I managed an average useful generation this summer of 1,000Wh per day from my 330Wp solar trailer. It was capable of much more on blue sky days, but a 250W 25km/hour legal torque sensored pedelec, even pulling a trailer in hilly terrain is not capable of consuming all it can produce!
Most ebike journeys are rather less than my 75 mile daily average, so could be powered by a much smaller panel.
For example, my daily commute is 2.5 miles each way, ridden on high assist and needs about 100Wh for the return trip. If the bike lives all day outside charging in the summer half of the year that only needs a 33W solar panel to keep it going, and even my smallest 400Wh battery is plenty to smooth over the duller days.
That solar car program was interesting, but for most people putting the solar on their house roof and charging from the mains will make more economic sense. Their business model so far is 'build exclusive and expensive to fund a future cheaper mass market version'.
For those lucky enough to have space for a garage, south facing and unshaded, just the garage roof covered in solar can produce enough energy to drive a small electric car several thousand miles a year. Just not directly.
(Single garage, 3m x 6m, pitched roof, one side facing south. About 11m2 roof plane, so about 1.5kWp solar system. At least 800kWh/kWp/year in most parts of UK, so 1,200kWh generated per year. Small electric car consumes 100 to 200Wh per mile. Using 150 as reasonable midrange value, 1,200,000 / 150 = 8,000 miles per year. Double garage? Double the numbers. Flat roof? Halve the numbers.)