Quote - I have this lingering suspicion that, if solar could be used as a weapon, the efficiency would be more equal to nuclear plants. And, while we're at it, if they could run tanks on batteries, we'd have affordable electric cars. Not that I'm railing against the military-industrial complex, or anything.

If solar could reach the energy density useful as a practical weapon, then it's usefulness as a power source would go up appreciably because the energy density would be higher. It has nothing to with no one wanting to develop it because it can't be used as a practical weapon.

In fact, as an aside, modern militaries such as that of the US are very interested in energy efficiency, alternate energy sources and the like. The reason is the weakness of all militaries: logistics. If someone developed super-high efficiency solar cells the Pentagon would be all over that because it would allow them to cut the logistical requirements (in terms of things like fuel), especially to units in the field or at forward bases, making the units more flexible as they wouldn't have to rely as much on the logistical tail, and the people taking care of the logistics could focus more on the things that go bang and boom and less on carrying in simple things like fuel to keep generators running.