On Jan 14, 2015, at 6:13 AM, Robert Bruninga via EV <[email protected]> wrote:
> Most people only have so much roof available for solar energy. And > it is not enough for our total energy needs. On the contrary. To within back-of-the-envelope precision, the residential rooftop surface area in the US alone receives enough solar energy, at today's off-the-shelf hardware store efficiencies, to provide all the energy needs for the entire planet. Electricity and transportation and manufacturing and everything else included for the whole population, just from residential US rooftops. Of course, it's not hard to find examples of homes that fall far short. An apartment in a skyscraper in the middle of Manhattan, for example, or somebody at the bottom of a canyon in the middle of a forest in Alaska. But the general rule is for people to have at least a few times as much surface area as they need for themselves, with lots and lots having several times as much as they need. Here's a good article on the subject, including a map that shows half a dozen hypothetical 8% efficiency PV installations, each of which by itself is enough for the entire planet: http://physics.ucsd.edu/do-the-math/2011/12/wind-fights-solar/ So, though there will certainly be edge cases where photovoltaic efficiency is the biggest concern -- with NASA leading the charge -- in the overwhelming majority of situations, it's the financial return on investment that's going to decide how best to make use of this particular abundant resource. >> Solar thermal makes sense if you want heat. It's really GOOD at making heat! > > Which I dont need 7 months of the year. Your tap water is 120°F for seven months of the year? > And which I do need in the winter when it is producing HALF the heat for its > size. Even if your solar thermal unit is only able to raise the temperature in the tank to 80°F, it takes much, much less electricity to heat 80°F water to 120°F than it does to heat 40°F water to 120°F. Again, the efficiency of new generations of heat pump water heaters may well change the financial equation, but, even if it does, it's not for the reasons you're giving. Cheers, b& -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 801 bytes Desc: Message signed with OpenPGP using GPGMail URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20150115/053a15a7/attachment.pgp> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
