Reducing the Drag of Rigid Solar Panels Mounted on a Van

[sebcbien]

Hello,
First post here !
I've designed an airfoil profile to help reduce the drag of rigid solar panels mounted on top of campers / vans etc.
Sorry I cannot post links as I'm new

I already shared the designs here:
http://sprinter-source.com/forums/in...threads/93869/

and also on thingiverse:
Front: http://thingiverse.com/thing:4708973
Rear: http://thingiverse.com/thing:4719660

Those profiles can be printed with 3D printer and cut and assembled at the desired length.
Those profiles are straightforward and mimic a drop/airfoil profile.

I'm posting here because there is a more difficult problem:

rigid solar panels are preferred because they are more durable and more powerful by size.
They allow heat to escape under the panel and this geatly enhance the power output, a hot panel produces way less than a colder one.

So ..
With my profiles, I "solve" the front and rear drag, but there are two more edges, "inside" the panel:

Sorry I cannot post images or links, hope you will understand.

And if there was no problem with the cooling, I think the shape of the deflector would be simple to prevent the airflow to be trapped inside the aluminium frame.

Maybe some of you master aerodynamics study softwares or have good ideas of what's better to do ?

Thanks and sorry for the non clickable links
*edited after 5 post to have links ;-)

[oil pan 4]

Glue semi flexible panels to the roof.

[JulianEdgar]

Originally Posted by sebcbien

Hello,
First post here !
I've designed an airfoil profile to help reduce the drag of rigid solar panels mounted on top of campers / vans etc.
Sorry I cannot post links as I'm new

I already shared the designs here:
sprinter-source.com/forums/index.php?threads/93869/

and also on thingiverse:
Front: thingiverse.com/thing:4708973
Rear: thingiverse.com/thing:4719660

Those profiles can be printed with 3D printer and cut and assembled at the desired length.
Those profiles are straightforward and mimic a drop/airfoil profile.

I'm posting here because there is a more difficult problem:

rigid solar panels are preferred because they are more durable and more powerful by size.
They allow heat to escape under the panel and this geatly enhance the power output, a hot panel produces way less than a colder one.

So ..
With my profiles, I "solve" the front and rear drag, but there are two more edges, "inside" the panel:

Sorry I cannot post images or links, hope you will understand.

And if there was no problem with the cooling, I think the shape of the deflector would be simple to prevent the airflow to be trapped inside the aluminium frame.

Maybe some of you master aerodynamics study softwares or have good ideas of what's better to do ?

Thanks and sorry for the non clickable links

The front profile looks fine but I doubt the flow stays attached to the rear profile - I'd guess it needs to be much longer. However, very easy to test this with short tufts.

I don't know what you mean by 'inside edges'. If you mean the lower surface is not smooth, I'd place a cover under the solar panel and then use some vents to allow cooling air to pass above the cover. If that is the case, I can suggest how you'd do this.

[sebcbien]

Originally Posted by oil pan 4

Glue semi flexible panels to the roof.

Hello,
Thanks, but NOT a solution, sorry, too easy
It's about power and heat.
Heat cannot escape under a glued solar panel and overheat.
This gives solar panel with poor lifetime and poor power (power decrease a lot with heat, increase a lot with cool)
Flexible solar panels are limited in power by design.
That's why you see way more hard panels on van roofs than flexibles ones.

[sebcbien]

Originally Posted by JulianEdgar

The front profile looks fine but I doubt the flow stays attached to the rear profile - I'd guess it needs to be much longer. However, very easy to test this with short tufts.

I don't know what you mean by 'inside edges'. If you mean the lower surface is not smooth, I'd place a cover under the solar panel and then use some vents to allow cooling air to pass above the cover. If that is the case, I can suggest how you'd do this.

Hello, as I'm new I cannot post pictures or links.

Yes, it's the lower surface that is not smooth at the start but the problem is mostly at the end, it's an aluminium U profile that traps the flow.
Cover under the solar panel it's not a solution either, as I responded in the previous post, heat is a major factor that has to be taken in account.

Please have a look at the last picture I posted here:
http://sprinter-source.com/forums/in...threads/93869/

As for the length, yes I understand, I also thought it should be longer.
The profiles are quite small (3cm height) what length would you suggest by experience ?
Keep in mind that they are vans and campers, it usually not go over 100kph for a very long time.

[JulianEdgar]

I suggested a cover under the panel and vents to allow cooling air to flow. That would be fairly easy to arrange. (But I was thinking of how the vents would work when you are moving, not stopped.)

Perhaps instead just use a gentle fairing that doesn't have to extend too far forward - make up a mock-up and tuft test to see if it retains attached flow. You could probably use dense mesh for this fairing to aid panel cooling.

Before making any changes to the rear end caps, I'd also tuft test these to see if they're working.