An analysis of kinetic energy recovery systems and their potential for contemporary internal combustion engine powered vehicles

The Internal Combustion Engine has played an incomprehensible role in contemporary society ever since its invention. Oil shortages will almost certainly eventually lead towards a search for propulsion from renewable sources, but for the time being there is no sign of any significant alternative for everyday transport. Any product that offers a fuel economy improvement is of benefit to both the individual and the environment. As vehicles speed up, they convert stored energy into kinetic energy. As the mass or velocity increases, the kinetic energy will also increase. It is for this reason that light commercial vehicles on our roads have so much kinetic energy when travelling at speed. The concept of being able to recover this energy when braking is the foundation for regenerative braking or Kinetic Energy Recovery. The energy captured is then stored to be used in the future: in most cases it is converted back into kinetic energy to bring the vehicle back to speed. The technology is particularly effective in drive cycles consisting of frequent stop-start driving. This project seeks to investigate the feasibility of a mechanical Kinetic Energy Recovery System for implementation via a retrofit on existing light commercial vehicles. In order to be effective, the system must be cost effective and easy to implement. The objective was to design a system able to be fitted to a large number of vehicle platforms and with a reasonable payback period. A literature review was carried out to discern the most appropriate system for light commercial vehicles. Existing systems were analysed and their benefit was appraised from a retrofit stance. A flywheel system was chosen due to its recent success in F1 and its very high energy density amongst other factors. A system was designed to be fitted to a representative vehicle, with potential to be fitted to other platforms. The theory of operation, driveline configuration and attachment options were developed. The system was modelled in Creo and a Matlab code was developed to calculate the potential fuel savings under different circumstances using drive cycles. The dissertation found that the technology was conceptually viable. A vehicle of mass 2680kg with load would save $0.91 per 100km (6.9% saving). If the vehicle were fully laden, the fuel saving would be $1.64 per 100km (7.6% saving). The total cost of the system was found to be $2680. The repayment period ranged from 5-8years to a best case scenario of 3-4 years