Kinetic Energy Recovery System Research Articles

Determination of optimal characteristics of braking energy recovery system in vehicles operating in urban conditions

The results of the research presented in this article characterize the influence of various factors on the current processes of the kinetic energy recovery system (KERS) for recovering kinetic energy of vehicles with electromechanical or electric drive (hybrid and electric cars) under braking. The article presents the basic limits of variations in accelerations and initial speeds during braking in urban traffic using WLTC (Worldwide harmonized Light-duty vehicles Test Cycles) as an example. Relationships affecting braking recovery are identified, which makes it possible to determine the power of the braking forces acting on a vehicle. Relationships between the initial braking speed, acceleration of deceleration, and recovery power are determined based on the relationships between the propulsion power and energy analysis. The resulting field of values for changes in regenerative braking power allows us to get an idea of the characteristics of KERS elements. The presented diagram describing changes in the maximum braking force power depending on the initial speed and acceleration of deceleration of a vehicle provides an insight into the possible ranges of the effective operation of the energy recovery system. As a result of a theoretical experiment, it was established that the vehicle mass affects the maximum power of regenerative braking. Based on the results of theoretical research, it is possible to determine the maximum current and power absorbed by an electric energy storage unit. The obtained relationship between the speed and acceleration in the process of active deceleration allows us to get an idea of the possible modes of charging the electric energy storage unit. Tests in road conditions, conducted with the use of several types of vehicles and test models with a hybrid engine, confirm the results of the research. The approaches presented in this article and the obtained results are indicative of the regularities of regenerative braking in vehicles operated in the road network, which makes it possible to select the optimal characteristics of an electric propulsion drive and ensure high fuel energy and environmental efficiency of vehicles at a minimum cost.

A regenerative braking system for internal combustion engine vehicles using supercapacitors as energy storage elements - Part 1: System analysis and modelling

In this two-part work, an electric kinetic energy recovery system (e-KERS) for internal combustion engine vehicle (ICEV) is presented, and its performance evaluated through numerical simulations. The KERS proposed is based on the use of a supercapacitor as energy storage, interfaced to a brushless machine through a properly designed power converter. In part 1, the system is described and analysed, and the mathematical model used for the simulations is presented. For each component of the KERS, the real efficiency, and the power or energy limitations are adequately considered. In part 2, the energetic and economic advantages attainable by the proposed KERS are evaluated using MATLAB Simulink, considering a widely diffused passenger car and two reference driving cycles (ECE-15 and Artemis Urban). Energy savings of the order of 20% were found, with a slight increase in vehicle weight (+2%) and with an overall commercial cost that would be compensated in 5 years thanks to the fuel economy improvement, to which corresponds an equal reduction of CO2 emissions. The low complexity of the system, never proposed for ICEV, the moderate weight of its components, and their availability on the market, make the solution presented ready for the introduction in current vehicle production.

A regenerative braking system for internal combustion engine vehicles using supercapacitors as energy storage elements - Part 2: Simulation results

In this two-part work, an electric kinetic energy recovery system (e-KERS) for internal combustion engine vehicle (ICEV) is presented and its performance evaluated through numerical simulations. The KERS proposed is based on the use of a supercapacitor as energy storage, interfaced to a brushless machine through a properly designed power converter. In Part 1, the system is described and analysed, and the mathematical model used for the simulations is presented. For each component of the KERS, the real efficiency and the power or energy limitations are adequately considered. In Part 2, the energetic and economic advantages attainable by the proposed KERS are evaluated using MATLAB Simulink, considering a widely diffused passenger car and two reference driving cycles (ECE-15 and Artemis urban). Energy savings of the order of 20% were found, with a slight increase in vehicle weight (+2%) and with an overall commercial cost that would be compensated in 5 years thanks to the fuel economy improvement, to which corresponds an equal reduction of CO2 emissions. The low complexity of the system, never proposed for ICEV, the moderate weight of its components, and their availability on the market, make the solution presented ready for the introduction in current vehicle production.

