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stmbtwle

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Reply with quote  #11 
Disagree.

Normally, unglazed PV panels are mounted so there is airflow behind the panel. If this airflow is cut off by whatever means you've lost roughly 50% of your cooling. If this cooling isn't replaced, the panel WILL run hotter with a corresponding loss in output.

The hybrid panels listed, if I read it right, also have glazing above them to retain the heat. Without any water flow they're going to get just as hot as any other stagnated collector. That may be where the 105C they mention comes from.


Just took some temps with my IR thermometer:

The roof of my houseboat is currently 115F. The main PV panels (4" off the roof) are 127F, except for the upwind one which is 120F.

The small panel running my Aretha is 125F. The Aretha internal air temp is at 118 (it's water "cooled").

Ambient air temp is 95F.

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Willie, Tampa Bay

SolarInterested

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Reply with quote  #12 
Quote:
Originally Posted by stmbtwle
... Normally, unglazed PV panels are mounted so there is airflow behind the panel. If this airflow is cut off by whatever means you've lost roughly 50% of your cooling. If this cooling isn't replaced, the panel WILL run hotter with a corresponding loss in output.

Agree. I hadn't thought of the insulating effect of whatever is used to carry the water.

Quote:
... The hybrid panels listed, if I read it right, also have glazing above them to retain the heat. Without any water flow they're going to get just as hot as any other stagnated collector. That may be where the 105C they mention comes from.

I'm not seeing any glazing but there's not really any cross section of the panels shown.


Quote:
... Just took some temps with my IR thermometer: The roof of my houseboat is currently 115F. The main PV panels (4" off the roof) are 127F, except for the upwind one which is 120F. The small panel running my Aretha is 125F. The Aretha internal air temp is at 118 (it's water "cooled"). Ambient air temp is 95F.

Thanks for these.

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Both temperature rise and airflow are integral to comparing hot air collectors
stmbtwle

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Reply with quote  #13 
In the exploded diagram in the presentation PDF there's an extra layer of something above the cells. Doesn't say what it is though. Literature says they have panels optimized for thermal (which would benefit from extra glazing), and panels optimized for power (which would not). So it's possible they have both. It would sorta depend on your priority.

It brings up a couple ideas for DIY, though. Fan-cooling PV panels, or installing PV panels inside existing collectors to power fans or pumps.

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stmbtwle

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Reply with quote  #14 
I can see a problem with the original idea. Solar thermal is largely seasonal, where PV is year-round. In the summer, the panels will still need to be cooled, but what are you going to do with all that heat?
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SolarInterested

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Reply with quote  #15 
Domestic hot water.
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Both temperature rise and airflow are integral to comparing hot air collectors
stmbtwle

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Reply with quote  #16 
I'm not so sure. A PV array big enough to be useful is going to be a couple hundred sq ft, (mine is ~400). That's a LOT of DHW.

Then there's the temperature difference. At say 130F/55C for DHW, you're not going to accomplish much cooling of the PV. For that you're going to need a really big heat reservoir (swimming pool?) or some way to dump the heat.

In colder climates where you need space heating in the summer, it might make sense.

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Reply with quote  #17 
If you do have to dump the heat then there's the question if it's worthwhile after the cost of pumping the water etc.

Looking at winter operations at higher latitudes (freezing temperatures)wouldn't the PV panels be warmed above ambient temperatures decreasing their performance?


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Both temperature rise and airflow are integral to comparing hot air collectors
stmbtwle

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Reply with quote  #18 
I believe you're right. Freezing temperatures aren't something I'm really familiar with! [wink]
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colinmcc

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Reply with quote  #19 
Here are the spec sheets for 3 different Solimpek PV-T panels. Apparently they will be in the US market 'soon'.. Not sure if they will officially get to Canada though. I'd love to get my hands on one and play with it! ;-) Unfortunately all are 72 cell PV panels and don't look as though they would 'play nicely' with enphase micro inverters when cold.. I believe the company is originally from Turkey in Europe so I guess the frozen north doesn't figure into their calculations. A 60 cell unit with the ability to cool the PV by taking heat from the back panel in summer would get my creative juices going though.

 
Attached Files
pdf MinGen_PowerHybrid240.pdf (1.19 MB, 7 views)
pdf MinGen_PowerVolt200.pdf (379.98 KB, 1 views)
pdf PowerTherm180.pdf (369.93 KB, 4 views)

Nessie

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Reply with quote  #20 
I would like to revisit this topic as I am considering using a Back-Pass type collector behind to PV Panels to recover the heat generated by he PV Panels. There are some commercial options out there namely Solarwall http://solarwall.com/en/products/pvthermal.php These seem to using the perforated metal sheet as the PV mounting frame. My thoughts are to use the "standard" mesh behind the PV Panels and blow/suck air between the mesh and the rear insulation.
i have a heat pump which heats the swimming pool with a COP of 5 so Put in 2kW ( from the PV.s) and get i0kW heat into the pool. However, when you wish to use the heating the ambient air has dropped seriously affecting the COP of the pump. The hot air from the PV/T system will heat a small room where the heat pump is located to maintain a temperature of +25DegC. Has anyone done any work on hot air collectors with PV Panels ?
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