{"id":12856,"date":"2012-12-14T03:00:55","date_gmt":"2012-12-14T08:00:55","guid":{"rendered":"http:\/\/blogs.scienceforums.net\/swansont\/?p=12856"},"modified":"2012-12-14T03:00:55","modified_gmt":"2012-12-14T08:00:55","slug":"deja-vu-all-over-again","status":"publish","type":"post","link":"http:\/\/blogs.scienceforums.net\/swansont\/archives\/12856","title":{"rendered":"Deja Vu All Over Again?"},"content":{"rendered":"

I ran across a bit touting some new lamp, called GravityLight, which would give you “free” lighting \u2014 all you have to do is lift a weight. My first reaction was a flashback to the Gravia lamp, which I critiqued<\/a> in the first few months of this blog. Turns out the Gravia was a concept piece that had over-reached the light output and duration that was possible \u2014 it was only capable of putting out a few tens of milliWatts to generate the light, well short of what was promised.<\/p>\n

But the GravityLight appears to be the real deal, and it’s being funded on indiegogo<\/a> as a replacement for kerosene lamps in areas without a power grid. The difference? It promises less light over a shorter time, plus a slight increase in efficiency of LEDs, and that’s all the difference you need. Instead of 800 lumens of light, sent in all directions, you get a beam from the LEDs. If you drop the output from 4*pi steradians (i.e. all directions) to, say, 1\/8 of that, it’s the equivalent of just 100 lumens, and super-bright LEDs have a luminous efficacy of about 100 lumens per Watt, meaning you only need ~1 Watt output for such a light.<\/p>\n

The previous system could only supply ~17 milliWatts of power, but that was because the energy was promised over a 4-hour period. If you release the same energy over a shorter time, the power is greater. A 20kg mass raised a little over a meter is 200 Joules, so that’s a Watt for 200 seconds. If you lower the light output, via dimming or making a narrower beam, or you use a greater mass and\/or raise it higher, it will last longer.<\/p>\n","protected":false},"excerpt":{"rendered":"

I ran across a bit touting some new lamp, called GravityLight, which would give you “free” lighting \u2014 all you have to do is lift a weight. My first reaction was a flashback to the Gravia lamp, which I critiqued … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[39,53,63],"tags":[],"class_list":["post-12856","post","type-post","status-publish","format-standard","hentry","category-physics","category-tech","category-video"],"_links":{"self":[{"href":"http:\/\/blogs.scienceforums.net\/swansont\/wp-json\/wp\/v2\/posts\/12856","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/blogs.scienceforums.net\/swansont\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/blogs.scienceforums.net\/swansont\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/blogs.scienceforums.net\/swansont\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/blogs.scienceforums.net\/swansont\/wp-json\/wp\/v2\/comments?post=12856"}],"version-history":[{"count":0,"href":"http:\/\/blogs.scienceforums.net\/swansont\/wp-json\/wp\/v2\/posts\/12856\/revisions"}],"wp:attachment":[{"href":"http:\/\/blogs.scienceforums.net\/swansont\/wp-json\/wp\/v2\/media?parent=12856"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/blogs.scienceforums.net\/swansont\/wp-json\/wp\/v2\/categories?post=12856"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/blogs.scienceforums.net\/swansont\/wp-json\/wp\/v2\/tags?post=12856"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}