Hi, in this page i will show you how to power a notebook from solar energy
First you need to know how much power your computer needs, you can see this from the power supply charger, in my case an ultrabook with a maximum consumption of about 40W.
Now you need to choose a solar panel with a higher output power, bigger is, the better is, this is important for a not optimal angle of the panel, and sometimes not clear sky, you have to secure the panel in a sunny position, I haven't enough space, so my 50W polycrystalline solar panel is placed in a balcony with dowels (removable).
I tried to power directly at about 19V the computer with the solar panel, but in my case, the computer does not accept it, so i used a dc/dc buck converter (or step-down ) adjustable, recommended efficient models with a toroidal transformer.
At this point I set the converter at 19V, after adding a pair of diode (silicon for very low leakage current), the computer will go a bit of solar energy and a bit from the plug, or exclusively from the plug automatically, depending on the climate, it is important to adjust the trimmer to a voltage just above the other power source, because the current absorbed first is the greater.
If there is too much sun, you can try to unplug the power supply from the plug to undo consumption from the power supply, 40W is the power consumed by charging the batteries and also using the computer, when the batteries are fully charged the consumption at most reach about 20W, also it depends on the computer's work done.
In my case, in addition the solar panel can power a dc/dc converter to 4V for some lights and a multi socket usb car.
I hope you like it.
More info at: http://electrogreen.altervista.org/computer-solare/