Regenerative braking is a method to capture and store the kinetic energy of a moving item, and then be used to reaccelerate it. Regenerative braking is not industry specific, but can be difficult to implement cost effectively. In most application a heavy load must be stopped and started frequently. The action of starting and stopping is controlled to limit power required.
In industrial applications, the acceleration time and the deceleration time is usually easy to determine and microprocessor controlled.
In an automotive drive train application, the braking energy will be much greater than the accelerating energy for a much shorter time.
Electric regenerative braking in industrial applications is not known for being efficient. Generating and storing energy over a wide rpm and torque range is difficult. All systems have an operating voltage. When a generator rpm varies, so does the voltage output. The amperage varies with load. All the variable speed control electronic systems I have looked, at are not averaging much over 80% efficient driving a varying load over their operating speed range. I have not found any data on the efficiency of any regenerative system. In wind power the varying wind speed creates their power generation difficulty, most systems control the speed by varying the prop pitch. Some of the new systems are using power electronics, but the cost and efficiency has not proven to off set the cost of prop pitch control.
The most common application for hydraulic regenerative braking is in hydraulic elevators. Most have a hydraulic cylinder to raise the car, when letting the load down the flow pressure is diverted to accumulators. Hydraulic hybrid drives currently being developed use a swash plate pump/motor and valves to divert the flow and pressure to accumulators. Neither of these systems have great efficiencies base on the calculation I have done.
One of the greatest challenges in regenerative braking is converting low energy inputs to a higher energy level required for peek acceleration power.
For these reasons I do not think current electric or hydraulic hybrids will be a long term winners in saving energy.
In theory if all the kinetic energy could be captured and reused for reacceleration, the only power required for a vehicle is to overcome wind, and rolling resistance and climbing hills.
