Hydraulic/electric synergy system (HESS) design for heavy hybrid vehicles

Energy storage source is one of the key factors constraining the development of hybrid drive technology. Single energy storage source is difficult to satisfy the hybrid vehicle’s requirements for both energy density and power density. This paper presents a hydraulic/electric synergy system (HESS) for heavy hybrid vehicles to overcome the existing drawbacks of single energy storage source. The key components in the synergy system are sized to improve the fuel economy potential while satisfying the vehicle performance constraints. In order to achieve optimal fuel economy, energy control strategy tailored specially to the synergy system is designed to manage the power distribution between multiple energy sources based on theirs characteristics. The experiments and simulations demonstrate that the proposed synergy system can provide good fuel economy and overall system efficiency.     

A hierarchical energy management strategy for fuel cell/battery/supercapacitor hybrid electric vehicles

In this paper, a hierarchical energy management strategy (EMS) based on low-pass filter and equivalent consumption minimization strategy (ECMS) is proposed in order to lift energy sources lifespan, power performance and fuel economy for hybrid electrical vehicles equipped with fuel cell, battery and supercapacitor. As for the considered powertrain configuration, fuel cell serves as main energy source, and battery and supercapacitor are regarded as energy support and storage system. Supercapacitor with high power density and dynamic response acts during great power fluctuations, which relives stress on fuel cell and battery. Meanwhile, battery is used to lift the economy of hydrogen fuel. In higher layer strategy of the proposed EMS, supercapacitor is employed to supply peak power and recycle braking energy by using the adaptive low-pass filter method. Meantime, an ECMS is designed to allocate power of fuel cell and battery such that fuel cell can work in a high efficient range to minimize hydrogen consumption in lower layer. The proposed EMS for hybrid electrical vehicles is modeled and verified by advisor-simulink and experiment bench. Simulation and experiment results are given to confirm effectiveness of the proposed EMS of this paper.     

Health-aware frequency separation method for online energy management of fuel cell hybrid vehicle considering efficient urban utilization

Frequency separation methods (FSMs) are frequently used to implement energy management of fuel cell hybrid vehicle (FCHV), due to their flexible online implementation and resilience under diverse driving environments. However, predefined static rules of FSM generally result in inefficient operation of FCHV and rapid deterioration of sources. Additionally, allocated limits of storage devices are likely to be violated in the conventional FSM. With this inspiration, the paper proposes a novel health-aware FSM (HFSM) to appropriately distribute the traction power among energy sources of FCHV with efficient urban utilization. The power separation rules of HFSM are tuned in an instantaneous manner to concurrently realize the fuel economy, lifespan extension and allocated storage limits. Within HFSM, an online optimizer is formulated, which introduces the concept of soft/hard limitations and rationalized cost structure to adequately quantify the fuel consumption and health degradation of fuel cell. An adaptive droop adjustment is then integrated with HFSM to consistently realize the storage limitations. Compared to conventional FSM, considerable improvements in the fuel economy and fuel cell service life are observed over an extended iterative loop of standard urban driving cycles.     

Hydrogen economy for a sustainable development: state-of-the-art and technological perspectives

Sustainable energy is becoming of increasing concern world-wide. The rapid growth of global climate changes along with the fear of energy supply shortage is creating a large consensus about the potential benefits of a hydrogen economy coming from renewable energy sources. The interesting perspectives are over-shadowed by uncertainties about the development of key technologies, such as renewable energy sources, advanced production processes, fuel cells, metal hydrides, nanostructures, standards and codes, and so on. The availability of critical technologies can create a base for the start of the hydrogen economy, as a fuel and energy carrier alternative to the current fossil resources. This paper will explore the rationale for such a revolution in the energy sector, will describe the state-of-the-art of major related technologies (fuel cell, storage systems, fuel cell vehicles) and current niche applications, and will sketch scientific and technological challenges and recommendations for research and development (R&D) initiatives to accelerate the pace for the widespread introduction of a hydrogen economy.     

Fuel economy of hydrogen fuel cell vehicles

On the basis of on-road energy consumption, fuel economy (FE) of hydrogen fuel cell light-duty vehicles is projected to be 2.5–2.7 times the fuel economy of the conventional gasoline internal combustion engine vehicles (ICEV) on the same platforms. Even with a less efficient but higher power density 0.6 V per cell than the base case 0.7 V per cell at the rated power point, the hydrogen fuel cell vehicles are projected to offer essentially the same fuel economy multiplier. The key to obtaining high fuel economy as measured on standardized urban and highway drive schedules lies in maintaining high efficiency of the fuel cell (FC) system at low loads. To achieve this, besides a high performance fuel cell stack, low parasitic losses in the air management system (i.e., turndown and part load efficiencies of the compressor–expander module) are critical.     

Evaluation of the energy efficiency evolution in the European road freight transport sector

In this paper, we evaluate energy efficiency in the European freight transport sector over three decades, according to a variety of indicators, methodologies and databases. The aim is, on the one hand, of determining major drawbacks in energy efficiency metrics, on the other hand, identifying a possible trend in the sector. The present analysis shows that energy efficiency evaluation is generally subject to misinterpretation and distortion with regard to the methods and data source adopted. Two different indicators (energy intensity and fuel economy) were initially taken into account to select the most suitable for evaluating vehicles’ efficiency. Fuel economy was then adopted and measured according to two different methodologies (top–down and bottom–up). We then considered all the possible sources of distortion (data sources employed, methods of data detection, speed of detection, power enhancement, size factor) with the aim of accomplishing a sound estimation. Fuel economy was eventually divided with the maximum power available (adjusted fuel economy), to account for the power shift of vehicles, that represents a further efficiency improvement.     

Hydrogen: automotive fuel of the future

This work presents a perspective on the production and use of hydrogen as an automotive fuel. Hydrogen has been hailed as the key to a clean energy future primarily because it can be produced from a variety of energy sources, it satisfies all energy needs, it is the least polluting, and it is the perfect carrier for solar energy in that it affords solar energy a storage medium. Efforts are underway to transform the global transportation energy economy from one dependent on oil to that based on sustainable hydrogen. The rationale behind these efforts is that hydrocarbon-based automobiles are a significant source of air pollution, while hydrogen-powered fuel cell vehicles produce effectively zero emissions. Besides the transportation area, fuel cells can also reduce emissions in other applications such as the residential or commercial distributed electricity generation. Hydrogen is the perfect partner for electricity, and together they create an integrated energy system based on distributed power generation and use. A discussion on the sources of hydrogen in the near- and long-term future as well as the cost of hydrogen production is provided.     

Changes in fuel input of electricity sector in Hong Kong since 1982 and their implications

Since 1982, the electricity sector in Hong Kong, which accounts for more than half of the total energy consumption, has undergone two major changes in terms of the type of fuels used for power generation. In 1982, it switched from oil to coal generation. In 1994, nuclear power was introduced; and in 1996, natural gas was imported for power generation. Given the dominance of electricity in the energy economy, these changes led to drastic modifications in the fuel mix and the geographical sources of energy supply for Hong Kong. This study analyses the rationale behind the above changes in fuel selection, the impact on the fuel mix and the geographical sources of energy supply, the security of energy supply, and the cost of power.     

Brazilian hybrid electric-hydrogen fuel cell bus: Improved on-board energy management system

The present paper unveils the technology developed for a series hybrid battery-dominant electric-hydrogen fuel cell plug-in city bus. It possesses a homemade power train with three electric energy sources, which are the grid-charged energy, the one produced by the fuel cell that works at constant power and acts as a range extender and that resultant from the regeneration of kinetic energy. Emphasis was given to the design of the hybridization energy engineering that has predominance of power in batteries and predominance of energy with hydrogen. The remarkable amount of 46.6% of the total energy input reaches the motor axle for effective motion and a fuel economy of 6.7 kg H₂/100 km was achieved. A total owner cost analysis has shown that computation of capital, operational and fueling costs makes the present bus 133% more expensive than a conventional diesel powered one. Commercialization prospects, and also social and environmental impacts are analyzed.     

