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146-497: A solid oxide fuel cell (or SOFC ) is an electrochemical conversion device that produces electricity directly from oxidizing a fuel . Fuel cells are characterized by their electrolyte material; the SOFC has a solid oxide or ceramic electrolyte. Advantages of this class of fuel cells include high combined heat and power efficiency, long-term stability, fuel flexibility, low emissions, and relatively low cost. The largest disadvantage

292-534: A d 2 2 D s 2 + ( 1 + ν ) ln ⁡ ( D s u p D l o a d ) ) {\displaystyle \sigma _{cr}={\frac {3F_{cr}}{2\pi h_{s}^{2}}}+{\Biggl (}(1-\nu ){\frac {D_{sup}^{2}-D_{load}^{2}}{2D_{s}^{2}}}+(1+\nu )\ln \left({\frac {D_{sup}}{D_{load}}}\right){\Biggr )}} Where: σ c r {\displaystyle \sigma _{cr}} = failure stress of

438-403: A cathode , and an electrolyte that allows ions, often positively charged hydrogen ions (protons), to move between the two sides of the fuel cell. At the anode, a catalyst causes the fuel to undergo oxidation reactions that generate ions (often positively charged hydrogen ions) and electrons. The ions move from the anode to the cathode through the electrolyte. At the same time, electrons flow from

584-490: A cogeneration power plant in hospitals, universities and large office buildings. In recognition of the fuel cell industry and America's role in fuel cell development, the United States Senate recognized October 8, 2015 as National Hydrogen and Fuel Cell Day , passing S. RES 217. The date was chosen in recognition of the atomic weight of hydrogen (1.008). Fuel cells come in many varieties; however, they all work in

730-676: A SOFC system are less than those from a fossil fuel combustion plant. The chemical reactions for the SOFC system can be expressed as follows: SOFC systems can run on fuels other than pure hydrogen gas. However, since hydrogen is necessary for the reactions listed above, the fuel selected must contain hydrogen atoms. For the fuel cell to operate, the fuel must be converted into pure hydrogen gas. SOFCs are capable of internally reforming light hydrocarbons such as methane (natural gas), propane, and butane. These fuel cells are at an early stage of development. Challenges exist in SOFC systems due to their high operating temperatures. One such challenge

876-471: A battery, except as hydrogen, but in some applications, such as stand-alone power plants based on discontinuous sources such as solar or wind power , they are combined with electrolyzers and storage systems to form an energy storage system. As of 2019, 90% of hydrogen was used for oil refining, chemicals and fertilizer production (where hydrogen is required for the Haber–Bosch process ), and 98% of hydrogen

1022-812: A century later following the invention of the hydrogen–oxygen fuel cell by Francis Thomas Bacon in 1932. The alkaline fuel cell , also known as the Bacon fuel cell after its inventor, has been used in NASA space programs since the mid-1960s to generate power for satellites and space capsules . Since then, fuel cells have been used in many other applications. Fuel cells are used for primary and backup power for commercial, industrial and residential buildings and in remote or inaccessible areas. They are also used to power fuel cell vehicles , including forklifts, automobiles, buses, trains, boats, motorcycles, and submarines. There are many types of fuel cells, but they all consist of an anode ,

1168-405: A cobalt co-catalyst. Oxide anodes including zirconia-based fluorite and perovskites are also used to replace Ni-ceramic anodes for carbon resistance. Chromite i.e. La 0.8 Sr 0.2 Cr 0.5 Mn 0.5 O 3 (LSCM) is used as anodes and exhibited comparable performance against Ni–YSZ cermet anodes. LSCM is further improved by impregnating Cu and sputtering Pt as the current collector. The electrolyte

1314-651: A complete, closed-loop system: Solar panels power an electrolyzer, which makes hydrogen. The hydrogen is stored in a 500-U.S.-gallon (1,900 L) tank at 200 pounds per square inch (1,400 kPa), and runs a ReliOn fuel cell to provide full electric back-up to the off-the-grid residence. Another closed system loop was unveiled in late 2011 in Hempstead, NY. Fuel cells can be used with low-quality gas from landfills or waste-water treatment plants to generate power and lower methane emissions . A 2.8 MW fuel cell plant in California

1460-449: A concentrated solution of KOH or NaOH which serves as an electrolyte. H 2 gas and O 2 gas are bubbled into the electrolyte through the porous carbon electrodes. Thus the overall reaction involves the combination of hydrogen gas and oxygen gas to form water. The cell runs continuously until the reactant's supply is exhausted. This type of cell operates efficiently in the temperature range 343–413   K (70 -140 °C) and provides

1606-531: A few disadvantages associated with YSZ as anode material. Ni coarsening, carbon deposition, reduction-oxidation instability, and sulfur poisoning are the main obstacles limiting the long-term stability of Ni-YSZ. Ni coarsening refers to the evolution of Ni particles in doped in YSZ grows larger in grain size, which decreases the surface area for the catalytic reaction. Carbon deposition occurs when carbon atoms, formed by hydrocarbon pyrolysis or CO disproportionation, deposit on

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1752-597: A fuel-to-electricity efficiency of 50%, considerably higher than the 37–42% efficiency of a phosphoric acid fuel cell plant. Efficiencies can be as high as 65% when the fuel cell is paired with a turbine, and 85% if heat is captured and used in a combined heat and power (CHP) system. FuelCell Energy, a Connecticut-based fuel cell manufacturer, develops and sells MCFC fuel cells. The company says that their MCFC products range from 300 kW to 2.8 MW systems that achieve 47% electrical efficiency and can utilize CHP technology to obtain higher overall efficiencies. One product,

1898-493: A here-to-fore neglected innate, vital force, which he termed "animal electricity," which activated nerves and muscles spanned by metal probes. He believed that this new force was a form of electricity in addition to the "natural" form produced by lightning or by the electric eel and torpedo ray as well as the "artificial" form produced by friction (i.e., static electricity). Galvani's scientific colleagues generally accepted his views, but Alessandro Volta rejected

2044-412: A high operating temperature provides an advantage by removing the need for a precious metal catalyst like platinum, thereby reducing cost. Additionally, waste heat from SOFC systems may be captured and reused, increasing the theoretical overall efficiency to as high as 80–85%. The high operating temperature is largely due to the physical properties of the YSZ electrolyte. As temperature decreases, so does

2190-403: A higher current to be supplied. Such a design is called a fuel cell stack . The cell surface area can also be increased, to allow higher current from each cell. In the archetypical hydrogen–oxide proton-exchange membrane fuel cell (PEMFC) design, a proton-conducting polymer membrane (typically nafion ) contains the electrolyte solution that separates the anode and cathode sides. This

2336-432: A hot water storage tank to smooth out the thermal heat production was a serious disadvantage in the domestic market place where space in domestic properties is at a great premium. Delta-ee consultants stated in 2013 that with 64% of global sales the fuel cell micro-combined heat and power passed the conventional systems in sales in 2012. The Japanese ENE FARM project stated that 34.213 PEMFC and 2.224 SOFC were installed in

2482-568: A hydrogen source would create less than one ounce of pollution (other than CO 2 ) for every 1,000 kW·h produced, compared to 25 pounds of pollutants generated by conventional combustion systems. Fuel Cells also produce 97% less nitrogen oxide emissions than conventional coal-fired power plants. One such pilot program is operating on Stuart Island in Washington State. There the Stuart Island Energy Initiative has built

