fresnel hot water

[joshua46v10]

has anyone thought about using a Fresnel lens (well a lot of them really) for the glazing on solar hot water panels, if so what were your thoughts. is it worth it.

[picmacmillan]

hi josh..there has been lots of posts on this topic..just click  the search the board button on the right and type in fresnel..there is a whack of posts that will pop up...hope this helps...good luck on your project ..pickster

[alcul8r]

Essentially, you are confusing heat with temperature.

Yes, Fesnel lenses are impressive when they set wood on fire by just passing over it.  No, they will not heat water better than the equivalent area of glass.

[The Crazy Noob]

That's true but the lenses allow you to use an area that is bigger than the actual collector and focus all the sunlight from the big area on the smaller collector and so the temperature of the water will be higher than without the lenses.

[Derek]

Here's what I've noticed when working with fresnel lenses:

First of all, they are somewhat of a fire hazard for using with anything, so be careful.  

Second, for it to really work, you will need to have your pipes at about half way between the lenses and the focal point.  This WILL make the area hotter obviously, but heres the thing.  If the lens is not Exactly aligned with the angled of the sun, the light may divert at an angle and miss what you are trying to heat, and then also completely shade the area you DO want to heat.

The only way I see a fresnel lense working there would be if you had a tracking system.  But I'd just stick with dual pane glass for the glazing.  I think a 2 by 2 foot area with glass with heat water more than just a single fresnel lense concentrated on a single point.