Well, somewhat. The amount of precision that the physical worlds demand in the construction of the fuel pellets, and the amount of energy involved in using them, guarantee that you need an extremely expensive mechanical process for the fuel. So, while physically you probably can extract energy from the pellets, it'd be like a steam train powered by gold bars instead of coal.
This assumes that the only way to get energy is by burning stuff in oxygen. That may not be a safe assumption. Imagine an atmosphere with some amount of fluorine, for instance.
If you have the tech to fuse hydrogen the amount of fuel you would need for a nearly unlimited amount of energy is tiny, you would save very little by harvesting it off a comet/asteroid.
If you have an unlimited supply of energy, you can pretty much recover whatever. The only elements hopelessly lost are those that involve nuclear reactions.
IF petawatt-scale power is possible (and that's a big if), one of the cool things you could do is bottle it and send it where it's needed.
Literally.
How?
Turn it into oil. Crack seawater to get hydrogen and separate out CO2 that's dissolved as gas and carbonate. Fisher-Tropsch glue the two together.
With a petawatt of power, even if the process were only 50% efficient (which is roughly what US Naval Research Lab, Brookhaven National Lab, and MIT research suggest, you'd be synthesizing about 2,580 billion barrels of oil annually. The US currently consumes about 6 billion barrels, and total global extraction in 2013 was 317 billion barrels. That's 368 bbl/year per person on the planet (US consumption is 19 bbl/person-year).
So, yes, that's overkill, but you could put the additional energy to use, oh, say, sequestering carbon from the atmosphere (which, say, the surplus oil you're synthesizing pretty much is).
And if you burn the oil somewhere else later, it's actually pretty much OK. The stuff'll be clean (it's pure hydrocarbon, no contaminants), it's carbon-neutral (though if you're sucking seawater out of a single spot on the globe that might be an issue (we know that messing with ocean pH is a Less Than Desirable thing.
But it turns out we've got a pretty considerable global infrastructure for doing just that with oil.
Mind: I don't think fusion power will happen any time soon, possibly not ever. But if we actually did have that much power to play with, we could probably sort it reasonably well.
This got me thinking about what we could and could not do if we had a magical a energy-unbottlenecker, say an infinite capacity battery with arbitrary power output.
These become much cheaper:
- Transport: synthesise fuel from CO2 + seawater. Or charge a battery.
- Water: electrolysis of seawater.
- Food grown anywhere: Light + water + fertiliser can be made from commonly available materials. Soil is a bit trickier, but I think you could bootstrap up with composting.
- Global warming: pull CO2 out of the air.
- Raw materials (concrete, metals): all cheaper to extract with free energy.
- producing medicine
Still really hard:
- making new treatments
- inflation of housing prices
- escaping earth's gravity (need bounce per ounce)
- world peace
- writing books
- politics
The oxygen would be the hard part. You'd want a temperature of about 2 billion degrees Kelvin and have it compressed to a density of about 4 million kg/ml.
That's a lot of activation energy, but it takes money to make money. Err, takes energy to make energy.
They would need to solve the problem that was easy on land: how do you release an energy from one resource to thermally pricess other resource (food at first but then metals).
Well, if energy were cheap enough you could just dig huge, multi-level tunnels, fill them full of grow lights, and raise all the grass-fed beef you wanted.
It's the same with water -- there's plenty of water in the ocean. If energy were cheap enough, you could just distill seawater and get all the freshwater you wanted.
Sure. If energy was cheap enough, you could get gold (and just about everything else) from sea water.
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