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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 15:42:17 -0400
- In-reply-to: <5d6022a7-48e9-39e5-d3fa-ad6fe9825016@gmail.com>
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On Sun, Jul 23, 2017 at 01:20:05PM -0400, Richard Pieri wrote: > On 7/23/2017 12:29 PM, grg wrote: > > 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. > > When new under good conditions. Those numbers drop as conditions change > (extremes of heat and cold) and batteries wear out. > > > http://www.sandia.gov/ess/docs/pr_conferences/2014/Friday/Session10/04_Vishwanathan_V_Powin_Dispatchable_Battery.pdf > > And what are their numbers after 3, 4 or 5 years? Actually, the coulombic efficiency (CE, the battery's component of the overall charge/discharge efficiency) of lithium-ion batteries stays well above 99% for the full life of the battery, and even improves a bit as the battery ages. What drops as batteries age is instead the total capacity of the battery. Here's a source - behind a paywall, but the abstract is free and gives the relevant highlights: "A solid-state high-voltage (5 V) lithium battery is demonstrated to deliver a cycle life of 10,000 with 90% capacity retention. The solid electrolyte enables the use of high-voltage cathodes and Li anodes with minimum side reactions, leading to a high Coulombic efficiency of 99.98+%." http://onlinelibrary.wiley.com/doi/10.1002/aenm.201401408/abstract;jsessionid=CBDD74C72BBF0C1C53B7FBB1AC2DB1B5.f04t03 In the paper they show that a conventional li-ion battery holds 90% of the original charge after 3000 cycles (~9 years of daily cycling); and after those 9 years it actually has the highest coulombic efficiency (CE) of its life so far, well over 99%. (That's their baseline; the paper's goal is to present a battery improvement which has that performance to 10,000 cycles = 30 years instead of just 3,000 cycles = 9 years.) So actually, in contrast to your claim, the efficiency goes up a bit as they age and "wear out". Oh, I found a non-paywalled version of that paper (formatting's not nearly as nice as the paywalled version, but hey, it's free): https://www.osti.gov/pages/biblio/1185480-solid-electrolyte-key-high-voltage-lithium-batteries > > 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. > > That's because people and livestock can seek shelter in foul weather, > and plants grow and heal or at the least can be plowed under and the > land replanted. None of these describe thousands of square kilometers of > solar panels. Nor do those characteristics describe millions of homes and buildings. How many buildings do you think are destroyed in Kansas by tornados each year? Hundreds, for a survival rate of 99.99%. So no, it's not because cows are running away from approaching tornados or because they're sharing Farmer John's storm cellar, it's actually because 99.99% of the spots in Kansas don't have a tornado land on them. > > 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. > > Then you're insulating them which means they'll be that much hotter when > charging during warm months. See previous about heat being bad for > batteries. I guess you'll be surprised to learn that the ground is actually an effective heat sink; see the ground loops in heat pumps, which provide air conditioning by sinking the removed heat into the ground. Here's a source for you: https://energy.gov/energysaver/geothermal-heat-pumps Excerpting: "Geothermal heat pumps (GHPs)...have been in use since the late 1940s. They use the constant temperature of the earth as the exchange medium instead of the outside air temperature. Although many parts of the country experience seasonal temperature extremes -- from scorching heat in the summer to sub-zero cold in the winter -- a few feet below the earth's surface the ground remains at a relatively constant temperature...The GHP takes advantage of this by exchanging heat with the earth through a ground heat exchanger." > > 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? > > You're ignoring the atmosphere. Actually, I already addressed that in previous emails when discussing the "insolation" issue (instead of the "noon" issue here): 1370 W/m^2 in space, of which ~1000 W/m^2 makes it to the surface on average. In case it wasn't clear (no pun intended), it's the atmosphere which is responsible for that difference. --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...
- References:
- [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...
- From: grg-webvisible+blu at ai.mit.edu (grg)
- [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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