Here is an application note from Microchip describing how to get maximum power out of a solar panel.
The focus of this application note is to identify how to get the maximum power out of a solar panel to power a remote application. The Maximum Power Point Converter is essentially a DC-to-DC converter, where the DC input voltage is a solar panel and the output voltage is 28 volts. The intent of the converter is to show how to take the solar panel and generate a voltage capable of recharging a 24-volt battery.