This is so far off from what's going to actually happen that it will boggle your mind. Since we already have a grid infrastructure, all we need to do is improve that and make it more resilient and modular which is relatively easy. Then all that remains is supplying the grid to meet peak demand which decentralized renewables can easily do. Add fusion, geothermal, space-based solar and even fission and you have superabundance. Energy is not something the Universe is short on. I'm far more concerned about the effects of overabundance of energy than under because the Biosphere requires homeostasis.

Also manufacturing is going to evolve to new forms of rapid 3D printing and nanotechnology which is very energy efficient. Self-building robots (auxons) will create solar and fusion powered manufacturing hubs in the asteroid belt far away from the closed ecosystem of Earth.

Also you can see even in winter (which is summer in the Souther Hemisphere) the Sun lights and warms the world well above absolute zero and efficient solar cells and wind turbines can work well.

As for energy storage the options are growing by the day including molten salts, deep earth storage, gravitational storage, ultra capacitors, flow batteries and more.

On top of this AI will aid us in quickly finding ever more efficient materials and methods so I think you have missed the exponential curve of discovery in your thinking. We are in the "knee" of the curve now.

What you are absolutely correct about is the current world is unsustainable.