I just meant volume in the sense of "amount, " not any particular measurement method (though all of the relevant ones are equivalent for a mixed gas). I said both GWP and amount together matters, not just one of them by itself. If the amount is very small compared to 1/17,000 of the CO2 emitted, then its effect is small. If its effect was considered insignificant, and now is four times that previously thought, then its effect is still small but could be significant.
In the article, a GHG effect greater than "even that of the world’s largest coal-fired power plants" means one power plant, not all of them together. That comparison is only true if all of the NH3 is released (note the words "potential greenhouse impact" and "if released"), while in fact most is destroyed during use (84% according to NASA, 98% according to industry). That means that getting rid of all of the NH3 produced (at today's rate) is equivalent to shutting down one coal plant (or maybe 2 of them), and 84-98% is already destroyed in the manufacturing process. And we're talking about basically all semiconductor manufacturing as the main source of NH3, not just PV. NH3 does not appear to be a significant drawback to PV, any more than its energy input during manufacture. It's a red herring in the context of PV. Sure, it's a great idea regulate NH3 and reduce its emissions especially to the extent that it is easy, but it's not a good reason to avoid PV. That's why the point of the original sources is that NH3 needs to be re-evaluated as a significant greenhouse gas, but they don't talk about solar power at all (except a brief mention that it is one of the applications of NH3). Without a number for NH3 emissions per (lifetime) PV generation capacity, or detrimental effects of NH3 besides its role as a greenhouse gas, there is no real basis for your argument that NH3 is an "important drawback" for PV. -- Rich On Sat, Aug 8, 2009 at 2:38 PM, Ryan Hottle<[email protected]> wrote: > Rich... > > Definition of GWP (Global Warming Potential > http://unfccc.int/ghg_data/items/3825.php) is the comparison on a per > molecule basis of how much radiative forcing a given gas has compared to CO2 > which is fixed as 1 (it's not a perfect index... but tries to makes things, > as best as possible, apple to apple comparisons. Thus it's actually the > number of molecules in the atmosphere that matter ppm/b/t not the volume > ppm/b/tv per se. > > 1 NF3 molecule = 17,000 CO2 molecules in terms of warming. So saying that > it's a matter of volume and that the volume is small and therefore it is a > signficant problem really just doesn't hold water. Further the growth in > emissions of NF3 has been geometric, suggesting that we should be taking a > close look at it now instead of later when it becomes more of a problem. > The main thrust of the paper your provide suggests that: > > "With 2008 production equivalent to 67 millionmetric tons of CO2, NF3 has a > potential greenhouse impact > larger than that of the industrialized nations’ emissions of > PFCs or SF6, or even that of the world’s largest coal-fired > power plants." > > Perhaps this is small beans compared to the whole, but not insignificant and > I'm just suggesting that it shouldn't be ignored. This seems like a fairly > important drawback of PV, unless, of course, we're able to manufacture PV > without NF3s as the article you linked to suggests is quite possible. [...] > Best, > Ryan > > On Fri, Aug 7, 2009 at 9:33 PM, Rich Bernstein <[email protected]> wrote: > >> On Wed, Aug 5, 2009 at 6:08 PM, Ryan Hottle<[email protected]> wrote: >> > Thanks Rich, >> > This is helpful... Yet, you're right, where's the data? >> > >> > NASA I tend to trust... company publications not so much. Any gas which >> has >> > risen from 0.02 ppt to 0.454 ppt in the past thirty some years and has a >> GWP >> > (Global Warming Potential) of 17,000 times that of CO2 (CO2 GWP = 1) is >> > certainly of some concern. I.e. can't simply be written off as a "big >> coal" >> > conspiracy. We shouldn't let our desire for certain technologies allow >> to >> > manipulate >> >> It's the combination of GWP and volume that matters. And total volume >> is very small. It's just four times bigger than they previously >> thought. Before they thought it was small enough to be basically >> irrelevant (compared to CO2), now it might be enough to matter (even >> though we're still talking 0.15%). [...] _______________________________________________ For more information about sustainability in the Tompkins County area, please visit: http://www.sustainabletompkins.org/ RSS, archives, subscription & listserv information for: [email protected] http://lists.mutualaid.org/mailman/listinfo/sustainabletompkins Questions about the list? ask [email protected] free hosting by http://www.mutualaid.org
