Hewu Wang

New energy vehicles in China: policies, demonstration, and progress

Since 2009, China has become the largest new vehicle market in the world. To address the energy security and urban air-pollution concerns that emerge from rapid vehicle population growth, China has initiated the Thousands of Vehicles, Tens of Cities (TVTC) Program to accelerate the new energy vehicle (NEV) commercialization. In this paper, we summarize the efforts made by the Chinese government since 1995 in the areas of research and development, demonstration, and communalization of NEVs; evaluate the progress of NEV demonstration; and provide some recommendations for future development. Our analysis has determined that the deployment of NEVs for the TVTC Program is lagging behind the original plan and, on average, only 26–36% of the goals have been attained by October 2011. Although China has approved many NEV models for sale, significantly more than 50% of them are not in production. On the other hand, stimulated by the policy shift, electric vehicle production has increased considerably, thereby contributing 23% and 44% of the total NEV production in 2010 and 2011, respectively. Additionally, because of the constraints imposed by price and technology maturity, lead-acid battery technology is a substantial factor in the high-volume sales of top NEV car models.

Study of combustion characteristics of a compression ignition engine fuelled with dimethyl ether

Abstract This paper presents the combustion characteristics of a light-duty direct-injection diesel engine operating on dimethyl ether (DME). The indicated pressure diagrams and injector needle lifts are recorded and the combustion characteristics are demonstrated and compared with those of an engine operated on diesel fuel. The experimental and calculated results show that the DME engine has a longer delay of injection and duration of injection, a lower maximum cylinder pressure and rate of pressure rise, as well as a shorter ignition delay compared with those of a diesel engine. The DME engine has a low mechanical load and combustion noise, a fast rate of diffusion combustion and a shorter combustion duration than that of a diesel engine. It has the ideal pattern of compression ignition engine heat release.

Study on the performance and emissions of a compression ignition engine fuelled with dimethyl ether

Abstract The paper presents the research results of a light-duty direct injection diesel engine operating on dimethyl ether (DME). The effects of the main parameters of the combustion system, such as plunger diameter, nozzle type, fuel delivery advance angle, protruding distance of the nozzle tip from the bottom plane of the cylinder head and swirl ratio, on the performance of the DME engine are investigated. The indicator diagrams are taken after optimizing the combustion system and characteristics of combustion and emissions are measured for DME and diesel operation. The results show that, by adding a pressure pump in the fuel supply system, the vapour lock of DME in the fuel system is eliminated. The engine runs smoothly on DME over a wide range of speeds and loads. The effective thermal efficiency of the DME engine is 3 per cent higher than that of the diesel engine, and a low rate of pressure rise, low combustion noise, smokeless combustion and low NO x emissions of the DME engine can be achieved. The results demonstrate good characteristics in reducing emissions for a diesel engine operating on DME.

Energy management of plug-in hybrid electric vehicles with unknown trip length

Abstract This paper proposes a novel control strategy for plug-in hybrid electric vehicles (PHEV). The minimization of the utility factor weighted fuel consumption (FC UFW ), which represents the average fuel consumption in numerous trips, is firstly proposed as the objective of the energy management. In previous studies, the trip length is usually assumed to be known. Then, if it is shorter than the all-electric range (AER), a Charge Depleting–Charge Sustaining (CDCS) strategy leads to the minimum fuel consumption; otherwise, a blended strategy that spends down battery energy almost uniformly brings the minimum fuel consumption. Nevertheless, the trip length is not always known before trip in real life. To deal with the cases of unknown trip length, this paper proposes a Range ADaptive Optimal Control (RADOC) strategy to minimize the FC UFW , which utilizes the statistical information of the trip length. The RADOC strategy was verified by dynamic programming and was found to be somewhere in between the blended and CDCS strategies. Depending on the nature of the trips, the RADOC strategy was found to improve FC UFW between 0.10% and 4.07% compared with the CDCS strategy. The RADOC strategy is very close to the CDCS strategy when the PHEV is used in regular daily driving. On the contrary, the RADOC solution exhibits a “uniform battery discharging” behavior similar to the blended strategy for urban utility vehicles or taxis. The behavior of the RADOC strategy is also studied for different battery sizes and driving cycles.

Survey of daily vehicle travel distance and impact factors in Beijing

Abstract Due to the importance of distribution of the Daily Vehicle Kilometers Travelled (DVKT) to design the powertrain of the Battery Electric Vehicle (BEV) and Plug-in Hybrid Electric Vehicle (PHEV), as well as to predict the energy and emission reduction caused by BEV and PHEV market penetration, a comprehensive survey was carried out in Beijing in the year of 2009, and more than 500 questionnaires including DVKT and the related factors were collected. The analysis results show that the average DVKT of the private passenger vehicle in Beijing was 46.35 km, and 68.2% of the travels were within 50 km while only 9.1% were longer than 100 km. The detailed analysis implied that the travel purpose is the most important impact factor of DVKT. With the same electric range, the BEV can cover approximately 5% more of the daily trips in Beijing than in the U.S. With the same charge depleting range, the average fuel consumption of the PHEV used in Beijing is 10-40% lower than that in the U.S.