2628-455: A hydrogen-rich gas in the anode, eliminating the need to produce hydrogen externally. The reforming process creates CO 2 emissions. MCFC-compatible fuels include natural gas, biogas and gas produced from coal. The hydrogen in the gas reacts with carbonate ions from the electrolyte to produce water, carbon dioxide, electrons and small amounts of other chemicals. The electrons travel through an external circuit, creating electricity, and return to

2774-420: A motor or power a light. A galvanic cell whose electrodes are zinc and copper submerged in zinc sulfate and copper sulfate , respectively, is known as a Daniell cell . The half reactions in a Daniell cell are as follows: In this example, the anode is the zinc metal which is oxidized (loses electrons) to form zinc ions in solution, and copper ions accept electrons from the copper metal electrode and

2920-507: A pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from substances that are already present in the battery. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied. The first fuel cells were invented by Sir William Grove in 1838. The first commercial use of fuel cells came almost

3066-459: A potential of about 0.9   V. Alkaline anion exchange membrane fuel cell (AAEMFC) is a type of AFC which employs a solid polymer electrolyte instead of aqueous potassium hydroxide (KOH) and it is superior to aqueous AFC. Solid oxide fuel cells (SOFCs) use a solid material, most commonly a ceramic material called yttria-stabilized zirconia (YSZ), as the electrolyte . Because SOFCs are made entirely of solid materials, they are not limited to

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3212-730: A potentially more useful metric is the failure stress of a material, as this depends on sample dimensions instead of crack diameter. Failure stresses in SOFCs can also be evaluated using a ring-on ring biaxial stress test. This type of test is generally preferred, as sample edge quality does not significantly impact measurements. The determination of the sample's failure stress is shown in the equation below. σ c r = 3 F c r 2 π h s 2 + ( ( 1 − ν ) D s u p 2 − D l o

3358-770: A power-plant-to-wheel efficiency of 22% if the hydrogen is stored as high-pressure gas, and 17% if it is stored as liquid hydrogen . Stationary fuel cells are used for commercial, industrial and residential primary and backup power generation. Fuel cells are very useful as power sources in remote locations, such as spacecraft, remote weather stations, large parks, communications centers, rural locations including research stations, and in certain military applications. A fuel cell system running on hydrogen can be compact and lightweight, and have no major moving parts. Because fuel cells have no moving parts and do not involve combustion, in ideal conditions they can achieve up to 99.9999% reliability. This equates to less than one minute of downtime in

3504-414: A primary cell which solved the problem of polarization by introducing copper ions into the solution near the positive electrode and thus eliminating hydrogen gas generation. Later results revealed that at the other electrode, amalgamated zinc (i.e., zinc alloyed with mercury ) would produce a higher voltage. William Grove produced the first fuel cell in 1839. In 1846, Wilhelm Weber developed

3650-425: A requirement, as in enclosed spaces such as warehouses, and where hydrogen is considered an acceptable reactant, a [PEM fuel cell] is becoming an increasingly attractive choice [if exchanging batteries is inconvenient]". In 2013 military organizations were evaluating fuel cells to determine if they could significantly reduce the battery weight carried by soldiers. In a fuel cell vehicle the tank-to-wheel efficiency

3796-537: A series of experiments (see oil drop experiment ) to determine the electric charge carried by a single electron . In 1911, Harvey Fletcher, working with Millikan, was successful in measuring the charge on the electron, by replacing the water droplets used by Millikan, which quickly evaporated, with oil droplets. Within one day Fletcher measured the charge of an electron within several decimal places. In 1923, Johannes Nicolaus Brønsted and Martin Lowry published essentially

3942-638: A significant problem to SOFC operation. The presence of various kinds of load and Thermal stress during operation requires high mechanical strength. Additional stresses associated with changes in gas atmosphere, leading to reduction or oxidation also cannot be avoided in prolonged operation. When electrode layers delaminate or crack, conduction pathways are lost, leading to a redistribution of current density and local changes in temperature. These local temperature deviations, in turn, lead to increased thermal strains, which propagate cracks and Delamination . Additionally, when electrolytes crack, separation of fuel and air

4088-401: A six-year period. Since fuel cell electrolyzer systems do not store fuel in themselves, but rather rely on external storage units, they can be successfully applied in large-scale energy storage, rural areas being one example. There are many different types of stationary fuel cells so efficiencies vary, but most are between 40% and 60% energy efficient. However, when the fuel cell's waste heat

4234-411: A system or device that converts energy is measured by the ratio of the amount of useful energy put out by the system ("output energy") to the total amount of energy that is put in ("input energy") or by useful output energy as a percentage of the total input energy. In the case of fuel cells, useful output energy is measured in electrical energy produced by the system. Input energy is the energy stored in

4380-475: A uniform and well-regulated heating process at startup. SOFC stacks with planar geometry require on the order of an hour to be heated to operating temperature. Micro-tubular fuel cell design geometries promise much faster start up times, typically in the order of minutes. Unlike most other types of fuel cells , SOFCs can have multiple geometries. The planar fuel cell design geometry is the typical sandwich type geometry employed by most types of fuel cells, where

4526-437: A welding machine. In the 1960s, Pratt & Whitney licensed Bacon's U.S. patents for use in the U.S. space program to supply electricity and drinking water (hydrogen and oxygen being readily available from the spacecraft tanks). In 1991, the first hydrogen fuel cell automobile was developed by Roger E. Billings. UTC Power was the first company to manufacture and commercialize a large, stationary fuel cell system for use as

Solid oxide fuel cell - Misplaced Pages Continue

4672-572: Is flow batteries , in which the fuel can be regenerated by recharging. Individual fuel cells produce relatively small electrical potentials, about 0.7 volts, so cells are "stacked", or placed in series, to create sufficient voltage to meet an application's requirements. In addition to electricity, fuel cells produce water vapor, heat and, depending on the fuel source, very small amounts of nitrogen dioxide and other emissions. PEMFC cells generally produce fewer nitrogen oxides than SOFC cells: they operate at lower temperatures, use hydrogen as fuel, and limit

4818-419: Is a common oxidizing agent, but not the only one. Despite the name, an oxidation reaction does not necessarily need to involve oxygen. In fact, a fire can be fed by an oxidant other than oxygen; fluorine fires are often unquenchable, as fluorine is an even stronger oxidant (it has a weaker bond and higher electronegativity , and thus accepts electrons even better) than oxygen. For reactions involving oxygen,

4964-449: Is a dense layer of ceramic that conducts oxygen ions. Its electronic conductivity must be kept as low as possible to prevent losses from leakage currents. The high operating temperatures of SOFCs allow the kinetics of oxygen ion transport to be sufficient for good performance. However, as the operating temperature approaches the lower limit for SOFCs at around 600 °C, the electrolyte begins to have large ionic transport resistances and affect

5110-472: Is currently necessary for lower temperature fuel cells such as PEMFCs , and are not vulnerable to carbon monoxide catalyst poisoning. However, vulnerability to sulfur poisoning has been widely observed and the sulfur must be removed before entering the cell. For fuels that are of lower quality, such as gasified biomass, coal, or biogas , the fuel processing becomes increasingly complex and, consequently, more expensive. The gasification process, which transforms

