Big and heavy are the two things which are very difficult and thus expensive when you want to throw them into space, even in LEO. The amount of energy required to lift this stuff into orbit will exceed what it can return as power.
...and completely ignoring the idea of building using materials already outside the gravity well, or development of alternative lift methods that are more efficient. Rockets are at best like 70% efficient for lifting loads into orbit (under ideal circumstances, in practice it's lower). You're saying it's *impossible* to *ever* do better? I won't deny it might be difficult to do better, but claiming it's impossible is short-sighted.
Big is irrelevant, heavy is the issue. If you think it will NEVER be possible to build a structure of the appropriate size using less material or lighter material, then we'll just have to disagree. Personally, I think you're ignoring the fact that we can build much larger structures in micro-gravity with much less material because they are under a lot less stress. Just look at how thin and light solar sails are, they cover huge areas with a tiny amount of material.
Physics dictate the size of this thing. Physics will dictate how much power it can transfer, how much it will loose and how much it will have to collect. Physics will dictate how much solar collection area you will need, engineering may be able to approach that someday. Physics will mandate how much energy it will take to get everything necessary into the proper locations.
I don't dispute any of this. I agree.
You will be able to engineer lighter structures, but not smaller ones.
At the risk of repeating myself, size is irrelevant in space. You have all the room you need. Between size and weight, the only relevant issue here is weight, and you've just agreed that we can likely engineer lighter structures.
There is a lower limit on the weight of this structure, regardless of the properties of the materials we can engineer.
Agreed, but neither you nor I are in any position to say what that lower limit is, or assert that that lower limit is absolutely too high to ever be practical.
You might be able to engineer cheaper ways of getting something into orbit, but you cannot change the minimum energy required by physics.
Obviously. I've never claimed you could change the energy requirements for a given mass, but like I've said already, there are ways around that. Like using material which is already up the well, using lighter materials or better construction that uses less material. Using better lift efficiencies, lighter or less material, or eliminating the need to lift stuff out of the well altogether could all go a long way to making it more practical. I'm not saying it IS possible, even with these improvements it might not be; but I AM saying that declaring it impossible now and forever is unwarranted.
Physics is your problem. It defines a system that is so massive that there is no way it ever gets to be cost effective to build...
No, physics is not the problem, it's just one of the constraints on the problem. You can't possibly *know* that the lower limit on mass is too massive to be practical. Unless you can predict the future, new developments in material science could change that in a heartbeat.
...because by my calculations, it will take more energy to create and operate this thing than you can ever hope to recover. That makes it uneconomical too.
Calculations which are based on the constraints of current materials, structural engineering techniques, lift efficiency and the necessity of lifting resources out of a gravity well. Change any one of those things and your calculations are no longer valid. You seem mighty confident that it's impossible to change ANY of them. Me, I'm not so much of an absolutist.
With respect to it taking more energy to create and operate than you can hope to recover, that all depends on how much we can reduce construction and operating costs, and how long we can prolong operational lifetime. Reducing construction and operation costs and extending operational lifetimes, are the very *definition* of "engineering problem". When photovoltaics were first invented, they were so expensive to make, and had such short lifetimes that we needed much more energy to make the things than we would recover over their operational lifetime. However with recent developments, PV devices now return between 15x-60x their construction energy over their operating lifetime. I see no reason to believe that the same isn't possible for microwave transmission systems.
Personally I think there are much better uses for our time and resources spent on developing new energy sources. Things which are way more cost effective and promising than this nutty idea of throwing solar panels into space and beaming the energy home. Can we say fusion? That's a much better and more effective way to produce energy that we know is theoretically possible too. The remaining engineering problems of fusion are close to workable solutions and the physics, while daunting, do not mandate that we build engineering solutions which are massive in size and complexity.
I agree completely with all of this (except the size contention - it doesn't matter in space). I never said orbital microwave energy transmission was the best solution to our energy problems, or that there weren't better alternatives. I just take issue with your claim that it will never, ever be a practical approach because of the limitations of physics. I agree that it is not practical now, but the major obstacles are ones of engineering. At this point we simply don't know enough about what the physical limitations even are, to be able to confidently declare the endeavour absolutely impractical.
Seems very likely to me we can master these problems and if we did, there would be no need for your pet energy solution where the laws of physics demand massive structures in very harsh environments and equally massive development and deployment costs.
Orbital transmission of energy via microwaves is not my "pet energy solution" - I have no investment in it other than to say that declaring it impossible or impractical forever, due to unknown limits of physics, is quite premature.
If you want to talk actual, currently practical, energy solutions, we don't even need to bother speculating about fusion reactors - we should just be building more fission reactors. The issues of metldowns and containment of radioactive byproducts are already quite well understood, and we already have workable engineering solutions to them. In the event of failure, modern reactor designs wind down instead of causing a chain-reaction meltdown. Storing radioactive byproducts is a mature field of engineering, with advances being made all the time. Any leaks are localized, less harmful and much easier to deal with than the global issue of fossil fuel byproducts just being released into the air.
Fusion can wait, the only practical way forward to meet our energy needs in the short term without causing massive environmental problems is to build more fission reactors.