What Are the Different Types of Fuel Cells?

Fuel cell is a chemical device that directly converts the chemical energy possessed by fuel into electrical energy. It is also called an electrochemical generator. It is the fourth power generation technology after hydro, thermal and atomic power. Because the fuel cell converts Gibbs free energy in the chemical energy of the fuel into electrical energy through an electrochemical reaction, it is not restricted by the Carnot cycle effect, so it has high efficiency. In addition, the fuel cell uses fuel and oxygen as raw materials; There are no mechanical transmission parts, so there is no noise pollution, and very little harmful gas is emitted. Therefore, from the perspective of energy conservation and ecological environment protection, fuel cells are the most promising power generation technology. ^[1]

A power generation device that directly converts chemical energy of fuel and oxidant into electrical energy through an electrochemical reaction. Fuel cells can theoretically operate at thermal efficiency close to 100%, and are highly economical. Due to the limitations of various technical factors and the energy consumption of the entire device system, the total conversion efficiency is currently in the range of 45% to 60% for various fuel cells that are currently in actual operation. If exhaust heat utilization is considered, it can reach more than 80%. In addition, the fuel cell device contains no or few moving parts, works reliably, requires less maintenance, and is quieter than traditional generator sets. In addition, the electrochemical reaction is clean and complete, and rarely produces harmful substances. All this makes the fuel cell regarded as a promising energy power unit. ^[2]

Fuel cell is a kind of energy conversion device. It is based on the principle of electrochemistry, that is, the principle of primary battery. It directly converts the chemical energy stored in fuel and oxidant into electrical energy, so the actual process is redox reaction. Fuel cell is mainly composed of four parts, namely anode, cathode, electrolyte and external circuit. Fuel gas and oxidant gas are introduced from the anode and cathode of the fuel cell, respectively. The fuel gas emits electrons on the anode, and the electrons are conducted to the cathode through an external circuit and combined with the oxidizing gas to generate ions. Under the action of an electric field, ions migrate to the anode through the electrolyte, react with the fuel gas, form a loop, and generate an electric current. At the same time, due to its own electrochemical reaction and the internal resistance of the battery, the fuel cell also generates a certain amount of heat. In addition to conducting electrons, the cathode and anode of the battery also act as catalysts for the redox reaction. When the fuel is a hydrocarbon, the anode requires higher catalytic activity. The cathodes and anodes are usually porous to facilitate the introduction of reaction gases and the discharge of products. The electrolyte plays a role of transferring ions and separating fuel gas and oxidizing gas. In order to prevent the short circuit in the battery caused by the mixture of two gases, the electrolyte is usually a dense structure. ^[3]

The main components of a fuel cell are: Electrode,

A fuel cell is a device that directly converts the chemical energy of a fuel into electrical energy. In theory, as long as the fuel is continuously supplied, the fuel cell can continuously generate electricity, which has been hailed as the fourth generation power generation technology after hydropower, thermal power, and nuclear power. ^[5]

Alkaline fuel cell (AFC) is the earliest developed fuel cell technology and was successfully applied in the field of space flight in the 1960s. Phosphoric acid fuel cell (PAFC) is also the first generation of fuel cell technology, which is the most mature application technology at present, and has entered commercial applications and mass production. Due to its high cost, it can only be used as a regional power station to supply power and heat on site. Molten carbonic acid fuel cell (MCFC) is the second-generation fuel cell technology, which is mainly used in equipment for power generation. The solid oxide fuel cell (SOFC) is the third generation with its all-solid structure, higher energy efficiency, and wide adaptability to various fuel gases such as gas, natural gas, and mixed gas. The fuel cell. ^[6]

