{"id":622,"date":"2007-05-22T18:12:08","date_gmt":"2007-05-22T23:12:08","guid":{"rendered":"http:\/\/www.spaceelevatorblog.com\/?p=622"},"modified":"2007-05-22T18:24:43","modified_gmt":"2007-05-22T23:24:43","slug":"the-space-elevator-and-solar-power-satellites-sps","status":"publish","type":"post","link":"https:\/\/www.spaceelevatorblog.com\/?p=622","title":{"rendered":"The Space Elevator and Solar Power Satellites (SPS)"},"content":{"rendered":"<p><a href=\"\/media\/SPS.abo.fi.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" width=\"200\" src=\"\/media\/tn_SPS.abo.fi.jpg\"  height=\"150\" style=\"width: 200px; height: 150px\" \/><\/a>For me, the &#8220;killer app&#8221; of Space Elevator Development has always been the economically viable deployment of Solar Power Satellites.\u00a0 It promises unlimited, clean energy from the sun, captured by SPS and beamed to earth-based rectennas and from there, channeled into the earth&#8217;s power grids.\u00a0 The problem has always been, as I understood it, getting these SPS into orbit cheaply enough so they could be economically viable, and this is still true.<\/p>\n<p>But there&#8217;s a BIG difference between making SPS a commercially viable enterprise and making SPS able to generate the lion\u2019s share of earth&#8217;s energy usage.\u00a0 In my naivet\u00e9, I had hoped they would be one in the same, that we could replace most or all of our polluting energy sources with SPS.\u00a0 Sadly, unless my calculations are way wrong, this turns out to be not the case.<\/p>\n<p>Here\u2019s the basic numbers (I\u2019ll explain where I got them later on in the posting):<\/p>\n<ul>\n<li>The performance numbers of SPS are projected to be on the order of 2kg\/kW (Henson \/ URSI \/ Wikipedia)<\/li>\n<li>A 200T ribbon (140T payload) can handle 125 trips per year (Edwards-Westling)<\/li>\n<li>This equals a lift capacity of 17,500T per year, per ribbon<\/li>\n<li>This equals ~8.75 GW per year, per ribbon<\/li>\n<li>Planet-wide energy usage is project to increase ~.5TW per year (EIA)<\/li>\n<li>This means it will take ~60 of these ribbons to handle just the INCREASE in planet-wide energy usage, not making a dent at all in currently generated power<\/li>\n<\/ul>\n<p>I hope my numbers are wrong because they mean that, unless SPS efficiency can be increased by at least an order of magnitude (or two), a SE-SPS solution may be commercially viable, but will not seriously decrease the release of CO2 and other pollutants into our atmosphere.<\/p>\n<p>Another interesting number I came up with is that a space-based solar power array sufficient to power the planet in the year 2030 would be approximately equal in area to the country of India and the rectennas would need to be approximately equal in area to the country of Italy.\u00a0 Well, I thought it was interesting\u2026<\/p>\n<p>I invite everyone to try and prove my numbers wrong \u2013 I\u2019ll be very happy if you can show that I\u2019ve overstated the problem somewhere\u2026<\/p>\n<p>Where did I get my numbers?<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignright\" width=\"90\" src=\"\/media\/KeithHenson.jpg\"  height=\"120\" style=\"width: 90px; height: 120px\" \/>I got the SPS performance number from a presentation by <a href=\"http:\/\/en.wikipedia.org\/wiki\/Keith_Henson\">Keith Henson<\/a>.\u00a0 This presentation (PowerPoint format <a href=\"\/media\/A-2000-tonne-per-day-Space-Elevator1.ppt\">here<\/a>, pdf format <a href=\"\/media\/a2000tonneperdayspaceelevator1.pdf\">here<\/a>) is quite interesting.\u00a0 He presents the 2kg\/kW number as an aside; his proposal is for a \u201cdirect drive\u201d Space Elevator (as opposed to the Edwards-Westling \u201claser-drive\u201d version).\u00a0 I went to a couple of other sources to try and verify his number.\u00a0 <a href=\"http:\/\/en.wikipedia.org\/wiki\/Solar_power_satellite\">Wikipedia<\/a> gives a range of .5kg \u2013 10kg per kW.\u00a0 A <a href=\"http:\/\/ursi.ca\/SPS-2006sept.pdf\">White paper<\/a> by the International Union of Radio Science (URSI) gives a number of 1kg\/kW for their proposal.\u00a0 So 2kg\/kW seemed reasonable to me.\u00a0 Incidentally, I had blogged about his \u201cdirect-drive\u201d proposal earlier, <a href=\"http:\/\/www.spaceelevatorblog.com\/?p=318\">here<\/a>.<\/p>\n<p>The 140T \/ 125 trips per year number comes directly from the Edwards-Westling book, <a href=\"http:\/\/www.amazon.com\/Space-Elevator-Earth-Space-Transportation\/dp\/0974651710\/ref=pd_bbs_sr_1\/002-0056284-6556039?ie=UTF8&amp;s=books&amp;qid=1179874838&amp;sr=8-1\">The Space Elevator<\/a>.<\/p>\n<p>The projected, yearly, planet-wide energy increase comes from the US Governments Energy Information Administration <a href=\"http:\/\/www.eia.doe.gov\/\">website<\/a>.\u00a0 This website contains all sort of fascinating information and I had a lot of fun poking around in it.<\/p>\n<p>This information, in part, led me to the conclusion that only the profit-motive is strong enough to drive the development of the Space Elevator, not the ability to solve our global energy and\/or pollution problems.\u00a0 I presented this at the recently completed SESI conference and blogged about it <a href=\"http:\/\/www.spaceelevatorblog.com\/?p=579\">here<\/a>.<\/p>\n<p>One final note; Keith Henson was recently interviewed by RUSirius.\u00a0 You can find the podcast <a href=\"http:\/\/www.rusiriusradio.com\/2007\/05\/01\/show-104-keith-hensons-space-elevator\/\">here<\/a>.\u00a0 It\u2019s a long podcast; they actually begin talking about at 10:03 into it.\u00a0 I strongly recommend you review Keith\u2019s proposal before you listen to this rather rambling\u00a0podcast \u2013 otherwise it may not make much sense to you.<\/p>\n<p><em>(The picture is from <\/em><a href=\"http:\/\/www.abo.fi\/~mlindroo\/OutSpace\/sts_pspa.jpg\"><em>www.abo.fi<\/em><\/a><em> &#8211; click on it for a larger version)<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>For me, the &#8220;killer app&#8221; of Space Elevator Development has always been the economically viable deployment of Solar Power Satellites.\u00a0 It promises unlimited, clean energy from the sun, captured by SPS and beamed to earth-based rectennas and from there, channeled into the earth&#8217;s power grids.\u00a0 The problem has always been, as I understood it, getting [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[],"class_list":["post-622","post","type-post","status-publish","format-standard","hentry","category-news-announcements"],"_links":{"self":[{"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=\/wp\/v2\/posts\/622","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=622"}],"version-history":[{"count":0,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=\/wp\/v2\/posts\/622\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=622"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=622"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.spaceelevatorblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=622"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}