A new application of the UltraBattery to hybrid fuel cell vehicles

This study involves investigation of fuel cell hybrid vehicles. The main power source in the dynamic configuration is a proton exchange membrane fuel cell. An energy performance comparison is conducted between the use of a lithium‐ion battery (Automotive Energy Supply Corporation, Japan) and the UltraBattery (Furukawa Battery Company, Japan) as auxiliary power sources. The MATLAB/Simulink for simulation is used to observe dynamic behavior and overall performance. This study describes the simulation frameworks of the proton exchange membrane fuel cell, ultracapacitor, lead–acid battery, and UltraBattery. Then, the Economic Commission for Europe 40 driving cycle is used to test and investigate the performance of the fuel cell hybrid vehicle. Four energy output models are adopted to simulate the energy demand and the energy motor output of the dual power source, namely the high‐load demand, general demand, low‐load demand, and charge models. The simulation results indicate that the lithium battery recycles 0.1% more work compared with the UltraBattery. Regarding fuel economy, the UltraBattery is only 0.1% inferior to the lithium battery. The expected cost of an UltraBattery with the same specifications is 35% less than that of a lithium battery. Considering fuel economy and cost simultaneously, the UltraBattery can compete with the lithium battery. Copyright © 2015 John Wiley & Sons, Ltd.     

Wind energy status in electrical energy production of Turkey

Main electrical energy sources of Turkey are thermal (lignite, natural gas, coal, fuel oil, etc.) and hydraulic. Most of the thermal sources are derived from natural gas. Turkey imports natural gas; therefore, decreasing usage of natural gas is very important for both economical and environmental aspects. Because of disadvantages of fossil fuels, renewable energy sources are getting importance for sustainable energy development and environmental protection. Among the renewable sources, Turkey has very high wind energy potential. However the installed wind power capacity is only 0.22% of total economical wind potential. In this study, Turkey's installed electric power capacity, electric energy production is investigated and also Turkey current wind energy status is examined.     

A comparative review on power conversion topologies and energy storage system for electric vehicles

Fossil fuel depletion and its adverse impact on global warming is a major driving force for a recent upsurge in the development of hybrid electric vehicles technologies. This paper is a conglomeration of the recent literature in the usages of an energy storage system and power conversion topologies in electric vehicles (EVs). An EV requires sources that have high power and energy density to decrease the charging time. Commonly used energy storage devices in EVs are fuel cells, batteries, ultracapacitors, flywheel, and photovoltaic arrays. The power output from energy storage sources is conditioned to match load characteristics with the source for maximum power delivery. A DC-DC converter topology performs this task by way of transforming voltage under the condition of power invariance. In addition, power electronics is also required to power DC/AC motors efficiently with precise control as these motors provide tractive efforts and acts as prime movers. This paper therefore brings out a critical review of the literature on EV's power conversion topologies and energy storage systems with challenges, opportunities and future directions by systematic classification of EVs and energy storage.     

Fuel economy and life-cycle cost analysis of a fuel cell hybrid vehicle

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.     

A mobile off-grid platform powered with photovoltaic/wind/battery/fuel cell hybrid power systems

Cross utilization of photovoltaic/wind/battery/fuel cell hybrid-power-system has been demonstrated to power an off-grid mobile living space. This concept shows that different renewable energy sources can be used simultaneously to power off-grid applications together with battery and hydrogen energy storage options. Photovoltaic (PV) and wind energy are used as primary sources and a fuel cell is used as backup power. A total of 2.7 kW energy production (wind and PV panels) along with 1.2 kW fuel cell power is supported with 17.2 kWh battery and 15 kWh hydrogen storage capacities. Supply/demand scenarios are prepared based on wind and solar data for Istanbul. Primary energy sources supply load and charge batteries. When there is energy excess, it is used to electrolyse water for hydrogen production, which in turn can either be used to power fuel cells or burnt as fuel by the hydrogen cooker. Power-to-gas and gas-to-power schemes are effectively utilized and shown in this study. Power demand by the installed equipment is supplied by batteries if no renewable energy is available. If there is high demand beyond battery capacity, fuel cell supplies energy in parallel. Automatic and manual controllable hydraulic systems are designed and installed to increase the photovoltaic efficiency by vertical axis control, to lift up & down wind turbine and to prevent vibrations on vehicle. Automatic control, data acquisition, monitoring, telemetry hardware and software are established. In order to increase public awareness of renewable energy sources and its applications, system has been demonstrated in various exhibitions, conferences, energy forums, universities, governmental and nongovernmental organizations in Turkey, Austria, United Arab Emirates and Romania.     

Economic analysis of hydrogen-powered data center

The data center needs more and more electricity due to the explosive growth of IT servers and it could cause electricity power shortage and huge carbon emission. It is an attractive and promising solution to power the data center with hydrogen energy source. The present work aims to conduct an economic analysis on the hydrogen-powered data center. Configurations of hydrogen-powered and traditional data centers are compared and the differences focus on backup power system, converter/inverter, fuel cell subsystem, carbon emission, hydrogen and electricity consumptions. Economic analysis is conducted to evaluate the feasibility to power the data center with hydrogen energy source. Results show that electricity price increasing rate and hydrogen cost are the main factors to influence economic feasibility of hydrogen-powered data center. When the electricity price keeps constant in the coming two decades, the critical hydrogen price is about 2.8 U.S. dollar per kilogram. If the electricity price could increase 5% annually due to explosive growth of electric vehicles and economy, critical hydrogen price will become 6.4 U.S. dollar per kilogram. Hydrogen sources and transportation determine the hydrogen price together. Hydrogen production cost varies greatly with hydrogen sources and production technologies. Hydrogen transport cost is greatly influenced by distances and H₂ consumptions to consumers. It could be summarized that the hydrogen-powered data center is economic if hydrogen could be produced from natural gas or H₂-rich industrial waste streams in chemical plant and data center could not be built too far away from hydrogen sources. In addition, large-scale hydrogen-powered data center is more likely to be economic. Solar hydrogen powered data center has entered into a critical stage in the economic feasibility. Solar hydrogen production cost has restrained the H₂ utilization in data center power systems now, since it could be competitive only when more strict carbon emission regulation is employed, hydrogen production cost reduces greatly and electricity price is increasing greatly in the future. However, it could be expected solar hydrogen-powered system will be adopted as the power source of data centers in the next few years.     

Two new control strategies: For hydrogen fuel saving and extend the life cycle in the hydrogen fuel cell vehicles

With the acceleration of the development process of hydrogen fuel cell electric vehicles (HFCEV), it has become very important to maximize the energy stored in the vehicle and to use the vehicle with high efficiency. This paper puts forward how to cooperate with a proton exchange membrane fuel cell (PEMFC) as the primary energy source, a lithium-ion battery (LiB) and a supercapacitor (SCAP) as the energy storage technology. Furthermore, this paper examines the effect of two new control strategies developed for HFCEV in different road models on the vehicle fuel economy and life cycle of the system components. Both control strategies applied to the system can be easily applied to the different HFCEVs with minor changes due to the simplicity of their structure and parameters. The simulation results of the study have indicated that the impact of control strategies created in different road conditions on the power of energy sources, the life cycle of system components, system efficiency and fuel economy parameters of HFCEV.     

