Re: How do I heat water with a frsnel lens most effectively?

Dear Jacob

I can only give you some general physical advice:

The basic idea of the lense is to concentrate the sun's energy in a small 
volume. A lense focuses parallel sun beams in a focus point. As long as the 
focus point is within the water volume, the geometry doesn't matter for the 
"input" side. You can use the shadow of a vertical rod to find the 
right position towards the sun. Stacking dosen't help. The inner of the 
water vessel should be black to reduce back reflections. Now comes the 
important point: The vessel has to be very well insulated to avoid heat 
losses. Best would be a 'thermos'(but how to build the top ?). A normal 
glass flask could be placed in a box filled with e.g. wool.
For similar project you have to surf in the internet yourself. Have fun.