I suspect they can be done with some creative thinking or iterating on something that can be built today. Just a few ideas from reading Vaclav Smil books and not sleeping enough.

1. Small thermodynamic engines. Batteries suck: they have mysterious chemistries, and the best ones use elements not common in the earth’s mineral content, which have problems like occasionally catching fire in spectacular ways. Hydrocarbons are used in cars and by life for a reason: you can’t beat 12,000 Wh/kg using lithium anything (which is more like 200 Wh/kg). Imagine a little heat engine that runs on olive oil or ethanol to power your laptop or phone. Fuel up once a year. Hell make them without plugs. People started thinking about this using MEMS technologies during the nanotech craze of the 90s and 00s. They still think about it, using little turbines and wankels and such. Probably not the right approach, but there might be a way to make these approaches work. There might be better kinds of little engines that are more suited to the scales they function at. Certainly there must be options other than using MEMS and silicon.  Don’t give me any crap about environmental BS from burning a couple of eyedroppers worth of ethanol; batteries and copper wires are way worse for the environment. Fuel cells would be nice also, but I assume they have enough problems there is some good reason why we don’t have them in our laptops now.
2. Mesh electrical networks instead of hub and spoke. I think this will happen as renewables become more important. The hub and spoke model of power transmission has historical reasons for existing; thermodynamic solutions we have work better for larger installations. Big dams, big turbines work better than little things. But now we’re building lots of intermittent generators: wind, solar. We also have reasonably efficient gizmos for making power on a small scale when it’s dark and no wind. Batteries can play a role here too, and already do to a limited extent. They’re not connected together in any sane way at present, probably because of lack of imagination and standards. It would be nice from an infrastructure and individual agency point of view to have power delivery more under individual or at least local control. The grid presently works the way it does because of history and the fact that large installations are more thermodynamically efficient, but the direction is towards less dense “free” forms of energy and decentralization: might as well push more in that direction. Imagination stuff: you have a hybrid vehicle which could provide power at night, or act as a battery. Small turbine or Stirling generators for night time. Of course this requires political will, which is in short supply in the West. This will get shipped first in small places at the equator, like El Salvador. Perhaps in off grid coops in the west. Especially if they have:
3. High power microwave transmitters and transformers. Imagine transmitting large amounts of power via microwave beam instead of pumping megavolts over wires. You can theoretically use little waveguides to transport tremendous amounts of power.  You can also transmit power over line of sight the way they do with microwave transmission in the telephone system. The military has done some decent work here and  they have ways to transform to DC power. Gyrotrons are pretty efficient: 45%. I suspect they could be more efficient. They’re only about a hundred kilowatts though. End to e