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DougWantsALeaf

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May 10, 2013
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On the SL model, have the solar cell power a small battery temp control system. Even if it can't maintain temperature in very hot or cold weather, it could still "help" keep the temp closer to the optimal temps.
 
It puts out about 4-5 watts. Not enough to accomplish anything.

DougWantsALeaf said:
On the SL model, have the solar cell power a small battery temp control system. Even if it can't maintain temperature in very hot or cold weather, it could still "help" keep the temp closer to the optimal temps.
 
DougWantsALeaf said:
wow, that's really horrible. Had thought it was a little better then that. surprised they even bothered with it.

It's more of a cosmetic statement than anything else. I really hate having to explain to the curious that this is the case.

If they'd wanted to do something useful they could have powered a small fan to expel heated air from the cabin.
 
DougWantsALeaf said:
wow, that's really horrible. Had thought it was a little better then that. surprised they even bothered with it.

its a feel good thing. Are you familiar with the Gen 3 Prius with the sunroofs? They are also PV and they powered a circulation fan that helped to keep the interior "cooler" of course, sometimes it was cooling it down to 100º which i guess was better than 120 right?

But look at the size of those panels. They are like 20X larger than the LEAFs and a lot of times, the energy was barely enough to run the fan at low speed. Had to have full direct Sun to get anything out of it
 
Ok,

For the math or science wiz out there. If you were to cover the entire roof with the latest record breaking solar panel (which just hit north of 44% energy capture), and it was in near direct sun for 6 hours, how many watts or Kw could be theoretically captured?
 
^^^
Some previous discussion at http://www.mynissanleaf.com/viewtopic.php?f=27&t=6316" onclick="window.open(this.href);return false;.

http://en.wikipedia.org/wiki/Solar_cell_efficiency#Comparison_of_energy_conversion_efficiencies" onclick="window.open(this.href);return false; has a chart that I've seen elsewhere before about efficiency of various solar panel technologies. I'm not even close to being an amateur on the subject but from what understand, the panels that can produce power from the widest set of wavelengths (http://en.wikipedia.org/wiki/Multijunction_photovoltaic_cell#Multi-junction_cells" onclick="window.open(this.href);return false; ?) are generally very expensive and used only in applications where power output is absolutely needed and keeping the weight and size down is critical (e.g. space applications).
 
Admittedly to use the multilayer cells, it would be space craft expensive to get the 44+%, but would be curious to understand how many miles could charge in a day a kind of a best case.

For single layer, your at 25.7% max per latest news I have seen, so just over half of a best case.
 
There is about 3000 Watts in a square meter of Sunlight to be had.
so assuming 44% efficiency, that's about 1320Watts which at 12V would be around 110 amps.
So if the entire leaf roof was used, it could probably do some serious charging of that 12V battery.
It would be nice to know what that panel on the Leaf is capable of.
Normally there's about 2A on a trickle charge so unless there's a really efficient panel there, I seriously doubt it can do much.


Zurc.
 
Zurc said:
There is about 3000 Watts in a square meter of Sunlight to be had.
Not quite. The actual figure at the surface of the earth is about 1000 watts per square meter. If you go above the atmosphere, it is closer to 1366 watts per square meter. Neither comes close to 3000 watts.

so assuming 44% efficiency, that's about 1320Watts which at 12V would be around 110 amps.
So if the entire leaf roof was used, it could probably do some serious charging of that 12V battery.
It would be nice to know what that panel on the Leaf is capable of.
The roof is not normally aimed direcly at the sun. (The sun is not directly overhead. If the sun is 30 degrees above the horizon, you would only get half as much energy. Actually less, as it goes through more atmosphere.)

The maximum efficiency of a single junction solar cell is only about 37 percent as I recall, and the real panels are lower, around 18 - 20 percent, even less in implementation due to gaps between the cells, etc..

If you get 150 watts from the top of a leaf, you would be doing pretty good.
Normally there's about 2A on a trickle charge so unless there's a really efficient panel there, I seriously doubt it can do much.
More realistically, the trickle charge panel likely produces about 0.04 amps.
 
You can get the same trickle charge by keeping a small panel on your dash. I got a couple of them from Harbor Freight, just to keep my pickup ready for use. Cost around $15. Truck sits for months and the parasitic draw from it's alarm system eventually drains the Optima battery. One panel is enough, but once I left the dome light on after a trip and needed to actually put it on a charger to use it a few weeks later, so now it has 2 hooked up directly to the battery. They are about 6" X 12" or so and come with suction feet and some different connectors, including the lighter size and a pair of clamps.

Maybe I should replace the dome light with an LED...
 
and don't forget the extra weight you add due to the generally much heavier solar panels compared to the material the body is generally made of.

In the end you will end up getting less range due to lugging all the extra weight. Solar panels are good for stationery use, except only in space in satellites where the surface area is so large the weight really doesn't matter what with zero gravity.
 
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