I believe they were called Hydrocaps and existed before the 2000 year article you found below. Yep, I just did a google search and found them http://www.solar-electric.com/hydrocaps.html There are quite a few other hits for "hydrocap" Dave From: "Ed Browne" > I did a search to find such devices. I didn't but came up with this > interesting article: > http://www.feer.com/articles/2000/0012_21/free/p056innov.html > Do you know where you saw the aftermarket devices? -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu