Complete Traction Electric Equipment Sets for Hybrid Buses

Hybrid vehicles are widely used in many cities because of their lower rates of fuel consumption and for environmental initiatives. This paper presents the fuel consumption rate analysis of multiple parallel and series drive train type hybrid buses operating in the City of Edmonton, Alberta, Canada, on different urban routes. Based on an analysis of real time daily bus data, the optimal choice between the different types of hybrid buses for Edmonton Transit System (ETS) urban routes is presented and discussed.

There are lots of studies about hybrid electric vehicles (HEVs) because of the global warming and energy problems. Series and parallel HEVs are the common types of many developing hybrid vehicle types. Series HEV uses engine only as the generator for the battery but parallel HEV utilizes engine for driving and generating of the vehicle. In this paper, backward simulations based on dynamic programming were conducted for the fuel economy analysis of two different types of hybrid transit buses depending on driving cycles. It is shown that there is a relation between the type of HEV and the characteristics of driving cycles. Regarding the aggressiveness, the series hybrid bus is more efficient than the parallel system on highly aggressive driving cycle. On the other hand, the parallel hybrid bus is more efficient than the series system on low aggressive driving cycle. Based on this results of the paper, it is expected to choose more efficient type of the hybrid buses according to the driving cycle.

<div class="htmlview paragraph">This paper presents model-based predictions of the performance of diesel, compressed natural gas (CNG), and hybrid buses on bus routes in the City of San Francisco. The bus route details were obtained by recording time-series measurements of speed and grade during actual runs of buses on the city streets under different traffic conditions. The transit buses' physical and mechanical characteristics were obtained from manufacturers' data and chassis dynamometer testing of the buses on different city cycles. Both the bus routes and the bus performance characteristics were put into the simulation package ADVISOR from the National Renewal Energy Laboratory (NREL).</div> <div class="htmlview paragraph">The most extreme results were for the San Francisco routes that have high grades. The high grades cause performance and emissions problems for both the diesel and CNG buses relative to the hybrid bus. A large portion of the performance and emissions problems can be directly related to the hydraulic torque converter that is currently used on most diesel and CNG city buses. At conditions that are typical of high grades, the hydraulic torque converters have quite poor efficiencies. Since the hybrid bus has a direct electric drive system, it does not suffer the efficiency problems to the same degree as the diesel and CNG buses.</div> <div class="htmlview paragraph">This paper also illustrates that bus performance modeling has reached a stage where it can help city bus systems evaluate bus performance before the buses are put into service. For example, it is expected that global positioning systems (GPS) will provide detailed time, speed, location, and grade information for all the bus routes in typical cities during different times of the day with different traffic conditions. This information can then be used with both old and new specifications for bus technologies to predict performance on the actual routes for which they could be used. In this way, a bus transit system could optimize bus routing assignments to minimize cost and emissions on a wide variety of routes.</div>

Undoubtedly, the issue of increasing the fuel economy of passenger commercial vehicles is one of the most important, since the annual increase in the cost of fuel leads to an increase in the fixed costs of not only transport companies, but also small and medium-sized businesses. Using a hybrid power train (HPT) can reduce fuel consumption in the urban cycle, which is important for commercial vehicles used to deliver goods and passengers within the city, especially when it comes to megacities where traffic is difficult and average speeds are not high. Unfortunately, the cost of cars with a HPT, such as Toyota Prius, Lexus RX 450H, Ford Fusion Hybrid and others, remains quite high and cannot be fully compensated just at the expense of fuel economy.

