Hi Geek, I've been saying all along that if you regularly ride long distances, an electric bicycle isn't for you. If you need to go more than 20 miles on a regular basis, look elsewhere.
That was my experience - I owned electric for several years, and they were cool and all, but the range was limited. As my riding strength slowly rose, I found that I didn't want an engine that turned into a heavy passenger about 25km into the trip. I sold both my e-bikes and got a normal pushbike and my god was it suddenly a whole lot more useful, the range was easily doubled for the same effort, and the bike was a lot cheaper.
However, pursuant to this thread, I have thought for quite some time that a solution in which the bike used capacitors and regenerative braking, without any other battery at all might still be an improvement on the basic pushbike, at least in my location, which is quite hilly. Here's my reasoning:
It's about smoothing the pedaling required. Human pedaling is efficient in a narrow power band. Hills kill this, after a certain point, a certain steepness. The capacitor only needs to be able to store enough for one hill climb - the largest hill on your route. Energy is then recaptured on the downhill (during which you continue pedaling), and whatever the energy shortfall is, is then gradually recaptured at a very low rate along any flats. Once the cap is full, the recharging drag can be dropped. So the rider doesn't stop pedaling at any point, but because they spend less time at the most inefficient range for the human body, their overall personal energy expenditure is less, and so their effective range and probably average speed too, are improved. The ride is also considerably more comfortable. And the bike has no range limits at all, nor would it ever need recharging (although a recharger would obviously be possible, and you would probably top it up when you got to any resting point, if a power socket was available, which would take a very short amount of time).
I know that the drag and weight losses in this setup are not insignificant - my thinking, however, is that in making the use of the human engine more efficient, the gains might outweigh the losses. The style of riding would probably change a lot - you would come down hills slower, and go up them faster. Which is a safer way to ride, considering the pathetic traction that pushbikes have. One of the main reasons to blast down a hill (other than that it feels awesome and scary) is to build up kinetic energy that you can use on the flat or going up the hill on the other side. But this is quite a wasteful method of energy storage, the wind resistance very quickly balances out all of the potential energy gains. I'd envisage a rider cresting a hill with a depleted cap, switching the thing into aggressive recharge mode, and coming off the top of the hill at no more than average riding speed on the flat, pedaling as they go, until the cap is full (at which point they might as well turn off recharging and maximize the kinetic energy (and save time) by letting the bike reach top speed).
Obviously this setup would not be beneficial on flat terrain, it would really only be extra weight, unless you were going short distances and recharging, or if headwinds were a problem (consider the headwind to be the uphill and the tailwind to be downhill, and similar effort reductions might result, but only for short trips there and back, or ones that zigzag the wind (like a postman might be making)).
I don't know if this would be more efficient than just having an appropriately wide gear ratio for the bike. That's an obvious choice if you have hills that are seriously steep, it's light and cheap. But it doesn't get around the fluctuating speed you get in hilly terrain, with the big energy losses reached at top speed. Essentially I'm describing a bike that strikes me as could be useful in my town, Auckland, for average sized commutes. I would find value in a bike that could climb Queen St once (about 90 meters), with me assisting at a steady output. I'm thinking there are a lot of hilly towns where a similar bike would be useful - San Fransisco, maybe?
No real idea if this idea is viable, if the weight and conversion losses outweigh the human efficiency improvement. Gut feel is that it would depend on the terrain, and the human. A strong rider would laugh at the very thought of missing out on a nice hill climb and the chance to have their heart hit 200bpm. A commuter might like not having to change clothes.