5256-410: Is due to the fact that the consumption of reacting species in the reactant flows causes a drop in reactant concentration as it travels along the cell, which causes a drop in the local potential near the tail end of the cell. The concentration polarization occurs in both the anode and cathode. The anode can be particularly problematic, as the oxidation of the hydrogen produces steam, which further dilutes

5402-415: Is focused on reducing or replacing Ni content in the anode to improve long-term performance. The modified Ni-YSZ containing other materials including CeO 2 , Y 2 O 3 , La 2 O 3 , MgO, TiO 2 , Ru, Co, etc. are invented to resist sulfur poisoning, but the improvement is limited due to the rapid initial degradation. Copper-based cerement anode is considered as a solution to carbon deposition because it

5548-639: Is greater than 45% at low loads and shows average values of about 36% when a driving cycle like the NEDC ( New European Driving Cycle ) is used as test procedure. The comparable NEDC value for a Diesel vehicle is 22%. In 2008 Honda released a demonstration fuel cell electric vehicle (the Honda FCX Clarity ) with fuel stack claiming a 60% tank-to-wheel efficiency. It is also important to take losses due to fuel production, transportation, and storage into account. Fuel cell vehicles running on compressed hydrogen may have

5694-399: Is inert to carbon and stable under typical SOFC oxygen partial pressures (pO 2 ). Cu-Co bimetallic anodes in particular show a great resistivity of carbon deposition after the exposure to pure CH 4 at 800C. And Cu-CeO 2 -YSZ exhibits a higher electrochemical oxidation rate over Ni-YSZ when running on CO and syngas, and can achieve even higher performance using CO than H 2 , after adding

5840-479: Is lost. Conversely, loss of oxygen or gain of hydrogen implies reduction. Electrochemical reactions in water are better analyzed by using the ion-electron method , where H , OH ion, H 2 O and electrons (to compensate the oxidation changes) are added to the cell's half-reactions for oxidation and reduction. In acidic medium, H ions and water are added to balance each half-reaction . For example, when manganese reacts with sodium bismuthate . Finally,

5986-485: Is no longer guaranteed, which further endangers the continuous operation of the cell. Since SOFCs require materials with high oxygen conductivity, thermal stresses provide a significant problem. The Coefficient of thermal expansion in mixed ionic-electronic perovskites can be directly related to oxygen vacancy concentration, which is also related to ionic conductivity. Thus, thermal stresses increase in direct correlation with improved cell performance. Additionally, however,

Solid oxide fuel cell - Misplaced Pages Continue

6132-601: Is often important to focus on the ohmic and concentration polarizations since high operating temperatures experience little activation polarization. However, as the lower limit of SOFC operating temperature is approached (~600 °C), these polarizations do become important. Above mentioned equation is used for determining the SOFC voltage (in fact for fuel cell voltage in general). This approach results in good agreement with particular experimental data (for which adequate factors were obtained) and poor agreement for other than original experimental working parameters. Moreover, most of

6278-494: Is possible to account for different properties of the SOFC. There are many parameters which impact cell working conditions, e.g. electrolyte material, electrolyte thickness, cell temperature, inlet and outlet gas compositions at anode and cathode, and electrode porosity, just to name some. The flow in these systems is often calculated using the Navier–Stokes equations . Ohmic losses in an SOFC result from ionic conductivity through

6424-482: Is produced by steam methane reforming , which emits carbon dioxide. The overall efficiency (electricity to hydrogen and back to electricity) of such plants (known as round-trip efficiency ), using pure hydrogen and pure oxygen can be "from 35 up to 50 percent", depending on gas density and other conditions. The electrolyzer/fuel cell system can store indefinite quantities of hydrogen, and is therefore suited for long-term storage. Solid-oxide fuel cells produce heat from

6570-585: Is referred to as the heart of the PEMFC and is usually made of a proton-exchange membrane sandwiched between two catalyst -coated carbon papers . Platinum and/or similar types of noble metals are usually used as the catalyst for PEMFC, and these can be contaminated by carbon monoxide , necessitating a relatively pure hydrogen fuel. The electrolyte could be a polymer membrane . Phosphoric acid fuel cells (PAFCs) were first designed and introduced in 1961 by G. V. Elmore and H. A. Tanner . In these cells, phosphoric acid

6716-438: Is said to be the largest of the type. Small-scale (sub-5kWhr) fuel cells are being developed for use in residential off-grid deployment. Combined heat and power (CHP) fuel cell systems, including micro combined heat and power (MicroCHP) systems are used to generate both electricity and heat for homes (see home fuel cell ), office building and factories. The system generates constant electric power (selling excess power back to

6862-594: Is the cells' short life span. The high-temperature and carbonate electrolyte lead to corrosion of the anode and cathode. These factors accelerate the degradation of MCFC components, decreasing the durability and cell life. Researchers are addressing this problem by exploring corrosion-resistant materials for components as well as fuel cell designs that may increase cell life without decreasing performance. MCFCs hold several advantages over other fuel cell technologies, including their resistance to impurities. They are not prone to "carbon coking", which refers to carbon build-up on

7008-479: Is the high operating temperature which results in longer start-up times and mechanical and chemical compatibility issues. Solid oxide fuel cells are a class of fuel cells characterized by the use of a solid oxide material as the electrolyte . SOFCs use a solid oxide electrolyte to conduct negative oxygen ions from the cathode to the anode . The electrochemical oxidation of the hydrogen , carbon monoxide or other organic intermediates by oxygen ions thus occurs on

7154-676: Is the length where porous, ionic and electronically conducting pathways all meet, directly relates to the electrochemically active length in the cell. The larger the length, the more reactions can occur and thus the less the activation polarization. Optimization of TPB length can be done by processing conditions to affect microstructure or by materials selection to use a mixed ionic/electronic conductor to further increase TPB length. Current SOFC research focuses heavily on optimizing cell performance while maintaining acceptable mechanical properties because optimized performance often compromises mechanical properties. Nevertheless, mechanical failure represents

7300-528: Is the potential for carbon dust to build up on the anode, which slows down the internal reforming process. Research to address this "carbon coking" issue at the University of Pennsylvania has shown that the use of copper-based cermet (heat-resistant materials made of ceramic and metal) can reduce coking and the loss of performance. Another disadvantage of SOFC systems is the long start-up, making SOFCs less useful for mobile applications. Despite these disadvantages,

7446-506: Is used as a non-conductive electrolyte to pass protons from the anode to the cathode and to force electrons to travel from anode to cathode through an external electrical circuit. These cells commonly work in temperatures of 150 to 200 °C. This high temperature will cause heat and energy loss if the heat is not removed and used properly. This heat can be used to produce steam for air conditioning systems or any other thermal energy-consuming system. Using this heat in cogeneration can enhance

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7592-436: Is used to heat a building in a cogeneration system this efficiency can increase to 85%. This is significantly more efficient than traditional coal power plants, which are only about one third energy efficient. Assuming production at scale, fuel cells could save 20–40% on energy costs when used in cogeneration systems. Fuel cells are also much cleaner than traditional power generation; a fuel cell power plant using natural gas as

