What's a good way to generate solar electricity while driving?

For almost a decade I am extremely happy with my 2 iSun They don't go to the roof though. I have them right on top of the dashboard. I have never tried to charge a laptop though. But they are quite sufficient in charging mobile phones, portable gps's and rechargeable batteries. Being more then 10 years old, I guess technology must have enhanced. Given that they still do what I want them to do, I don't look for more modern solutions. Already ten years ago there were panels up for the job

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While browsing through some kickstarter projects I came across a portable solar panel device, that seems quite interesting and something you might be looking for. I am considering backing this project, especially since it comes with a handy carrying device and my iSuns seems to provide less power after a decade of trustworthy service.

The flexible panels that these guys sell are pretty good.

You can rest them on the dashboard or across the parcel shelf. They have excellent power output.

However- you are in a car, why not use the excess power from the alternator? Either the 12v DC from the lighter socket our use an inverter for high voltage AC.

From the comments below, I think a couple of you have entirely misread my answer. Solar power is far better for the environment, obviously, but the amount of power your engine generates is far in excess of what you need to charge the battery and power your electricals. When I have my invertor fully loaded up I can't notice any difference in engine load, unlike when I use the AC, which is a really high load. Even my 600w amp and subs don't come close to the load the AC causes.