# Overview of Clean Automotive Thermal Propulsion Options for India to 2030
## 2 The Current and Future Technological State-of-the-Art
### Advanced Internal Combustion Engine Solutions for Near Zero Emissions
#### 2.4.6 Regenerative Braking  
This technology was invented back in 1886 to convert kinetic energy into electric energy and store it in batteries or super-capacitors. The modern form of regenerative braking such as the Kinetic Energy Recovery System (KERS) uses the same principle to capture the kinetic energy from braking. KERS is being widely researched and implemented in hybrid and electric powertrain vehicles. It is successfully implemented in F1 and LMP1-H hybrid cars.  
A new concept developed, known as electric KERS can store energy and provide it back to other systems by being connected to traction batteries or other electronics such as an electric turbocharger or an electric pump in the engine [43]. The technology of KERS was introduced in Formula 1 during the 2011 season and was mandated by the FIA in all the cars [44]. As per [43], most of the F1 and LMP1 hybrid-powertrain car companies such as Toyota and Porsche have shown a deep interest in harvesting the energy in every way possible.  
Vehicles implementing this type of technology are more fuel-efficient and the fuel consumption reduction can reach 30-50% by a regenerative braking technology in any hybrid electric vehicle [45]. The technology is integrated with the powertrain of hybrid and electric cars such as Toyota Prius and Nissan Leaf. In passenger vehicles, there are very low accelerations and implementing KERS does not put any constraint on driving style. KERS has been integrated with petrol-powered engines in large-sized sedans to provide improvements in fuel economy of about 20-25% and improvements in fuel consumption may be achieved by coupling KERS in smaller diesel turbocharged engines [46]. The author stated that the results of the car fuel economy on the New European Driving Cycle validated vehicle model with a 1.6 L turbocharged direction injection engine which would normally require 0.0.35 kg of fuel to cover full cycle (4.7 L/100 km in urban sector cycle and 3.8 L/100 km in full cycle), required 3.5 L/100 km (0.12 kg) of fuel to cover the urban cycle and 3.2 L/100 km (0.29 kg) of fuel to cover full cycle, improving fuel efficiency by 25% and 17%, respectively. Therefore, it was concluded that KERS implemented with the high-speed flywheel with a CVT concept permits efficient regenerative braking and torque through considerable improvements in fuel efficiency, consequently reducing fuel consumption and CO\({}_{2}\) emissions. [PERSON] et al [47] suggests a fuel efficiency improvement of 29.4% in the rural driving cycle and 51.7% in urban conditions by implementing regenerative braking technology.  
For road commercial heavy goods vehicles, claimed reduction of fuel consumption and CO\({}_{2}\) by 15-25% have been published [48]. A case in India where regenerative braking is being implemented at the Delhi metro, which became the first rail project in the world to receive 0.4 million tonnes of carbon credits for the consecutive period of ten years from 2007 to 2017. By implementing regenerative braking in locomotives, the Delhi Metro was able to lower its energy usage by approximately 30% [49].