This is the unspecified version of the paper.This version of the publication may differ from the final published version. Permanent repository link AbstractHybrid vehicles of different configurations and utilizing different energy storage systems have existed in development for many decades and more recently in limited production. They can be grouped as parallel, series or complex hybrids. Another classification is micro, mild and full hybrids which makes the distinction on the basis of functionality. The common energy storage systems in hybrid vehicles are batteries, supercapacitors and high speed flywheels. This paper aims to review a specific type of hybrid vehicle which involves the internal combustion engine (ICE) as the prime mover and the high speed flywheel as an energy storage device. Such hybrids are now attracting considerable interest given their potential for low cost. It is hence timely to produce a review of research and development in this subject. The flywheel is coupled to the drive line with a continuous variable transmission (CVT). The CVT can be of various types such as electrical, hydraulic or mechanical but usually in this case it is a non-electrical one. Different configurations are possible and the paper provides a timeline of the development of such powertrains with various examples. These types of hybrid vehicles have existed as prototypes for many decades and the authors believe that their development has reached levels where they can be considered serious contenders for production vehicles.

This is the published version of the paper.This version of the publication may differ from the final published version. Permanent repository link AbstractThe development of battery electric vehicles (BEV) must continue since this can lead us towards a zero emission transport system. There has been an advent of the production BEVs in recent years; however their low range and high cost still remain the two important drawbacks. The battery is the element which strongly affects the cost and range of the BEV. The batteries offer either high specific power or high specific energy but not both. To provide the BEVs with the characteristic to compete with conventional vehicles it is beneficial to hybridize the energy storage combining a high energy battery with a high power source. This shields the battery from peak currents and improves its capacity and life. There are various devices which could qualify as a secondary storage system for the BEV such as high power battery, supercapacitor and high speed flywheel (FW). This paper aims to review a specific type of hybridisation of energy storage which combines batteries and high speed flywheels. The flywheel has been used as a secondary energy system in BEVs from the early 1970s when the oil crises triggered an interest in BEVs. Since the last decade the interest in flywheels has strengthened and their application in the kinetic energy recovery system (KERS) in Formula 1 has further bolstered the case for flywheels. With a number of automotive manufacturers getting involved in developing flywheels for road applications, the authors believe commercial flywheel based powertrains are likely to be seen in the near future. It is hence timely to produce a review of research and development in the area of flywheel assisted BEVs.

Energy storage devices are an essential part of hybrid and electric vehicles. The most commonly used ones are batteries, ultra capacitors and high speed flywheels. Among these, the flywheel is the only device that keeps the energy stored in the same form as the moving vehicle, i.e. mechanical energy. In order to connect the flywheel with the vehicle drive line, a suitable means is needed which would allow the flywheel to vary its speed continuously, in other words a continuously variable transmission (CVT) is needed. To improve the efficiency and speed ratio range of the variators, a power spilt CVT (PSCVT) can be employed. This paper discusses the kinematics of PSCVT used to connect the flywheel to the driveline. A methodology describing the characteristic equations of speed ratio, power flow and efficiency of the PSCVT for various types including power recirculating and multi regime in both directions of power flow has been presented. An example of a PSCVT for a flywheel energy storage system (FESS) is computed using the derived equations and the results compared.

One of the primary features of a micro-hybrid vehicle is the automatic shutdown and restart of the engine to avoid engine idling when the vehicle is at rest. The system strategy and its calibration have important significance for the driveability of the vehicle in terms of the vehicle launch behaviour.An unsatisfactory vehicle launch is defined as an inferior launch performance of the vehicle resulting in a stalled engine, a launch with negative vehicle acceleration, and an aborted engine restart due to the inability of the vehicle to provide torque as demanded by the user. In this research, micro-hybrid system optimization for reduction in the percentage of impaired vehicle launch events in real-world usage has been conducted on a start-stop vehicle. The design for the six-sigma process was followed for the optimization study. A high-fidelity electrical and powertrain system and a longitudinal vehicle dynamics model for a start-stop vehicle have been developed. The model has been validated with experimental data. The drivers' behaviour for vehicle launch events from a customer clinic of start-stop vehicles has been used as an input to the model. Using design of experiments, the system has been optimized to maximize the percentage of successful launch events in real-world usage.

Citation: Dhand, A. and Pullen, K. R. (2013). Simulation based study of battery electric vehicle performance in real world cycles. International Journal of Electric and Hybrid Vehicles, 5(4), pp. 327-343. doi: 10.1504/IJEHV.2013.059372 This is the unspecified version of the paper.This version of the publication may differ from the final published version. Permanent AbstractThe development of battery electric vehicles (BEV) must continue since this offers the leading route towards a zero emission transport system. The fuel flexibility of the BEV offers the greatest potential to utilize power from renewable or low emission sources to be used in the transport system. However the limited range and high cost of the BEV remain important issues to be addressed. The battery is the element which strongly affects the cost and range of the BEV. The batteries offer either high specific power or high specific energy, but not both. This paper presents the modelling of a BEV which is used to study the potential for improvement in its energy efficiency. The battery model types have been discussed. The vehicle and other component models have been described. The choice of model parameters and the control strategy has been explained. The simulations have been performed on homologation and real world cycles for different scenarios. Results show significant potential for improvement in the energy efficiency of the BEV in real world usage by the utilization of a secondary energy storage device.