On Mon, Aug 24, 2009 at 8:25 AM, Darryl McMahon <[EMAIL PROTECTED]>wrote:
> > Evacuated vacuum tube systems are gaining in favour for solar water > heating locally in recent years, though I'm still not a fan. They just > seem overly complex and expensive for their gains over low-tech approaches. > > The advantage of evacuated tubes is that they are more immune to outside temperature. Flat plate collectors, to varying degrees, lose efficiency as the outside temperature goes down. Evacuated tubes have a much lower degradation as the outdoor temp goes down. In -20F outdoor conditions, they can still produce 200+ water. Or, in hazy overcast conditions, they can still produce hot water when a flat plate collector might not have enough incoming radiation to overcome the losses. However.... much of the time, it's sunny enough that it doesn't matter -- like an a typical 50F day with good sun... why bother with the additional expense. The other drawback is that they are so well insulated that they do not melt snow off themselves. So, if used in a snowy climate, they need to be mounted where snow cannot get on them (vertical south facing wall), or else they get icebound and don't work. Z -------------- next part -------------- An HTML attachment was scrubbed... URL: /pipermail/attachments/20090824/f22081cc/attachment.html _______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/sustainablelorgbiofuel Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (70,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/
