Electric City Research Articles

The Electric City as a Solution to Sustainable Urban Development

ABSTRACTComprehensive frameworks for sustainable urban development have been advanced by many scholars and global institutions in recent years. These frameworks are broad and overlapping in nature, but each has its own structure and emphasis. We review a cross-section of these frameworks, examining their foundations and general predictions for an urban future. From this review, we cultivate an argument that continued progress toward sustainable urban development hinges on low-carbon electrification. Our position for electric cities is supported by the sustainability literature and by empirical evidence gathered from the world's largest cities, which shows that economy, physical environment, and basic service delivery improve with per capita electricity consumption. We close with an overview of the challenges associated with urban electrification.

Crashworthiness Design for an Electric City Car against Side Pole Impact

Electric vehicles are increasingly popular as an alternative to fossil fuel vehicles. The presence of batteries and electric motors poses different risks in collision accidents. The deformation of the batteries could spark a fire or explosion that in turn could endanger the passengers. The prototype of an Indonesian electric city car is currently being developed, which includes a battery pack located underneath the passenger compartment and electric motors in the front compartment. A crashworthiness design against side pole impact, in accordance with the Euro NCAP standard, was simulated numerically. In order to reduce the risk of battery explosion, an impact energy absorbing structure is proposed for implementation at the sides of the batteries. The structure of the four-passenger hatchback electric city car was modeled using all-shell elements with material properties for common automotive application and analyzed using the finite element method with dynamic plasticity capability. For the preliminary design, the minimum deformation of the batteries that can cause battery explosion was used as the failure criteria. From a number of design alternatives, the use of aluminum foam as impact energy absorber produced sufficient protection for the battery pack against side pole impact, hence effectively reducing the risk to an acceptable limit.

Performance Evaluation of a Newly Designed Robotized Gearbox for Electric City Buses

Automated manual transmissions (AMT) play an important role in reducing energy consumption in electric vehicles. However, a major concern that limits the usage of AMTs is their poor gear shifting quality that reduces the driving comfort. In this study, a new pneumatically driven robotized gearbox without clutch and synchronizer is introduced and a gear shifting control scheme is developed for an electric city bus. A six speed manual transmission has been robotized (automated) by using two pneumatic double acting cylinders, four three position double solenoid air control valves and a transmission control unit. The speeds of the electric motor and the output shaft of the gear mechanism are well synchronized during shifting process. Experimental study carried out on a prototype electric bus revealed that the new design improves the gear shifting quality such that the shift speed is quite fast and the shift jerk is within the acceptable. The performance of the proposed gearbox has been also compared with that of fixed ratio gearbox and the comparative test results showed that, thanks to the proposed gearbox system, the electric motor is operated efficiently within rated torque limits and the energy consumption is reduced to a large extent. DOI: http://dx.doi.org/10.5755/j01.mech.23.5.14060

Lifecycle costs and charging requirements of electric buses with different charging methods

Electric city buses and high power charging systems have been rapidly developed in recent years. Battery electric buses are energy efficient and emission free but due to the expensive technology, lifecycle costs can be much higher in comparison to diesel or hybrid buses. This research presents a lifecycle cost analysis for a fleet operation of electric city buses in different operating routes. The objective is to define charging power and battery requirements as well as energy consumption and lifecycle costs. A specific simulation tool was developed to comprehensively evaluate electric buses in different operating conditions. The tool allows to systematically generate and simulate different operating scenarios with a chosen bus configuration, charging method and operating route. Based on the simulation results and predefined cost parameters, lifecycle costs are calculated for each operating scenario. The considered charging methods include overnight, end station and opportunity charging. Simulation results are presented for four operating routes which were measured from existing bus lines in Finland and California, USA. The results show that high energy capacity of the battery system is crucial for the overnight charging buses to achieve adequate daily operation whereas the battery size has a minor impact on the energy consumption and lifecycle costs of the fast charging buses. The lifecycle costs of electric buses are heavily impacted by capital costs including purchase costs of the buses and charging devices. When considering 12 years of service life, the end station charging electric buses can have slightly lower lifecycle costs than diesel buses but on average they have 7% higher lifecycle costs. The overnight charging buses have on average 26% and opportunity charging buses 35% higher lifecycle costs than diesel buses.