The electrification of vehicles from the automotive and public transport industries can reduce harmful emissions if implemented correctly, but there is little evidence of whether the electrification of heavy freight transportation vehicles (HFTVs), such as multi-articulated vehicles, used in the freight industry could see the same benefits. This work studied heavy multi-articulated freight vehicles and developed a comparative analysis between electric and conventional diesel power trains to reduce their total emissions. Real-world drive cycle data were obtained from a heavy multi-articulated freight vehicle operating around Melbourne, Australia, with a gross combination mass (GCM) of up to 66,000 kg. Numerical models of the case study freight vehicle were then simulated with diesel, through-the-road parallel (TTRP) hybrid and electric power trains over the five different drive cycles with fuel and energy consumption results quantified. Battery weights were added on top of the real-world operating GCMs to assure the operational payload did not have to be reduced to accommodate the addition of electric power trains. The fuel and energy consumptions were then used to estimate the real-world emissions and compared. The results showed a positive reduction in tailpipe emissions, but total greenhouse emission was worse for operation in Melbourne if batteries were charged off the grid. However, if Melbourne can move towards more renewable energy and change its emission factor for generating electricity down to 0.49 kg CO2-e/kWh, a strong decarbonization could be possible for the Australian road freight industry and could help meet emission reduction targets set out in the 2015 Paris Agreement.

The bond graph method is used to model dynamics of various one-mode and two-mode series-parallel configurations of hybrid electric vehicle power trains. Proper handling of causalities results in minimum-realization models convenient for various simulation, analysis, and control design studies. The same, unified model structure can be used to describe the dynamics of all considered hybrid power trains. Several alternative variants of the power train dynamics model are also derived for various structures of driveline submodel.

In many cities worldwide, modern fleets have been introduced to reduce gaseous and particle emissions from city buses. To date, most emission studies are limited to a few vehicles, making a statistically significant assessment of control options difficult, especially under real-world driving conditions. Exhaust emissions of 234 individual city buses were measured under real-world stop-and-go traffic conditions at a bus stop in Gothenburg, Sweden. The buses comprised models fulfilling Euro III-VI and EEV (Enhanced Environmentally Friendly Vehicle) standards with different engine technologies, fuels, and exhaust after-treatment systems, and also included hybrid-electric buses (HEV). Both gaseous (NOx, CO, HC, and SO2) and size-resolved particle number (PN) and mass (PM) emission factors (EF) were calculated for vehicles using compressed natural gas (CNG), diesel (DSL), Rapeseed Methyl Ester (RME) and Hydro-treated Vegetable Oil (HVO) equipped with various after-treatment technologies, e.g., diesel particulate filter (DPF), selective catalytic reduction (SCR) and exhaust gas recirculation (EGR) systems. The highest median EFPN was obtained from Euro VHEV-HVO-SCR buses (MdEFPN = 18×1014 # kg-1) when their combustion engines were used though 53% of their accelerations were below detection limits indicating the use of their electrical engine. The highest MdEFPM was obtained from the Euro V-DSL-SCR buses (MdEFPM = 150 mg kg-1) and the lowest from EEV-CNG buses (below detection threshold) and Euro VIHEV-HVO- SCR+EGR+DPF buses (MdEFPM = 19 mg kg-1). The highest MdEFNOx was obtained from the Euro V-RME-SCR (MdEFNOx = 30 g kg-1) and Euro VHEV-HVO-SCR buses (MdEFNOx = 24 g kg-1), and the lowest from CNG buses (MdEFNOx = 4.8 g kg-1) and Euro VIHEV-HVO-SCR+EGR+DPF buses (MdEFNOx = 7.4 g kg-1). Hybrid buses can give higher PN emissions compared to traditional diesel engines, likely due to downsized combustion engines. Replacing diesel by biodiesel fuel reduced MdEFPM significantly but increased MdEFNOx which may be due to the higher combustion temperature and oxygen contents of the fuel (for RME). Overall, the EEV-CNG buses performed the best regarding both the MdEF and low contribution to the high emitters. It was also found that a small (5%) proportion of the buses contributed significantly (14-30%) to the total emissions. Identification and monitoring the maintenance of the high emitters in the fleets should be considered for the improvement of air quality.

