Updated the simulation to have a better representation of solar power and vehicle speed. The solar power is a function of the angle overhead and has a slight bias for northern latitudes so that the time between sunrise and sunset is about 14 hours. The vehicle speed is calculated as a linear function of solar power with a maximum speed of 4.5 ft/s as determined empirically. The plot was updated to show solar power instead of voltage since power is what really drives the surfboard's speed.