Well for any decent solar cell you're still going to need (very) rare metals such as tellurium and indium. Those supposedly green energy sources rely on depletable materials just as much as any other alternative, and they're inefficient to boot; with the biggest problem being (imo) the inconsistency in your energy supply. It's completely dependant on external factors over which we have no influence.
And apparently sand causes scratches on the panels which over time could greatly reduce efficiency. I don't know how much damage over what amount of time we're talking about - but safe to say that the best places to deploy panels are usually windy, sandy places. If I imagine the technology being used on a national or worldwide scale as the dominant energy source maintenance must be a true nightmare, if only due to the sheer number of panels needed. That said, I believe nuclear power is going to be our best bet for the future, until a energy source is discovered that's actually viable. I've got hopes for fusion but given the required circumstances to produce more output than input its debut as an energy source could be long off.
My advice; go nuclear and for once start investing heavily in space agencies such as NASA and the ESA. Taking into account population growth and the rest of the world catching up technologically and thus needing more of... everything, we're going to need to get our basic building materials from somewhere else, because I doubt the supplies of our earth can sustain the growing number of people who need massive amounts of stuff.
Meet asteroid;
At 1997 prices, a relatively small metallic asteroid with a diameter of 1 mile (1.6 km) contains more than $20 trillion US dollars worth of industrial and precious metals.[1] In fact, all the gold, cobalt, iron, manganese, molybdenum, nickel, osmium, palladium, platinum, rhenium, rhodium and ruthenium that we now mine from the Earth's crust, and that are essential for economic and technological progress, came originally from the rain of asteroids that hit the Earth after the crust cooled.
He's got plenty of stuff.
If average living standards in India and China start to compare to that of the western world we are so fucked.