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Thought experiment: roof rack solar array

5K views 4 replies 5 participants last post by  strouthesm 
#1 ·
I was looking at the roof rack I'm not using (I don't cycle or camp) and thinking, what could I do with a solar panel up there? I'm sure this has been hashed over with Prius/Volt/etc fans, but let's consider ...

  • Eyeballing it looks approximately the size of a normal house solar panel, assume so
  • My 20% efficient LG panels produce about 2kWh during a good summer day. Naturally orientation plays a big role, but assume this for the moment
  • Plenty of inverter choices, from 12VDC (many) to 240VAC (e.g. Enphase - with a frequency source and controller, not the right application of an Enphase inverter but you get the idea)
  • 2kWh can be stored in two lithium batteries the size of the Bolt 12V battery, or just two SLA
  • People seem to get 3-4 mpkWh, so 2kWh will give say 8 miles range.
  • About a 3% range boost, good in an emergency, but otherwise not too useful
  • However continuing the thought, one could consider a design where the whole package is external, with the batteries and electronics stored under the panel. EVSE's are dirt simple, you could pull out a cable and charge up your car an extra 8 miles potentially off your panel.
  • Perhaps a better use case is 12V in the cabin - say cabin conditioning? Cooling it during the summer and heating during the winter (depends on the region, but a relatively clear winter day will still generate about 1kWh
  • Or for the camping fans (who might want a cargo carrier up there anyhow) maybe a way to get a few kWh without hitting the battery

Interesting to think about. A nice slim panel rider shouldn't impact aerodynamics much.
 
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#3 ·
Roof racks are not aerodynamically efficient. Dragging around the weight of a panel at sub-optimal angles for a few measly watts isn't worth it.

Best to keep the panels on the house roof where there is no weight penalty, no aerodynamic penalty, and the angle can be optimized.
 
#4 ·
I was looking at the roof rack I'm not using (I don't cycle or camp) and thinking, what could I do with a solar panel up there?
I like what the top-trim Prius does (and other cars may do this too) - use a built-in solar panel to power the HVAC fan when the car is stopped. It keeps the interior of the car cool whenever the sun is out (which is exactly when you need it). Brilliant idea, and one that all cars should have IMHO.
 
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