7738-690: Is used, the CO 2 is released when methane from natural gas is combined with steam, in a process called steam methane reforming , to produce the hydrogen. This can take place in a different location to the fuel cell, potentially allowing the hydrogen fuel cell to be used indoors—for example, in forklifts. The different components of a PEMFC are The materials used for different parts of the fuel cells differ by type. The bipolar plates may be made of different types of materials, such as, metal, coated metal, graphite , flexible graphite, C–C composite , carbon – polymer composites etc. The membrane electrode assembly (MEA)

7884-541: Is written in Kröger-Vink Notation as follows: Cathode materials must be, at a minimum, electrically conductive. Currently, lanthanum strontium manganite (LSM) is the cathode material of choice for commercial use because of its compatibility with doped zirconia electrolytes. Mechanically, it has a similar coefficient of thermal expansion to YSZ and thus limits stress buildup because of CTE mismatch. Also, LSM has low levels of chemical reactivity with YSZ which extends

8030-474: The "Father of Magnetism." He discovered various methods for producing and strengthening magnets. In 1663, the German physicist Otto von Guericke created the first electric generator, which produced static electricity by applying friction in the machine. The generator was made of a large sulfur ball cast inside a glass globe, mounted on a shaft. The ball was rotated by means of a crank and an electric spark

8176-613: The Electrochemical Society journal Interface in 2008, wrote, "While fuel cells are efficient relative to combustion engines, they are not as efficient as batteries, primarily due to the inefficiency of the oxygen reduction reaction (and ... the oxygen evolution reaction, should the hydrogen be formed by electrolysis of water). ... [T]hey make the most sense for operation disconnected from the grid, or when fuel can be provided continuously. For applications that require frequent and relatively rapid start-ups ... where zero emissions are

8322-603: The Latin for "glass" ), or positive, electricity; and "resinous," or negative, electricity. This was the two-fluid theory of electricity , which was to be opposed by Benjamin Franklin 's one-fluid theory later in the century. In 1785, Charles-Augustin de Coulomb developed the law of electrostatic attraction as an outgrowth of his attempt to investigate the law of electrical repulsions as stated by Joseph Priestley in England. In

8468-412: The conductivity and electrolytic dissociation of organic acids . Walther Hermann Nernst developed the theory of the electromotive force of the voltaic cell in 1888. In 1889, he showed how the characteristics of the voltage produced could be used to calculate the free energy change in the chemical reaction producing the voltage. He constructed an equation, known as Nernst equation , which related

8614-830: The electrodynamometer . In 1868, Georges Leclanché patented a new cell which eventually became the forerunner to the world's first widely used battery, the zinc–carbon cell . Svante Arrhenius published his thesis in 1884 on Recherches sur la conductibilité galvanique des électrolytes (Investigations on the galvanic conductivity of electrolytes). From his results the author concluded that electrolytes , when dissolved in water, become to varying degrees split or dissociated into electrically opposite positive and negative ions. In 1886, Paul Héroult and Charles M. Hall developed an efficient method (the Hall–Héroult process ) to obtain aluminium using electrolysis of molten alumina. In 1894, Friedrich Ostwald concluded important studies of

8760-511: The ionic conductivity of YSZ. Therefore, to obtain the optimum performance of the fuel cell, a high operating temperature is required. According to their website, Ceres Power , a UK SOFC fuel cell manufacturer, has developed a method of reducing the operating temperature of their SOFC system to 500–600 degrees Celsius. They replaced the commonly used YSZ electrolyte with a CGO (cerium gadolinium oxide) electrolyte. The lower operating temperature allows them to use stainless steel instead of ceramic as

8906-415: The mechanical balance of plant , the air preheater , prereformer , afterburner , water heat exchanger , anode tail gas oxidizer , and electrical balance of plant , power electronics , hydrogen sulfide sensor and fans. Internal reforming leads to a large decrease in the balance of plant costs in designing a full system. The ceramic anode layer must be very porous to allow the fuel to flow towards

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9052-428: The waste heat produced by the primary power cycle - whether fuel cell, nuclear fission or combustion - is captured and put to use, increasing the efficiency of the system to up to 85–90%. The theoretical maximum efficiency of any type of power generation system is never reached in practice, and it does not consider other steps in power generation, such as production, transportation and storage of fuel and conversion of

9198-489: The DFC-ERG, is combined with a gas turbine and, according to the company, it achieves an electrical efficiency of 65%. The electric storage fuel cell is a conventional battery chargeable by electric power input, using the conventional electro-chemical effect. However, the battery further includes hydrogen (and oxygen) inputs for alternatively charging the battery chemically. Glossary of terms in table: The energy efficiency of

9344-494: The Ni catalytic surface. Carbon deposition becomes important especially when hydrocarbon fuels are used, i.e. methane, syngas. The high operating temperature of SOFC and the oxidizing environment facilitate the oxidation of Ni catalyst through reaction Ni + 1 ⁄ 2 O 2 = NiO. The oxidation reaction of Ni reduces the electrocatalytic activity and conductivity. Moreover, the density difference between Ni and NiO causes volume change on

9490-448: The TPB, a potential cathode material must be able to conduct both electrons and oxygen ions. Composite cathodes consisting of LSM YSZ have been used to increase this triple phase boundary length. Mixed ionic/electronic conducting (MIEC) ceramics, such as perovskite LSCF , are also being researched for use in intermediate temperature SOFCs as they are more active and can make up for the increase in

9636-441: The activation energy of the reaction. The interconnect can be either a metallic or ceramic layer that sits between each individual cell. Its purpose is to connect each cell in series, so that the electricity each cell generates can be combined. Because the interconnect is exposed to both the oxidizing and reducing side of the cell at high temperatures, it must be extremely stable. For this reason, ceramics have been more successful in

9782-473: The aforementioned electronically conducting circuit. This phenomenon is what distinguishes an electrochemical reaction from a conventional chemical reaction. Understanding of electrical matters began in the sixteenth century. During this century, the English scientist William Gilbert spent 17 years experimenting with magnetism and, to a lesser extent, electricity. For his work on magnets, Gilbert became known as

9928-458: The anode and cathode electrolytes in addition to the electron conduction path. The simplest ionic conduction path is to provide a liquid junction. To avoid mixing between the two electrolytes, the liquid junction can be provided through a porous plug that allows ion flow while minimizing electrolyte mixing. To further minimize mixing of the electrolytes, a salt bridge can be used which consists of an electrolyte saturated gel in an inverted U-tube. As

10074-420: The anode side. More recently, proton-conducting SOFCs (PC-SOFC) are being developed which transport protons instead of oxygen ions through the electrolyte with the advantage of being able to be run at lower temperatures than traditional SOFCs. They operate at very high temperatures, typically between 600 and 1,000 °C. At these temperatures, SOFCs do not require expensive platinum group metals catalyst , as

10220-402: The anode surface, which could potentially lead to mechanical failure. Sulfur poisoning arises when fuel such as natural gas, gasoline, or diesel is used. Again, due to the high affinity between sulfur compounds (H 2 S, (CH 3 ) 2 S) and the metal catalyst, even the smallest impurities of sulfur compounds in the feed stream could deactivate the Ni catalyst on the YSZ surface. Current research

10366-493: The anode that results in reduced performance by slowing down the internal fuel reforming process. Therefore, carbon-rich fuels like gases made from coal are compatible with the system. The United States Department of Energy claims that coal, itself, might even be a fuel option in the future, assuming the system can be made resistant to impurities such as sulfur and particulates that result from converting coal into hydrogen. MCFCs also have relatively high efficiencies. They can reach

