Although there is an adequate supply of solar energy reaching the earth's surface to meet our needs, there are certain hurdles that collecting solar energy in space could overcome.
1. Sometimes, you may have noticed, it's night. A constellation of orbital arrays could be positioned to collect solar energy 24 hours per day.
2. Weather. Clouds interfere with terrestrial arrays.
3. Photo voltaic (solar) arrays are delicate. Winds, heat, rain, snow, sleet, hail, falling acorns, etc. are all potentially damaging to solar arrays.
Of course, collecting energy in orbit brings a much more challenging problem than any of these: how do you get it to earth? I've seen articles that talk about "beaming" energy to the earth's surface, but I've yet to see anything that explains how this could be done in a cost-efficient manner without creating dangerous electro-magnetic fields.
Don't forget that the same sort of people who propose these sorts of projects are the sort that point out that it's technically possible to build a ladder that could reach orbital altitudes, or that we could grow all of our food hydroponically on the moon. "Practical" is a word that is frequently lost on such visionaries.