Development of a Kinetic Energy Recovery System Using an Active Electromagnetic Slip Coupling

The active electromagnetic slip coupling kinetic energy recovery system (KERS), introduced in this paper, is potentially a cost effective, yet efficient method of energy transfer between a vehicle and a lightweight flywheel. The transferred torque, as well as the coupling status, is determined by controlling its windings currents. The proposed system can work at any slip safely, including negative and positive values, between the primary and the secondary shafts as the slip power is converted into electrical power, and thus can be recovered. The proposed KERS may be less costly and less complicated than flywheel batteries as it needs only one electric machine and one power electronic converter. Moreover, it is capable of capturing much more mechanical power than its electrical ratings. Furthermore, since a great part of the energy exchange takes place in mechanical form, only a fraction of the captured energy needs to be processed by the power electronic converter. In this paper, mathematical modeling and simulations are performed using the space vector modeling method. Also, for the proof of the concept prototype of the system has been built, tested, and the results are verified.

Electro-Mechanical EV Powertrain With Reduced Volt-Ampere Rating

Transmotor-based flywheel energy exchange is a low-cost yet highly efficient method of energy transfer between vehicle wheels and a lightweight flywheel. This method utilizes one dual-rotor electric machine that enables us to overcome some of the shortcomings of the conventional electric kinetic energy recovery systems (KERS).The proposed system is capable of capturing far more mechanical power than its electrical power ratings. Furthermore, since a significant part of the energy exchange takes place in mechanical form, only a small fraction of the initial kinetic energy needs to be processed by the electrical energy storage device and the power electronic drive system. In this paper, the proposed Transmotor-based KERS has been compared with the conventional electric KERS. Mathematical modeling and simulations were performed using a space vector modeling method for both conventional electric KERS and the proposed system. Results show that the proposed system is capable of capturing a great part of kinetic energy of a vehicle during deceleration and storing it in a lightweight flywheel to be used for the next acceleration while keeping the electrical ratings of the KERS relatively low. Experimental results are also presented for the proof of the concept.

Control Algorithm for Non-isolated Supercapacitor Based Kinetic Energy Recovery System

Control Algorithm for Non-isolated Supercapacitor Based Kinetic Energy Recovery System

Novel Design of Flat Spiral Spring based Regenerative Braking System

Objectives: In this paper, design of the mechanical system and the kinematic analysis of the regenerative braking have been presented. The mechanism has been proposed to store brake energy in a spiral spring and release it back to the vehicle transmission. Methods/Statistical Analysis: First, the mechanism was modelled in Autodesk Inventor software package and the model then imported to Solid-Works Motion for kinematic analysis. The kinematic simulation was carried out for all the three modes of operation, viz. the idle mode, braking mode and the energy recovery mode. The analysis results were as per the desired output. Once the model was established, the individual components were transferred to ANSYS Static Structural to evaluate and optimize the design. Finally, the spiral spring being the main energy storing device was analyzed for variation in moment and deflection with its thickness and width. Findings: This concept of low-cost Kinetic Energy Recovery System (KERS) can store energy that is lost during braking in a spiral spring and release it smoothly to the vehicle whenever required. The paper presents the simple and lucid design of the mechanism that uses the combinations of planetary gear and one-way clutch. The system can be implemented on bicycle where use of other energy recovery techniques is restricted due to their various limitations. A sample calculation on amount of energy to be stored has been performed to find out the spring parameters so that the calculation can be replicated and the system can be customized for each vehicle. Application/Improvements: The designed setup is flexible and can be installed with ease on a wheel hub. This system will assist the driver during acceleration and thus will improve the overall performance of the vehicle. Keywords: Energy Harvesting, Flat Spiral Spring, Mechanism Design, Mechanical KERS, Regenerative Braking System

Analytical study on different blade-shape design of HAWT for wasted kinetic energy recovery system (WKERS)

