Circuits in the Sun: Solar Panel Physics

Typical commercial solar panels consist of approximately 60 individual photovoltaic cells connected in series. Since the usual Kirchhoff rules apply, the current is uniform throughout the circuit, while the electric potential of the individual devices is cumulative. Hence, a solar panel is a good analog of a simple resistive series circuit, except that the devices generate (rather than burn!) electrical power. For example, in order to sustain the current flow, each device must generate the requisite current. As a result, the least efficient device limits the current throughout. Photovoltaic cells also have a more complicated current-voltage (I–V) characteristic, which determines the optimal load for power extraction. These considerations, among others, make the solar panel an excellent platform for exploring the physics of electric circuits.