very interesting flickr page on modifications

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Especially about the level of insulation!

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Hi  

Peter Brown wrote:Link comes up with 'page not found'

Try removing "page1" from the link:
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Interesting bit about the heat from the steel roof damaging the solar panel, although he doesn’t say how he proved the heat caused the failure.

Brod

Looks to be some good quality workmanship in that thread.

brodco wrote:
Interesting bit about the heat from the steel roof damaging the solar panel, although he doesn’t say how he proved the heat caused the failure.

Agreed - I've never really understood the logic behind these claims of heat damage. The argument seems to be that you need airflow underneath the panel to keep it cool - but when the van is not moving you won't get a lot of airflow, and many rigid panels are boxed in underneath anyway, so there isn't any at all.

I'd be prepared to bet that heat conduction from the panel to the steel roof underneath (which is after all cooler because it is in the shade of the panel) will not be significantly worse than to the surrounding air...

Hi  

-mojo- wrote:
Agreed - I've never really understood the logic behind these claims of heat damage.

I’ve heard of it but I’ve never seen any convincing evidence.

I had a quick look at the specs for a few solar panels and the maximum working / storage temperature seems to be around 85 to 90 degrees C. That should be continuous so I’d expect the temperature to be a bit higher than that before any permanent damage occurred.

I know steel vehicle roofs get hot in the sun but I’d be surprised if they got that hot (I’ve never measured it so perhaps I would be surprised).

I think (as with many equipment failures) there are a lot of assumptions being made. Like any electrical device there will be a certain percentage of early failures, and with any single failure you can’t be sure it’s not one of these.

Then there are other possibilities, for example if they’re glued down to the roof could flexing or vibration have an effect. Of course I’m not saying that this particular problem was caused by any of these (I haven't got any evidence either), just that it’s very easy to make assumptions without any actual evidence.

Brod

The other issue that occurred to me was the different rates of thermal expansion between steel and aluminium/plastic (quite a few flexible panels now seem to have ~plastic~ backing sheets, where previously they were all aluminium). For aluminium based ones, there is a significant difference with a steel roof, while there is very little with GRP (which set my mind at rest, as mine is bonded to the GRP roof).

However... I think it's far more likely that whatever glue you stick it on with will stretch, rather than it deforming the panel's backing sheet!

Are flexible panels better - other than cosmetically on some vans where they show from below??

If not, why do people choose them? (Genuine question.)

If they are better, it wouldn't be difficult to raise them an inch or so from the roof on several two inch wide strips of high density foam. It would be plenty strong enough, and would glue very securely to both van roof and solar panel with Sikaflex. It could be made to look very neat as well.

Or am I missing something obvious??