On May 25, 2014, at 7:26 AM, Cor van de Water via EV <ev@lists.evdl.org> wrote:
> I'd like to know where you heard that (incorrect) tidbit
> about solar panels having more energy content than they generate.

My assertion, more specifically, was that that was true for places that weren’t 
essentially cloudless deserts.  And you’re right, and I’m wrong.

I was misremembering the primary source of my information as David JC MacKay’s 
_Sustainable Energy Without the Hot Air_, backed by two different friends in 
different PV manufacturing companies who’ve told me about the energy costs of 
refining silicon to the point at which you can make a PV panel that will pass 
quality control.  Which, if I’d been remembering correctly, would have made me 
secure in my assertion.  However it seems only the two anecdotal sources 
support the high-embedded-cost notion, and they’re not quantifiable.


"The energy yield ratio (the ratio of energy delivered by a system over its 
lifetime, to the energy required to make it) of a roof-mounted, grid-connected 
solar system in Central Northern Europe is 4, for a system with a lifetime of 
20 years (Richards and Watt, 2007); and more than 7 in a sunnier spot such as 
Australia. (An energy yield ratio bigger than one means that a system is A Good 
Thing, energy-wise.) Wind turbines with a lifetime of 20 years have an energy 
yield ratio of 80.”


http://sunlightsolar.com/img/PV-Embodied-Energy_Home-Power-mag.pdf   pp. 34



These various sources calculate the payback time in relatively normal environs 
as being between 1.5 and 12 years.  Which, given the number of variables being 
hand-waved about, is a reasonable degree of variation, and in all cases less 
than 20.

So, thank you for correcting me.


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