Dgaetano wrote:Sunpower makes a 320 Watt panel that's essentially the same size as the Leaf roof (that's a 19% efficiency panel). San Diego gets 5.5 hours of usable sun a day. So that's 1.76 kwh a day, or just under a fuel bar.
I think you'll be lucky to get half of that, even if you park outside in unobstructed sunlight. The solar panels need to be pointed directly at the sun. The LEAF is not a flat surface pointed at the sun. And if you have a Solar Panel the size of the LEAF roof, your color options are limited - Solar panels don't come in Cayenne Red or Ocean Blue...
Of course, it could be nice because all the other cars would be parked in the parking space lines, while all the LEAFs will be crossing the lines for the best sun facing angle, all worshipping the sun!
If a lamp post shades the panels, a building or a tree casts a shadow, the cells are wired in a series or series / parallel arrangement so shading one cell can dramatically reduce the output.
The sun, under peak conditions is about 1000W/m**2. Solar panel efficiencies are in the 13 - 22% range. That's 130 to 220 watts/m**2, ideally.
SunPower® solar cells currently hold the world record in efficiency at 22.4 percent.
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LEAF roof area for solar is around 60" x 42" or 1.5m x 1.1m = 1.65m**2
215 to 360 watts ideally for the roof.
Arbitrarily estimating various factors for not being perpendicular (facing) the sun throughout the day (declination for the latitude and time of year, not tracking the sun...) would derate around 70%, the sun not being at ideal output, panels not at ideal temperature, atmospheric dust or light smog blocking some light etc. - derate 80%. 70% x 80% = 56%.
56% * 215 to 360 watts ideally = 120 to 200 watts practically
Others on the forum can come up with better numbers, but I think it's pretty clear that for the roof alone, you won't get more than 250 watts. Other surfaces will have less ideal facing to the sun and even greater aesthetic impact, so limiting to the roof seems pretty reasonable.
100 - 200 watts won't run the AC or heat full force, it won't be enough to maintain temperature on hot days. If the AC is capable of utilizing low power, it would make the car much cooler or warmer than it would be with no fan and no AC. (if cars wre well insulated, this low power could come close to maintaining temperature, but they aren't and there is a lot of single pane window area in a car.)
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I see the Sunpower 315 is 19% efficient and meaures 61.39" x 41.18" with a max power of 320W. If all the derating factors came to 62%, this panel would produce 200 Watts. It weighs 41 lbs, though if the frame were removed and it was integrated into the LEAF body, it might add only 20 pounds to the weight of the car. This panel certainly sets the upper bound for power from the roof at 300 watts or less real world. According to SunPower there aren't any panels that are more efficient (power produced / unit area (well technically incident sunlight energy)).
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The solar panels must not affect the aerodynamics of the car or add more than a couple pounds to the weight or they will cause more losses while driving than the power they generate. So bolting a commercial solar module to the roof with a 1 inch module edge exposed in the airflow around the LEAF body would be a big net energy loser due to poor aerodynamics!
Blue Nissan Leaf SL+QC rsrvd 4/21/10 order 11/24/10 delivered 5/29/11 (Apr May Jun Jul Jun May Jun) Polar Bear Hug 12/11/2010
1999 Green GM EV1, 7.2kW Solar Electric (PV); 2002 RAV4 EV; Carbon Neutral since 2010
It's time to LEAF! LEAF Oil behind!