Complex sentence: It was a 15-inch model built by William G. Cobb of the General Motors Corporation, and consisted of 12 selenium photoelectric cells which used solar energy (or a strong light source) falling on them to create electric current to power a tiny electric motor.
Split into simpler sentences: It was a 15-inch model built by William G. Cobb of the General Motors Corporation. It consisted of 12 selenium photoelectric cells and sun energy (or a strong light source) falling on them created electric current to power a tiny electric motor.