Low profile solar panel install

[Dendisch]

I know that aerodynamics is not one of the Sprinters strong points. Still it bothered my personal esthetic taste to put solar panels on top of it that stick straight up. So I used a little different method for installing my solar panels. I wanted a low profile, but still use traditional instead of flexible solar panels.

First I mounted 6” wide 1/8” thick flat aluminum brackets to the roof rails. Instead of spanning the whole roof the brackets extended only to the panels. At the end point they rest directly on the roof with spacers and a small piece of VHB adhesive tape. Three of the four panels were then mounted onto the flat aluminum using the common z brackets. For the angled front panel I shaved off some of the front panel frame to make it thinner. I added some narrow 1/8” aluminum flat and angle pieces to regain the stiffness. For the front right corner I couldn’t attach to the roof rail, because it was already occupied by the awning bracket. I mounted to the awing bracket instead using an angle bracket. The rounded leading edge was created from a 4” ABS pipe section cut. Most of the bolts are M6 stainless steel carriage bolts.

Is it worth it? Making all the custom brackets is for sure a lot more work than using commercially available direct mount brackets (e.g. from Hein). Cost is similar or a little higher. The lower front edge may help a little with fuel economy, but considering the size compared to other extra items such as awning, MaxFan, and window flares the effect is probably barely measurable.

So in summary I really like it but I wouldn’t recommend it to anybody unless you have a lot of extra time at hand and are as crazy about your particular design as I am.

Cheers,
Denis

 

[marklg]

Actually, the trailing edge is also very significant to the aerodynamics. An abrupt trailing edge can result in disturbed flow and more drag, although there are special cases where they deliberately direct the air from the trailing edge in a certain direction. I can't see much from your pictures as to what is done on the trailing edge. An airfoil has a rounded leading edge and a tapered, long trailing edge.

Regards,

Mark

 

[gltrimble]

I have a second piece of aluminum left over that I may use for the trailing end of the panels.

 

[Roamers]

GL, i am considering panel layout like yours, but plan to add filler pieces on both sides of the roof vent to maintain a flat surface.

Thoughts?

 

[Dendisch]

I have a second piece of aluminum left over that I may use for the trailing end of the panels.

Nice. I like the clean look with the extra trim at the front edge, all in black. I might add something similar later at the panel sides. I'm still not done with my interior, so it's lower on the to do list.

 

[Dendisch]

Actually, the trailing edge is also very significant to the aerodynamics. An abrupt trailing edge can result in disturbed flow and more drag, although there are special cases where they deliberately direct the air from the trailing edge in a certain direction. I can't see much from your pictures as to what is done on the trailing edge. An airfoil has a rounded leading edge and a tapered, long trailing edge.

Regards,

Mark

Hi Mark, yes, you are right, that's why trucks sometimes have panels at the rear to direct the airflow inwards.
Currently I don't have anything at the trailing edge. When I get to adding fairings to the side I may add one with a very small angle to the rear covering about the length of the MaxFan.
Denis

 

[HarryN]

It isn't a big deal, but just be aware that on most solar panels, drilling into the side of the panel frame ends the warranty.

I am not sure if warranty even matters as far as a solar panel on a van roof. They take a lot of abuse.

 

[gltrimble]

GL, i am considering panel layout like yours, but plan to add filler pieces on both sides of the roof vent to maintain a flat surface.

Thoughts?

Good idea if you can do it in a simple, lightweight, rattle-free way. Possibly sheet plastic that can snap on and off for cleaning And access.

 

[Rocksnsalt]

I have a second piece of aluminum left over that I may use for the trailing end of the panels.

View attachment 164909
View attachment 164910

Hello, do you happen to have a pic of your solar brackets on the awning side?
Thanks

 

[aksotar]

the mounts Hein sells are pretty low to begin with… I have a single 335w panel, drilled mounting holes in the panel sides and the top of mine is almost flush with the top of the crossbars instead of being on top of them, I also used the half round crossbars…there’s just enough of a space to be able to clean under them if needed…

 

[autostaretx]

Of course solar panels like to have an inch or two of clearance beneath the panels for air flow (convection and ram-air cooling of panel).
A panel in the sun can reach 145 F quite easily ... with the air gap.
You might measure yours when it's sunny and then run the numbers given the panels' thermal efficiency rating.

