The rule of thumb is that in bright, direct sunlight, about 1kW of light energy falls on a square meter of surface area. At 20% efficiency, a high but generally achievable number, that would mean you'd be able to collect 200W continuously. The realities of keeping the panel aimed, etc., and real-world efficiency numbers might bring that down to a more realistic 100W continuous per square meter of collecting area. I'm not sure I'd want a 1 sq-m sail on the back of my bike, but it wouldn't be THAT bad.
But that would keep you going. Not all that fast, and only while the sun is shining, but it would keep you moving. I'd bet our Zeros could maintain 35 mph on 100 watts. In ten hours, that's a 350-mile day if you never took a break (or had multiple riders riding in shifts).
Is there something wrong with the back of my envelope here?