Research into fusion went down a blind alley; a means of escape may be at hand
economist.com
economist.com
actually i think it is quite opposite - the inertial confinement approaches have from the start been the most promising, and they are relatively easy to miniaturize - thus paving the way for the neutron weapons without fission primary. No first-rate power - who already has nuclear weapons and thus has no real need for new types of neutron weapons - is interested in second-grade players obtaining such weapons bypassing the need for fission primary, as all the hurdles related to fission primary is what provides for non-proliferation.
Thus all the government funded research has been only in non-miniaturizable (as seen decades back) Tokamak and laser confinement. Sandia Z-machine (great inertial confinement approach) could have been burning DT targets at the end of 199x, yet they started to do it only 15 years later (at least officially) - somebody definitely wasn't in a rush :) With tremendous progress in solid state lasers i kind of curious what fate (ie. government funding) is waiting for NIF as upgrading its warehouse size 3% efficient lasers to container size 20-50% efficient solid state would obviously be in order. Yet it doesn't seems it is going to happen - the last monthly NIF's status update was in May 2014 and officially it has stopped ignition experiments and back to material research (simulating plutonium compression in the nukes)
This was the fate of the UK's JET experiment at Culham (the Joint European Torus, predecessor to ITER): once they finally bit the bullet and went to actual fusion containment experiments, the "hot" reactor became a lot less accessible for tinkering and reconfiguration. So you don't take that step until you're real sure you don't want to play with your plasma containment experiment any more.
Wait, really? How?
So one day your cruiser class naval ship starts boiling the ocean around it while it fires of its lasers and rapid fire rail gun.
"More likely, cheap photovoltaic and energy-storage technology will mean that much of humanity’s energy comes from a different fusion reactor—one 150m kilometres away, called the sun."
5 billion years of evolution haven't given us solar powered animals that can run around. It seems like there are some significant hard limits on solar technology.
Energy storage technology actually makes nuclear much more practical... the big problem it faces is that it generates very consistent power, but power demand fluctuates by time of day.
What do you think animals run on? Gasoline? Plants are like batteries, storing solar energy. Animals, including humans, charge up by consuming these plants. And for those who don't eat plants, they eat charge up by eating the animals who charge up on the plants.
Fossil oil qualifies too, but the fact it's all ancient stored solar energy rather than solar energy captured now makes it vastly different. Oil produced by capturing solar power now should qualify as "solar power" just as much as photovoltaics.
You can consider the solar->plant->animal cycle to effectively be similar to using solar panels. Using solar panels directly would be inefficient without batteries anyways, so the solar->plant->animal cycle is directly analogous to how we would use solar panels.
Obviously our tissue is much well less adapted to so many hours of sunlight compared to plants. Also even plants only absorb a relatively small part of the light spectrum (none of the green light). Also even plants required compounds from the earth and the air to actually harvest the energy to store so it's a pretty complicated process to do in an actively moving human.
I don't see why you would expect animals to evolve a way to "capture sunlight" (though some do: http://umich.uloop.com/news/view.php/77109/4-incredible-phot...) when it's far more efficient from the standpoint of the animal to eat plant matter.
Pretty much every animal that can run around is solar powered, consuming as fuel an energy storage medium for which the input energy is gathered by (mostly stationary) solar collectors. (Or consuming other animals, which are themselves fuel synthesized from such fuel or other animals, etc.)
> It seems like there are some significant hard limits on solar technology.
What hasn't been produced by evolution isn't strong evidence of hard limits of any technology, so even if the premise was true, that still wouldn't justify this conclusion.
The point is valid: the density of solar exposure at the surface of earth, times the capture/conversion rate to chemical energy, is too low to support animal life. As demonstrated by billions of years of evolution.
Animals eating plants, on the other hand, involves collecting solar power for weeks or months, then using that collected energy over weeks or months. Animals eating other animals might involve collecting solar power for years, or a decade or two at most, but no more.
Global solar flux is clearly sufficient to sustain all animal life on the planet because that's exactly what it does, while it's clearly insufficient to sustain current oil usage because we're using it orders of magnitude faster than it was produced.
Where do you think animals are getting their energy from, if not from the sun?
Much, but not all.
> Oil came from algae which grew from sunlight.
Sure, oil is indirect solar power. The problem with oil is that's rapid consumption of a stockpile accumulated over a much longer time, which produces sustainability and carbon-balance problems.
