You can copy/paste the text if you wish. We just ask you to refer to us as information source. Fuel cell with introduction, types with description, application and uses. You can download the full document in pdf format here. Benefits of the fuel cell technology. Stacks and systems. Now moving from the single fuel cell unit to real- world systems, what do we have to add to get them all setup and why? Company specializing in alkaline fuel cell technology, derived from ammonia. Company profile, history, management, patents, publications and product catalog. A fuel cell vehicle (FCV) or fuel cell electric vehicle (FCEV) is a type of hybrid vehicle which uses a fuel cell, instead of an engine, in combination with a storage device, such as a battery, to power its on-board electric. Since Apollo 13 many people have asked me, 'Did you have suicide pills on board?' We didn't, and I never heard of such a thing in the eleven years I spent as an astronaut and NASA executive. I did, of course, occasionally. Similar to all electrical devices the output power of a fuel cell is equal to the current multiplied by the voltage. While the current may be in theory indefinitely increased by increasing the reaction area between hydrogen- and oxygen- containing reactants, the voltage, i. The basic principle of a fuel cell section). Moreover, potential losses inevitably occur in a fuel cell due to slow kinetics of the electrode reactions, especially at the cathode where the reaction rate is about 1. Therefore, under operational load the actual voltage of a single fuel cell is in the 0. V range. Useful voltages are generally achieved by interconnecting multiple unit fuel cells in series. This is the concept of . In this configuration, the conductive interconnecting element is in contact with both the anode of one cell and with the cathode of the adjacent cell, hence the name . Flow channels are grooved on each side for gas distribution and water removal. Bipolar plate materials are highly impermeable to gases in order to avoid harmful fuel and oxidant mixtures: these materials are mainly graphite, polymer- graphite composites and metals such as stainless steel or aluminum (most often coated with a corrosion- resistant alloy). Bipolar stacking has been up to now the most simple and the most conventional configuration in most types of fuel cell systems, particularly low- temperature systems. Apollo program; Country of origin: United States: Responsible organization: NASA: Purpose: Manned lunar landing: Status: completed: Program history; Cost: $25.4 billion (1973) Program duration: 1961–1972: First flight: AS. The fuel cell concept was first demonstrated by William R. Grove, a British physicist, in 1839. The cell he demonstrated was very simple, probably resembling this: Electrolysis setup. By application of a voltage across the two. Emergency Return The Malfunction. The first check of the situation after the malfunction found that two of the three fuel cells, which were the prime source of power for the mission, had been lost. The crew's reaction to this. The Apollo Flight Journal The Apollo On-board Computers By Phill Parker . 16, No.10, October 1974 (pp. The Fifth Mission: The First Lunar Landing. Apollo 11 was a Type G mission, a piloted lunar landing demonstration. The primary objective of the Apollo program was to perform a. In other words, Apollo needed to create something fresh and different – something that looked like nothing else. Apollo designers didn’t want folks linking the Arrow’s design cues to some other vehicle or with a styling. For high- temperature systems such as SOFCs however, sealing issues due to large temperature gradients during operation have driven research toward alternative arrangements, leading to the development of a tubular design. In tubular stacking, the elements of the fuel cell assembly (anode/electrolyte/cathode) are arranged concentrically forming a hollow cylinder. Fuel is fed on the anode side, either through the inside or along the outside of the cylinder, and oxidant is fed on the cathode side. Series connection is accomplished by vertical addition of the cells (in the height direction) while parallel connection is accomplished by horizontal addition of the cells (in the same plan). The tubular design is well suited for high- temperature applications since it minimizes the number of seals in the fuel cell system thus alleviating problems due to unmatching expansion coefficients. Planar stacking is a second alternative to the bipolar arrangement, in which cells are connected laterally rather than vertically. Several planar designs have been explored, mostly for small- scale systems: the banded- membrane design, in which the anode of one cell is connected to the cathode of the adjacent cell across the band; and the flip- flop design, in which there is interconnection of unit cells on the same side of the band thanks to alternate anodes and cathodes. The main advantage of this third arrangement is a better volumetric packaging, yet at the expense of increased resistance losses. Besides the fuel cell stack, referred to as the fuel cell subsystem, the other subsystems that are needed to keep the whole system running can be classified into three categories: 1. The thermal management (cooling) system. The fuel delivery/processing system. The power electronics (and safety) system for power regulation and monitoring. The components that draw electrical power from the fuel cell causing parasitic power losses are called ancillaries. For example, an actively cooled fuel cell system will employ an ancillary device like a fan, a blower or a pump for cooling fluid circulation. Ancillaries include thermal, water and air management systems. As fuel cells are usually about 3. A cooling system is required for fuel cells that cannot benefit from natural heat regulation by the ambient, i. The cooling fluid can be either a gas (air), or a liquid (distilled water or aqueous