Indeed - numbers don't lie.
A decent family car has no more roof surface than max 15 x 6ft
or about 90 sqft. At current (low cost) solar panel efficiency,
the max you could get out of that is around 12W per sqft (at perfect
of irradiation, so in practice, a lot less!) which means you might get
around 1kW from this roof, or about 5 kWh per day since the sun moves
along the sky so you can count on approx 5 full sun hours each day.
That means that if you drive less than 20 miles avg per day, you can
drive on the solar roof alone if you keep it in full sun all day. No
parking under trees or in covered parking garage or behind a building.
If you want to do a 200 miles trip (besides battery capacity concerns)
you need to park and charge your car for 10 days straight to accumulate
the approx 50 kWh that is needed to go that distance. Question is if
your pack will contain that. More likely your pack will be half that
size, you you can charge 5 days straight and go 100 miles at freeway
speed, maybe this is sufficient to do 200 miles at 25 MPH but who wants
to sit for 8 hours doing residential street speed?

BTW, which car has a flat 90 sqft straight roof surface and is

Cor van de Water
Chief Scientist
Proxim Wireless Corporation
Email: Private:
Skype: cor_van_de_water Tel: +1 408 383 7626

-----Original Message-----
From: EV [] On Behalf Of Lawrence Rhodes
via EV
Sent: Friday, September 26, 2014 3:52 PM
Subject: [EVDL] Building a true road going solar EV. Help everyone.

It seems that the numbers don't lie.  There is now a proven design which
will allow you very good range with a small battery pack and good speed.
The Stella.  My next project after the electric motorcycle will be a
road going vehicle with a top of solar panels.  The Stella proves ugly
is good at least for a family solar car.  I'm going to build mine using
a Leaf battery pack.  It will be heavier than the Stella and have more
battery capacity  but that is not set in stone.I will make a tear drop
tube frame and cover it using light plastic or abs sheet.  The vehicle
will look like a tadpole with a wide tail.  The Stella proves you can
have a very blunt front edge and still have efficient CD.  I'll use four
hub motors.   Seating for four or 6 will be slightly recumbent.  Small
space in rear for storage.  It will be very similar to the Stella in
looks but a lot simpler.  I don't want to reinvent the wheel.  It would
be nice if it could cruise at 25 or
 thirty mph and still charge the battery.    However I'd be happy if it
would charge in a day of bright sunlight and have a 200 mile range.  Now
to source the parts.  That's where the group can help.  The Stella used
individual solar panels laminated into the roof of the vehicle.  What is
the best to use to get at least 1.2kw?  Bicycle hub motors.  What are
the most efficient for the money?  Using four if they are all 10000 watt
motors this should do the job for freeway speeds.  A Rudman charger of
some sort unless the solar panels are enough.  Simple disc brakes when
not using regen.  I'll be making the frame from bicycle chromoly.  I'm
going to try to get Zzipper to make the windshield..  All comments are
welcome.  Lawrence Rhodes
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