Here is a picture of the Raspberry PI setup to log the data from a GPS, and fueled by a solar panel.
This one has the small touchscreen from Adafruit (zoom on it). The tray and the breadboard are not mandatory in this setting.
Next step will be to use two servos to orient the solar panel so it faces the sun. This would be based on the project available on Google Code. That's the cool thing about using Java on the Raspberry PI. Whatever works in Java works on it.