TheSamba.com :: View topic

Wed Jan 22, 2014 2:47 pm

So it seems that in the luggage solar panel discussion we have come to the conclusion that we are unable to, currently, buy a 80W or greater solar panel that will fit in the luggage rack..Next choice, mounted to the roof.

Those with the panels on main part of the roof. Has anyone found a panel that isn't too thick. By that I mean the thickness of the frame. When I pull into my garage, my closed roof vent just clears the the garage door. So I would be looking for something probably not much thicker than the closed roof vent (I'll go out and measure this soon).

I know we've talked about flexible and semiflexible which would be great but I understand that they don't have the "capture power", so to speak of a rigid solar panel. Please educate me if I am wrong

Cheers
Al

Wed Jan 22, 2014 3:11 pm

yycwesty wrote:

I know we've talked about flexible and semiflexible which would be great but I understand that they don't have the "capture power", so to speak of a rigid solar panel. Please educate me if I am wrong

Cheers
Al
I was eyeballing these panels. At 112" long I'm not sure the top is long enough for the whole thing. But they're 68W each and with 2 up top it would be decent power. They have pretty good reviews from what i could tell. http://www.amazon.com/Uni-Solar-PVL-68-PowerBond-D...panel+roll

Wed Jan 22, 2014 4:06 pm

The thicknesss on a solar panel is just the frame. You could always remove the aluminum frame work on them and use some sort of thinner channel frame work. However it's good to leave breathing space under the panel, which is usually why the frames are thicker than they need to be.

Wed Jan 22, 2014 4:35 pm

here is a thin panel
http://www.ebay.com/bhp/semi-flexible-solar-panel

Wed Jan 22, 2014 5:20 pm

I have looked at those panels but I understand they are not as efficient as a solid panel..Perhaps I'm wrong
Al

Wed Jan 22, 2014 6:46 pm

I have 3 solar panels that are encased to a stainless plate.
They are for marine use you can even walk on them.
I have 2 mid ships on the van for the fridge/propex.
1 up front on a pelican case in the cargo space for the
2 house bats.
Works killer.
I got them from Arizona Solar. Good web site.

Wed Jan 22, 2014 7:03 pm

2bollox

Are the thin flexible or rigid..How many watts..What height do they sit when mounted. Any pics..So many questions, so little time LOL

Cheers
Al

Wed Jan 22, 2014 9:32 pm

Thin film panels, unless you just absolutely cannot use anything else, are a waste of time. Their efficiency is not very good (remember even good panels are only about 18% efficient). Worse, the most power is generated by having the panel perpendicular to the sun's rays. Anything less than that means less energy per unit area. Flexible panels, by definition, are not going to meet that requirement unless mounted to a solid flat surface. Oh, gee... they make panels like that, don't they...

Folks need to look into the "off the grid" web sites that describe the basics of photovoltaic panels. Spending time there will save pouring a lot of money down the rat hole, reinventing existing practice and skills.

Wed Jan 22, 2014 10:42 pm

RBEmerson wrote: Thin film panels, unless you just absolutely cannot use anything else, are a waste of time. Their efficiency is not very good (remember even good panels are only about 18% efficient). Worse, the most power is generated by having the panel perpendicular to the sun's rays. Anything less than that means less energy per unit area. Flexible panels, by definition, are not going to meet that requirement unless mounted to a solid flat surface. Oh, gee... they make panels like that, don't they...

The new efficiency level for thin film flexible mount cells is 20.4%.

(http://www.sciencedaily.com/releases/2013/01/130118064733.htm)

While it's true that highest yield from a solar panel is when it's oriented perpendicular to the suns rays, I've noticed most campers don't go to the trouble of adjustable mounts. A little more wattage will offset the curved-as-opposed-to-flat mounting deficit quite easily.

Here are some possibilities, though I'm sure some of the efficiencies claimed are optimistic...

http://www.ebay.com/bhp/semi-flexible-solar-panel

Sun Mar 16, 2014 9:45 pm

I'd be happy to use adhesive to hold a 100W panel to the Westy roof, I'm just unsure if 19.9% efficiency is worth the money and effort. :?
I'm truly a "weekender".
http://gpelectric.com/products/solar-flex-kits-modules

Sun Mar 16, 2014 11:25 pm

Solar panels are generally not direct surface mounted because of the heat that they generate when generating power from sunlight. The space between the mounting surface and the panel is necessary to provide for a convection space for air to cool the intersitual space.

Sun Mar 16, 2014 11:31 pm

Solar panels are generally not direct surface mounted because of the heat that they generate when generating power from sunlight. The space between the mounting surface and the panel is necessary to provide for a convection space for air to cool the intersitual space.

So if this statement is true, why do most semi flexible panels state that you can mount them directly to the roof of your boat RV etc?

