Typical I–V curves under nominally full Sun at three representative tilt angles are shown in Fig. 3. The mechanisms of light absorption and current generation in a solar cell have been recently described by Feldman.5 In short, incident photons excite electrons, which experience electric drift across the junction of a semiconductor diode. When an external circuit is present, the motion of charge has the capacity to deliver power to a load. The relationship between current and voltage generally follows the Shockley diode equation with an additional illumination-dependent current source.6 Maximum current is generated when the solar panel is perpendicular to the incident light rays, which occurred with the panel tilted approximately 30° from vertical during the measurements presented in Fig. 3. When the panel is adjusted to an angle θ away from the optimal orientation, the incident flux is reduced by a factor of cos θ7 A small increase in reflection loss may also contribute to the reduction of power generation as θ is increased. Differences between the measured and expected current shown in Fig. 3 may be attributed to atmospheric variations in the solar flux (i.e., variable cloud cover).