DIY Solar Concentrator: Difference between revisions
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=Parabolic | =Existing Open Source Designs= | ||
==OSE France's Design== | |||
*Whats the deal with OSE France's main page, http://www.opensourceecologie.org/ ? As of 2/17/19 ~19:20 it appears to be down | |||
*[https://www.instructables.com/id/Solar-OSE-Solar-concentrator-for-steam-generation/ The instructable for this] | |||
=Parabolic Tube= | |||
*http://www.ffwdm.com/solar/solar-index.htm - $110 USD per kW of heat? | *http://www.ffwdm.com/solar/solar-index.htm - $110 USD per kW of heat? | ||
:*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. | |||
==BOM== | ==BOM== | ||
*$25 per | *$25 per 6 foot evacuated Tube, no inner tube - water directly in glass? - [https://www.ebay.com/itm/solar-hot-water-heater-vacuum-tubes-30-tube-sets-free-pick-up-California-/273691205462] - affordable. | ||
https://www.ebay.com/itm/solar-hot-water-heater-vacuum-tubes-30-tube-sets-free-pick-up-California-/273691205462] | |||
=Calculations= | |||
*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 = 363K. Double to 726K - max 450C. | |||
*At this point, conduction and convection play a good role. | |||
*We need T to be 1.3x this | |||
*We need 482K, or 1.33x this K | |||
*1.33^4 = 3.1 - so only 3x concentration is needed if there were no other losses | |||
*Convective loss calculator - [https://www.engineersedge.com/heat_transfer/convection.htm] | |||
=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] | |||
Latest revision as of 19:51, 17 February 2019
Existing Open Source Designs
OSE France's Design
- Whats the deal with OSE France's main page, http://www.opensourceecologie.org/ ? As of 2/17/19 ~19:20 it appears to be down
- The instructable for this
Parabolic Tube
- http://www.ffwdm.com/solar/solar-index.htm - $110 USD per kW of heat?
- 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.
BOM
- $25 per 6 foot evacuated Tube, no inner tube - water directly in glass? - [1] - affordable.
Calculations
- 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.
- We need T to be 1.3x this
- We need 482K, or 1.33x this K
- 1.33^4 = 3.1 - so only 3x concentration is needed if there were no other losses
- Convective loss calculator - [4]
Links
- Paper on Medium Temperature Concentrators - overview for tech up to 250C. We need 200C for saturated water. [5]