Question: Maximum Latitude for New Tesla Solar Roof?

minogully

Active Member
Joined
Apr 20, 2016
Messages
124
Location
Ontario, Canada
Tesla Owner
Model 3
Country
Country
#1
Since the tiles become opaque at street level, my thought is that the higher the latitude, the lower the sun is on the horizon and the more blocked the light becomes. So, is there a maximum latitude where these tiles are no longer cost effective?
 

Topher

Energy Curmudgeon
Joined
May 11, 2016
Messages
591
Location
Maine
Tesla Owner
Reservation
Country
Country
#3
It seems unlikely that the panels truly 'become opaque'. If the majority of the light coming from the panel at a given angle is from the first reflectiion (i.e. the top surface), it will appear to someone seeing it, that it is only that surface. This does not preclude a substantial amount of light still passing through that first surface. If you look at a window obliquely during the day, you will mostly see a reflection, not a view of the interior, this does not mean that sunlight is not passing into that interior.

Thank you kindly.
 

Badback

Valued Community Member
TOO Supporting Member
Joined
Apr 7, 2016
Messages
1,111
Location
Prior Lake, MN
Tesla Owner
Reservation
Country
Country
#4
For any given latitude, there is an ideal angle for the solar cells. For my location, it's 37 degrees. My PV array, which is being installed today, is on a roof that is at 40 degrees, not ideal but close. If the solar roof is part of new construction, then the roof angle can be optimized. Otherwise, compromises in performance will happen.
 

garsh

Dis Member
Moderator
TOO Supporting Member
Joined
Apr 4, 2016
Messages
11,281
Location
Pittsburgh PA
Tesla Owner
Model 3
Country
Country
#5
There are various tricks that can be done with specialized glass to reflect/refract light that can probably compensate for having a non-ideal slope on your roof. I'm interested in more details from Tesla on this subject too.
 

Topher

Energy Curmudgeon
Joined
May 11, 2016
Messages
591
Location
Maine
Tesla Owner
Reservation
Country
Country
#6
For any given latitude, there is an ideal angle for the solar cells.
Well it is a trifle more complicated than that. Orientation (from true South) changes the ideal angle, as does weather patterns, and whether you are grid connnected or stand-alone. But basically, the efficiency loss for non-ideal siting are pretty small for small deviations, a few percent or so. For my area, any unobstructed, unshaded roof, facing anything from East through South to West, and angle from flat to over 45 degree slope, produces cheaper electricity than the grid.

There are various tricks that can be done with specialized glass to reflect/refract light that can probably compensate for having a non-ideal slope on your roof.
Not really. It is a matter of geometry, power is dependent on the shape of the panel when projected normal to the sun direction. That is the total sunlight that can be intercepted. Refracting can't compensate for what isn't there.

Thank you kindly.
 

garsh

Dis Member
Moderator
TOO Supporting Member
Joined
Apr 4, 2016
Messages
11,281
Location
Pittsburgh PA
Tesla Owner
Model 3
Country
Country
#7
Not really. It is a matter of geometry, power is dependent on the shape of the panel when projected normal to the sun direction. That is the total sunlight that can be intercepted. Refracting can't compensate for what isn't there.
Older solar panels end up reflecting a lot of light. For example: Family's agony over neighbour's solar panels that reflects sunlight directly into their home. And I believe that oblique angles to the sun tended to increase reflection. That's what I'm hoping they can fix with specialized glass - actually direct more light to the solar cells and reflect less of it.
 

Topher

Energy Curmudgeon
Joined
May 11, 2016
Messages
591
Location
Maine
Tesla Owner
Reservation
Country
Country
#8
Older solar panels end up reflecting a lot of light. For example: Family's agony over neighbour's solar panels that reflects sunlight directly into their home. And I believe that oblique angles to the sun tended to increase reflection. That's what I'm hoping they can fix with specialized glass - actually direct more light to the solar cells and reflect less of it.
There is an angle where light will reflect off a piece of glass rather than pass through it. I think this is related to the refractive index. One solution that is sometimes used, to the complaint above, is to bumpify the surface, this doesn't actually reduce the fraction that is reflected, just makes it more spread out. Getting more to make it to the cell beneath requires more glass magic than I ken.

Thank you kindly.
 

KenR

Active Member
Joined
Aug 9, 2016
Messages
38
Location
Centerview, Mo
Country
Country
#9
For any given latitude, there is an ideal angle for the solar cells. For my location, it's 37 degrees. My PV array, which is being installed today, is on a roof that is at 40 degrees, not ideal but close. If the solar roof is part of new construction, then the roof angle can be optimized. Otherwise, compromises in performance will happen.
Nothing says the solar panels MUST be installed on the roof. When i got the quote last fall, the installer recommended installing them at ground level to avoid "inevitable" roof maintenance issues... i have the space in the yard, so that's the way I'll probably go.
 

RickDeckard

Active Member
Joined
Apr 7, 2017
Messages
64
Location
Longueuil Québec
Country
Country
#10
"
Nothing says the solar panels MUST be installed on the roof.
"
That is true but I think the reason why the current discussion is focused on roof considerations is because people have questions related to the upcoming "New Tesla Solar Roof" (as opposed to traditional solar panels).