Market perspectives of stationary fuel cells in a sustainable energy supply system—long-term scenarios for Germany

Because of high efficiency, low environmental impacts and a potential role in transforming our energy system into a hydrogen economy, fuel cells are often considered as a key technology for a sustainable energy supply. However, the future framing conditions under which stationary fuel cells have to prove their technical and economic competitiveness are most likely characterised by a reduced demand for space heating, and a growing contribution of renewable energy sources to heat and electricity supply, which both directly limit the potential for combined heat and power generation, and thus also for fuel cells. Taking Germany as a case study, this paper explores the market potential of stationary fuel cells under the structural changes of the energy demand and supply system required to achieve a sustainable energy supply. Results indicate that among the scenarios analysed it is in particular a strategy oriented towards ambitious CO₂-reduction targets, which due to its changes in the supply structure is in a position to mobilise a market potential that might be large enough for a successful fuel cell commercialisation. However, under the conditions of a business-as-usual trajectory the sales targets of fuel cell manufacturers cannot be met.     

世界能源消费形势刍议

能源是现代社会文明和经济发展的生命线,经济愈发展,社会愈进步,对能源的依赖程度也愈高。各能源机构都预测,在本世纪中叶以前,世界能源总需求仍会进一步增长,世界人口的增长亦将促进能源需求的增长。今后经济和能源需求的增长将主要集中在发展中国家,从地区来看,将主要来自亚洲和大洋洲发展中国家,其次是中东和北非以及拉丁美洲。本世纪以来,在一次能耗消费构成中,煤炭和天然气所占比例上升,石油和一次电力(主要是核能)所占比例有所下降。目前水电和核能仍是最大的非化石能源,两者合计占一次能源消费比例约为12%。尽管风能、太阳能、生物质能等来势迅猛,但毕竟基数很小,在本世纪前半叶化石能源仍将居主导地位。由于煤层气、页岩气勘探开发技术日趋成熟,使得天然气(包括非常规天然气)的储量和产量迅速增长。2035年天然气可能占到世界能源消费总量的25%,从而成为超过煤炭、仅次于石油的第二大能源。由于非常规原油储量和产量的迅速增长,弥补了常规原油储量和产量的下滑。石油替代燃料的研究受到普遍重视,目前研究中的四大石油替代燃料领域有:气体燃料、合成燃料、醇醚类燃料和生物质燃料,其中发展最快而又比较普遍的是生物燃料。从长远看生物燃料会有较大发展空间,但未来20~30年内很难实现大规模替代,几十年内石油仍然是生产运输燃料的主要原料。     

Agent-based power sharing scheme for active hybrid power sources

The active hybridization technique provides an effective approach to combining the best properties of a heterogeneous set of power sources to achieve higher energy density, power density and fuel efficiency. Active hybrid power sources can be used to power hybrid electric vehicles with selected combinations of internal combustion engines, fuel cells, batteries, and/or supercapacitors. They can be deployed in all-electric ships to build a distributed electric power system. They can also be used in a bulk power system to construct an autonomous distributed energy system. An important aspect in designing an active hybrid power source is to find a suitable control strategy that can manage the active power sharing and take advantage of the inherent scalability and robustness benefits of the hybrid system. This paper presents an agent-based power sharing scheme for active hybrid power sources. To demonstrate the effectiveness of the proposed agent-based power sharing scheme, simulation studies are performed for a hybrid power source that can be used in a solar car as the main propulsion power module. Simulation results clearly indicate that the agent-based control framework is effective to coordinate the various energy sources and manage the power/voltage profiles.     

Critical challenges in the system development of direct alcohol fuel cells as portable power supplies: An overview

Direct alcohol fuel cells (DAFCs) are considered a reasonable alternative power source because alcohol has a much higher energy density than hydrogen. Most DAFC development has focused on small portable application by using passive systems. DAFCs with active feed systems have appeared as potential portable power sources for larger applications, as they are easily handled, simple systems with smaller volumes than polymer electrolyte membrane fuel cells (PEMFCs). A general active DAFC system consists of a fuel and oxidant supplying system, product management and fuel concentration control. However, system development and commercialization are constrained by various critical challenges. This paper highlights the critical challenges of the fuel cell system rather than fundamental problems in the membrane electrode assembly (MEA), including fuel feed fluctuation, contaminant poisoning, two-phase flow, low power density, and heat and water management.