Wasted kinetic energy recovery system (WKERS) is a wind renewable gadget installed above a cooling tower outlet to harvest the discharged wind for electrical regeneration purpose. The previous WKERS is operated by a horizontal axis wind turbine (HAWT) with delta blade design but the performance is still not at the optimum level. Perhaps, a better blade-shape design should be determined to obtain the optimal performance, as it is believed that the blade-shape design plays a critical role in HAWT. Hence, to determine a better blade-shape design for a new generation of WKERS, elliptical blade, swept blade and NREL Phase IV blade are selected for this benchmarking process. NREL Phase IV blade is a modern HAWT’s blade design by National Renewable Energy Laboratory (NREL) research lab. During the process of benchmarking, Computational Fluid Dynamics (CFD) analysis was ran by using SolidWorks design software, where all the designs are simulated with linear flow simulation. The wind speed in the simulation is set at 10.0 m/s, which is compatible with the average wind speed produced by a standard size cooling tower. The result is obtained by flow trajectories of air motion, surface plot and cut plot of the applied blade-shape. Besides, the aspect ratio of each blade is calculated and included as one of the reference in the comparison. Hence, the final selection of the best blade-shape design will bring to the new generation of WKERS.

Reaction Wheel Actuation for Improving Planar Biped Walking Efficiency

Reaction wheel systems (RWSs) are beneficial in improving bipedal walking stability, and theoretical work has shown that they can also improve the efficiency of preplanned walking motions. This work provides the first demonstration of RWS-related efficiency improvements on a physical robot and identifies the energy-saving paradigm. Gaits for a five-link planar biped are generated via trajectory optimization with and without reaction wheels. Comparisons of the resulting system behavior show a 5–10% efficiency advantage for robots with an RWS under typical walking conditions and a larger advantage near regions of marginal dynamic feasibility. The savings are mainly accomplished by enabling trajectories with better joint motor utilization, not by minimizing impact losses or acting as a kinetic energy recovery system. The RWS also improves centroidal angular momentum regulation, with the reduction in centroidal angular momentum amplitude reaching 30% at high speeds. Simulations and experiments with a five-link planar biped validate the efficiency improvements seen in optimization. This demonstrates the viability of using efficient inertial actuators to improve the efficiency of complex walking robots.

Kinetic Energy Recovery System in a Bus Application

Kinetic Energy Recovery System in a Bus Application

Kinetic energy recovery systems in motor vehicles

The article draws attention to the increasing environmental pollution caused by the development of vehicle transport and motorization. Different types of design solutions used in vehicles for the reduction of fuel consumption, and thereby emission of toxic gasses into the atmosphere, were specified. Historical design solutions concerning energy recovery devices in mechanical vehicles which used flywheels to accumulate kinetic energy were shown. Developmental tendencies in the area of vehicle manufacturing in the form of hybrid electric and electric devices were discussed. Furthermore, designs of energy recovery devices with electrical energy storage from the vehicle braking and shock absorbing systems were presented. A mechanical energy storing device using a flywheel operating under vacuum was presented, as were advantages and disadvantages of both systems, the limitations they impose on individual constructions and safety issues. The paper also discusses a design concept of an energy recovery device in mechanical vehicles which uses torsion springs as the main components of energy accumulation during braking. The desirability of a cooperation of both the mechanical- and electrical energy recovery devices was indicated.

Characterisation of vibration input to flywheel used on urban bus

Vibration induced from road surface has an impact on the durability and reliability of electrical and mechanical components attached on the vehicle. There is little research published relevant to the durability assessment of a flywheel energy recovery system installed on city and district buses. Relevant international standards and legislations were reviewed and large discrepancy was found among them, in addition, there are no standards exclusively developed for kinetic energy recovery systems on vehicles. This paper describes the experimentation of assessment of road surface vibration input to the flywheel on a bus as obtained at the MIRA Proving Ground. Power density spectra have been developed based on the raw data obtained during the experimentation. Validation of this model will be carried out using accelerated life time tests that will be carried out on a shaker rig using an accumulated profile based on the theory of fatigue damage equivalence in time and frequency domain aligned with the model predictions.

The Creation of Mechatronic Recovery Energy System for Mobile Machines

This paper describes general approach for creation the effective kinetic energy recovery system in mobile machines using flywheels. It’s should be a mechatronic system. The system with accelerometer-gyroscope and proportional, integral and differential controller (PID-regulator) is proposed as example of automatic control.

