Revision as of 18:56, 17 February 2019

Parabolic Tube

But this requires replacement of insides with a u- copper tube, which is a valiant effort. Tbis is because evacuated tubes have a closed heat exchanger mechanism - a closed copper tube with heat exchanger bulb.
Unless one can find low cost u-tube heat exchangers, the evacuated system appears to be too complicated compared to plain black tubes.
Does not appear highly relevant to saturated water storage.

$25 per 6 foot evacuated Tube, no inner tube - water directly in glass? - [1] - affordable.

Max T that a metal can get when in full sun in 90C - see nice explanation at [2] combined with Stefan Boltzmann constant - [3]
So we see that the max temp in K varies as the 4th root of power density hitting the object. For example, to double the temp in K, need 16x solar concentration.
90C = 363K. Double to 726K - max 450C.
At this point, conduction and convection play a good role.

Paper on Medium Temperature Concentrators - overview for tech up to 250C. We need 200C for saturated water. [4]

@@ Line 10: / Line 10: @@
 *Max T that a metal can get when in full sun in 90C - see nice explanation at [https://physics.stackexchange.com/questions/186910/how-hot-can-metal-get-in-sunlight] combined with Stefan Boltzmann constant - [https://en.m.wikipedia.org/wiki/Stefan–Boltzmann_constant]
 *So we see that the max temp in K varies as the 4th root of power density hitting the object. For example, to double the temp in K, need 16x solar concentration.
-*90C =
+*90C = 363K. Double to 726K - max 450C.
+*At this point, conduction and convection play a good role.
+*
 =Links=
 *Paper on Medium Temperature Concentrators - overview for tech up to 250C. We need 200C for saturated water. [https://academic.oup.com/ijlct/article/9/3/214/808795#14051557]