Fuel Cell Fundamentals 2nd Edition Answers.rarl
FIGURE 2. Flow chart of the conventional installation of a microbial fuel cell at the secondary treatment stage, placing downstream a solid contact tank, a secondary settler, tube, and recycled sludge pump station (Logan, 2008).
Fuel Cell Fundamentals 2nd Edition Answers.rarl
FIGURE 3. Flow chart of a microbial fuel cell installation at the secondary treatment stage with the use of a membrane bioreactor receiving the required power from the cell (Logan, 2008; AlSayed et al., 2020).
There are several methods that can be used to treat industrial effluents containing heavy metals, such as solvent extraction, filtration, ion exchange, coagulation, sedimentation, oxidation, and adsorption. However, these techniques have several disadvantages; for example, high cost, low removal efficiency, regeneration, and the problem of secondary contaminations . Therefore, it is proposed to implement new techniques which are more cost effective, have a higher removal efficiency and have less susceptibility to secondary contamination. Among these methods is the use of microbial fuel cell (MFC) technology.
Microbial fuel cells can be used to produce energy while treating a wastewater containing heavy metals to decrease their concentrations to the allowable levels before discharge into the environment. Metal pollutants, such as chromium, copper, vanadium and mercury, have been removed using two chambered MFC cells [16,17]. Heavy metals in MFCs are removed through the reduction of the cathode metal in the anaerobic cathodic chamber, while in the anodic chamber, organic matters are used as sources of carbon and electron donors . It has been demonstrated that such processes as biosorption and precipitation reactions (i.e., sulfides and hydroxides) greatly aided in the removal of heavy metals from wastewater in the MFC system . Table 2presents a summary of previous studies on the removal of different metals using MFC technologies along with the maximum removal and maximum power generation.
As Cummins looks to the future, we see a shift in the energy market. With that change comes new possibilities and opportunities beyond our traditional product set. To better serve our customers and our planet, Cummins is innovating new, sustainable forms of power and bringing a wide range of new possibilities to the New Power product portfolio, providing a way to produce clean hydrogen to power hydrogen fuel cells, supply industrial processes or produce green chemicals like fertilizers, renewable natural gas and methanol.
The hydrogen produced from an electrolyzer is perfect for use with hydrogen fuel cells. Working much like a battery, fuel cells do not run down or need charging and produce electricity and heat as long as fuel is supplied. You can learn more about batteries and fuel cells here. The fuel cells use the hydrogen to generate electricity with zero emissions at the point of use. That means no fossil fuels or harmful emissions come from the tailpipe.
Even better, when the electrolyzer system is powered by a renewable energy source, such as a hydropower from the Columbia River Dams, the hydrogen produced is considered renewable and CO2-free from well to wheel. Learn more about well to wheel emissions in all-electric and fuel cell applications.
Cummins made a bold entry into the hydrogen economy in September 2019 with the acquisition of Hydrogenics, a global hydrogen fuel cells and electrolyzer technology manufacturer. Cummins continues to make quick progress in innovating new products and applications in the hydrogen space, and currently, there are two different types of electrolyzers offered by Cummins:
Interest in hydrogen-powered rail vehicles has gradually increased worldwide over recent decades due to the global pressure on reduction in greenhouse gas emissions, technology availability, and multiple options of power supply. In the past, research and development have been primarily focusing on light rail and regional trains, but the interest in hydrogen-powered freight and heavy haul trains is also growing. The review shows that some technical feasibility has been demonstrated from the research and experiments on proof-of-concept designs. Several rail vehicles powered by hydrogen either are currently operating or are the subject of experimental programmes. The paper identifies that fuel cell technology is well developed and has obvious application in providing electrical traction power, while hydrogen combustion in traditional IC engines and gas turbines is not yet well developed. The need for on-board energy storage is discussed along with the benefits of energy management and control systems.