10512-478: The anode to the cathode through an external circuit, producing direct current electricity. At the cathode, another catalyst causes ions, electrons, and oxygen to react, forming water and possibly other products. Fuel cells are classified by the type of electrolyte they use and by the difference in start-up time ranging from 1 second for proton-exchange membrane fuel cells (PEM fuel cells, or PEMFC) to 10 minutes for solid oxide fuel cells (SOFC). A related technology

10658-423: The anode to the cathode), as is the case in all other types of fuel cells. Oxygen gas is fed through the cathode, where it absorbs electrons to create oxygen ions. The oxygen ions then travel through the electrolyte to react with hydrogen gas at the anode. The reaction at the anode produces electricity and water as by-products. Carbon dioxide may also be a by-product depending on the fuel, but the carbon emissions from

10804-425: The anode's job is to use the oxygen ions that diffuse through the electrolyte to oxidize the hydrogen fuel . The oxidation reaction between the oxygen ions and the hydrogen produces heat as well as water and electricity. If the fuel is a light hydrocarbon, for example, methane, another function of the anode is to act as a catalyst for steam reforming the fuel into hydrogen. This provides another operational benefit to

10950-546: The atoms, ions or molecules involved in an electrochemical reaction. Formally, oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic . An atom or ion that gives up an electron to another atom or ion has its oxidation state increase, and the recipient of the negatively charged electron has its oxidation state decrease. For example, when atomic sodium reacts with atomic chlorine , sodium donates one electron and attains an oxidation state of +1. Chlorine accepts

11096-513: The balanced equation is obtained: An electrochemical cell is a device that produces an electric current from energy released by a spontaneous redox reaction. This kind of cell includes the Galvanic cell or Voltaic cell, named after Luigi Galvani and Alessandro Volta , both scientists who conducted experiments on chemical reactions and electric current during the late 18th century. Electrochemical cells have two conductive electrodes (the anode and

11242-463: The cathode). The anode is defined as the electrode where oxidation occurs and the cathode is the electrode where the reduction takes place. Electrodes can be made from any sufficiently conductive materials, such as metals, semiconductors, graphite, and even conductive polymers . In between these electrodes is the electrolyte , which contains ions that can freely move. The galvanic cell uses two different metal electrodes, each in an electrolyte where

11388-548: The cathode. There, oxygen from the air and carbon dioxide recycled from the anode react with the electrons to form carbonate ions that replenish the electrolyte, completing the circuit. The chemical reactions for an MCFC system can be expressed as follows: As with SOFCs, MCFC disadvantages include slow start-up times because of their high operating temperature. This makes MCFC systems not suitable for mobile applications, and this technology will most likely be used for stationary fuel cell purposes. The main challenge of MCFC technology

11534-413: The cathode. These ions can then diffuse through the solid oxide electrolyte to the anode where they can electrochemically oxidize the fuel. In this reaction, a water byproduct is given off as well as two electrons. These electrons then flow through an external circuit where they can do work. The cycle then repeats as those electrons enter the cathode material again. Most of the downtime of a SOFC stems from

11680-462: The cell substrate, which reduces cost and start-up time of the system. Molten carbonate fuel cells (MCFCs) require a high operating temperature, 650 °C (1,200 °F), similar to SOFCs . MCFCs use lithium potassium carbonate salt as an electrolyte, and this salt liquefies at high temperatures, allowing for the movement of charge within the cell – in this case, negative carbonate ions. Like SOFCs, MCFCs are capable of converting fossil fuel to

11826-470: The conductivity for oxygen ions in SOFC can remain high even at lower temperatures (current target in research ~500 °C), material choices for SOFC will broaden and many existing problems can potentially be solved. Certain processing techniques such as thin film deposition can help solve this problem with existing materials by: The cathode , or air electrode , is a thin porous layer on the electrolyte where oxygen reduction takes place. The overall reaction

11972-405: The contact area that ions can be conducted through, which would lower the cells efficiency. Perovskite materials (mixed ionic/electronic conducting ceramics) have been shown to produce a power density of 0.6 W/cm2 at 0.7 V at 800 °C which is possible because they have the ability to overcome a larger activation energy . Chemical Reaction: H 2 +O ——> H 2 O+2e However, there are

12118-429: The cost of the fuel cell itself. These factors become especially critical for systems with lower power output or greater portability requirements. Solid oxide fuel cells have a wide variety of applications, from use as auxiliary power units in vehicles to stationary power generation with outputs from 100 W to 2 MW. In 2009, Australian company, Ceramic Fuel Cells successfully achieved an efficiency of an SOFC device up to

12264-551: The crystal structure and control defect concentrations can also play a significant role in increasing the conductivity. Another way to decrease ohmic resistance is to decrease the thickness of the electrolyte layer. An ionic specific resistance of the electrolyte as a function of temperature can be described by the following relationship: where: δ {\displaystyle \delta } – electrolyte thickness, and σ {\displaystyle \sigma } – ionic conductivity. The ionic conductivity of

12410-597: The development of his first crude fuel cells. He used a combination of sheet iron, copper, and porcelain plates, and a solution of sulphate of copper and dilute acid. In a letter to the same publication written in December 1838 but published in June 1839, German physicist Christian Friedrich Schönbein discussed the first crude fuel cell that he had invented. His letter discussed the current generated from hydrogen and oxygen dissolved in water. Grove later sketched his design, in 1842, in

12556-549: The diffusion of nitrogen into the anode via the proton exchange membrane, which forms NOx. The energy efficiency of a fuel cell is generally between 40 and 60%; however, if waste heat is captured in a cogeneration scheme, efficiencies of up to 85% can be obtained. The first references to hydrogen fuel cells appeared in 1838. In a letter dated October 1838 but published in the December 1838 edition of The London and Edinburgh Philosophical Magazine and Journal of Science , Welsh physicist and barrister Sir William Grove wrote about

12702-412: The discovery of thermoelectricity by Thomas Johann Seebeck . By the 1810s, William Hyde Wollaston made improvements to the galvanic cell . Sir Humphry Davy 's work with electrolysis led to the conclusion that the production of electricity in simple electrolytic cells resulted from chemical action and that chemical combination occurred between substances of opposite charge. This work led directly to

12848-404: The efficiency of phosphoric acid fuel cells from 40 to 50% to about 80%. Since the proton production rate on the anode is small, platinum is used as a catalyst to increase this ionization rate. A key disadvantage of these cells is the use of an acidic electrolyte. This increases the corrosion or oxidation of components exposed to phosphoric acid. Solid acid fuel cells (SAFCs) are characterized by

12994-553: The electrical potential between the juncture points of two dissimilar metals when there is a temperature difference between the joints. In 1827, the German scientist Georg Ohm expressed his law in this famous book "Die galvanische Kette, mathematisch bearbeitet" (The Galvanic Circuit Investigated Mathematically) in which he gave his complete theory of electricity. In 1832, Michael Faraday 's experiments led him to state his two laws of electrochemistry. In 1836, John Daniell invented

