Being able to use the same amount of energy cheaper is only half the equation. I'd be more interested in what we can do with 10x as much energy at the same price, or 100x. Could open up entirely new industries or make things that are currently infeasibly expensive novelties into commonplace materials.

One obvious win would be desalination plants to allow mass scale water production in areas with little or no fresh water but access to ocean water. Right now that's only economically feasible in limited cases, to my understanding.

Massive scale hydroponics at all latitudes, too. Why be limited to what the sun can grow, when we can grow our own sun right here on Earth?

You may be lucky enough to enjoy limitless food and water, but a substantial part of the world does not and it's going to get worse before it gets better as our population approaches 10 billion in the next 30 years. A lot of that water is going to need to come from desalinization, which is basically an energy problem. Vertical farming may help us when it comes to agricultural water demand, but it's also very energy intensive. Both problems reduce to energy problems.

Hunger and access to water are largely already political problems, and like I said, energy is going to get cheaper fast in the coming years (shifting them further into the political realm).

Vertical farming is going to provide perishable produce to rich people, so it's kind of weird to end on that point given where you started.

I stand by what I said. You're looking at how we meet our needs for food and water today. I'm looking at how we'll do so for 10 billion people, with a larger percentage of them consuming more resources like us Westerner's enjoy.

Vertical farming hardly enters the picture today, and we currently pick a lot of the low hanging or unsustainable fruit where water is concerned. But we're going to have to do a lot of desalinization going forward, and we're also going to need to take a good percentage of farming indoors because we just don't have the land and water resources to do otherwise.

Vertical farming works for more than just lettuce and tomatoes - the thing is it's uneconomical so far. The technology needs to get cheaper and more widespread, and the inputs of energy, water, and fertilizers need to get cheaper. Advances in materials, building technology, and transportation would also help. Cheaper energy helps with everything.