Domestic status of fuel cells

Research on fuel cells in China began in 1958, and the Tianjin Power Supply Research Institute of the former Ministry of Electronics Industry carried out the earliest research on MCFC. Driven by the aerospace industry in the 1970s, China's fuel cell research showed its first climax. In the meantime, two types of alkaline asbestos membrane type hydrogen-oxygen fuel cell system (kw class AFC) successfully developed by the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences have passed routine space environment simulation tests. In 1990, the Changchun Institute of Applied Chemistry of the Chinese Academy of Sciences undertook the research task of the PEMFC of the Chinese Academy of Sciences. In 1993, the direct methanol proton exchange membrane fuel cell (DMFC) research began. In 1991, the Harbin Power Plant Complete Equipment Research Institute of the Ministry of Power Industry developed a MCFC principle battery composed of 7 single cells. During the Eighth Five-Year Plan period, more than a dozen domestic institutions, including the Dalian Institute of Chemical Physics, the Chinese Academy of Sciences, the Shanghai Institute of Ceramics, the Institute of Chemical Metallurgy, and Tsinghua University, conducted research on SOFC. By the mid-1990s, China had entered the second climax of fuel cell research due to the promotion of the Ministry of Science and Technology and the Chinese Academy of Sciences to include fuel cell technology in the "Ninth Five-Year Plan" for scientific and technological research.

The fuel cell

Chinese scientists have made a lot of progress in fuel cell basic research and individual technologies, and have accumulated certain experience. However, due to the small amount of investment in fuel cell research over the years, there is still a large gap with developed countries in terms of the overall level of fuel cell technology. Relevant departments and experts in China attach great importance to fuel cells. In 1996 and 1998, they held special discussions on the development of fuel cell technology in China at the Xiangshan Science Conference, emphasizing the importance and necessity of independent research and development of fuel cell systems. . In recent years, China has strengthened its research on PEMFC. In 2000, the Dalian Institute of Chemical Physics and the Institute of Electrical Engineering of the Chinese Academy of Sciences have completed all the tests on 30kW fuel cells for vehicles. Xu Guanhua, Vice Minister of Science and Technology announced at the 16th EVS conference that China will install the first fuel cell electric vehicle in 2000. The relevant overview of previous participation in fuel cell research is as follows:

1: Research status of PEMFC

The fuel cell

The earliest PEMFC development in China was the Changchun Institute of Applied Chemistry. The institute began to study PEMFC with the support of the Chinese Academy of Sciences in 1990. The work mainly focused on the preparation of catalysts, electrodes, and the development of an external reformer for methanol. . In 1994, he was the first to carry out research work on direct methanol proton exchange membrane fuel cells. The institute has established long-term collaborative relationships with CaseWesternReserve University in the United States and the Russian Hydrogen and Plasma Institute. The Dalian Institute of Chemical Physics of the Chinese Academy of Sciences carried out research on PEMFC in 1993 and did a lot of work on electrode technology and battery structure. It has now developed a single cell with a working area of 140 cm ² and an output power of 0.35 W / cm ² .

Fudan University began the development of direct methanol PEMFC in the early 1990s, mainly studying the preparation of polybenzimidazole films and electrode preparation processes. Xiamen University has collaborated with the University of Hong Kong and CaseWesternReserve University in the United States to conduct research on direct methanol PEMFC.

In 1994, Shanghai University and Beijing University of Petroleum cooperated in the research of PEMFC ("Eighth Five-Year Plan"), mainly studying the preparation of catalysts, electrodes, and electrode membrane assemblies

The fuel cell

Craft.

Beijing Institute of Technology started research on PEMFC in 1995 under the auspices of the Ministry of Ordnance Industry. The current density of a single cell is 150 mA / cm ² .

The Institute of Engineering Thermophysics of the Chinese Academy of Sciences began to study PEMFC in 1994. It mainly uses computational heat transfer and computational fluid dynamics methods to compare various gas supply, humidification, heat removal and drainage schemes, and proposes improved heat and mass transfer. Program.

Tianjin Power Source Research Institute started research on PEMFC in 1997. It plans to introduce 1.5kW batteries from abroad and carry out research based on analysis and absorption of foreign advanced technology.

In 1995, Beijing Fuyuan Co., Ltd. and Canadian New Energy Co., Ltd. cooperated in the research and development of PEMFC. A 5kW PEMFC prototype has been successfully developed and orders have been accepted.

