[Jack Simth]

Originally posted by narf poit chez BOOM:
*sigh* a few solar power satalites are all a country needs...

At present, in theory, satelites could be constructed that would capture enough energy to power things sure - but there are some catches:
1) Size: There isn't too terribly much difference in the wattage the sun delivers to a square foot on Earth as it does to a square foot in space, ignoring for the moment the day/night cycle and weather - any such satellite would need to be absolutely enourmous, which causes some difficulties in getting it up there.
2) Transmission and Transmission Safety: Once you have the satellite up there, collecting energy, you have to get all that energy back down where you want to use it. Sure, you could maser it down or something, but what then happens when a solar storm causes the satellite to wander slightly off course? For a communications or weather satellite, a small change in facing doesn't much matter, as there isn't enough energy in the transmissions to mean anything; it can be corrected with manuvering jets or gyroscopes at a later time, with the only drawback being the use of fuel (for jets only) and the downtime. For a power sat, with the distances involved, an extremely minor change in facing could very well cause all that energy to destroy a city, as it turns into heat and causes very bad fires at an unprepared site rather than being properly converted at a prepared site (a large change in facing wouldn't be as bad, as the distance involved means it is more likely to miss Earth entierly). This is complicated by several factors: the Earth is moving, the satelite is orbiting (probably spinning, too), the moon tugs on things, et cetera.
3) Expense (part of 1, in many ways): For the moment, it is ludicrously expensive to get something into orbit. The expense a solar sat would entail would likely makes other, earth-bound energy production mechanisms such as nuclear power plants positively cheap in comparison, although the majority of that is likely the initial expense rather than the ongoing matenince costs.
4) Transmision loss: Every time you ship energy around - especially when changing the form the energy is in - an amount is lost to a waste form of energy that you can't use (heat, mostly). The most expensive solar panels are around what 20% (?) efficency - which means that only one-fifth of the light that hits them is turned into useful electricity, the rest is lost. Changing that electricity into microwaves for transmission intruduces another ineffeciency, as does capturing the microwaves on the ground and converting them back into electricity. By the time the energy has finally reached the ground, we'll probably be lucky to manage 1% overall capture. That can be made up for in size, of course, but then you get back to 1 and 3.
5) Unknown effects: There really isn't any way of knowing beforehand what the effect of pouring that much energy through the air in a concentrated beam will do to such things as the weather, both long term and short, even assuming you can get past 2.

It is very likely all of those can, given time and research, be overcome. For now, however, ground-based energy production is more feasable ... but that will likely not stay true forever.