Letters to the Editor
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Batteries
Boko
This study is on grid-tied system (approximately 90% of PV is grid-tied these days). Such systems have no batteries because when the system is making less power than needed, it is bought from the grid. When the system is making more power than needed, it is sold to the grid.
John Q
On what basis you you say that solar thermal electric (Stirling engine) or CPV is less polluting overall? Both of these systems use a lot of materials, and in the case of Sterling engines, consumables (like motor oil and coolant).
In any event, different types of systems are useful for different applications. Solar thermal electric and CPV might be more cost effective than flat plate PV in powerplants in the long run (the jury is still out, despite hype to the contrary). Conversely, flat plate PV is definitely the best way to do distributed generation at the point of use - on rooftops and so on. These can be quite sizable systems when sited on big box stores, warehouses, etc. and directly displace peak load which is quite beneficial, economically and environmentally.