2: Research Overview of MCFC

The fuel cell

There are not many units conducting MCFC research in China. Harbin Power Supply Equipment Research Institute has studied MCFC in the late 1980s, and stopped research in this area in the early 1990s.

In 1993, the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences started research on MCFC with the funding of the Chinese Academy of Sciences. Homemade LiAlO2 micropowders were prepared by cold rolling and tape casting. MCFC separators were assembled and the single cells were assembled. Reached the international level in the early 1980s.

In the early 1990's, the Changchun Institute of Applied Chemistry of the Chinese Academy of Sciences also began research on MCFC, and made great progress in the preparation of LiAlO ₂ micropowder and the use of intermetallic compounds as anode materials for MCFC.

The University of Science and Technology Beijing launched MCFC research in the early 1990s under the auspices of the National Natural Science Foundation. It mainly studied the interaction between electrode materials and electrolytes, and proposed the use of intermetallic compounds as electrode materials to reduce its dissolution.

3: Research Brief of SOFC

The fuel cell

The earliest SOFC research was carried out by the Shanghai Institute of Ceramics, Chinese Academy of Sciences. They carried out SOFC research in 1971, mainly focusing on the research of SOFC electrode materials and electrolyte materials. In the 1980s, under the funding of the National Natural Science Foundation of China, the research on SOFC began. The system has studied the preparation of zirconia film materials, cathode and anode materials, and the structure of monomer SOFC by the casting method. Technology of Zirconia Nanopowder and Dense Ceramics. Jilin University began research on the electrolyte, anode and cathode materials of SOFC and assembled them into single cells under the funding of the Jilin Provincial Youth Science Fund in 1989, and passed the appraisal by the Jilin Provincial Science and Technology Commission. In 1995, it received funding of RMB 4.5 million from the Jilin Province Planning Commission and the State Planning Commission.

The fuel cell

Electrode, electrolyte, sealing and connecting materials, etc., the open circuit voltage of the single cell reaches 1.18V, the current density is 400mA / cm ² , and the battery pack with 4 single cells connected in series can make the radio and recorder work normally.

In 1991, the Institute of Chemical Industry and Metallurgy of the Chinese Academy of Sciences carried out research on SOFC under the auspices of the Chinese Academy of Sciences. From the development of materials, tube and flat-type single cells were produced, with a power density of 0.09W / cm ² to 0.12W / cm ² The current density is 150 mA / cm ² to 180 mA / cm ² , and the operating voltage is 0.60 V to 0.65 V. In 1994, the institute introduced a 20W 30W block laminated SOFC battery pack from the Institute of Electrochemistry of the Ural Branch of the Russian Academy of Sciences, with a battery life of 1200h. Based on the analysis of the laminated structure in Russia, the tubular structure in the Westinghouse in the United States, and the Siemens plate structure in Germany, they designed a new hexahedral structure that absorbs the advantages of the tube type without sealing. The battery cell combination uses metal felt flexible connection , And can be made by conventional ceramic preparation technology.

South China University of Technology started the SOFC research in 1992 with the support of the National Natural Science Foundation of China, the Natural Science Foundation of Guangdong Province, the Li Ka-shing Research Fund of Shantou University, and the Foshan Fund of Guangdong. Using methane as fuel directly, the maximum output power is 4mW / cm ² , the current density is 17mA / cm ² , and continuous operation for 140h, the battery performance is not significantly reduced.

