how best to utilise eco 100w power supply / to improve fuel economy?

[Synchronicity]

I'm a little tipsy here so forgive the mistakes-

I'm planning on installing several sunslick brand flexible solar panels on the roof of my van. The van is quite long, i have invested in the panels already which were on sale. Total capacity is 27 + 27 + 14 + 14 watts = 82 watts total i think (continuous power peak sunlight).

This will apparantly do the following:

1) Allow me to power a laptop, recharge mobiles, AA batteries, perhaps an in car amplifier.

2) reduce heat throughput to the cabin & cargo space (that's a cool side effect of installing solar panels on any roof, they essentially absorb heat)

3) As most of these things won't be used full time, i'll have the capability to charge a car battery. Store power for later and all that. i already have a charge controller + inverter.

Basically my question is this: can this auxillary (and free) source of power in any way be used to aid fuel economy? i don't mean with .one of those hoax engine mods, but possibly with an aero mod - something like wheel spats which can be deployed from inside the car for high speed driving. or a rear high pressure air spay at the rear to help airflow. i thought you folks might know best...

[Daox]

It certainly can help mileage. Look up alternator delete.

[GRU]

so you need to take electrical energy generated by the panels and use it to lower the engine load...

you can either delete the alternator and have the electronics run on batteries alone or/and remove a/c compressor and replace with electric motor (if you want a/c)

[oil pan 4]

For my oversized truck 100w less accessory loss should get me 0.1mpg.
But since alternators and the belt drive are less than 50% efficient 100w of solar could restore up to 200w worth of crank power.

[Ryland]

If you want your panels to produce any power you need to remember that they need to be pointed at the sun, not straight up, unless you live on the equator and it's noon, you can pretty easily put a meter on your panels and see the output drop as you go for a nice angle to flat, here in the winter you need to adjust the angle to be closer to straight up and down.