There's also, at least on a global-energy-system scale, the issue of efficiency. Solar thermal (I'm thinking of solar towers and the like) can heat a medium to

There's also, at least on a global-energy-system scale, the issue of efficiency. Solar thermal (I'm thinking of solar towers and the like) can heat a medium to about 300, maybe 400 C, and if I'm not mistaken using a conventional steam turbine that can give you a Carnot efficiency of ~25%, maybe 30%. Real generators engineered today are on the level of 90% efficiency, meaning that a solar thermal plant can - practically - convert ~20% of incident solar energy to electricity. Commercial PV will likely not reach that level of efficiency for years, and there are - probably - good ways to improve thermal efficiency beyond this 20%. Of course, thermal generators required direct incidence (don't work well on diffuse light), but the long and short of it is that with thermal we (may) need about half the total area we would need for PV. (On the other hand, PV can practically uses space - rooftops - which is inaccessible for thermal.) Nice blog, by the way :-)