13140-447: The electricity into mechanical power. However, this calculation allows the comparison of different types of power generation. The theoretical maximum efficiency of a fuel cell approaches 100%, while the theoretical maximum efficiency of internal combustion engines is approximately 58%. Values are given from 40% for acidic, 50% for molten carbonate, to 60% for alkaline, solid oxide and PEM fuel cells. Fuel cells cannot store energy like

13286-406: The electrolyte and electrical resistance offered to the flow of electrons in the external electrical circuit. This is inherently a materials property of the crystal structure and atoms involved. However, to maximize the ionic conductivity, several methods can be done. Firstly, operating at higher temperatures can significantly decrease these ohmic losses. Substitutional doping methods to further refine

13432-432: The electrolyte is sandwiched in between the electrodes. SOFCs can also be made in tubular geometries where either air or fuel is passed through the inside of the tube and the other gas is passed along the outside of the tube. The tubular design is advantageous because it is much easier to seal air from the fuel. The performance of the planar design is currently better than the performance of the tubular design, however, because

13578-405: The electrolyte. Consequently, granular matter is often selected for anode fabrication procedures. Like the cathode, it must conduct electrons, with ionic conductivity a definite asset. The anode is commonly the thickest and strongest layer in each individual cell, because it has the smallest polarization losses, and is often the layer that provides the mechanical support. Electrochemically speaking,

13724-434: The electron and its oxidation state is reduced to −1. The sign of the oxidation state (positive/negative) actually corresponds to the value of each ion's electronic charge. The attraction of the differently charged sodium and chlorine ions is the reason they then form an ionic bond . The loss of electrons from an atom or molecule is called oxidation, and the gain of electrons is reduction. This can be easily remembered through

13870-416: The electron is assigned to the atom with the largest electronegativity in determining the oxidation state. The atom or molecule which loses electrons is known as the reducing agent , or reductant , and the substance which accepts the electrons is called the oxidizing agent , or oxidant . Thus, the oxidizing agent is always being reduced in a reaction; the reducing agent is always being oxidized. Oxygen

14016-500: The equation below, fracture toughness decreases as porosity increases. K I C = K I C , 0 exp ⁡ ( − b k p ′ ) {\displaystyle K_{IC}=K_{IC,0}\exp {(-b_{k}p')}} Where: K I C {\displaystyle K_{IC}} = fracture toughness K I C , 0 {\displaystyle K_{IC,0}} = fracture toughness of

14162-524: The equations used require the addition of numerous factors which are difficult or impossible to determine. It makes very difficult any optimizing process of the SOFC working parameters as well as design architecture configuration selection. Because of those circumstances a few other equations were proposed: where: This method was validated and found to be suitable for optimization and sensitivity studies in plant-level modelling of various systems with solid oxide fuel cells. With this mathematical description it

14308-442: The flat plane configuration of other types of fuel cells and are often designed as rolled tubes. They require high operating temperatures (800–1000 °C) and can be run on a variety of fuels including natural gas. SOFCs are unique because negatively charged oxygen ions travel from the cathode (positive side of the fuel cell) to the anode (negative side of the fuel cell) instead of protons travelling vice versa (i.e., from

14454-411: The fuel cell stack because the reforming reaction is endothermic, which cools the stack internally. The most common material used is a cermet made up of nickel mixed with the ceramic material that is used for the electrolyte in that particular cell, typically YSZ (yttria stabilized zirconia). These nanomaterial-based catalysts , help stop the grain growth of nickel. Larger grains of nickel would reduce

14600-441: The fuel cell. Polarizations result from ohmic resistance of oxygen ions conducting through the electrolyte (iRΩ), electrochemical activation barriers at the anode and cathode, and finally concentration polarizations due to inability of gases to diffuse at high rates through the porous anode and cathode (shown as ηA for the anode and ηC for cathode). The cell voltage can be calculated using the following equation: where: In SOFCs, it

14746-460: The fuel stream as it travels along the length of the cell. This polarization can be mitigated by reducing the reactant utilization fraction or increasing the electrode porosity, but these approaches each have significant design trade-offs. The activation polarization is the result of the kinetics involved with the electrochemical reactions. Each reaction has a certain activation barrier that must be overcome in order to proceed and this barrier leads to

14892-463: The fuel. According to the U.S. Department of Energy, fuel cells are generally between 40 and 60% energy efficient. This is higher than some other systems for energy generation. For example, the internal combustion engine of a car can be about 43% energy efficient. Steam power plants usually achieve efficiencies of 30-40% while combined cycle gas turbine and steam plants can achieve efficiencies above 60%. In combined heat and power (CHP) systems,

15038-412: The gain of oxygen implies the oxidation of the atom or molecule to which the oxygen is added (and the oxygen is reduced). In organic compounds, such as butane or ethanol , the loss of hydrogen implies oxidation of the molecule from which it is lost (and the hydrogen is reduced). This follows because the hydrogen donates its electron in covalent bonds with non-metals but it takes the electron along when it

15184-506: The grid when it is not consumed), and at the same time produces hot air and water from the waste heat . As the result CHP systems have the potential to save primary energy as they can make use of waste heat which is generally rejected by thermal energy conversion systems. A typical capacity range of home fuel cell is 1–3 kW el , 4–8 kW th . CHP systems linked to absorption chillers use their waste heat for refrigeration . The waste heat from fuel cells can be diverted during

15330-400: The half-reactions. By multiplying the stoichiometric coefficients so the numbers of electrons in both half reaction match: the balanced overall reaction is obtained: The same procedure as used in acidic medium can be applied, for example, to balance the complete combustion of propane : By multiplying the stoichiometric coefficients so the numbers of electrons in both half reaction match:

15476-467: The hydrocarbon fuels with air or steam in a device upstream of the SOFC anode. SOFC power systems can increase efficiency by using the heat given off by the exothermic electrochemical oxidation within the fuel cell for endothermic steam reforming process. Additionally, solid fuels such as coal and biomass may be gasified to form syngas which is suitable for fueling SOFCs in integrated gasification fuel cell power cycles . Thermal expansion demands

15622-477: The idea of an "animal electric fluid," replying that the frog's legs responded to differences in metal temper , composition, and bulk. Galvani refuted this by obtaining muscular action with two pieces of the same material. Nevertheless, Volta's experimentation led him to develop the first practical battery , which took advantage of the relatively high energy (weak bonding) of zinc and could deliver an electrical current for much longer than any other device known at

15768-402: The ion's oxidation state is reduced to 0. This forms a solid metal that electrodeposits on the cathode. The two electrodes must be electrically connected to each other, allowing for a flow of electrons that leave the metal of the anode and flow through this connection to the ions at the surface of the cathode. This flow of electrons is an electric current that can be used to do work, such as turn

15914-462: The ions are reunited with the electrons and the two react with a third chemical, usually oxygen, to create water or carbon dioxide. Design features in a fuel cell include: A typical fuel cell produces a voltage from 0.6 to 0.7 V at a full-rated load. Voltage decreases as current increases, due to several factors: To deliver the desired amount of energy, the fuel cells can be combined in series to yield higher voltage , and in parallel to allow

16060-474: The ions deposit at the copper cathode as an electrodeposit. This cell forms a simple battery as it will spontaneously generate a flow of electric current from the anode to the cathode through the external connection. This reaction can be driven in reverse by applying a voltage, resulting in the deposition of zinc metal at the anode and formation of copper ions at the cathode. To provide a complete electric circuit, there must also be an ionic conduction path between

