Another Solar question

[ianc]

Does anyone have practical experience of using panels like these: http://www.ebay.co.uk/itm/100W-40W-...831575?pt=UK_Gadgets&var=&hash=item3a843f1bd7
The semi flexible ones.

When I've read elsewhere here about flexible panels they have generally been "Amorphous" but these seem to be either Mono or Poly.

The application is the roof of the camper (There's a surprise!). I have a reasonable amount of room but the van is pretty high (3.5m) and so these panels offer a way of limiting the weight high up. They also look as if they'd be more robust than the standard frame type ones.

Thanks

Ian

 

[Borrego60]

I have never used them, my are the Powerfilm that fold.

 

[geordie4x4]

Hi Ian,
Yes I have a 100w thin panel that is attached to the top of a hard shell roof top tent. My panel is semi flexible aluminium backing and 2.5mm thick, I have it attached to the fiberglass top with silicone sealer and small stainless screws. From the website you posted, it looks to be the same brand as you are looking at (but I do see that ebay sellers often "borrow" photographs ).

I spend a lot of time off road and travelling in quite harsh terrain, it has proven to be very robust, except that you can scratch the plastic film with tree branches in the bush. Real light weight at only about 2.5 kg compared to the 14kg pannels that I previously had on my roof rack for the same wattage.

I will post a few photos when I am home again.

I have just put a deposit on a new James Baroud hard shell roof top camper so I am now looking to get some new thinner panels with EVA plastic backing for my new rooftop tent project. The main difference that I want is to not have a junction box on top of the panel, I want the cable out the back so it is completely flat. Unfortunately it seems hard to find pannels that have no junction box on top and some of them are extremely expensive for top end offshore yachating applications.

 

[geordie4x4]

Here is a photo of the panel on the roof top camper.

The monocrystalline panels also seem to have a much higher output per unit area than the poly or amorphus panels so that is something to look at the size and shape of panel to fit the roof space you have.

Another new thing is the MPPT (Maximum Power Point Tracking) regulators which make better use of the voltage available from the panel to achieve more power output from the same panel.

 

[Joe917]

Ian, I think you are better off with a typical aluminium frame panel. You will have more choice of panel size and mounting is very easy. MPPT is advantageous but not as much so for smaller panels. The weight is not bad, I doubt you would notice a difference.

 

[geordie4x4]

Hi Joe917,
not intending to knock your opinion, but obviously I have already made my choice to go with the thin, light weight, high efficiency panels so I am a little bias on that side of it.

But responding to the comment about having more choice of panel size with a standard framed panel, I can't agree with that as things have changed a lot in what is available and you will find a far greater variety of size options now in thin panels. I am now looking at longer narrow panels as opposed to more square rectangular ones. There is now a good variety available.

 

[ianc]

Thanks for the feedback guys

 

[geordie4x4]

Thanks for the feedback guys

Your welcome ianc.

Another point that may come up regarding mounting to a flat surface is heat.
The panels do reduce in efficiency when they get hot. So you can see in my photo, I have mounted it up over the ribbing in the camper roof to allow a bit of airflow. But this really only makes 5 to 10% difference in very hot conditions like here in Australia with days over 35 to 45C.

As the thin panel will hold less heat anyway, mounting with adhesive to a flat surface is only a minimal difference and not noticeable in a cool climate anyway.

 

[Joe917]

If you have a roof that is flat such as a Vario build I have seen an aluminum frame panel would require minimal roof penetrations to attach, would allow air space to cool the panel and would provide tropical roof effect to help reduce cabin temperatures. Maybe there are reasons to go with more expensive less efficient flexible panels but in your build I can't see them.
Cheers.

 

[LeishaShannon]

Reliability of the thin panels has been an issue. The cells used in them are not flexible as they're the same ones used in rigid mono panels, the flex comes from the gaps between the panels so the electrical connections between the panels are under stress.
The panels are not as efficient as what you can buy in the rigid format either. Their 100W model = .8 m2 , the 300W LG panels we're using are 1.6m2 , so you're talking about a 50% energy gain for the same roof area with rigids.
As mentioned above, temperature has an effect on panel output of around .4 % per degree above 25c. If the panels are mounted flat on your roof they're not going to get good ventilation under them which will mean higher cell temps. That heat is also going to pass through into your camper. We've mounted ours 100mm off the roof of the camper which provides a "second roof" that keeps the sun off the camper and allows good ventilation under the panels.
They are marginally lighter, but not as much as you'd think. 100W = 3.5Kg according to the ebay ad or 10.5Kg for 300W. Our 300W panels are 16Kg.

If weight was more of a concern than roof area i'd consider them, but for us roof area vs power was the primary concern so we went rigid.

 

[geordie4x4]

Yes I can see your point if you have a big vehicle with a big flat roof area and weight is not an issue, but heat is, then you quite right the frame panels sitting up off the roof are a better option.

But as far as efficiency per unit area, some of the semi-flexible panels (including the ones I have and the new ones I am looking at for my new top) now use the E20 mono cells which are the most efficient per unit area of anything available so that is really not only confined to framed panels anymore. Ones I have been looking at are 100W and 0.56m2 so they are as efficient as the larger LG panels and might even use the same cells. The older amorphus cell flexible panels were definitely less efficient but not the new ones available now.

Flex is an issue only if the panels are going to flex all the time. But for mounting on a hard roof, I would have thought the only flex is when they are curved gently to follow the shape i.e. a curved roof and then stuck down.

Although a plastic covering is tough, it can scratch or dull in the sun, glass covering is more certain of lasting longer term but I figure that I will only be keeping my camper ten years or so before I upgrade or change to something else newer and better anyway.

Weight depends a lot on the different panels also the frame and mounting hardware. 16 kg for 300W is prety good if it includes the mountings etc, I took my old BP solar (twin 50W) 100w panels off the roofrack and they were 12.5 kg without the mountings. The new panels I am looking at are EVA plastic backed, 1.4 kg each for 100W panels. I plan to glue them on so there will be no holes except for the one for the cable.

So yes the choice depends a lot on the situation and the use they are going to get.

Regarding the original post, he was asking about weight savings so yes, I think there is a definite advantage to be gained. For my purpose, clearly I am happy with the flexible panels as they conform neatly to the aerodynamic shape roof top tent I want, but I'm not so concerned about heat transfer.

On a camper with a big or flat roof it might be a different matter.

 

[Thespoon]

Hi all….I just installed 8 flexible 100w mono crystalline panels on the roof (composite Panel) of my new camper. The reason why I used them are mainly weight and size. I also glued them first onto a 10mm Corflute panel and then to the roof. This way I have some airflow underneath and reduce the heath transfer to the roof panel. (Thats the idea any way)
I haven't been able to test it yet as the camper is still under construction.
I will keep you informed.

Regards

Adrian

 

[ianc]

I like the air gap idea. Will the Coreflute last? and does it mean you can no longer walk on the panels I wonder?

 

[geordie4x4]

800W Wow that is a decent power supply.

The coreflute is a good idea.

Ianc, I see that you can also get polycarbonate skylite sheeting that is much the same construction as coreflute but super strong.

 

[Thespoon]

As a said…..the camper is still under construction, so nothing has been tested yet but the panels can still be walked on, the Corflute has a maximum temperature tolerance of 80deg C. How long they are going to last is a good question as this set up is all a bit new. I bought the panels of eBay, although they are advertised as 100W panels they are more like 80W, so 640W all up is a more realistic figure.