Exponential growth in solar PV
The EPIA’s recent estimate that solar PV installations grew 129% from 2007 to 2008 is excellent news.
While growth is likely to be stunted in 2009 (due in part to the collapse of the Spanish economy, last year’s biggest market) this is the kind of trend that should warm greens’ hearts, and not the planet. One factor which works to solar’s advantage is the recent collapse in polysilicon prices back to “normal” levels — which will improve silicon-photovoltaics’ cost-competitiveness, even as some companies’ profit margins will be squeezed. 
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While wind energy is cost-competitive with fossil fuels, the rule of thumb is that it can’t be used for more than about 20% of the grid, due to its intermittent nature. Basically, to accomodate large amounts of wind, you need to be able to turn other sources of power on or off instantaneously — to account for situations where the wind dies down or comes up suddenly. That means hydro (which accounts for about 20% of worldwide power generation; quelle coincidence!).
While solar is also intermittent, a big advantage it carries over wind is that it only provides energy during peak usage hours (from morning to evening). Which generally makes it easier to tie into the grid. While wind energy production will continue to overshadow (heh) solar electricity for a few years — generation capacity is currently about 120 GW to 5 GW — solar’s ease of grid tie-in should help it surpass wind perhaps a decade from now.
For now, the next milestone for solar will be to outpace nuclear; in 2007 new nuclear generation capacity was about 2 GW. Solar installations in 2008 were about 3 GW peak, which normalizes to about 1 GW (since solar doesn’t provide energy at night, and provides a lower-than-peak amount of power in the morning and evening).