With the development of rail transportation, there are mainly two primary systems at present in terms of power supply: one is railway system electrification (i.e. via overhead catenary or third rail) and the other the on-board diesel engine generated electricity. Introduced in Germany by Siemens in 1879 , the railway electrification systems are mainly applied for urban railways, high-speed trains, and high-density operations. On the other hand, on-board diesel-electric systems were introduced in the USA in the 1920s . Diesel-electric systems were initially popular in North America and nowadays are the most common freight locomotive around the world. The popularity of diesel engines in rail applications is due to the high compression ratio of diesel engines and the diesel ignition process which achieves up 45% thermal efficiency. The connected electric drive system, alternator, and traction motors deliver typically 88% of this energy to the wheels. However, the diesel fuel combustion with air causes harmful emissions that impact air quality and result in greenhouse gases (GHG). Currently, modern science and technology have provided options for on-board power supply which can be considered to reduce harmful emissions and allow rail transportation using clean power sources, avoiding primary fossil fuels. Of particular interest is the use of hydrogen fuel cells (FC) which is a clean (zero emission) on-board source of electrical power. Such alternative clean power systems can be hybridised with traditional diesel engine systems or hybridised with energy storage systems (ESS) consisting of batteries and/or supercapacitors and/or flywheels.
It was pointed out in  that using hybrid power systems combining FC and LIB is an effective approach to reduce the emissions of rail vehicles for non-electrified lines. Several challenges, including the implications of having hydrogen fuel cells on passenger services and options for the applications of ESS for hybrid systems, were addressed by the authors, and they expected that several technological breakthroughs would appear in the near future. Among them, the development of a rail vehicle FC hybrid system suitable for an efficient combination with current train control systems is a key issue to be solved, and the evaluation of safety with on-board hydrogen was another objective . Safety evaluation standards and related regulations for high-pressure hydrogen containers and hydrogen manufacturing facilities must also be prepared for commercial services.
Electricity can be produced in an FC by using clean hydrogen generated by renewable energy sources such as solar, wind, hydro or hydrogen-rich hydrocarbon fuels, and it is then fed directly into a rail vehicle propulsion system or stored in batteries . An FC locomotive could be built with the same power capability as a diesel-electric one, but there are significant challenges with on-board fuel storage and/or the need for frequent refilling stations. The FC locomotive would, of course, be less noisy and have less vibration. If the storage/refilling problem could be solved, hydrogen FC technology could provide a long-term local zero emissions with fast refuelling techniques (like diesel), flexibility, self-electrification, integration with renewable energy sources, and a low-noise operation. It is pointed out in  that a PEMFC, which operates at moderate temperatures (80 C) and is best fitted to non-permanent demand cycles, has been proposed for applications like light rail and trams, commuter and regional trains, shunt/switch locomotives, and underground mine locomotives. A solid oxide fuel cell (SOFC), on the other hand, has higher efficiency than other types of FCs, but needs to work at a high operating temperature (1,000 C). Given the steady duty cycles of freight or heavy haul locomotives which meet the SOFC regime requirement, it has been seen as a promising technology for this type of rail transportation. The following tables list the data provided in some literature which would give the vision for the development of some hydrogen FC locomotives in the near future.
Various types of FCs can be considered as rail vehicle power supplies with regard to performance, cost, reliability, and durability . Higher temperature fuel cells are drawing more attention due to no use of expensive metal catalyst and because exhaust thermal energy can be managed efficiently with other thermal systems for cogeneration. Higher temperature fuel cells are SOFCs, and molten carbonate fuel cells (MCFCs), and lower temperature cells are PEMFCs, phosphoric acid fuel cells (PAFCs), and alkaline fuel cells (AFCs). Figure 2 shows some popular fuels cell technologies.
It is believed that comprehensive mathematical modelling and advanced simulation methods can provide precise insight into the issues arising in the designs and optimisations of hydrogen fuel cell (FC)-powered hybrid rail vehicles [73, 74]. The main objective is to use a reputable train model and suitable simulation techniques to study the performance of a hydrogen FC-powered hybrid train system consisting of traction motors, hydrogen FC and ESS, etc. To numerically examine such a rail vehicle system, electrochemical, logical, and physical equations are adopted to build numerical models. Five subsystems can be defined according to their roles within such a system [75,76,77]: 350c69d7ab