<div class="section abstract"><div class="htmlview paragraph">Hybrid powertrains are replacing conventional combustion drives at an accelerating rate, while offering a reduction in fuel consumption and toxic exhaust emissions. The large share of hybrid solutions in engine vehicles has been observed for the compact class and in SUVs. The Authors of this study proposed an energy flow assessment in the hybrid powertrain system of an SUV in various driving conditions: urban, extra-urban and motorway. The tests were performed in accordance with the stipulations of the RDC test conditions and its requirements. The tests were carried out on a Toyota RAV4 HEV equipped with a 2.5 dm<sup>3</sup> engine in a hybrid drive system along with Li-Ion batteries, which had an energy capacity of 1.11 kWh (4.3 Ah). The research was carried out on an urban route in Poznan as well as in its vicinity using three drive modes of the drive system: Eco, Normal and Sport. Based on the results of energy flow tests, it was found that, regardless of the initial state of charge (SOC) of battery, the vehicle would reach constant SOC values in the second phase of the test - in the extra-urban driving phase. Such conditions stabilize after about 30 km of urban driving. The differences in the range of these SOC values were around 10%. Due to the conditions of motorway driving, the SOC changes were very small and amounted to about 3-5% while covering about 20 km (in this driving mode). The tests confirmed the slight influence that the driving mode (eco, normal, sport) had on the final measured charge values: for discharge, charging or regeneration. The share of time operating in electric mode for individual test phases was also determined, and it was approximately 65-68%, 25-30% and 5-8% in the urban, extra-urban and motorway phases, respectively.</div></div>

In recent years the interest for electric vehicles is strongly growing. Together with the spreading of private electric vehicles also public transports are using electric buses. Series hybrid buses are often a good choice for reducing pollution, consumptions and to allow short tracks in pure electric mode. In this paper a series hybrid electric bus is described. The bus, realized in the framework of a project financed by the Italian Ministry of Economic Development, is a 12 meters public city bus. For this vehicle the innovation of connecting the storage system directly on the DC bus has been performed. This choice implies the necessity of studying proper control strategies in order to decouple the traction power from the generated power and to increase the efficiency of the diesel generator onboard. In this paper some control strategies are proposed and the results are analyzed by means of numerical simulation.

This paper comparatively examines three different electrochemical energy storage systems (ESSs), i.e., a Li-ion battery pack, a supercapacitor pack, and a dual buffer, for a hybrid bus powertrain operated in Gothenburg, Sweden. Existing studies focus on comparing these ESSs, in terms of either general attributes (e.g., energy density and power density) or their implications to the fuel economy of hybrid vehicles with a heuristic/nonoptimal ESS size and power management strategy. This paper adds four original contributions to the related literature. First, the three ESSs are compared in a framework of simultaneous optimal ESS sizing and energy management, where the ESSs can serve the powertrain in the most cost-effective manner. Second, convex optimization is used to implement the framework, which allows the hybrid powertrain designers/integrators to rapidly and optimally perform integrated ESS selection, sizing, and power management. Third, both hybrid electric vehicle (HEV) and plug-in HEV (PHEV) scenarios for the powertrain are considered, in order to systematically examine how different the ESS requirements are for HEV and PHEV applications. Finally, a sensitivity analysis is carried out to evaluate how price variations of the onboard energy carriers affect the results and conclusions.

Hybrid powertrain technologies are successful in the passenger car market and have been actively developed in recent years. Optimal topology selection, component sizing, and controls are required for competitive hybrid vehicles, as multiple goals must be considered simultaneously: fuel efficiency, emissions, performance, and cost. Most of the previous studies explored these three design dimensions separately. In this paper, two novel frameworks combining these three design dimensions together are presented and compared. One approach is nested optimization which searches through the whole design space exhaustively. The second approach is called enhanced iterative optimization, which executes the topology optimization and component sizing alternately. A case study shows that the later method can converge to the global optimal design generated from the nested optimization, and is much more computationally efficient. In addition, we also address a known issue of optimal designs: their sensitivity to parameters, such as varying vehicle weight, which is a concern especially for the design of hybrid buses. Therefore, the iterative optimization process is applied to design a robust multi-mode hybrid electric bus under different loading scenarios as the final design challenge of this paper.