Battery electric vehicle parameters design targeting to cost-benefit objective

Developing electric vehicle can reduce crude oil consumption and carbon emission sharply to resolve the problems of energy crisis and climate change of China. EVs require large batteries for energy storage, which affect electric vehicle cost, weight, and performance. More all electric range (AER) means more dispalcement of the fosill fuel, but lead to too expensive to afford for Chinas consumers. The electric vehicle design method to tadeoff between performance and cost is very valuable.This paper discussed the parameter optimization design method targeting cost-benefit objective. It analyses the impact of maximum speed, AER on energy efficiency and market competitiveness, based the survey data annalysis of vehicle kilometers daily traveled(VKDT), duty cycle analysis, etc.The mathematic model was proposed to account for the effects of additional batteries on fuel consumption, cost, etc. It can be find that when charged daily, AER of 50km or less, in China, using average small-capacity EVs is less expensive and releases fewer GHGs than conventional vehicles (CVs). By cost-benefit analysis, it can be concluded that for the first generation pure electric vehicle, the micro-size electric suitable for the first phase of development.

Electric power system for Chinese fuel cell city bus

A state-of-the-art Chinese fuel cell city bus using a hybrid power system is proposed. This comprises a PEM fuel cell and Ni/MH batteries to combine the high energy density of fuel cells with the high power density of batteries. A DC/DC converter is placed between the fuel cell and the battery to control the electric power flow. This article presents a novel control strategy for efficient fuel cell operation and optimization of the hybrid power system for the bus. The control strategy is able to regulate the output current of the fuel cell and the charging current or voltage for the battery, while limiting the discharge current of the battery. It can achieve a higher efficiency, longer fuel cell lifetime and higher drive performance. The hybrid fuel cell power system and the proposed control strategy were verified using dynamometer and road test experiments. The experimental results demonstrate that the control strategy has great flexibility and generality, and also validate that the peak power capacity of the active hybrid power source and the vehicle drive performance can be significantly enhanced.

A GPS-based research on driving range and patterns of private passenger vehicle in Beijing

The driving range and patterns of private passenger vehicle in Beijing are discussed in this paper, basing on the advanced GPS travel survey. From the sample of 106 cars, 1652 days and 3920 trips collected in the second half of 2012 and early 2013, the distribution of daily driving range, time and frequency are calculated out. The results show that in Beijing, the daily vehicle kilometers travelled of the year 2012-2013 is 33.5km, and the driving time is 1.6h per day. Besides, there are 2.4 driving trips per day on average, when the average range is 14.1km per trip. The battery electric vehicle (BEV) may cover 80% daily travel with the all-electric range (AER) set as 60km. If the BEV is charged reasonably, its applicability and endurance will be better.

Parameters Optimization of PHEV Based on Cost-Effectiveness from Life Cycle View in China

Plug-in hybrid electric vehicle (PHEV) technology combining the merits of Battery electric vehicle (BEV) and Hybrid electric vehicle (HEV), has the potential to reduce greenhouse gas (GHG) emissions, and petroleum consumption in the transportation sector. However, the cost-benefit of PHEVs mainly determined by battery technology, optimal powertrain design, and vehicle kilometers daily traveled and charging habits. Targeting to cost-benefit, the optimal design method was presented, taking battery cycle life Vs DOD data, driving data, battery performance data into consideration. The method provided optimal vehicle designs to realize minimum life cycle cost, and maximum petroleum consumption under different scenarios. For A-segment equivalent PHEV (similar to a F3DM), under Shanghai urban driving conditions, it can be find that while PHEVs with present traction battery technology, 30 km AER was most life cycle cost-effective to obtain maximum petroleum displacement based on Shanghai driving data. Large capacity battery lead to petroleum displacement not so much as cost increased. At China electricity price off peak, Li-ion battery pack costs must fall below ¥2.0/Wh to be cost competitive with equivalent internal combustion engine vehicles (ICEs).

An assessment of PHEV energy management strategies using driving range data collected in Beijing

This paper assesses three typical plug-in hybrid electric vehicle (PHEV) energy management strategies by comparing the average fuel consumptions (AFC) based on the daily driving range data of Beijing. The three different strategies are developed first: with the all-electric charge-sustaining (AECS) strategy, the vehicle is propelled only by the motor until the SOC is depleted; with the fixed blended strategy, the vehicle utilizes both motor and engine according to some fixed ratio in the charge depleting stage; and with the adaptive blended strategy, the vehicle utilizes both motor and engine at an variable ratio adapted to the driving range. Then, the AFC assessment methods for the corresponding strategies are illustrated. For the strategies with the fixed charge depleting range, the utility factor method prescribed by SAE is available; for the strategy with the variable charge depleting range, a mathematic expectation method is proposed. The conclusion comes at last: with the same components, the lowest AFC is 1.2542 L/100km, with the adaptive blended strategy; and the highest AFC is 2.4130 L/100km, with one of the fixed blended strategy; for the vehicle used in the study, the AECS is the best strategy unless the blended strategy is adapted to the driving range; and it is suggested the AFC be considered instead of the specific trip fuel consumption in the strategy optimization.