International status of fuel cells

Developed countries have taken the development of large-scale fuel cells as a key research project, and the business community has invested heavily in research and development of fuel cell technologies. Many important results have been achieved, making fuel cells to replace traditional generators and internal combustion engines. Widely used in power generation and automobiles. It is worth noting that this important new power generation method can greatly reduce air pollution and solve the problem of power supply and power grid peak shaving. 2MW, 4.5MW, 11MW complete sets of fuel cell power generation equipment have entered commercial production, and various levels of fuel cell power plants Has been completed in some developed countries. The development and innovation of fuel cells will be like the revolution in internal combustion engines that replaced manpower to create an industrial revolution a hundred years ago. It will also be like the computer revolution that popularized the invention of computers to replace manpower's computing, graphics, and document processing. The development of network communications will change the information revolution in people's habits . The potential of high efficiency, pollution-free, short construction period, easy maintenance and low cost of fuel cells will ignite the green revolution of new energy and environmental protection in the 21st century. Today, in North America, Japan, and Europe, fuel cell power generation is rapidly entering the stage of industrial-scale application with the momentum of catching up, and it will become the fourth generation power generation mode after thermal power, hydropower, and nuclear power in the 21st century. The rapid development of fuel cell technology in foreign countries must cause us to pay enough attention. It is a topic that the energy and power industries have to face squarely.

Phosphoric Acid Fuel Cell (PAFC)

The fuel cell

Affected by the worldwide oil crisis in 1973 and the research and development of the United States PAFC, Japan decided to develop various types of fuel cells. PAFC, as a large-scale energy-saving power generation technology, was developed by the New Energy Industry Technology Development Agency (NEDO). Since 1981, research and development of 1000kW on-site PAFC power plant has been conducted. In 1986, the development of a 200kW on-site power generation device was carried out to apply to PAFC power generation devices in remote areas or commercial use. Fuji Electric is Japan's largest supplier of PAFC battery stacks. As of 1992, the company had supplied 17 sets of PAFC demonstration units to domestic and foreign countries. Fuji Electric completed the research on the operation of decentralized 5MW equipment in March 1997. As field equipment, a total of 88 types of equipment of 50kW, 100kW and 500kW have been put into use. The following table shows the operating conditions of the power generating units delivered by Fuji Electric Co., Ltd., which have exceeded the target life of 40,000 hours by 1998.

Toshiba began developing in the second half of the 1970s with a focus on decentralized fuel cells, and then developed a series of 11 MW and 200 kW units for decentralized power supplies. The 11MW unit is the world's largest fuel cell power generation equipment. It was built in the Tokyo Electric Power Company's Gotsui Thermal Power Station in 1989. After successful power generation in early March 1991, it conducted more than five years of field tests until May 1996, with cumulative operating time exceeding 20,000 hours, achieving a power generation efficiency of 43.6% under rated operating conditions. In the field of small-scale on-site fuel cells, Toshiba and IFC Corporation of the United States established ONSI in 1990 to commercialize on-site fuel cells, and later began to sell the field-type 200kW equipment "PC25" series to the world. PC25 series fuel cells have been in operation since the end of 1991. By April 1998, a total of 174 units had been sold to the world. Among them, one machine installed in a company in the United States and the Osaka Gas Company No. 2 installed in the Umeda Center in Osaka, Japan, have cumulatively exceeded 40,000 hours of operation time. From the perspective of the life and reliability of the fuel cell, the cumulative operating time of 40,000 hours is the long-term goal of the fuel cell. Toshiba ONSI has completed the development of the official commercial PC25C model, which has already been put on the market. PC25C won the Japan Trade and Industry Award as a pioneer of new energy in the 21st century. Starting from the commercialization of fuel cells, the device was evaluated as having high advanced, reliable and superior environmental equipment. Its manufacturing cost is $ 3000 / kW. The cost of the commercial PC25D model will be reduced to $ 1500 / kW, its volume will be reduced by 1/4 compared to the PC25C model, and its quality will only be 14t. In 2001, the first PC25C fuel cell power station will be ushered in China. It will be mainly funded by Japan's MITI (NEDO). This will be China's first fuel cell power station.

