• Energy Research
• 11. Sustainability close
• CN close
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• Journal of Power Sources close

Abstract “Energiewende”, which roughly translates as the transformation of the German energy sector in accordance with the imperatives of climate change, may soon become a byword for the corresponding processes most other developed countries are at various stages of undergoing. Germany's notable progress in this area offers valuable insights that other states can draw on in implementing their own transitions. The German state of North Rhine-Westphalia (NRW) is making its own contribution to achieving the Energiewende's ambitious objectives: in addition to funding an array of ‘clean and green’ projects, the Virtual Institute Power to Gas and Heat was established as a consortium of seven scientific and technical organizations whose aim is to inscribe a future, renewable-based German energy system with adequate flexibility. Thus, it is tasked with conceiving of and evaluating suitable energy path options. This paper outlines one of the most promising of these pathways, which is predicated on the use of electrolytically-produced hydrogen as an energy storage medium, as well as the replacement of hydrocarbon-based fuel for most road vehicles. We describe and evaluate this path and place it in a systemic context, outlining a case study from which other countries and federated jurisdictions therein may draw inspiration.

Abstract Plug-in hybrid electric vehicles (PHEVs) have a large battery pack, and the depth of discharge (DOD) significantly affects the battery longevity. In this paper, the battery degradation is considered in the co-optimization of battery size and energy management for PHEVs using convex programming. The impact of DOD on battery degradation and energy management is also investigated. The cost function consists of fuel consumption, electrical energy consumption, and equivalent battery life loss. A real-world speed profile collected from the urban city bus route up to about 70 km is used as an input to evaluate the proposed method. The results suggest that, for both cases with and without battery degradation, the total cost curve with respect to the preset final state of charge (SOC) is an upward parabola, where the optimal DOD can be identified, and the optimal battery size and energy management can be determined. The results also show that, with an initial SOC of 0.9, the proposed method can reduce the total cost by 3.6 CNY compared to other existing studies with the fixed final SOC. Moreover, a sensitivity analysis is conducted to explore the effect of battery price and initial SOC on the optimal DOD and total cost.

Abstract The most promising vehicle engine that can overcome the problem of present internal combustion is the hydrogen fuel cell. Fuel cells are devices that change chemical energy directly into electrical energy without combustion. Pure fuel cell vehicles and fuel cell hybrid vehicles (i.e. a combination of fuel cell and battery) as energy sources are studied. Considerations of efficiency, fuel economy, and the characteristics of power output in hybridization of fuel cell vehicle are necessary. In the case of Federal Urban Driving Schedule (FUDS) cycle simulation, hybridization is more efficient than a pure fuel cell vehicle. The reason is that it is possible to capture regenerative braking energy and to operate the fuel cell system within a more efficient range by using battery. Life-cycle cost is largely affected by the fuel cell size, fuel cell cost, and hydrogen cost. When the cost of fuel cell is high, hybridization is profitable, but when the cost of fuel cell is less than 400 US$/kW, a pure fuel cell vehicle is more profitable.

Abstract In recent years, the demand for an increased number of vehicle functions by legislation and customer expectations has introduced many electronic control systems and electrical driven units in vehicles and has resulted in steadily increasing electrical loads. Moreover, due to heavy urban traffic conditions, the idling time fraction has increased and reduced the power generation of the alternator. In the vehicle design phase, in order to avoid an over- or under-design problem of the electric power system, it is necessary to understand both the characteristics of each component of the vehicle electric power system and the interactions between the components. For this purpose, model and simulation algorithms of the vehicle power system are required. In this study, the vehicle electric power system, which is mainly composed of a generator and battery, is modelled and evaluated. Among the various proposed battery models, two types are compared in terms of accuracy and ease-of-use. These two models are distinguished by the consideration of inrush current at the beginning of charging and discharging. In addition, a variable terminal voltage alternator model (VTVA model) is proposed, and is compared with a constant terminal voltage alternator model (CTVA model). Based on the major component model, a simulation algorithm is developed and used to perform a case study. Compared with real data from the vehicle, the simulation results of energy generation and consumption are comparable.

