"The insolation on the average single-family home's roof at today's efficiency is virtually always some multiple, generally some very significant multiple, of the home's electricity use.
I do solar thermal testing. You can use 1000W/m^2 as a useful number for estimation. I have seen 1300W/m^2 on a very dry winter day (North Carolina), and 1100 -1200 W/m^2 is just normal clear day irradiation (insolation is sort of out of fashion as it is confused with insulation). I heard Elon Musk claim that you could provide all the current global power use with 100 square miles of PV. A friend and I roughed that out and he is not far off (there are a lot of assumptions you can make to vary it one way or another). But, the point is clear enough - a whole lot of energy lands on the earth from the sun. You can barely see 100 m^2 from orbit. On Fri, Jan 9, 2015 at 3:35 PM, Ben Goren via EV <[email protected]> wrote: > On Jan 9, 2015, at 8:29 AM, EVDL Administrator via EV <[email protected]> > wrote: > > > I'm no expert, but I suppose it might come to pass if PV efficiency jumps > > and cost tumbles, > > PV efficiency is already plenty. The insolation on the average > single-family home's roof at today's efficiency is virtually always some > multiple, generally some very significant multiple, of the home's > electricity use. And said multiple is again virtually always more than > adequate to charge a vehicle. > > And materials are and for some time have been the cheapest component of a > PV installation. What costs all the money is first and foremost the labor; > qualified electricians aren't cheap, especially those who both have > experience with high voltage DC and are competent roofers. And, many > places, the legal paperwork -- all the permits and inspections and utility > company writeoffs and what-not -- winds up costing more than the bill of > materials. > > The key ingredients we really need are twofold: solar roofing > installations that can take the place of and be installed by today's > low-skill roofing laborers (perhaps with an electrician just for the final > run from the roof to the breaker box) and less-expensive battery > technology. The former exists in various prototypes that keep getting > mentioned in press releases, and the latter is something well known to the > EV crowd. > > > "Aargh, no clean underwear, and I can't do laundry because we're at 7% > and I > > still have to charge the car. I wonder if the car has enough charge left > > for a trip to the store to buy some." > > That just means the system is under-sized. In such a case, either you > should have spent more for a bigger system, or you knew what you were > getting into and therefore budget your energy use accordingly. Low income > households already face similar problems...do I pay the electric bill with > the last $50 remaining on this credit card's limit, or do I use the money > to buy groceries for the kids? > > > "Sorry, boss, I can't come in to work until this afternoon. Joe ran the > > house flat with his welder last night, and I won't have enough juice to > > charge my car until the sun comes up." > > If Joe's a contractor, he should be showing up with his own power supply > (such as one of the many industrial EVs we've seen Bruce mention with their > own power plugs) to run the welder in this future -- or, otherwise, first > making sure that the site he's visiting has the spare capacity to power the > welder. And if Joe lives in the home, it's his own damned fault. > > > Also, the cost of storage (lithium battery? what?) > > It's a big question today, but I suspect we'll have a clear winner in the > next several years at the most. Nickel-iron batteries live longer than > people but cost more than any other type of battery. Lead acids are pretty > cheap but die after a few years and cost significantly more over a > lifetime. But there may well be a market in EV batteries old enough to be > less than optimal for vehicular use but still with plenty left in them for > an off-grid system. I could see leasing / renting of battery systems > becoming popular, with the company that owns the batteries responsible for > ensuring a minimum kWh capacity of the pack in exchange for whatever fees > they charge, similar to what we've speculated Tesla might offer with their > car battery swaps. > > > would have to decline by, oh, I dunno, say, 90%? > > Nowhere near as much. > > In many parts of the country, the payback time for a complete off-grid > solution is better than the payback time for money market funds and other > financial instruments. That is, if you're invested in the stock market or > especially your bank, you'll be wealthier at the end of a decade or three > if you pull the money out and put it into an off-grid system. > > But that requires a significant amount (to most people) of available > capital. > > But it also means that a business -- such as Solar City -- can afford to > invest its own capital (or borrowed funds) to install such a system and > become an ad-hoc utility and still make a marginal profit. > > That's with today's technology...and it's only getting better. > > > I have no idea whether such a quantum leap in PV and energy storage tech > is > > on the horizon. Absent one, though, I suspect your estimate of "ten to > > twenty years" is probably a bit optimistic. > > But that's just it. It's doable _and_economical_ today, if you have the > capital to invest. No more revolutionary breakthroughs are required to > bring it to the masses; only gradual refinements of the types we regularly > see and expect, perhaps coupled with some entrepreneurial innovation. > > 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/20150109/52f1e68d/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) > > -- Put this question to yourself: should I use everyone else to attain happiness, or should I help others gain happiness? *Dalai Lama * Tell me what it is you plan to do With your one wild and precious life? Mary Oliver, "The summer day." To invent, you need a good imagination and a pile of junk. Thomas A. Edison <http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 550-2430 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell (919) 513-0418 Desk [email protected] <[email protected]> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20150109/cb2a7104/attachment.htm> _______________________________________________ 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)
