What is the biggest hurdle for building a space based solar power system? is it the cost? All the space faring countries can come together and launch each part separately and then assemble them together just like the ISS right? Is it the transmission of power from the satellite to earth the problem? Which part of the earth has lowest atmospheric density?is it the polar regions? i don't know (i am thinking about laser beams) Considering the satellite to be at a geostationary orbit . Is it possible to have huge helium balloons along with receivers at a very high altitude to receive the laser beam(or microwaves ,which one is better?) so that the beam may not have travel too far in the atmosphere and lose it's intensity(is this a concern?). And there are also some concerns of people being exposed to high intensity microwaves if the receiving site is on the ground. Can the energy be stored in some kind of supercapacitors attached to the balloons ,i know supercapacitors don't really hold on to the energy for long ,is there any other way to store the energy for a long time? so that the energy stored can be harvested once in few years or something? Or is it economical to have the receiving base in places where population is very scarce? Like some uninhabited islands or polar regions?