Compressed air is not a very efficient way to store energy. The storage tanks are expensive and require inspection periodically. With a single stage compressor like the article shows you’ll be lucky to crack 10% efficiency so most of you’re pedaling is getting wasted as heat. Then you have to find a way to convert it to useful energy which probably incurs at least a some loss.

A normal ebike could be equipped to do the same thing far more efficiently. Lift the drive wheel off the ground and pedal against the re-gen brake, just unplug the battery and it can charge whatever you want.