> The point is valid: the density of solar exposure at the surface of earth, times the capture/conversion rate to chemical energy, is too low to support animal life. As demonstrated by billions of years of evolution.
Er, no, it does support animal life. IF it was too low to support animal life, than animal life could only exist by the equivalent of burning oil; e.g., it could only evolve with an accumulated stockpile of stored energy which it is burning down. That's not the case, so the negation of your conclusion is, in fact, proven by nature.
(And even evolution hadn't produced a mechanism that did that -- in which case we wouldn't be having this discussion -- that wouldn't prove it was impossible. Otherwise, all the technologies that we have developed for which there are no biological analogs produced by evolution would be impossible, which is clearly not the case.)
"Photosynthesis" is another difficult trick. It's believed that (with the exception of the amoeboid Paulinella chromatophora), all chloroplasts in eukaryotes derive from a single endosymbiotic event that took place over a billion years ago, though after the last common ancestor to animals and plants.
What you want requires both tricks to have occurred in the evolutionary history of a single animal.
As evolution doesn't go towards a global optimization, but only acts on what's available, the lack of directly solar powered animals does not place a low intrinsic limit on solar technology. An alternate evolutionary history, perhaps where something like Paulinella chromatophora acquired a chloroplast 1 billion years ago instead of 60 million years ago, may have resulted in the world you envision.
On the other hand, I agree, I see fusion as the future and I think it is necessary if we want to meet the future demand for energy.
I'd also love for us to become a space faring civilization, and for that, we need to be able to make our own little sun. We'd then be able to build our own self-contained solar system.
After all, if you look further enough down the chain, all energy we're using is solar. Yet, if you look even further down the chain, all energy is fusion.
Actually, that's exactly what evolution has given us. Nearly every living thing on the planet gets it's energy from the sun. Taking that a step further, nearly every bit of energy extracted from fossil fuels comes from stored solar energy.
Just as someone is getting sunlight someone is getting wind. So connect them all along the same distribution pipes. How much loss per mile is there now in a sealed cable? What is the possibility for reducing that?
The Oriental Hornet has been found to harness solar rays, but it largely active during the brightest hours of the day.
http://news.bbc.co.uk/earth/hi/earth_news/newsid_9254000/925...
Which of course is why we outsource our collector area to plants. That solves the storage problem too. Animals are solar powered, just indirectly.
Many(imo most) evolutionary solutions are clearly local maxima. Try s/solar powered/wheeled in your comment. I encourage you to learn more about evolution.
Right outside my window is my solar-powered lawn.
Consider a reactor that consists of two colliding beams. Should work great, right? Well, the reaction rate is minuscule, so you're wasting a whole bunch of energy in the ones that don't collide. It's a numbers game; in the sun there's a process that has a reaction rate of something like 1 in billions of years, but it's okay because there are orders of magnitude more protons in the sun.
The point of tokamaks and stellarators is that the field lines are closed, and you won't have leakage out of cusps like in mirror machines. You prop up the energy distribution with techniques like neutral beam injection and electron cyclotron resonance heating, since the ions tend to dump their energy to the electrons.
In other machines, mostly inertial confinement devices, the claim is that a pulsed mode of operation will be effective. However this remains to be shown, and some work (see Todd Rider's PhD thesis) claims to prove that such non-equilibrium schemes cannot reach breakeven.
What's especially nice about thermonuclear fusion is that it's feasible that the fusion reaction itself keeps the plasma hot enough.
> this means the vast majority of collisions will just send your ions pinging out of the magnetic bottle they are in
Here's the thing: collisions get less frequent the higher in energy you go. This seems counter-intuitive, but consider that the vast majority of "collisions" are actually weak Coulomb interactions at a large distance. If you're approaching an ion at very high speed, your trajectory is not deflected very much.
So while collisions are a major concern in stellerators in this sense, they are less so in tokamaks, where turbulence is the main limiting factor.
[1] By those smarter than me, that is. It's incredibly complicated.
I think having fusion is a danger for our civilization. People will use this energy for stupid things, like moving mountains; eventually, it will either heat up the planet or produce huge amount of toxic waste or use up all the water we will be able to find. It will be like with carbon fuels but order of magnitude worse.
I would much rather see our civilization to learn to live with the plentiful, yet on decent timescales sustainable, solar energy.