Hydrostatic Hybrid Bicycle

Several designs have been proposed on the 'bakery to power a hybrid bicycle with stored energy from batteries, springs, flywheels, or compressed air. I believe the ideal way to make a hybrid bicycle would be to use hydraulic pumps, reservoirs, hoses, valves, and motors to store and manage the power of pedaling.

A small fluid pump would fit between the pedals and provide power to a reservoir integrated into the frame. A system of valves and lines could carry the power to in-hub hydraulic motors for one or two wheel drive. During normal operation, the valves would effectively allow for different gearing for hills and level ground. Going downhill, one could use regenerative braking to store potential energy as hydraulic pressure for later use.

Adding a small moped motor with another hydraulic pump would allow for higher speeds and better hill-climbing ability. With pedalling and the motor combined, it would be possible to store up enough energy for brief runs at highway speeds, or quick bursts of power, depending on how big of a tank was used.

Hydrostatic drive systems have been widely baked on many kinds of construction equipment, so I think it would be relatively easy to scale down to a bicycle. Like construction equipment, you could even run power take-off hoses from your bike to power hydraulic tools and jacks. The system might loose some energy to heat, but this would be made up by the regenerative braking system.