>>48347
Yes, I'm kinda glad. Now I can casually use 5 liters of free hot water on many days during the summer. Have to make long term experiment how feasible this is as the year goes on.
Also thinking how much a difference could it make in electricity/gas use.

>additionally glass screen
Yes, they also fiddled with such boxes on that site (I can't find photos). Also with these type of cookers they suggest using a baking bag.
I did a ddg search and turns out bunch of companies do this commercially, selling solar cookers of all types. From parabolas, to boxes. I did not check prices.
>heat loss from convection.
Yes, that is a problem.

Now I'm also thinking about making a stand for the keg, and placing reflecting panels around in a half circle, or couple of rows of circles. It would make the process faster I think. Problem is they have to be set precisely to target the barrel, and with the Sun moving on lower and lower course, they have to be corrected after some days passed.