Heavy-duty vehicles OEMs have an increasing interest in alternative power train solutions. To gain benefits of hybrid power train, proper power bus control must be implemented. Control strategy refers to means necessary to meet duty cycle power demands while maintaining vehicle performance. Cascading controlling strategy division is proposed. Control method layering proposition is presented and control methods are divided into two categories, reactive and predictive methods. Finally these methods are implemented in series hybrid energy system model. Implemented reactive methods are load-based control, voltage-based control, voltage/load hybrid control and peak shaving control. Load data is measured data from electrical power train straddle carrier. One vehicle state predictive control method is implemented. Results are evaluated and discussed.

The public transportation in urban centers involve many challenges related to environment. One of these challenges is reduce air and noise pollution in big cities. In Sao Paulo, for instance, it is estimated that 98 % of the transport are made using buses with combustion engine, which are responsible for greatest part of air and noise pollution. Therefore, it is necessary to develop studies that help change the public transport policies in major cities, favoring the use of electric and hybrid buses. Thus, this paper aims to simulate the use of hybrid bus with fuzzy logic applied to improve the efficiency of this type of system. We made six simulations with MATLAB© software and Fuzzy Logic Toolbox, considering velocity, topography and battery status as input variables. The results showed an effective control of the fuzzy system, with the feasibility of combining this with others experts systems.

In part I of this paper, attention has been firstly paid to general aspects of the introduction of electric and hybrid vehicles to reduce the air pollution.It has been shown that the emissons by electric vehicle are significantly lower than for petrol and diesel vehicles, except for sulphur dioxide, but the last one is due to reduce significantly in the future.A discussion of the daily mileage led to the conclusion that the present-day car fleet is conceived for trips (more than 100 km) that only represent less than 10% of the total number of trips or at the most 30% (i. e. all those trips longer than 10 km) of the total number of trips. It must be particularly stressed that electric and hybrid vehicle technology is clearly still in the infancy of its development. The basic structure of the electric vehicle is quite simple. A tentative description of the mission characteristics of city cars, passenger cars, vans, minibuses and buses has been performed together with upper level of useful characteristics.The characteristics of future type of batteries and of presently available batteries have been given to allow a comparison with the 500 W/kg power density of a widespread typical internal combustion engine. In this part II, after a short description of the hybrid solutions, we will devote some space to the presentation of the State of the Art of the electric components of EV’s and HV’s. This presentation has two main goals:– to show that the today technology allows without doubt to “assemble” an electric or a hybrid vehicle:– to try to indicate the long way still to be covered before the grade of optimization of the vehicles with internal combustion engine (ICE), after a century of development, can be reached.The role of the infrastructure and of two important scientific associations (AVERE and CITELEC) will finally be explained in the third part as to their impact on the future development and introduction of EV’s and HV’s.

In recent times many research efforts are aimed at the development of aircraft hybrid propulsion technology as a means to minimize the aircraft environmental impact. The objective is to provide an additional assessment of the energy efficiency of the hybrid powered light aircraft in comparison with current state of the art Diesel powered aircraft. Typical 4-seat propeller airplane is chosen as a prototype and its flight performance model is created using open source data. The comparison is performed for a realistic flight profile including the power demands for go-around and flight to alternate destination airport. Parallel hybrid architecture is considered. A parametric study with variation of the mass, efficiency and energy capacity parameters of the hybrid power train is performed in order to determine the parameter regions where the hybrid power train has advantage over the Diesel one. The present study is based on the previous experience of the authors in assessing the energy efficiency of alternative power sources for the aviation.