Many projects require power in some form. Photovoltaic panels provide a rugged, durable, mass produced, and inexpensive platform for the system's energy production needs. PV panels are made from arrays of cells connected in serial and parallel.
Similar to battery packs, balancing solar cells helps to ensure maximum power production and longevity. Sealing cells against the weather and oxidization are challenges. As is encasing the cells in a durable medium which is transparent to the light wavelengths converted to electricity by the cells.
Individual solar cells typically measure 125mm square and produce approximately 0.5v @ 3W each @ 20% efficiency.