On Sat, 22 Jul 2017 20:08:24 -0400, Richard Pieri wrote: > On 7/22/2017 12:22 PM, Robert Krawitz wrote: >> 10x? Battery charging isn't that inefficient -- 85% for lead-acid >> batteries, for example >> (http://www.solar-facts.com/batteries/battery-charging.php). > > "Overall, an efficiency level of 85% is often *assumed*." > > Emphasis mine. The rest of that paragraph goes on to explain some of the > reasons why you can and will get less than this. Also, these are lead > acid batteries which have longer lifespans than the Li-ion batteries > Musk is selling, and they will hold to their higher efficiencies for longer.
But it's considerably more than 10% in practice, right? >> That's the least of the problems. You have to keep it in orbit, the >> beam has to keep station (that kind of concentrated beam had better >> not leak), and a geosync orbit is still eclipsed part of the time. > > At geostationary altitude a station is eclipsed from the sun for only 70 > minutes per day, and this is only when the sun is near the equatorial > plane. In practice, a geostationary PV station would have ~99.3% > exposure over the course of a year vs. a ground station which has at > best ~33% exposure, and that ~99.3% exposure is always "noon" vs. the > ground station's noon being a fraction of its exposure time. You still need storage for those blackouts (albeit less), right? >> Care to discuss what you see as the problems and how to go about >> addressing them? > > https://dothemath.ucsd.edu/2012/03/space-based-solar-power/ > covers them pretty well, and I do agree with the conclusion that SBSP > isn't worth it in the short term. Putting that much mass into orbit is > too expensive right now. The author is quite clear that he simply doesn't see this as being plausible any time soon. And no doubt batteries will improve along the way. -- Robert Krawitz <[email protected]> *** MIT Engineers A Proud Tradition http://mitathletics.com *** Member of the League for Programming Freedom -- http://ProgFree.org Project lead for Gutenprint -- http://gimp-print.sourceforge.net "Linux doesn't dictate how I work, I dictate how Linux works." --Eric Crampton _______________________________________________ Discuss mailing list [email protected] http://lists.blu.org/mailman/listinfo/discuss