16206-527: The isolation of metallic sodium and potassium by electrolysis of their molten salts, and of the alkaline earth metals from theirs, in 1808. Hans Christian Ørsted 's discovery of the magnetic effect of electric currents in 1820 was immediately recognized as an epoch-making advance, although he left further work on electromagnetism to others. André-Marie Ampère quickly repeated Ørsted's experiment, and formulated them mathematically. In 1821, Estonian-German physicist Thomas Johann Seebeck demonstrated

16352-646: The late 18th century the Italian physician and anatomist Luigi Galvani marked the birth of electrochemistry by establishing a bridge between chemical reactions and electricity on his essay "De Viribus Electricitatis in Motu Musculari Commentarius" (Latin for Commentary on the Effect of Electricity on Muscular Motion) in 1791 where he proposed a "nerveo-electrical substance" on biological life forms. In his essay Galvani concluded that animal tissue contained

16498-405: The lifetime of the materials. Unfortunately, LSM is a poor ionic conductor, and so the electrochemically active reaction is limited to the triple phase boundary (TPB) where the electrolyte, air and electrode meet. LSM works well as a cathode at high temperatures, but its performance quickly falls as the operating temperature is lowered below 800 °C. In order to increase the reaction zone beyond

16644-400: The load. At the anode a catalyst ionizes the fuel, turning the fuel into a positively charged ion and a negatively charged electron. The electrolyte is a substance specifically designed so ions can pass through it, but the electrons cannot. The freed electrons travel through a wire creating an electric current. The ions travel through the electrolyte to the cathode. Once reaching the cathode,

16790-653: The long term than metals as interconnect materials. However, these ceramic interconnect materials are very expensive when compared to metals. Nickel- and steel-based alloys are becoming more promising as lower temperature (600–800 °C) SOFCs are developed. The material of choice for an interconnect in contact with Y8SZ is a metallic 95Cr-5Fe alloy. Ceramic-metal composites called "cermet" are also under consideration, as they have demonstrated thermal stability at high temperatures and excellent electrical conductivity. Polarizations, or overpotentials, are losses in voltage due to imperfections in materials, microstructure, and design of

16936-609: The membrane to the cathode, but the electrons are forced to travel in an external circuit (supplying power) because the membrane is electrically insulating. On the cathode catalyst, oxygen molecules react with the electrons (which have traveled through the external circuit) and protons to form water. In addition to this pure hydrogen type, there are hydrocarbon fuels for fuel cells, including diesel , methanol ( see: direct-methanol fuel cells and indirect methanol fuel cells ) and chemical hydrides. The waste products with these types of fuel are carbon dioxide and water. When hydrogen

17082-482: The name). A single cell consisting of these four layers stacked together is typically only a few millimeters thick. Hundreds of these cells are then connected in series to form what most people refer to as an "SOFC stack". The ceramics used in SOFCs do not become electrically and ionically active until they reach very high temperature and as a consequence, the stacks have to run at temperatures ranging from 500 to 1,000 °C. Reduction of oxygen into oxygen ions occurs at

17228-467: The negatively charged electrons flow in one direction around this circuit, the positively charged metal ions flow in the opposite direction in the electrolyte. A voltmeter is capable of measuring the change of electrical potential between the anode and the cathode. Fuel cell A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen ) and an oxidizing agent (often oxygen) into electricity through

17374-424: The non-porous structure b k {\displaystyle b_{k}} = experimentally determined constant p ′ {\displaystyle p'} = porosity Thus, porosity must be carefully engineered to maximize reaction kinetics while maintaining an acceptable fracture toughness. Since fracture toughness represents the ability of pre-existing cracks or pores to propagate,

17520-490: The original fuel cell design by using a sulphonated polystyrene ion-exchange membrane as the electrolyte. Three years later another GE chemist, Leonard Niedrach, devised a way of depositing platinum onto the membrane, which served as a catalyst for the necessary hydrogen oxidation and oxygen reduction reactions. This became known as the "Grubb-Niedrach fuel cell". GE went on to develop this technology with NASA and McDonnell Aircraft, leading to its use during Project Gemini . This

17666-526: The performance. Popular electrolyte materials include yttria-stabilized zirconia (YSZ) (often the 8% form 8YSZ), scandia stabilized zirconia ( ScSZ ) (usually 9 mol% Sc 2 O 3 – 9ScSZ) and gadolinium doped ceria (GDC). The electrolyte material has crucial influence on the cell performances. Detrimental reactions between YSZ electrolytes and modern cathodes such as lanthanum strontium cobalt ferrite (LSCF) have been found, and can be prevented by thin (<100 nm) ceria diffusion barriers. If

17812-756: The period 2012–2014, 30,000 units on LNG and 6,000 on LPG . Four fuel cell electric vehicles have been introduced for commercial lease and sale: the Honda Clarity , Toyota Mirai , Hyundai ix35 FCEV , and the Hyundai Nexo . By year-end 2019, about 18,000 FCEVs had been leased or sold worldwide. Fuel cell electric vehicles feature an average range of 505 km (314 mi) between refuelings and can be refueled in about 5 minutes. The U.S. Department of Energy's Fuel Cell Technology Program states that, as of 2011, fuel cells achieved 53–59% efficiency at one-quarter power and 42–53% vehicle efficiency at full power, and

17958-449: The planar design has a lower resistance comparatively. Other geometries of SOFCs include modified planar fuel cell designs (MPC or MPSOFC), where a wave-like structure replaces the traditional flat configuration of the planar cell. Such designs are highly promising because they share the advantages of both planar cells (low resistance) and tubular cells. A solid oxide fuel cell is made up of four layers, three of which are ceramics (hence

18104-571: The polarization. The activation barrier is the result of many complex electrochemical reaction steps where typically the rate limiting step is responsible for the polarization. The polarization equation shown below is found by solving the Butler–Volmer equation in the high current density regime (where the cell typically operates), and can be used to estimate the activation polarization: where: The polarization can be modified by microstructural optimization. The Triple Phase Boundary (TPB) length, which

18250-412: The positively charged ions are the oxidized form of the electrode metal. One electrode will undergo oxidation (the anode) and the other will undergo reduction (the cathode). The metal of the anode will oxidize, going from an oxidation state of 0 (in the solid form) to a positive oxidation state and become an ion. At the cathode, the metal ion in solution will accept one or more electrons from the cathode and

18396-631: The previously theoretical mark of 60%. The higher operating temperature make SOFCs suitable candidates for application with heat engine energy recovery devices or combined heat and power , which further increases overall fuel efficiency . Because of these high temperatures, light hydrocarbon fuels, such as methane, propane, and butane can be internally reformed within the anode. SOFCs can also be fueled by externally reforming heavier hydrocarbons, such as gasoline, diesel, jet fuel (JP-8) or biofuels. Such reformates are mixtures of hydrogen, carbon monoxide, carbon dioxide, steam and methane, formed by reacting

18542-413: The raw material into a gaseous state suitable for fuel cells, can generate significant quantities of aromatic compounds. These compounds include smaller molecules like methane and toluene, as well as larger polyaromatic and short-chain hydrocarbon compounds. These substances can lead to carbon buildup in SOFCs. Moreover, the expenses associated with reforming and desulfurization are comparable in magnitude to

