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[Discuss] Eclipses Re: Great talks last night, however...
- Subject: [Discuss] Eclipses Re: Great talks last night, however...
- From: grg-webvisible+blu at ai.mit.edu (grg)
- Date: Sun, 23 Jul 2017 12:29:06 -0400
- In-reply-to: <14796dd4-4a0d-bdf6-0fd6-ca839ab3f709@gmail.com>
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On Sun, Jul 23, 2017 at 12:46:22AM -0400, Richard Pieri wrote: > > OK, so here you're saying that instead of a <10% charge/discharge > > efficiency, batteries actually have a 75%-80% charge/discharge efficiency? > > No. I'm saying that chemical batteries have *at best* a charge > efficiency of around 75-80% in the real world. OK, so you're saying that instead of single-digit percentages, there are real-world battery installations which get 75%-80% charge/discharge efficiency; meaning that if using them we'd only need to make 20%-25% more solar power, not 1000% more, to compensate for the loss in batteries. FWIW, here are some references which show measurements at 80%-90%, so I still think we'd only really need to generate 10%-20% more solar power instead of 20%-25%... but at these small numbers, these smaller differences don't at all affect whether solar+batteries is technically feasible. here's a report on an actual power grid battery system they built and deployed for a wind farm, reporting a measured 84%-86% charge/discharge efficiency: http://www.sandia.gov/ess/docs/pr_conferences/2014/Friday/Session10/04_Vishwanathan_V_Powin_Dispatchable_Battery.pdf for a wider range of design parameters (spanning 80%-90% efficiency) see fig.5: http://umanitoba.ca/outreach/conferences/phev2007/PHEV2007/proceedings/PluginHwy_PHEV2007_PaperReviewed_Valoen.pdf > > Agreed! And Utah, and Arizona, and New Mexico, and large parts of > > Colorado, Wyoming, Idaho, Oregon, and Washington by your map. And don't > > forget Great Plains states like Texas, Montana, North Dakota, South > > Dakota... hey, I think we're over 0.15%! > > There are three problems that I would consider breakers for these regions: > > First, you just described the heart of Tornado Alley. But somehow, 99.99% of people and corn and cows (not counting that unfortunate animal in the movie Twister) have managed to survive there. I'm betting solar panels will have a similar tornado survival rate, unless we decide to install them only at trailer parks. > Second, you can't charge Li-ion batteries when they are below freezing > (0C) which makes much of these areas useless for Musk's storage systems > for significant portions of the year. > > And third, high temperatures (above about 25C) reduces efficiency, and > it causes batteries to wear out faster than their published ratings > which means you'll be replacing them that much more frequently if you > set up your stations in the non-freezing areas. One standard solution to weather exposure would be to house them below the frost line, which is only 2'-3' deep in Kansas: https://www.ngs.noaa.gov/PUBS_LIB/GeodeticBMs/#figure13 You'll get a moderate temperature all year round. Luckily, the 10,000 km^2 solar+battery farm will still meet the entire US's energy needs even if you replace the batteries more frequently. > > Right - as in my prior email, when you do the math it comes out to a factor > > of pi (and 24/pi is 7.64 hours, within the range you give). > > No. It's significantly more than that because a geostationary station is > always at "noon" when it's exposed to the sun while a ground station's > noon is only a fraction of it's exposure period. Again, if you do the math, it's exactly pi. The equator is a circle; the sunlight incident on it is its shadow at this point in space, which is a line that is the diameter of Earth - on that line every point is always at "noon", and it would collect all the light the equator sees. Will ascii art help? --> ___ --> / | \ sunlight --> | | | --> \ | / --> --- The line has length Earth diameter D, the equator has length pi*D, and they'd both collect exactly the same sunlight. That D's worth of "always noon" sunlight is spread across the equator's circle, and averaging over a day every point on the equator sees the same amount, namely (D) / (pi*D) = 1/pi of the "always noon" solar influx. The factor you're looking for is exactly pi. > > FWIW, on that last non-technical bit, I and I wager many others on this > > mailing list see very many places in all the named locales which have good > > potential for solar. And that's one of the great things about solar power: > > Maybe good on small scales like homes and offices. Not so good for large > scale like replacing global dependence on fossil fuels. Actually, awesome for that. This thread has shown that a total of 10,000 km^2 of solar panels + batteries will provide all of the US's electrical needs using current technology, and that's true whether those 10,000 km^2 are in one place or spread over 10,000 places or in 10 million places. Arguably, the closer you put a panel to where the electricity is used, the more efficient your power distribution (a real advantage over nuclear plants, dams, coal-fired plants, etc.). In practice I expect a combination of some large sites and lots of tiny sites with a whole spectrum (no pun intended ;) in between, but as long as all the pieces add up to 10,000 km^2, for electricity generation you've completely replaced fossil fuels with solar+battery. --grg
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- [Discuss] Eclipses Re: Great talks last night, however...
- From: richard.pieri at gmail.com (Richard Pieri)
- [Discuss] Eclipses Re: Great talks last night, however...
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- [Discuss] Eclipses Re: Great talks last night, however...
- From: bill.n1vux at gmail.com (Bill Ricker)
- [Discuss] Eclipses Re: Great talks last night, however...
- From: richard.pieri at gmail.com (Richard Pieri)
- [Discuss] Eclipses Re: Great talks last night, however...
- From: bogstad at pobox.com (Bill Bogstad)
- [Discuss] Eclipses Re: Great talks last night, however...
- From: richard.pieri at gmail.com (Richard Pieri)
- [Discuss] Eclipses Re: Great talks last night, however...
- From: rlk at alum.mit.edu (Robert Krawitz)
- [Discuss] Eclipses Re: Great talks last night, however...
- From: richard.pieri at gmail.com (Richard Pieri)
- [Discuss] Eclipses Re: Great talks last night, however...
- From: richard.pieri at gmail.com (Richard Pieri)
- [Discuss] Eclipses Re: Great talks last night, however...
- From: grg-webvisible+blu at ai.mit.edu (grg-webvisible+blu at ai.mit.edu)
- [Discuss] Eclipses Re: Great talks last night, however...
- From: richard.pieri at gmail.com (Richard Pieri)
- [Discuss] Eclipses Re: Great talks last night, however...
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