On my Sprinter (dark blue roof), the panels can be at 145 F (in Seattle), and the (now shaded) dark roof is only 108 F.
(before the panels, it was the roof that got to 145 F)
My panels are rated to lose 0.45% of their peak power output per degree C above 25 C (77F) (voltage goes down, current goes up)
(their rated normal operating temperature is 113 F (45C))


--dick

 

[gltrimble]

Hello, do you happen to have a pic of your solar brackets on the awning side?
Thanks

The rigid mounting brackets on both sides of my panels are made from 3” stainless bar stock. The driver’s side is bent to provide just enough heigh for the panels to clear the high point of the van roof. The passenger side is a piece of 3”x4” bar stock with no bends attached to a 3” stainless hinge. The original factory roof rail has been mounted to the side of my Fiamma awning mount. The hinges allow for easy access for cleaning and maintenance.

 

[Rocksnsalt]

The hinges are a great idea.
they look too be standard house hinges?

 

[knobVANture]

Looks great! Love how low they’re mounted too. Thought I was crazy trying to make square holes for carriage bolts

 

[gltrimble]

The hinges are a great idea.
they look too be standard house hinges?

Yep, Home Depot. Found some more pictures. I did add a 1/2” of aluminum between hinge and bracket to level the panels.

 

[gltrimble]

Looks great! Love how low they’re mounted too. Thought I was crazy trying to make square holes for carriage bolts

That looks like a lot of work. I just tack welded stainless carriage screws to 1” stainless bar stock.

 

[Dann]

I used low profile brackets attached to the 80/20 roof rails and since my panels are not very close to the front of the van, I don't know if a trailing edge would really make a difference. I don't have a degree in aerodnamics but It looks like the slope of the front cabin would direct the airflow above them. The front Maxxfan must help a little also.

 

[Dendisch]

... The hinges allow for easy access for cleaning and maintenance.

Great idea! I wish I had seen this earlier. The next time I have to service my solar panels I will add hinges. Thanks!

 

[hein]

We offer the sliders that we use with our direct mount towers.

Pair of Roof rail sliders with studs for Sprinter Vans with OEM Rail

Enhance your Sprinter van with precision-fit roof rail sliders featuring studs. Elevate your journey with these OEM-compatible accessories.

diyvan.com

We also offer towers that we designed to work with 8020 crossbars:

Pair of Sprinter Tower Brackets for use with 8020(TM) 15 series crossbars

Enhance your 8020(TM) 15 Series with Sprinter Tower Brackets - durable, versatile, and easy-to-install solutions for elevated performance.

diyvan.com

(Warning: There are very low quality Chinese knock offs of our 8020 towers which we have seen fail from fatigue cracking)

All the best,
Hein
DIYvan

 

[3Play]

Of course solar panels like to have an inch or two of clearance beneath the panels for air flow (convection and ram-air cooling of panel).
A panel in the sun can reach 145 F quite easily ... with the air gap.
You might measure yours when it's sunny and then run the numbers given the panels' thermal efficiency rating.

On my Sprinter (dark blue roof), the panels can be at 145 F (in Seattle), and the (now shaded) dark roof is only 108 F.
(before the panels, it was the roof that got to 145 F)
My panels are rated to lose 0.45% of their peak power output per degree C above 25 C (77F) (voltage goes down, current goes up)
(their rated normal operating temperature is 113 F (45C))

View attachment 207805
--dick

The open section is still going to block air flow when moving, the constrained slot will cause high pressure and the result will be spill over out the front and maybe sides, with a horizontal vortex that will create more drag than the ramp. Ideally, the ramp should have some space below to allow for a small amount of air flow. Mine had a down sloping ramp with VGs on the top to reattach the separation bubble over the top. The resulting air flow through the gap below is flowing into an increased volume (low pressure area) because there should be a slight outflow from underneath the panels since the surrounding edges are open and the front is constricted.
Realistically, any forward movement will create enough flow under the panels if the sides are open. I mounted directly to the top of the ribs, so the flow is very restricted when parked. I have been thinking about installing a couple of fans to blow the underside of the panel cavity.
Another observation, if you already have roof vents and a ladder on the side, your airflow is already screwed.
Any raised perpendicular obstruction will not only create a separation, but it can actually affect an area of flow 2 to 4 times the width of the obstruction.
This is why a lot of factory roof racks started using ramps.