Abstract With the ever-growing need for lithium-ion batteries, particularly from the electric transportation industry, a large amount of lithium-ion batteries is bound to retire in the near future, thereby leading to serious disposal problems and detrimental impacts on environment and energy conservation. Currently, commercial lithium-ion batteries are composed of transition metal oxides or phosphates, aluminum, copper, graphite, organic electrolytes with harmful lithium salts, polymer separators, and plastic or metallic cases. The lack of proper disposal of spent lithium-ion batteries probably results in grave consequences, such as environmental pollution and waste of resources. Thus, recycling of spent lithium-ion batteries starts to receive attentions in recent years. However, owing to the pursuit of lithium-ion batteries with higher energy density, higher safety and more affordable price, the materials used in lithium-ion batteries are of a wide diversity and ever-evolving, consequently bringing difficulties to the recycling of spent lithium-ion batteries. To address this issue, both technological innovations and the participation of governments are required. This article provides a review of recent advances in recycling technologies of spent lithium-ion batteries, including the development of recycling processes, the products obtained from recycling, and the effects of recycling on environmental burdens. In addition, the remaining challenges and future perspectives are also highlighted.

Abstract In this paper, 2D models for direct carbon solid oxide fuel cells (DC-SOFCs) with in situ catalytic steam-carbon gasification reaction are developed. The simulation results are found to be in good agreement with experimental data. The performance of DC-SOFCs with and without catalyst are compared at different operating potential, anode inlet gas flow rate and operating temperature. It is found that adding suitable catalyst can significantly speed up the in situ steam-carbon gasification reaction and improve the performance of DC-SOFC with H2O as gasification agent. The potential of syngas and electricity co-generation from the fuel cell is also evaluated, where the composition of H2 and CO in syngas can be adjusted by controlling the anode inlet gas flow rate. In addition, the performance DC-SOFCs and the percentage of fuel in the outlet gas are both increased with increasing operating temperature. At a reduced temperature (below 800 °C), good performance of DC-SOFC can still be obtained with in-situ catalytic carbon gasification by steam. The results of this study form a solid foundation to understand the important effect of catalyst and related operating conditions on H2O-assisted DC-SOFCs.

Abstract The performance of Plug-in Hybrid Electric Vehicle (PHEV) depends on the energy management strategy (EMS). An optimal EMS guarantees the maximum use of the energy through electric power grid, coordinates power output of main power sources and exerts comprehensive advantages of both engine and motor. However, the current EMS cannot react to the dynamic driving cycles in the future and thus have a bad real-time performance. In order to solve these problems, a novel EMS based on rule-based energy strategy (RE), dynamic programming algorithm (DP) and equivalent fuel consumption algorithm (ECMS) is proposed. First, DP is used to extract the boundary of mode switching and shift schedule under three typical driving cycles in offline, especially, RE is corrected using the boundary of mode switching. Second, an instantaneous optimization strategy-ECMS is used to replace the Charge-Depleting Mode (CD) of RE for finding the real-time optimal solution in a wider range in online, in this part, owe to the fixed distance of urban public transport, a reference State of Charge (SOC) is formulated, and the Proportion-Integration (PI) algorithm is used to make the actual SOC always follow the reference SOC by adjusting the equivalent factor. Finally, combine all the above efforts, a real-time optimization EMS is proposed and validated through simulation and experiment. The results show that this approach can significantly enhance the vehicle drivability, with overall obvious improvement of the comprehensive performance qualification based on both fuel economy and drivability.

Three fuel cell city buses of the energy hybrid- and power hybrid-type were re-engineered with three types of drivetrain configuration to optimize the structure and improve the performance. The energy distribution, hydrogen consumption, state of charge (SOC) and the power variation rate were analyzed when different drivetrain configurations and parameters were used. When powered only by a fuel cell, the bus cannot recover the energy through regenerative braking. The variation of the fuel cell power is large and frequent, which is not good for the fuel cell. When the fuel cell is linked to a battery pack in parallel, the bus can recover the energy through regenerative braking. The energy distribution is determined by the parameters of the fuel cell and the battery pack in the design stage to reduce the power variation rate of the fuel cell. When the fuel cell and DC/DC converter connected in series links the battery pack in parallel, energy can be recovered and the energy distribution can be adjusted online. The power variation rate of both the fuel cell and the battery pack are reduced.

A state-of-the-art Chinese fuel cell city bus, using a hybrid power system is proposed. This comprises a proton exchange membrane 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 paper presents a novel control strategy for efficiency of the 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 by using dynamometer and road test experiments. The experimental results demonstrated that the control strategy has great flexibility and generality, and also validated that the peak power capacity of the active hybrid power source and the vehicle drive performance can be significantly enhanced.