Mon Mar 17, 2014 10:00 am

bosruten wrote: I'd be happy to use adhesive to hold a 100W panel to the Westy roof, I'm just unsure if 19.9% efficiency is worth the money and effort. :?
I'm truly a "weekender".
http://gpelectric.com/products/solar-flex-kits-modules

For solar panels, I think 19.9% efficiency is pretty darn good? right?
I think the "traditional" panels are in the 15-17% efficiency range, if I am not mistaken?

I've searched for those flexible panels, and can not find any that are reasonably priced? They seem to be 2-3x the cost of a normal rigid panel of a similar wattage.

Mon Mar 17, 2014 12:15 pm

Agreed..Hopefully the prices will come down in the near future

Mon Mar 17, 2014 12:23 pm

In case you haven't seen it, see my Renogy 100w panel install:

http://www.thesamba.com/vw/forum/viewtopic.php?t=582511&highlight=

This is your typical thicker aluminum frame panel, but I used special cabinet hinges to flush mount it and make it removable. According to your described situation, this may still be too high of a clearance, but I thought I would share. I love this panel setup--100w is just right, and I can park in shade, dismount the panel, add an extension cord to the solar panel, and keep the solar in the sun.

kourt

Mon Mar 17, 2014 1:18 pm

Kourt

I love the install of your panel and would dive into that in a second..Can you tell me if the panel sits any higher than the vent when closed..That is more or less what I'm using as a guideline. The other question would be, could you take those panels and mount them on a thinner aluminium frame the reducing thus overall thickness.

Al

Fri Mar 21, 2014 8:48 pm

My approach was a little different. I didn't want to permanently mount the panels since I am often changing things around trying to find a better solution to powering both a TruckFridge 45 (icebox), Dometic CF-50 (freezer), and the usual assortment of lights, stereo and water pumps. I went with six 30 watt Powerfilm foldable panels which I can fit (folded up) on one half of the bottom shelf under the sink. In addition, this allows me to run the panels on top of the van bungie corded to the racks (there's a definite heat shield effect). I am using aluminum (Kelty) tent poles as spreaders to keep things positioned. In a high wind, I would definitely have to take them down. This approach also allows me to reposition them into the sun while the van is parked in the shade. The angle of the pop-top also helps face the panels more towards the sun as well. Power from the panels is then routed to a Morningstar Sunsaver MPPT which in turned charges two 105 AhHr deep cycle batteries under the back seat. One battery is dedicated to the TruckFridge and the other to the Dometic. I’m still conducting tests and measuring the results, but generally with full sun, I seem to be running a slight energy surplus. However, on my last trip to Sequoia and staying at a partially shady campsite, my batteries were clearly running down and I was on an energy diet until we left the park.

P.S. Sorry about having all the spots on the rear hatch - coolant leak stains are tough to remove.

http://www.powerfilmsolar.com/
http://www.morningstarcorp.com/products/sunsaver-mppt/

Sat Mar 22, 2014 6:56 am

What's the combined wattage for the panels?

Agreed that MPPT is the only way to go. Morningstar is one of many MPPT providers - not knocking them, just commenting there are a number of providers. I do not recommend Blue Sky Energy - when the gear works, it's pretty good. When it doesn't, their warranty response is... more than a little lacking (BTDT).

How solar panels react to shading varies. The response is dependent on how the cells are wired internally. It's possible to wire a panel to tolerate some shade, but that adds complexity in the wiring, diodes, etc. which means higher cost. (Inside the panel, cells are wired in series for increased voltage, and then wired in parallel for increased current. If one or more cells, in any one series run of cells, is covered, all output stops because, in effect, there's now an open circuit in the series row of cells. Putting cells in parallel gets around that problem, but limits voltage out. It's just a matter of compromises - simple is cheaper but doesn't work as well, complex works better but is expensive.)

Finally, someone mentioned solar panel heating. I suppose there's some minor heating from inefficiencies in the wiring, etc. The real problem, though, is heating the panel. That is, cooler panels are more efficient than warmer panels. But, for panels to work well, they need to be exposed to direct sunlight (well duh!), which heats the panel. At best, allowing air to circulate under the panel, to cool it to some degree, is about the most to be hoped for.

Mon Mar 24, 2014 6:05 pm

I've been doing lots of research into this, and finally settled on this:
http://tinyurl.com/m982aho
The Renogy 100W Monocrystalline Bendable Solar Panel.
I didn't want to punch holes in the top, and felt funny about mounting what is essentially a wing on that thin fiberglass (I had visions of it ripping off during a sprint to 65 mph :shock: ).
I just ordered it, but Renogy called to tell me they were backordered for four weeks. :/ I'll post full install report when they arrive. Until then I'll have to make due with this:

;-)

Mon Mar 24, 2014 7:28 pm

Greetings,

As a followup, I've included some photos of my Renogy 100w roof mount panel.

The first photo is slightly above the plane of the panel, showing the rear perspective of the panel:

The second photo is inline with the top plane of the panel, which I hope expresses the very slight clearance above the skylight:

It's at most 1/2" above the skylight.

This Renogy panel is sold as a complete unit, so the solar module is not really removable from the frame.

I hope these photos are helpful.

kourt