Remember those "bottle"-type dynamos that rubbed against the side of your bike tire in order to power the lights? Well, they've gotten a high-tech makeover, in the form of the fork-mounted CadenceX generator – its creators say that it can replace the batteries currently needed for all bicycle electronics.
Created by Chicago-based startup PedalCell, the device features a rubber-edged wheel that spins as it presses lightly against the bike's front wheel rim. That spinning motion generates electricity, which is sent via wiring to a capacitor-equipped handlebar-mounted Smart Power Hub. That hub in turn regulates the current, feeding it out stably and consistently (again via wires) regardless of cycling speed.
Delivering a maximum of 20 watts, CadenceX isn't intended to power electric bikes' motors, but it could reportedly power just about any other bicycle-mounted electronic device – these could include lights, electronic shifting systems, phone chargers, cycling computers or actioncams. Additionally, because the capacitor stores a limited amount of power, those devices are able to keep running when the bike is stopped for short periods.
The generator's wheel does create some drag as it spins, although thanks to built-in sensors that detect the acceleration, speed and inclination of the bike, the resistance of that wheel is automatically turned down when the rider is travelling at slow speeds or climbing hills, and it's increased when they're braking.
Plans call for CadenceX to either be factory-integrated into third-party manufacturer's bikes (utilizing internal wiring), or to be retrofitted onto existing "fleet" bikes – it won't be available directly to consumers. The embedded version reportedly weighs about 270 grams, while the add-on system tips the scales at around 320 g.
And yes, you're right, bottle dynamos do still exist – according to PedalCell, however, their current typically isn't regulated, resulting in uneven power delivery. Wheel hub-integrated dynamos can also be used to run devices such as lights, but the company claims that its system generates much more power due to the fact that the rim spins monumentally faster than the hub. Additionally, unlike a hub dynamo, the CadenceX generator can be decoupled to eliminate drag when no power is needed.
PedalCell COO Adam Hokin tells us that the system will be included in a third-party e-bike launching this summer (Northern Hemisphere), with other partnerships following later this year and into 2020.
Source: PedalCell
If the company really says that, they don't understand a lot about how electricity or generators work. It may be easier and lighter to make the rim-driven version, but the amount of power available to the generator from your legs is going to be the same.
Adam here (COO of PedalCell). You bring up some excellent points. Power is power, and we aren't breaking the laws of physics (at least not yet). All power, no matter if it is captured via a hub or rim, is going to come from a rider's legs. The tricky bit comes into how can you produce high amounts of power from a rider's motion in a small, manageable package.
Why? There is a physical "power per rpm" constant that motors and generators abide by, leading to significant weight disadvantages to create a hub with a high standard of power. Essentially there's a spectrum; on one end you have small, low power generators, and the other are bulky high power generator behemoths. Finding the right mix between the two took years of generator winding and case design. A rim installation provided us a mechanical advantage to get a smaller generator to spin faster, thus increasing our power without much sacrifice in mass.
For a prime example, Neco's 3 phase hub (http://tinyurl.com/yx8rngjc) weighs 900+g yet only generates 2W at 20 km/h, 4X the weight with 1/7th the power of CadenceX.
Ultimately, we landed on a package that reached peak efficiency and high-power output at traditional riding speeds while maintaining a size that wouldn't hinder adoption within the cycling industry.
So, could you have a hub that creates power akin to CadenceX? Sure. Would it be practical from design, engineering, and packaging perspective? Most likely not.
It's also worth noting that none of this matters without smart power management electronics to make the generator's energy consistent, usable, and safe as well as minimize drag. Most other dynamos do not take advantage of such a system.
Hope this was helpful :)