Roof/Attic Ventilation under Solar Panels

[cebury]

I'm re-roofing today and I've been working around ventilation issues for each attic, trying to maximize the space for solar panels on the South & West facing sections. I'm using Ridge vents + dormer-style vents low.

Question: Would putting low-profile vents (like O'Hagen, that are 1-2" tall) UNDER the panel rack cause any problems? Basically:
1) Do panels & microinverters give off any significant heat? And is air temperature under panel racking > air temp in exposed roofing in direct light?
2) Would having such a vent, so close to the bottom of a panel on a 3" rack, cause any panel issues?

I assume everything would be fine, but would like other thoughts.

Thanks for your input,

[Ian S]

I'm re-roofing today and I've been working around ventilation issues for each attic, trying to maximize the space for solar panels on the South & West facing sections. I'm using Ridge vents + dormer-style vents low.

Question: Would putting low-profile vents (like O'Hagen, that are 1-2" tall) UNDER the panel rack cause any problems? Basically:
1) Do panels & microinverters give off any significant heat? And is air temperature under panel racking > air temp in exposed roofing in direct light?
2) Would having such a vent, so close to the bottom of a panel on a 3" rack, cause any panel issues?

I assume everything would be fine, but would like other thoughts.

Thanks for your input,

The panels do heat up significantly in sunlight and some of that heat will be re radiated off the back of the panel towards the roof. But you also have energy absorbed and converted to electricity in the panel and a large fraction of the re radiated heat will be away from the roof surface. Then you have the air gap between the roof and the panel that will limit the efficiency of the transfer of the heat from the backside of the panel to the roof surface. So I seriously doubt the temperature rise on the roof surface behind the panel would be any greater than if that surface was in full direct sun. I suppose you could try an experiment with one of those cheap IR thermometers available from Harbor Freight Tools and a black sheet of metal or plastic above the surface of the roof and compare temperatures measured.

[russ]

T I suppose you could try an experiment with one of those cheap IR thermometers available from Harbor Freight Tools and a black sheet of metal or plastic above the surface of the roof and compare temperatures measured.

More bad data has been generated using IR thermometers than possibly any other method in history - outside of making a WAG. The emissivity of most materials is different and varies with temperature - unless one is accustomed to the things and routinely uses one IR thermometers are close to useless.

If you try this a contact thermometer is far more accurate.

When I did this with my Schucco solar thermal panels I was surprised to find that the coolest place on the panel and roof was the face of the panel.

[Ian S]

More bad data has been generated using IR thermometers than possibly any other method in history - outside of making a WAG. The emissivity of most materials is different and varies with temperature - unless one is accustomed to the things and routinely uses one IR thermometers are close to useless.

True but in this case, you'd be measuring the same material (roof shingle) so that parameter would be held constant. But a suitable contact thermometer would work well too. Frankly. I don't see how the temperature of the roof under a panel could be significantly higher than that same roof exposed to the direct sun.