Almost all means of transportation are developing in terms of speed nowadays. Trains are becoming faster and faster, car manufacturers are competing with each other in order to determine which car accelerates better, etc. Probably the fiercest competition can be seen during Formula 1 race. A normal speed exceeds 300 km/h. Although, the racing track is not straight. So racers have to use brakes and steering wheels so that they can do pivots. And sometimes the speed should be reduced from 320 km/h to 120 km/h in a second so as not to make a car crash into the wall during the turn. Afterward, the car needs a rapid acceleration. For this purpose, KERS is used. KERS is a Kinetic Energy Recovery System.
Kinetic Energy Recovery System (KERS) is used for immediate recovery of the kinetic energy of a vehicle during rapid braking. The recovered energy is stored in a special reservoir for further use while accelerating, as a rule. The capacity of these reservoirs allows them to store up to 120 kilowatts for later purposes.
The process is quite complicated and it is impossible to understand it without specific knowledge. But the diagram reveals the basic principle of the KERS. Definitely, the most important stage is the second one. The technology converts kinetic energy into an electric one. The reason why this should be done is that kinetic energy can not be stored and used as well, of course. The next step is to make a Direct Current (DC) from Alternating Current (AC). Basically, the purpose is that DC power has higher efficiency and size to power characteristics. The Storage stage implies collecting this energy. Afterward, it can be used by pushing a button on the wheel. Energy is discharged what adds more power to the engine.
This technology is not so widely spread. However, scientists try to implement it in various fields. It has performed successfully during F1 races and now KERS is being tested on trams, motorbikes, bicycles, and trains.
https://en.wikipedia.org/wiki/Kinetic_energy_recovery_system
https://www.racecar-engineering.com/articles/the-basics-of-f1-kers/