18688-419: The reaction is balanced by multiplying the stoichiometric coefficients so the numbers of electrons in both half reactions match and adding the resulting half reactions to give the balanced reaction: In basic medium, OH ions and water are added to balance each half-reaction. For example, in a reaction between potassium permanganate and sodium sulfite : Here, 'spectator ions' (K , Na ) were omitted from

18834-493: The recombination of the oxygen and hydrogen. The ceramic can run as hot as 800 °C (1,470 °F). This heat can be captured and used to heat water in a micro combined heat and power (m-CHP) application. When the heat is captured, total efficiency can reach 80–90% at the unit, but does not consider production and distribution losses. CHP units are being developed today for the European home market. Professor Jeremy P. Meyers, in

18980-407: The result of practical limitations on mass transport within the cell and represents the voltage loss due to spatial variations in reactant concentration at the chemically active sites. This situation can be caused when the reactants are consumed by the electrochemical reaction faster than they can diffuse into the porous electrode, and can also be caused by variation in bulk flow composition. The latter

19126-405: The same general manner. They are made up of three adjacent segments: the anode , the electrolyte , and the cathode . Two chemical reactions occur at the interfaces of the three different segments. The net result of the two reactions is that fuel is consumed, water or carbon dioxide is created, and an electric current is created, which can be used to power electrical devices, normally referred to as

19272-504: The same journal. The fuel cell he made used similar materials to today's phosphoric acid fuel cell . In 1932, English engineer Francis Thomas Bacon successfully developed a 5 kW stationary fuel cell. NASA used the alkaline fuel cell (AFC), also known as the Bacon fuel cell after its inventor, from the mid-1960s. In 1955, W. Thomas Grubb, a chemist working for the General Electric Company (GE), further modified

19418-476: The same theory about how acids and bases behave, using an electrochemical basis. In 1937, Arne Tiselius developed the first sophisticated electrophoretic apparatus. Some years later, he was awarded the 1948 Nobel Prize for his work in protein electrophoresis . A year later, in 1949, the International Society of Electrochemistry (ISE) was founded. By the 1960s–1970s quantum electrochemistry

19564-445: The small deformation Electrochemistry When a chemical reaction is driven by an electrical potential difference , as in electrolysis , or if a potential difference results from a chemical reaction as in an electric battery or fuel cell , it is called an electrochemical reaction. Unlike in other chemical reactions, in electrochemical reactions electrons are not transferred directly between atoms, ions, or molecules, but via

19710-400: The solid oxide is defined as follows: where: σ 0 {\displaystyle \sigma _{0}} and E {\displaystyle E} – factors depended on electrolyte materials, T {\displaystyle T} – electrolyte temperature, and R {\displaystyle R} – ideal gas constant. The concentration polarization is

19856-764: The summer directly into the ground providing further cooling while the waste heat during winter can be pumped directly into the building. The University of Minnesota owns the patent rights to this type of system. Co-generation systems can reach 85% efficiency (40–60% electric and the remainder as thermal). Phosphoric-acid fuel cells (PAFC) comprise the largest segment of existing CHP products worldwide and can provide combined efficiencies close to 90%. Molten carbonate (MCFC) and solid-oxide fuel cells (SOFC) are also used for combined heat and power generation and have electrical energy efficiencies around 60%. Disadvantages of co-generation systems include slow ramping up and down rates, high cost and short lifetime. Also their need to have

20002-490: The temperature dependence of oxygen vacancy concentration means that the CTE is not a linear property, which further complicates measurements and predictions. Just as thermal stresses increase as cell performance improves through improved ionic conductivity, the fracture toughness of the material also decreases as cell performance increases. This is because, to increase reaction sites, porous ceramics are preferable. However, as shown in

20148-459: The thousands of hours. The alkaline fuel cell (AFC) or hydrogen-oxygen fuel cell was designed and first demonstrated publicly by Francis Thomas Bacon in 1959. It was used as a primary source of electrical energy in the Apollo space program. The cell consists of two porous carbon electrodes impregnated with a suitable catalyst such as Pt, Ag, CoO, etc. The space between the two electrodes is filled with

20294-472: The time. In 1800, William Nicholson and Johann Wilhelm Ritter succeeded in decomposing water into hydrogen and oxygen by electrolysis using Volta's battery. Soon thereafter Ritter discovered the process of electroplating . He also observed that the amount of metal deposited and the amount of oxygen produced during an electrolytic process depended on the distance between the electrodes . By 1801, Ritter observed thermoelectric currents and anticipated

20440-494: The use of mnemonic devices. Two of the most popular are "OIL RIG" (Oxidation Is Loss, Reduction Is Gain) and "LEO" the lion says "GER" (Lose Electrons: Oxidation, Gain Electrons: Reduction). Oxidation and reduction always occur in a paired fashion such that one species is oxidized when another is reduced. For cases where electrons are shared (covalent bonds) between atoms with large differences in electronegativity ,

20586-579: The use of a solid acid material as the electrolyte. At low temperatures, solid acids have an ordered molecular structure like most salts. At warmer temperatures (between 140 and 150   °C for CsHSO 4 ), some solid acids undergo a phase transition to become highly disordered "superprotonic" structures, which increases conductivity by several orders of magnitude. The first proof-of-concept SAFCs were developed in 2000 using cesium hydrogen sulfate (CsHSO 4 ). Current SAFC systems use cesium dihydrogen phosphate (CsH 2 PO 4 ) and have demonstrated lifetimes in

20732-446: The voltage of a cell to its properties. In 1898, Fritz Haber showed that definite reduction products can result from electrolytic processes if the potential at the cathode is kept constant. In 1898, he explained the reduction of nitrobenzene in stages at the cathode and this became the model for other similar reduction processes. In 1902, The Electrochemical Society (ECS) was founded. In 1909, Robert Andrews Millikan began

20878-540: Was called a solid polymer electrolyte fuel cell ( SPEFC ) in the early 1970s, before the proton-exchange mechanism was well understood. (Notice that the synonyms polymer electrolyte membrane and proton-exchange mechanism result in the same acronym .) On the anode side, hydrogen diffuses to the anode catalyst where it later dissociates into protons and electrons. These protons often react with oxidants causing them to become what are commonly referred to as multi-facilitated proton membranes. The protons are conducted through

21024-441: Was developed by Revaz Dogonadze and his students. The term " redox " stands for reduction-oxidation . It refers to electrochemical processes involving electron transfer to or from a molecule or ion , changing its oxidation state . This reaction can occur through the application of an external voltage or through the release of chemical energy. Oxidation and reduction describe the change of oxidation state that takes place in

21170-480: Was produced when a pad was rubbed against the ball as it rotated. The globe could be removed and used as source for experiments with electricity. By the mid-18th century the French chemist Charles François de Cisternay du Fay had discovered two types of static electricity, and that like charges repel each other whilst unlike charges attract. Du Fay announced that electricity consisted of two fluids: "vitreous" (from

21316-408: Was the first commercial use of a fuel cell. In 1959, a team led by Harry Ihrig built a 15 kW fuel cell tractor for Allis-Chalmers , which was demonstrated across the U.S. at state fairs. This system used potassium hydroxide as the electrolyte and compressed hydrogen and oxygen as the reactants. Later in 1959, Bacon and his colleagues demonstrated a practical five-kilowatt unit capable of powering

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