Hybrid cars

     Has anyone looked at putting solar collectors on cars, specifically the
new hybrid cars?

Larry

  Larry wrote:


Have you checked out one of the many solar powered car races?
http://www.formulasun.org/asc/
http://www.eurekalert.org/features/doe/2001-07/drel-tgs062002.php
http://dsc.discovery.com/news/briefs/20030616/solarcar.html

It's also been discussed before on this very newsgroup. The reason
why people don't put solar PV on cars is very simple, cars aren't
big enough. The math isn't very complex. A large American car is
roughly some 2 meters by 6 meters. This gives you an area of about
12 m^2. NREL has charts showing that most places in the United
States get an average of 4 to 5 kwh/m^2/day sunlight with less
during the winter and more during the summer. Ordinary PV cells are
around 12% efficient STC rating and 10% efficient in the real world.
This means you get around .5 kwh/m^2/day of electricity out of them.
Your 12 m^2 car will get some 6 kwh/day. A good electric car at about
1/4 the size and weight of a large American car can go about 3 miles
per kwh. An electric retrofit to an ordinary car gets about 1 mile/kwh.
Hybrids are very much like retrofits in size and weight so adding
PV panels to a very large one would get you maybe another 6 or so
miles range (more summer, less winter) and only if you park it in
the sun all day.

How can you PV power an electric car? Well, get a good electric car
first that will go 3 miles/kwh or more. These are usually somewhat
smallish cars. Then park it in an ordinary garage. These usually
measure some 7 x 8 meters (more or less). Cover the roof of this and
you can expect an average of 28 kwh/day. This would power your car
around 84 miles which would be more than enough for local driving.

Anthony

 2 x 6 meters? for a large American car?!? a freakin' ford excursion isn't
even that big (but it's close), and that's the absolute largest production,
crime-against-the-earth SUV made!!! holy crap!

But.... you're right, that IS even more ammunition backing to your argument
against solar-on-the-car.

Solar garage :-)

Andy

 
Probably relevant that a horse needs an acre of photosynthetic grass to
support.
As the horse is operating 100% of the time and a car only when needed an
electric horsepower would need 1/10 acre.

--
ddwyer

 
production,

argument

In defense of hybrid vehicles, I argue that solar power can have a huge
advantage.  I'm currently working on a system for my Honda Insight that will
integrate a solar panel while the car is parked for 8 hours a day.  The
standpoint, though, is not trying to substitue solar energy for gallons of
gas.  This has been clearly dismissed already.  My idea is to keep the SOC
(State of Charge) of the battery pack above a certain threshold.  In my car,
if the SOC drops below 50%, the car begins to force charge the battery by
sipping power off the foward momentum.  I've observed about a 10mpg decrease
when that happens.  If I can keep the battery above the 50% mark, I'll be
golden.

I did some analysis and I realized I only have a net loss of about 10% of
the usable capacity of the battery during my regular drive to work.  If I
could recover that loss while parked at work, I'd always have a fully
charged battery.  The usable capacity of my battery is 3.8Ah.  10% of that
is .38Ah.  I have an 80W panel that would give me 400Wh on a good day.  My
DC-DC converter gives me 200V, so that's 2Ah back in the battery.  Assuming
a bunch of efficiency losses, I'm still above the .38Ah that I need to
recover.

I have a long ways to get yet before I actually implement this, but so far
the numbers are promising.  The key here is to realize the solar panel is
simply a way to prevent the battery from force charging while I'm driving.
Those 10 mpg's are pretty considerable, if you consider the fact that that's
half the total mpg's of most cars on the road today.