Design and Analysis of Kinetic Energy Recovery System in Green Energy Vehicle

Design and Analysis of Kinetic Energy Recovery System in Green Energy Vehicle

GASTONE – Development of a New Powertrain Concept Based on the Integration of Electric Generation, Energy Recovery and Storage

The new challenge in the reduction of CO2 emissions by heavy duty trucks is leading to a technological evolution in powertrain efficiency.Towards this objective, the EU has funded in the frame of the 7th framework program the project GASTONE: a collaborative project between several private and public companies and institutions: CRF, FTP, Continental, GENTHERM, MAGNA and U. Politécnica de Valencia, targeting the development of a new powertrain concept based on the integration of electric generation, energy recovery and storage with engine system and control strategies.The main features of this CNG engine concept are:•The energy recovery from the exhaust gases heat with a cascade approach thanks to the adoption of an advanced thermoelectric generator and a turbo-generator.•The integration of a smart kinetic energy recovery system to substitute the alternator with a smarter electrical machine.•The electrification of the main auxiliaries (coolant and oil pumps, auxiliary e-supercharger and air conditioning compressor).The electrification process is supported by an improvement of the performance of the CNG engine (the actual average value is about 38%): this number is expected to rise by 4% thanks to the engine control strategy improvement, by 1% due to the introduction of the water charge air cooler, by 2% from the reduction of the belt drive and gear losses, by 1% from the system strategy and management optimization and by 7% from the exhaust heat recovery (thermo-electric generator plus turbo-generator).This paper presents the details of the new powertrain concept design, the simulation tool developed to support the design and optimize the system and a cost per function tool to perform an economic analysis in the hypothesis to introduce the system in the market.The obtained benefits are expressed in terms of fuel saving for a target real driving cycle and effects related to the new devices are developed and tested.The project is in the design phase and the paper collects a first estimation of results based on the design, strategy and control improvement.

Projects in a nutshell

Efficient and functional – air-cooled drive unit | Portable fuel cell turns diesel into electric power | Kinetic Energy Recovery System for road haulage | A novel aircraft with many capabilities | Galileo Online: GO! | New high energy density automotive battery system

Optimal Gear Ratio Planning for Flywheel-Based Kinetic Energy Recovery Systems in Motor Vehicles

An efficient computational methodology is proposed for optimal gear ratio planning in motor vehicle kinetic energy recovery systems (KERS) using a flywheel and continuously variable transmission (CVT). Initial modeling of a clutch-less KERS, comprising an input wheel, CVT, flywheel, and bearings, shows that the “least effort” or “minimum energy loss” optimal control problem can be formulated in two ways: one being a conventional two-state formulation involving input wheel angular velocity and CVT gear ratio, for which least effort control can be solved in simple cases with Pontryagin's maximum principle. The second formulation involves a single-state CVT gear ratio equation for which the input wheel angular velocity and acceleration appear as unknown time-dependent parameters. A novel multiparameter optimization methodology is proposed using the single-state formulation to find optimal CVT gear ratios by adopting two discrete time scales: one being a small time scale for numerical integration of the model, and the second involving discrete transitions, hundreds of times larger. Using Chebyshev polynomial expansions (CPEs) to initially generate sets of zero-energy-loss least effort kinematics for use as the time-dependent parameters in the CVT gear ratio equation, two solution approaches are developed. The first involves a single large discrete time transition, which only requires discretization of the input wheel angular acceleration at the start and end-of-transition. The second approach involves multiple large-scale discrete time transitions as a generalization of the first, but additionally needing discretization of the input wheel angular velocity, and the CVT gear ratio, plus dynamic programming to find the optimum. Both approaches are tested using the clutchless KERS model by assuming a “super CVT” gear ratio range (but with no restrictions for use with slipping clutches). Comparison with least effort control via Pontryagin's maximum principle shows that the single transition approach is in practice far superior. The single transition approach is then used to compare a minimum energy loss clutchless KERS gear ratio plan, with one obtained using constant input wheel angular acceleration as a benchmark. This comparison, involving power losses throughout the KERS, shows the very clear benefits of adopting an optimal gear ratio plan.

A Deep Dive into Kinetic Energy Recovery Systems — Part II

A Deep Dive into Kinetic Energy Recovery Systems — Part II

A Deep Dive into Kinetic Energy Recovery Systems — Part 1

A Deep Dive into Kinetic Energy Recovery Systems — Part 1

Review of battery electric vehicle propulsion systems incorporating flywheel energy storage

The 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.