http://thefraserdomain.typepad.com/energy/2007/11/googles-goal-re.html#comment-94252066

The first part of my favorite entry in this effort would be concentrating solar cogeneration.  10 sun trough concentration reduces the amount of PV cells by 90%, reducing the cost by 60% (1/10nth the PV cells are used, but the concentrating troughs add some cost), and tripling the usual efficiency of most PV cells in use now.

Like the typical ones used in this roof mounted system in solar insolation average NJ.  It's no shining desert, but no rain forest either.

http://msmith.typepad.com/smithelectricco/ 

 This system has a 8.5 year payback with subsidies, but coal has numerous subsidies too, in the form of tax breaks.  Tripling the efficiency for this system and cutting the cost by 60%, by hypothetically replacing it with the concentrating trough system would produce triple the kwh per year.  Thus cutting the payback to one third, and the original 8.5 years is cut to 5.1 years by the lower cost already.  For a 1.7  year payback.  After that the kwh are free.

That surely beats coal!  With it's ever increasing fuel costs.  Free after 1.7 years beats nearly everything.  Add to this the cogenerated heat to heat hot water and the payback drops even further.

A smart grid with this kind of solar power mounted on every suitable rooftop, and distributed wind, wave, water, and biogas from waste power generation.  And smart grid switching of loads to store and conserve energy.  And plugin hybrid vehicles employing smart grid vehicle to grid storage and charging.  And a switch to geo heat exchange heating/cooling. 

That kind of energy system design, which google has related expertise at (the internet switchable smart grid part), would not only be cheaper than coal.  It would impell an economic, foreign policy, and climate renaissance.