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Alkaline Fuel Cells(AFCs)
Published in Xianguo Li, Principles of Fuel Cells, 2005
Another major advantage is that alkaline fuel cells can use a wider range of possible catalysts, at least thermodynamically. For example, AFCs can possibly use non-Noble catalysts such as nickel which is less costly than the noble metals required for other low-temperature acid electrolyte fuel cells currently under development. In practice, however, low temperature, as well as high-performance high temperature AFCs use significant quantities of Noble metal catalysts to guarantee good performance and long lifetime. In U.S. space shuttle fuel cells, the anode consists of 10 mg/cm2 of pure Noble metal blacks (80% platinum and 20% Pd), the cathode contains 20 mg/cm2 of a mixture of 90% gold and 10% platinum. Operating at 0.86V per cell at 470 mA/cm2 on hydrogen and oxygen, this represents a Noble metal catalyst requirement of 74 mg/kW! The Elenco’s H2–air AFCs, developed as power source for buses, use supported platinum at a total loading of 0.7 mg/cm2 for the anode and cathode. With performance of 0.7V per cell at 100 mA/cm2, the Elenco cell requires 10 mg of platinum per kilowatt. Platinum loadings of 0.15 mg/cm2 have been suggested as being possible.
Polymers and Composites for Fuel Cell Applications
Published in Inamuddin, Mohd Imran Ahamed, Rajender Boddula, Tariq Altalhi, Polymers in Energy Conversion and Storage, 2022
The MEA (membrane electrode assembly) is the core of the fuel cell, so it must be designed properly, since the MEA’s purpose is to effectively regulate the movement of electrons released at the negative electrode (hydrogen oxidation) to the electron-consuming reaction at the positive electrode [89, 90]. In an alkaline fuel cell, this is normally accomplished by separating the cathodic and anodic reactions using a membrane that conducts protons (H+) and hydroxide ions. From the anode to the cathode, electrons are channeled into an external circuit. The anode and cathode reactions of polymer electrolyte fuel cells are regulated by regulating the flow and path of electrons, as shown in Equations (8.4 and 8.5).
Electrochemical Energy
Published in Prasanth Raghavan, Fatima M. J. Jabeen, Polymer Electrolytes for Energy Storage Devices, 2021
P. P. Abhijith, N. S. Jishnu, Neethu T. M. Balakrishnan, Akhila Das, Jou-Hyeon Ahn, Jabeen Fatima M. J., Prasanth Raghavan
From this review, it is clear that each energy storage system has its own strengths and weakness. High energy density and high power density are the two main properties required for an energy storage system. In most cases, supercapacitors provide low energy density and batteries provide low power densities. Rechargeable batteries are the best and most reliable sources for energy storage, of which lithium-ion batteries show the highest efficiency. Lithium-sulfur batteries are known to be the most efficient batteries capable of powering a smartphone for five continuous days. While comparing supercapacitors with batteries, the supercapacitors have a life expectancy of 10 to 15 years, whereas the batteries can last up to only 5–10 years. It has also been proved that supercapacitors can reach up to one million charge-discharge cycles, whereas typical batteries have only 500–1000 cycles, which makes supercapacitors suitable for use in various applications such as in automobiles, buses, trains, cranes, and elevators, where they are used for regenerative braking, short-term energy storage, or burst-mode power delivery. The simplicity of design and the cheap cost of the fuel cells is probably suitable for their applications in static power generation. Alkaline fuel cells are among the most efficient type of fuel cells, reaching up to 60% efficiency and up to 87% in combined heat and power generation. Of the fuel cells, polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) have attracted the greatest interest regarding applications such as distributed power generation, portable applications, and all applications concerning the automotive and transportation sector.
Integrated system based on ammonia alkaline fuel cell with heat recovery for multigeneration
Published in International Journal of Green Energy, 2022
Khaled H.M. Al-Hamed, Ibrahim Dincer
The present system has an overall energy efficiency of 49.3% which is higher than a standalone molten alkaline fuel cell that typically has an energy efficiency of 35.0%. This increase in efficiency is because of the more electricity produced using the Rankine cycles integrated into the fuel cell. Also, space heating and freshwater contribute slightly to the overall energy efficiency. For the overall exergy efficiency, it can reach a value of 49.8%. The overall energy and exergy efficiencies are close to each other in value because this system is an electricity-intensive system, meaning that the majority of the useful output is electricity. The reason that the overall exergy efficiency is higher than the overall energy efficiency is the difference in the value of the denominators in both expressions. The exergy value of the ammonia fuel is less than the higher heating value of ammonia which means this system is utilizing the exergy of ammonia in a better way than using its heat content. Another reason for this difference is that this integrated system produces much more power than the other useful outputs, namely space heating and freshwater.
Energy extraction from seaweed under low temperatures by using an alkaline fuel cell
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2018
Li Yang, Ying Wang, Xianhua Liu, Chunghyok Kim, Feng Dong, Shengling Li, Jie Ding, Yang Li, Irfan Muhammad, Pingping Zhang
The commonly used approaches to derive energy from marine algae include the production of methane, ethanol, and conversion to hydrogen, but those approaches are hindered by technology and economic problems (Thygesen et al. 2011; Wang et al. 2013). An alternative approach to drive energy from algae is to feed its hydrolysate into a fuel cell and extract energy from its oxidation to generate electricity.There have been some reports on algae-fed microbial fuel cells (MFCs). Velasquez-Orta, Curtis, and Logan (2009) used Chorella vulgaris and Ulva lactuca as fuel and produced maximum power densities of 0.98 W/m2 and 0.76 W/m2, respectively (Velasquez-Orta, Curtis, and Logan 2009); Rashid et al. (2013) used Scenedesmus sp as fuel and produced maximum power density reached 1.780 W/m2 (Rashid et al. 2013). However, the performance of algae-fed MFCs reported were extremely low. Alkaline fuel cell (AFC) has the advantages of high power density, low cost and low operating temperature. In addition, it has been reported AFC can use a wide variety of biomass sources, including alcohol, glucose, cellulose, reed and algae. The use of seaweed hydrolysates in AFC has been tested with red algae (Hao et al. 2014; Piana et al. 2010) and E. prolifera (Liu, Liu et al. 2016a) as raw materials. Enhanced electricity generation was obtained with power densities of 0.154 W/m2 and 3.810 W/m2, respectively. However, despite the promising results of previous work, the low power density and high cost of pretreatment remain major hindrances in practicing low-temperature biomass fuel cell technology. Compared with other substrates for fuel cells, biomass is relatively hard to be oxidized under low temperatures. For example, glucose molecule can release 24 electrons in the fuel cell theoretically. However, the maximum number of extracted electrons per glucose molecule had been shown to be less than two (Yang et al. 2015; Liu et al. 2013; Liu, 2018a; Hao et al. 2014).