Data-driven hierarchical control for online energy management of plug-in hybrid electric city bus

Abstract The pre-determined city bus routes and the availability of partial-trip information obtained through vehicular connectivity provides new opportunities for plug-in vehicles to plan electric energy reasonably. This paper presents a data-driven hierarchical control method for online energy management of plug-in hybrid electric city buses, which can learn from globally optimal solutions based on historical accumulated cycles while taking advantage of connectivity-enabled partial-trip information. The devised scheme comprises two levels of control modules. The upper battery state-of-charge planner trained using historical optimal data is employed for deriving a reference state-of-charge based on the current battery state, remaining trip length, and low/high speed ratios. The lower powertrain controller is then applied to regulate the engine operation according to the reference state-of-charge and powertrain states. This article presents two contributions: (1) both accumulated historical optimal data and partial-trip information are assimilated to augment the applicability of the control hierarchy, thus achieving better resilience to “unseen” driving patterns; (2) given limited resources of micro-controllers, the control strategy is proven to be a real-time implementable, close-to-optimal solution. A variety of results show that the proposed approach can achieve significant fuel savings (4.99%–14.80%) as compared to the charge depleting and charge sustaining strategy.

A distribution density-based methodology for driving data cluster analysis: A case study for an extended-range electric city bus

As each energy source in a multi-energy-source vehicle has its own high-efficient range, the fuel-saving performance of the vehicle is sensitive to driving conditions. In order to improve the vehicle fuel economy, the relationship of fuel consumption and driving condition type is needed to be established clearly as the basis of adaptive energy allocation strategy. This work proposes a two-steps methodology to establish such relationship through clustering micro-trips (which are segmented from driving data and used to indicate driving conditions) with a similar fuel consumption level together. The first step is to construct a fuel consumption-related feature vector by implementing correlation analysis for feature selection and applying principal component analysis for feature dimension reduction. The second step is to cluster micro-trips based on their density centers. This methodology is validated based on the driving data in Beijing, and three types of micro-trips are obtained from these driving data, and their average fuel consumptions are 8.5068, 12.7663 and 17.0686 L/100 km, respectively.

The influence of driving cycle characteristics on the integrated optimization of hybrid energy storage system for electric city buses

This paper analyzes the influence of different driving cycles on the integrated optimization of hybrid energy storage system, including the optimization of supercapacitor size and energy management strategy for the electric vehicle application. The driving cycle is divided into micro-trips, and a fuzzy pattern recognition algorithm is proposed to distinguish different micro-trips within a driving cycle. The intensity factor indicates how intensely the micro-trip drains energy from the hybrid energy storage system. The distribution of each driving cycle is analyzed by the probability density function. The integrated optimization of the hybrid energy storage system is conducted based on four driving cycles. Simulation results show that for different driving cycles, the optimal supercapacitor size and the on-line energy management strategy are directly determined by the maximum intensity factor. The driving cycles with similar maximum intensity factors can use same amount of supercapacitor modules and employ the same on-line energy management strategy. Therefore, the optimization results can be easily generalized to practical bus lines.

Optimization of Battery Capacity Decay for Semi-Active Hybrid Energy Storage System Equipped on Electric City Bus

In view of severe changes in temperature during different seasons in cold areas of northern China, the decay of battery capacity of electric vehicles poses a problem. This paper uses an electric bus power system with semi-active hybrid energy storage system (HESS) as the research object and proposes a convex power distribution strategy to optimize the battery current that represents degradation of battery capacity based on the analysis of semi-empirical LiFePO4 battery life decline model. Simulation results show that, at a room temperature of 25 °C, during a daily trip organized by the Harbin City Driving Cycle including four cycle lines and four charging phases, the percentage of battery degradation was 9.6 × 10−3%. According to the average temperature of different months in Harbin, the percentage of battery degradation of the power distribution strategy proposed in this paper is 3.15% in one year; the electric bus can operate for 6.4 years until its capacity reduces to 80% of its initial value, and it can operate for 0.51 year more than the rule-based power distribution strategy.

Piecewise tracking energy optimization approach for an extended-range electric city bus

Piecewise tracking energy optimization approach for an extended-range electric city bus

Social benefit analysis of reduced noise from electrical city buses in Gothenburg

