A friend, not on PICList, replied: > I think a three pin plug would be cheaper and the power density is likely to be rather a lot better for some years to come. To which, I said: 3 pin plugs are certainly cheaper. Power or energy density? Probably both. If you burn a 3 pin plug you'd notionally get about 400* Watt.hour compared to about 0.1 Wh for the battery energy storage. Battery (cell) is about 1/4 x the volume (back of head (no envelope) estimate) so about 1000 x the volumetric energy density. You can however only burn the plug once (usually) and as the battery has a cycle life far in excess of 1000 it would overall produce more energy out if you cycle it often enough. This, of course, requires more again energy in, so it, not unexpectedly, has the same core problem as Hydrogen as a fuel. * Medium chain hydrocarbons estimates at about 50 gram. Misc cellulose based (perhaps) plastics regarded as minimal. Metals deemed non combustible in this scenario. Hrdrocarbons estimated to produce about 8 kWh/kg total combustion so figure of 400 Wh may be adjusted down to account for thermal conversion efficiency if desired. Say 100 Wh delivered. If this was used to produce electricity with eg TEG at say 500k hot end (usually TEG material limited) and 320k cold end then Z_Carnot =3D (500-320)/500 =3D 36% so practical realisable maybe 10%-12% for a good TEG so delivered electrical ~~=3D 400 x 25% x 10% =3D 10 Wh. This is now only about 100 x the energy capacity of the battery. TEGs are not cheap so, depending on how many 3 pin plugs you burn in a given time, the battery MAY work out cheaper. Russell Sent from my no name PBTech assembled Win8.1_Abomination desktop. Hopefully. On 21 July 2014 15:11, RussellMc wrote: > Catalog/brochure for Taiyo Yuden hybrid battery / capacitors. > These have been available since about 2010 AFAI. > > > > http://www.yuden.co.jp/productdata/catalog/en/capacitor03_e.pdf > > > Useful capacity gain over 'conventional' double layer super caps. > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .