21世纪新能源之一——燃料电池

燃料电池是举世公认的21世纪绿色能源,也是继火电、水电、核电之后有可能成为工业大规模生产的第四种电力。燃料电池是一种化学电池,以氢、甲醇、乙醇、天然气、煤气、液化石油气、肼等可燃气体或液体为原料,故而得名“燃料电池”。其工作原理与普通的锰干电池、铅蓄电池相似,是利用燃料氧化反应时释放的能量直接将其转换成电能,所不同的是燃料电池的反应物———燃料和氧化剂(空气和氧)可以连续不断地供给电池,反应产物可以连续不断地从电池中排出,同时连续不断地输出电能和热能。实际上,燃料电池是应用电解水产生氢和氧的逆过程来达到发电…     

燃料电池知识——燃料电池的工作原理

燃料电池是将所供燃料的化学能直接变换为电能的一种能量转换装置，是通过连续供给燃料从而能连续获得电力的发电装置。燃料电池发生电化学反应的实质是氢气的燃烧反应。它与一般电池不同之处在于燃料电池的正、负极本身不包含活性物质，只是起催化转换作用。所需燃料（氢或通过甲烷、天然气、煤气、甲醇、乙醇、汽油等石化燃料或生物能源重整制取）和氧（或空气）不断由外界输入，因此燃料电池是名符其实的把化学能转化为电能的装置。[第一段]     

第4种发电站——燃料电池

当年阿波罗登月成功,极大地震动了世界。可是多数人并不了解,为登月飞船供应电力和饮水的是谁?原来它是燃料电池。燃料电池是继火力、水利、核能之后的第4种发电站。众所周知,水被电解以后变成氢和氧。燃料电池却是能让其发生反向反应的装置。它利用触媒,让氢和氧平稳地发生反应变成水,同时产生电流。燃料电池使用氢或天然气为燃料。它排放的有害气体极少;它没有运动机械,直接产生电流,噪音小;燃料电池可以分散地配置于耗电区内,避免了长途输电。由于燃料电池具有这些优点,因此它受到世界各国的重视和青睐。不过,燃料电池所需的触媒是贵金属…     

燃气轮机与混合装置的Yong性能比较

燃气轮机中的燃烧反应是一种高度不可逆的过程，因此Yong效率较低。燃气轮机一燃料电池混合装置则由于绝大部分燃料通过电化学反应来释放能量，只有未完全利用的燃料参加燃烧反应。用热力学第一定律和热力学第二定律对燃气轮机和它与燃料电池构成的混合装置进行了比较分析，研究了循环的Yong效率和各部件的性能对整个系统的影响，给出了混合装置中对提高系统性能具有重要影响的部件。     

定燃料流量和定燃料利用率时SOFC发电系统特性研究

在定燃料输入流量和定燃料利用率两种典型控制方式下,建立了固体氧化物燃料电池(SOFC)发电系统模型.研究了两种控制方式下的固体氧化物燃料电池堆的稳态特性,采用定燃料流量控制方式时考虑了燃料流量对SOFC稳态特性的影响.针对出现负荷改变和故障的情况,分别在两种典型控制模式下对SOFC发电系统进行了仿真,通过对仿真结果的比...     

氢燃料电池氢气利用率提升策略研究

针对燃料电池堆再循环管线的再循环速率低的问题,提出用于燃料电池的氢气供应系统的循环控制方案,根据再循环管线中再循环的气体量精确估计由吹扫阀吹扫的氢体浓度,通过反馈每种气体的吹扫量,调节吹扫阀的开度,提升氢气利用率,并对该方案进行仿真分析。仿真结果表明,燃料电池阳极侧氢气利用率明显提升,最高可达92.733%,可提高燃料电池堆的耐久性。     

燃气轮机与混合装置的[火用]性能比较

燃气轮机中的燃烧反应是一种高度不可逆的过程，因此焖效率较低。燃气轮机-燃料电池混合装置则由于绝大部分燃料通过电化学反应来释放能量，只有未完全利用的燃料参加燃烧反应。用热力学第一定律和热力学第二定律对燃气轮机和它与燃料电池构成的混合装置进行了比较分析，研究了循环的炯效率和各部件的性能对整个系统的影响，给出了混合装置中对提高系统性能具有重要影响的部件。图4表2参8：     

SOFC_MGT顶层循环混合发电系统改进

提出了典型顶层循环固体氧化物燃料电池/微型燃气轮机(SOFC/MGT)混合发电系统的改进措施:采用陶瓷质子膜对电池堆阳极反应产物进行分离,分离出来的氢气经过冷却、加压、预热后引入第二级电池堆的阳极继续进行电化学反应,并使第二级电池堆的反应产物与分离氢气后的剩余气体进入后燃烧室进行燃烧反应。结合具体的算例对这种SOFC两级串联/MGT混合发电新系统进行了模拟分析,结果表明:由于提高了发生电化学反应的氢气量,减少了发生燃烧反应的氢气量,使整个系统的火用损失显著降低,从而可使改进后的系统在相同的电池堆燃料利用率与相同的透平进口温度下比基准系统的发电效率提高2.92个百分点。该改进措施是提高SOFC/MGT混合发电系统的有效方法。     

燃料电池发展前景及其应用(上)

1燃料电池的发展前景 燃料电池发电装置每发电1000kWh排出的污染物小于1盎司,而常规燃烧装置为25磅。     

利用污水厂的废气发电

污水处理厂在净化水的同时，也排放出甲烷、硫化物和氮氧化物等废气污染环境。目前，美国纽约市的一家污水处理厂首次采用一种新的燃料电池装置把废气转变为电力和热量。该燃料电池采用的燃料是从甲烷中提取的氢。经过一年的使用证明．运行效果良好。该系统可生产200kW的电力，足以满足60户标准家庭所需的电力供应。     

燃料电池在车辆中应用的技术难关

近年来,人们对能源匮乏和环境污染问题日益重视,使得燃料电池汽车的研究开发成为汽车行业的热点。阐述了燃料电池汽车的结构及质子交换膜燃料电池(PEMFC)是燃料电池汽车动力源的首选;对燃料电池汽车目前存在的技术难关及发展形势进行了综述。最后,预测随着燃料电池技术的进步,燃料电池最终将完全取代内燃机成为车辆动力装置。     

Commercial vehicle auxiliary loads powered by PEM fuel cell

The commercial vehicles are in leadership in emission production for on-road vehicles. This high rate of emission is released in highly populated areas where diesel driven internal combustion engines are running in inefficient operating ranges. Except the propulsion, the internal combustion engine is powering the auxiliary devices such as refrigerator unit, etc. The auxiliary units are significant contributor to the overall pollutant production. In this paper the auxiliary load power supply for refrigerator unit is shifted from internal combustion engine to PEM fuel cell. The decrease in CO₂ accumulated emissions was estimated by simulation model containing vehicle model (tire, brake, differential, gearbox and driver model), diesel engine model and auxiliary power demand model. Four stroke diesel engine was modeled and investigated. For this investigation the fully filled truck was used for simulating 100% weight load. The gross weight is 7500 kg.The novelty of the approach is the simulation performed on realistic combination of city and urban road cycle. The focus was on modelling the realistic truck driving cycle in order to correctly predict emission and fuel consumption reduction. Since initial investigation are performed on constant load demand of fuel cell, simplified model of PEMFC was applied. PEM fuel cell stack was designed in order to meet the demands of auxiliary consumers. The H₂ consumption and size of hydrogen tank was estimated based on assumed 8-h daily drive. Finally, the migration of power supply for auxiliary units on commercial vehicle from internal combustion engine showed potential of fuel savings and CO₂ reduction of up to 9% for a given case on this specific test cycle.     

Modeling and thermal management of proton exchange membrane fuel cell for fuel cell/battery hybrid automotive vehicle

The proton exchange membrane fuel cell (PEMFC) stack is a key component in the fuel cell/battery hybrid vehicle. Thermal management and optimized control of the PEMFC under real driving cycle remains a challenging issue. This paper presents a new hybrid vehicle model, including simulations of diver behavior, vehicle dynamic, vehicle control unit, energy control unit, PEMFC stack, cooling system, battery, DC/DC converter, and motor. The stack model had been validated against experimental results. The aim is to model and analyze the characteristics of the 30 kW PEMFC stack regulated by its cooling system under actual driving conditions. Under actual driving cycles (0–65 kW/h), 33%–50% of the total energy becomes stack heat; the heat dissipation requirements of the PEMFC stack are high and increase at high speed and acceleration. A PID control is proposed; the cooling water flow rate is adjusted; the control succeeded in stabilizing the stack temperature at 350 K at actual driving conditions. Constant and relative lower inlet cooling water temperature (340 K) improves the regulation ability of the PID control. The hybrid vehicle model can provide a theoretical basis for the thermal management of the PEMFC stack in complex vehicle driving conditions.     

Optimization of fuel cell system operating conditions for fuel cell vehicles

Proton exchange membrane fuel cell (PEMFC) technology for use in fuel cell vehicles and other applications has been intensively developed in recent decades. Besides the fuel cell stack, air and fuel control and thermal and water management are major challenges in the development of the fuel cell for vehicle applications. The air supply system can have a major impact on overall system efficiency. In this paper a fuel cell system model for optimizing system operating conditions was developed which includes the transient dynamics of the air system with varying back pressure. Compared to the conventional fixed back pressure operation, the optimal operation discussed in this paper can achieve higher system efficiency over the full load range. Finally, the model is applied as part of a dynamic forward-looking vehicle model of a load-following direct hydrogen fuel cell vehicle to explore the energy economy optimization potential of fuel cell vehicles.     

An overview: Current progress on hydrogen fuel cell vehicles

The harmful consequences of pollutants emitted by conventional fuel cars have prompted vehicle manufacturers to shift towards alternative energy sources. Currently, fuel cells (FCs) are commonly regarded as highly efficient and non-polluting power sources capable of delivering far greater energy densities and energy efficiency than conventional technologies. Proton exchange membrane fuel cells (PEMFC) are viewed as promising in transportation sectors because of their ability to start at cold temperatures and minimal emissions. PEMFC is an electrochemical device that converts hydrogen and oxidants into electricity, water, and heat at various temperatures. The pros and cons of the technology are discussed in this article. Various fuel cell types and their applications in the portable, automobile, and stationary sectors are discussed. Additionally, recent issues associated with existing fuel cell technology in the automobile sector are reviewed.     

Dynamic performance assessment of the efficiency of fuel cell-powered bicycle: An experimental approach

Zero-emission fuel cell driven systems are regarded as promising technological advances in the future of the transportation industry that have the potential to replace internal combustion engines. The design, performance, and efficiency properties of a vehicle are often stated to be some of the key challenges in its commercialization. This paper highlights a polymer electrolyte membrane fuel cell (PEMFC)-powered system of an electric bicycle. The system consists of a 250-W fuel cell, ECU, battery pack, DC/DC converter, electric motor, and other supporting equipment. After introducing the different parts of the bicycle, its overall efficiency will be discussed in great detail. The efficiency of fuel cells is not specific; it is a subordinate to the power density where the system operates. Experimental work has been conducted to measure the values of the efficiency and energy flow. The results indicated a maximum fuel cell efficiency of 63% and an overall system efficiency of 35.4%. The latter value is expressed with regards to the Lower Heating Value (LHV) of hydrogen. All measurements were taken for the cruising conditions of the vehicle and its corresponding to power consumption. The results are superior to those of a standard internal ignition engine. The fuel cell performance is least efficient when functioning under maximum output power conditions.     