The city of Gothenburg is the second largest city in Sweden and has an ambitious traffic strategy to increase the share of public transport substantially until 2035. At the same time the city is growing due to urbanization and the densification of the city leads to an anticipated growth in city bus traffic. However, noise from buses might lead to negative consequences for the citizens and electrical buses could be a way to reduce noise and emissions from the public transport system. In this study a comparison of noise levels and social costs of bus types with different powertrains are presented. Initially, noise emissions from three bus types were measured on a test track. The propulsion noise was extracted and coefficients for the Nord2000 Road prediction model were adapted. The Nord2000 model was used to calculate facade noise levels in the city center, as well as in a smaller focus area. The predicted noise levels were used to calculate health effects according to DALYs, as well as social costs according to ASEK. In addition, indoor maximum noise levels were calculated for typical facade cases based on the measurements. The results show that the largest benefits from electrical buses are obtained during acceleration, for example, at bus stops, and for maximum levels indoors. However, these situations are not taken appropriately into account in current social cost models.The city of Gothenburg is the second largest city in Sweden and has an ambitious traffic strategy to increase the share of public transport substantially until 2035. At the same time the city is growing due to urbanization and the densification of the city leads to an anticipated growth in city bus traffic. However, noise from buses might lead to negative consequences for the citizens and electrical buses could be a way to reduce noise and emissions from the public transport system. In this study a comparison of noise levels and social costs of bus types with different powertrains are presented. Initially, noise emissions from three bus types were measured on a test track. The propulsion noise was extracted and coefficients for the Nord2000 Road prediction model were adapted. The Nord2000 model was used to calculate facade noise levels in the city center, as well as in a smaller focus area. The predicted noise levels were used to calculate health effects according to DALYs, as well as social costs accordi...

Modular body construction for an electric city vehicle

Modular body construction for an electric city vehicle

The role of utilities in developing low carbon, electric megacities

Development of electric cities, with low carbon power supply, is a key strategy for reducing global CO2 emissions. We analyze the role of electric utilities as important actors to catalyze the transition to electric cites, drawing upon data for the world's 27 megacities. Progress towards the ideal electric city is most advanced for Paris, Rio de Janeiro, Sao Paulo and Buenos Aires for low carbon electricity, while Indian megacities have relatively high use of carbon-intensive electricity as a percentage of total energy use. There is wide variety in the structure of markets for electricity provision in megacities, with a dominant, public utility being the most common model. We review literature on electricity sector business models and broadly propose future models dependent on the predominance of locally dispersed generation and the nature of the ownership of the electric grid within the city. Where a high proportion of electricity can be provided by locally distributed supply within a city, the role of utilities could predominantly become that of enabler of exchange with the grid, but new pricing structures are required. A further challenge for utilities in enabling the electric city is to provide a higher level of resilience to events that disrupt power supply.

A Power Planning Algorithm Based on RPL for AMI Wireless Sensor Networks.

The advanced metering infrastructure (AMI) is an architecture for two-way communication between electric, gas and water meters and city utilities. The AMI network is a wireless sensor network that provides communication for metering devices in the neighborhood area of the smart grid. Recently, the applicability of a routing protocol for low-power and lossy networks (RPL) has been considered in AMI networks. Some studies in the literature have pointed out problems with RPL, including sub-optimal path selection and instability. In this paper, we defend the viewpoint that careful planning of the transmission power in wireless RPL networks can significantly reduce the pointed problems. This paper presents a method for planning the transmission power in order to assure that, after convergence, the size of the parent set of the RPL nodes is as close as possible to a predefined size. Another important feature is that all nodes in the parent set offer connectivity through links of similar quality.

Experimental validation of electric bus powertrain model under city driving cycles

Battery electric city bus model has been created and validated with measurement results from a full-scale city bus prototype. The model utilises multi-physics modelling approach with multiple-domains from friction-tyre and transmission model to electrical drive and a simplified battery model. For the electrical drive model, four approaches to model the losses were studied. The modelled and measured motor torque, speed, current in the battery and inverter, and the bus speed were compared under two bus line driving cycles using three payloads. The simulated results were in good agreement with the experimental results; the error between the simulated and measured energy consumptions was 1.5% with the most accurate model.

Energy flow analysis of an electric city bus based on wavelet transform with Mallet prolongation

Summary In this paper, we propose a Haar wavelet with Mallet prolongation energy management strategy, a pure electric city bus produced by CENS Energy Tech Co, Ltd with a hybrid energy storage system that combines a lithium battery with an ultracapacitor is tested and modeled under a MATLAB-CRUISE joint simulation environment based on the experiments. In verifying its validity, the proposed method is compared with the common rule-based control strategy from the charging and discharging characteristics of the battery, the feedback efficiency of the ultracapacitor, and the overall system efficiency during China City Road Cycle. The results show in the proposed method that state of charge of the battery is more stable avoiding from the peak current shock, the battery life has been protected effectively, the ultracapacitor has been utilized more fully, and the vehicle performance is better for the tracking performance and control flexibility than the rule-based control strategy.

