Optimal driving strategy for a solar car on a level road

Every three years, solar cars from all over the world come to Australia to participate in the World Solar Challenge. In 1993 there were 52 cars in the race. Five cars finished within five days, each one breaking the previous race record and achieving an average speed exceeding 70 km/h. The performance of these cars depends on many factors: power, aerodynamics, traction efficiency, weight, reliability, and (not least of all) driving strategy. On a level road, the optimal driving strategy for an ideal car is essentially a speed-holding strategy. For a real car with inefficient energy storage, however, there are two distinct holding speeds. The lower speed is held when solar power is low and must be supplemented from stored energy. The upper speed is held when solar power is high, and excess energy is stored.