Study of a post-fire verification method for the activation status of hydrogen cylinder pressure relief devices

To safely remove from its fire accident site a hydrogen fuel cell vehicle equipped with a carbon fiber reinforced plastic composite cylinder for compressed hydrogen (CFRP cylinder) and to safely keep the burnt vehicle in a storage facility, it is necessary to verify whether the thermally-activated pressure relief device (TPRD) of the CFRP cylinder has already been activated, releasing the hydrogen gas from the cylinder. To develop a simple post-fire verification method on TPRD activation, the present study was conducted on the using hydrogen densitometer and Type III and Type IV CFRP cylinders having different linings. As the results, TPRD activation status can be determined by measuring hydrogen concentrations with a catalytic combustion hydrogen densitometer at the cylinder's TPRD gas release port.     

Design of an energy management technique for high endurance unmanned aerial vehicles powered by fuel and solar cell systems

A hybrid electric propulsion system with a power switching technique is tested in flights of long endurance unmanned aerial vehicle, interchanging power supply between fuel and solar cell systems. A fuel cell system consists of a sodium borohydride-based hydrogen generator, a 300 W scale proton-exchange membrane fuel-cell stack that is connected with a battery and a customized controller. The solar cell system consists of a maximum power point track device, a battery and 80 W solar arrays on each wing. These two power sources are controlled by a power switching technique using solid-state relays, which selectively permit either one of the two power sources, or both, to meet the load variation during flight. Using this method, both power sources are independently operated to deliver necessary power to satisfy the load demand, which means that it can extend flight endurance by alternating between solar and fuel cells with high-system reliability. The flight test is conducted over a period of 1.5 h to evaluate the designed hybrid power system by switching from fuel cell power to solar cell power, and vice versa, thereby proving system reliability as well as extending the operational time for flight.     

Thermal analysis and management of proton exchange membrane fuel cell stacks for automotive vehicle

The thermal management of a proton exchange membrane fuel cell (PEMFC) is crucial for fuel cell vehicles. This paper presents a new simulation model for the water-cooled PEMFC stacks for automotive vehicles and cooling systems. The cooling system model considers both the cooling of the stack and cooling of the compressed air through the intercooler. Theoretical analysis was carried out to calculate the heat dissipation requirements for the cooling system. The case study results show that more than 99.0% of heat dissipation requirement is for thermal management of the PEMFC stack; more than 98.5% of cooling water will be distributed to the stack cooling loop. It is also demonstrated that controlling cooling water flow rate and stack inlet cooling water temperature could effectively satisfy thermal management constraints. These thermal management constraints are differences in stack inlet and outlet cooling water temperature, stack temperature, fan power consumption, and pump power consumption.     

Multi-mode control strategy for fuel cell electric vehicles regarding fuel economy and durability

A proton electrolyte membrane (PEM) fuel cell system and a Li-ion battery (LIB) are two power sources in a fuel cell electric vehicle (FCEV). The fuel cell system is composed of a fuel cell stack and subsystems for air/hydrogen supply and cooling water. The operation procedure of the fuel cell system can be generally separated into several processes, e.g. starting up, normal/abnormal working and shutting down. In this paper, a multi-mode real-time control strategy for a FCEV is proposed. The strategy is established based on three typical processes (starting up, normal working, shutting down) of the fuel cell system, taking the fuel economy and system durability into consideration. The strategy is applied into a platform vehicle for the 12th 5-year project of “the next generation technologies of fuel cell city buses”. Experiments of the “China city bus typical cycle” on a test bench for the bus were carried out. Results show that, the fuel economy is 7.6 kg (100 km)⁻¹ in the battery charge-sustaining status. In a practical situation, a total driving mileage of more than 270 km can be achieved. Cycle testing also showed that, the degradation rate of the fuel cell was reduced to half of the original level. No performance degradation of the LIB system was observed in the cycling test.