Planning a sustainable urban electric power system with considering effects of new energy resources and clean production levels under uncertainty: A case study of Tianjin, China

This study develops a risk-aversion optimization model for an urban electric power system (RAOM-UEPS), taking into account stochastic uncertainties. The RAOM-UEPS can manage stochastic uncertainties and capture associated risks from the stochastic information. This enables managers to analyze the trade-off between system cost and system risk in detail. Then, as a case study, the RAOM-UEPS is applied to the planning of an urban electric power system in Tianjin. Here, three scenarios are considered, each with different proportions of new energy resources and clean production levels (i.e., energy conversion efficiencies). This study aims to develop an urban electric power system (UEPS) optimization model that support the city's transformation from a coal-fired dominated to a low-carbon electric power mix, as well as to promote the sustainable development of society as a whole. The proposed model can facilitate a sophisticated system analysis of energy supply, electric power conversion, capacity expansion, and environment management over multiple periods. The results suggest that coal is dominant in Tianjin's electric power system, which was the primary air-pollutants and CO2 contributor in electric power system. Improving clean production levels and the proportion of new energy resources could effectively save energy resources and mitigate air pollutants and CO2 emissions. These findings can provide a scientific basis for the sustainable development of regional electric power systems, as well as for transformation from coal-dominated to low-carbon electric power cities.

Carbon epoxy front hood for an electrical city vehicle

In the last decade fiber-reinforced polymer (FRP) had a very impressive development. Due to its physical and mechanical properties, this material is used in many high-end domains such as: aerospace, aviation, automotive, medical, engineering or building constructions. In the last period FRP are being intensely used in the automotive industry especially for the chassis manufacturing and other vehicle structural components. In this paper, the authors present the model of a carbon epoxy front hood of a two-passenger electrical car which is specially designed in urban area and which makes use of advanced FRP manufacturing.

Impact of power split configurations on fuel consumption and battery degradation in plug-in hybrid electric city buses

Power split configurations exhibit potential on decreasing fuel consumption. However, how to select the best power split configuration among all the possible configurations still need to be explored. In this paper, a one-dimensional searching ECMS (Equivalent Consumption Minimization Strategy) is developed to evaluate fuel consumption for input power split configuration. Additionally, a battery degradation model based on experimental data is applied to evaluate the battery degradation for input power split configuration. According to one-dimensional searching ECMS and battery degradation model, the impact of different input power split configurations on fuel consumption and battery degradation is investigated. Simulations show that configuration T1 has fuel consumption and battery degradation advantages for PHEV city bus application in China. These advantages are observed because the system efficiency operation points of configuration T1 are closer to the high efficiency area than the system efficiency operation points of other input power split configurations. Furthermore, according to the lever model and one-dimensional searching ECMS method, a power split configuration selection method is provided in this paper. The simulation results based on configuration selection method still indicate that configuration T1 appears to have the best fuel economy for PHEV city bus application. Moreover, configuration T5, with a lever length close to 0, exhibits the worst fuel consumption and battery degradation.

Can Power Be Restored in the Electric City? A Case Study of Scranton, Pennsylvania

Like many former industrial cities, Scranton is struggling. A 75-year population decline has eroded its tax base, and city officials have been unable to control costs — a combination that threatens to bankrupt the city. Scranton was classified as a distressed municipality under Pennsylvania Act 47 in 1992, yet nearly 25 years later its problems remain. This study analyzes the economic, fiscal, and political factors that contributed to Scranton’s decline and that have prevented it from recovering. It is a study in economic and fiscal forensics that provides lessons for other municipalities. We conclude by offering several recommendations to improve Scranton’s finances and economic outlook.

Impact of control strategy on battery degradation for a plug-in hybrid electric city bus in China

Series-parallel Plug-In Hybrid Electric Vehicle combine the advantages of series and parallel configurations and have been used in China. However, battery degradation in series-parallel Plug-In Hybrid Electric city bus applications still need to be investigated. In this paper, a simulation model is developed to simulate a series-parallel Plug-In Hybrid Electric city bus. The simulation model was validated experimentally and shown to agree well with the real system. Additionally, a semi-empirical battery life model was also developed and validated to estimate the battery degradation. According to the simulation model and battery life model, the impact of different control strategies for series-parallel Plug-In Hybrid Electric city buses on battery degradation was investigated. The simulation results showed that series-parallel Plug-In Hybrid Electric city buses with the Maximum Efficiency Control Strategy for series mode and Power Follower Control Strategy for parallel mode reduced battery degradation significantly.