glycol- based solution) depending on the heat dissipation capacity needs and the other characteristics of the fuel cell system. Given that the heat capacity of liquids is much greater than that of gases; consequently, small liquid- cooled devices will generally be far more efficient than their massive gas- cooled equivalents. In advanced fuel cell systems, the heat released by the stack can be purposely recovered for internal (1,2) and/or external (3) heating. Examples follow: (1)Heat can be used for conditioning reactant gases = pre- heating and humidification; (2)Heat can be used for providing energy to the endothermic reforming reaction of the fuel (see below); (3)Heat can be used for providing space and/or water heating in a house, passenger compartment warming in a car, etc. Cogeneration by heat recovery is a powerful means to increase the overall efficiency of fuel cells systems up to 8. It is very advantageous in high- temperature fuel cell systems, mainly PAFCs and SOFCs. Given that almost all practical fuel cells today use hydrogen or compounds containing hydrogen as a fuel, there are two primary options to feed a fuel cell: (1) in a direct way by pure hydrogen or (2) by integrated upstream processing of a . The fuel management subsystem will include a hydrogen reservoir related to the physical state of hydrogen stored: high- pressure gas cylinder (up to 7. K) for liquid hydrogen in extreme situations where mass storage capacity is especially important, e. The advantages of direct hydrogen feeding include high performance, simplicity, and the elimination of impurity concerns. But the current storage options, mainly in the form of compressed gas or reversible metal hydride, are not optimal yet.(2) In the second case, the system is more complex. Since hydrogen is not available as is, it must be derived from hydrogen- containing fuels called . Except a few hydrogen carriers that are directly usable in fuel cells systems including methanol in DMFCs and methane in SOFCs of MCFCs, a vast majority of them must be processed before they enter the fuel cell. This is possibly achieved in two different ways: 1. By direct electro- oxidation. By chemical reforming. A further distinction must be made between external reforming where the reaction takes place in a reformer separated from the fuel cell, and internal reforming where the reaction takes place at the catalyst surface inside the fuel cell. Direct electro- oxidation of the carrier fuel into hydrogen is attractive because it avoids the extra step of reforming it prior to the fuel cell reaction and all chemical reactors associated with it. Direct methanol fuel cells are based on this principle, and other simple compounds like ethanol and formic acid can also be employed. Unfortunately, the overall electrical efficiency of this category of fuel cells is significantly reduced due to the complexity of the reactions. As a result, the energy density gained by the absence of a reformer or a fuel reservoir can be largely offset by the low fuel efficiency and the need for larger stacks. Direct electro- oxidation is best applied in portable applications, where simple systems, minimal ancillaries, and low power are needed. External reformers are composed of several devices for successively treating chemically or physically the gas reactant (hydrogen carrier) and the products (including hydrogen). Several ways are possible, and the exact conditions will vary with the process and the hydrogen carrier. The most used process is steam reforming: fuel molecules are burned over a catalyst (nickel- , copper oxide- or zinc- based) under the presence of water steam at a few hundred degrees Celsius (. After reaction, a hydrogen- containing gas mixture is obtained that in certain cases has to be purified in multi- processing steps. This additional post- treatment is required to remove poisons for electrodes and feed the fuel cell with a pure hydrogen gas, which is an important requirement for low- temperature systems. Internal fuel reforming is possible for high- temperature fuel cells with certain fuels. In this case, the fuel is mixed with steam prior entering the fuel cell anode where it is both reformed into hydrogen and the usual co- products CO and CO2 and then split into protons in the fuel cell reaction. Under these high- temperature conditions, the presence of carbon monoxide is not an issue anymore since it serves as fuel. It is further processed in situ like hydrogen thus contributing to the fuel cell net efficiency. Although the different interplaying parameters are difficult to optimize, internal reforming is a promising solution because it gives an elegant (and economically winning) answer to a complex question. Fuel reforming is best applied in stationary applications, where fuel flexibility is important and the excess heat can be managed inside or outside the system. However, fuel reforming technology is not a current choice of authorities for transportation applications since the existing technologies do not meet the technical or economic targets, and only marginal improvement is expected in efficiency and emissions between a hybrid vehicle and an FC vehicle equipped with on- board reforming. For any of the fuel delivery/processing systems considered previously, gas pumps are used to feed the gas reactants in the fuel cell, and a water purge system must also be integrated. Last but not least, it is necessary to manage the direct power output of the fuel cell into usable power. The power electronics subsystem consists of: (1) Power regulation; (2) Power inversion; (3) Power monitoring and control; (4) Power supply management. Power conditioning corresponds to regulation and inversion of the fuel cell power output.(1)Regulation allows delivery of power at a voltage level that is stable over time from a fuel cell output power that most often is not.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
December 2016
Categories |