Proton exchange membrane fuel cell (PEMFC)

The well-known Canadian Ballard company is a global leader in PEMFC technology. Its applications range from vehicles to stationary power stations. Its subsidiary BallardGenerationSystem is considered to be a world leader in the development, production and marketization of zero-emission proton exchange membrane fuel cells. The initial product of BallardGenerationSystem is a 250kW fuel cell power station. Its basic component is a Ballard fuel cell, which uses hydrogen (obtained from methanol, natural gas or petroleum) and oxygen (obtained from air) to generate electricity without combustion. Ballard is working with many world-renowned companies to commercialize BallardFuelCell. BallardFuelCell has been used in stationary power plants: BallardGenerationSystem, GPU International Inc., AlstomSA and EBARA have jointly formed BallardGenerationSystem to jointly develop fuel cell power plants below the kilowatt level. After 5 years of development, the first 250kW power plant successfully generated power in August 1997 and was sent to Indiana Cinergy in September 1999. After thorough testing and evaluation, it improved the design performance and reduced costs, which led to the second The birth of a power plant, installed in Berlin, with a 250kW output, is also the first test in Europe. Soon Ballard's third 250kW power plant was also installed in Switzerland for field testing in September 2000. Then, in October 2000, through its partner EBARA Ballard, the fourth fuel cell power plant was installed at NTT in Japan Opened up markets in Asia. Testing in different regions will greatly promote the commercialization of fuel cell power plants. The first early commercial power plants will be available by the end of 2001. Below is a Ballard fuel cell device installed in Cinergy, USA, which is being tested.

The picture shows a 250kW PEMFC fuel cell power station installed in Berlin:

In the United States, PlugPower is the largest proton exchange membrane fuel cell development company. Their goal is to develop and manufacture economical fuel cell systems suitable for residential and automotive applications. In 1997, the PlugPower module was the first to successfully convert gasoline to electricity. PlugPower has developed its patented product, the PlugPower7000 residential distributed power system. Commercial products were launched in early 2001. The launch of domestic fuel cells will pose challenges to nuclear power plants and gas power stations. In order to promote this product, in February 1999, PlugPower and GEMicroGen established a joint venture company, which was renamed GEHomeGen7000, and GEMicroGen was responsible for global promotion. This product will provide 7kW of continuous power. GE / Plug claims to sell for $ 1500 / kW in early 2001. They expect that in five years time, mass-produced fuel cells will sell for $ 500 / kW. Assuming that 200,000 households each install a 7kW domestic fuel cell power generation device, the sum of which will be close to the capacity of a nuclear power unit. This decentralized power generation system can be used for peak power supply and increased power due to the decentralized system design. Stability, even if a few failures occur, the entire power generation system can still operate normally. Driven by Ballard, many car manufacturers participated in the development of fuel cell vehicles, such as: Chrysler, Ford, GM, Honda, Nissan, VolkswagenAG (Volkswagen) And Volvo, etc., many of the fuel cells they are using are produced by Ballard. At the same time, they also invested a lot of money into the development of fuel cells. Chrysler injected 450 million Canadian dollars into Ballard. Yuan was used to develop fuel cell vehicles, which greatly promoted the development of PEMFC. In 1997, Toyota produced a RAV4 sports car with a methanol reformer. It provided a full power of 50kW with a 25kW fuel cell and an auxiliary dry battery. The maximum speed can reach 125km / h and the travel range is Up to 500km. These big auto companies have fuel cell development plans. Although the timing of commercialization of fuel cell vehicles is still immature, several companies have set a timetable for starting mass production. Daimler-Benz announced that it will have an annual output by 2004. 40,000 fuel cell vehicles. Therefore, in the next ten years, it is very likely to reach 100,000 fuel cell vehicles.

Molten Carbonate Fuel Cell (MCFC)

In the early 1950s, molten carbonate fuel cells (MCFCs) attracted worldwide attention due to their prospects as large-scale civilian power generation devices. Since then, MCFC has developed very quickly, and it has made great improvements in battery materials, processes, and structures, but the battery's operating life is not ideal. By the 1980s, it had been used as the second-generation fuel cell, and it became the main research target for the realization of megawatt-scale commercial fuel cell power plants, and the development speed was increasing day by day. The main developers of MCFC are concentrated in the United States, Japan and Western Europe. Commercial production is expected in 2002.

The United States Department of Energy (DOE) in 2000 has allocated $ 44.2 million in research costs for stationary fuel cell power plants, of which 2/3 will be used for MCFC development and 1/3 will be used for SOFC development. The development of MCFC technology in the United States has been mainly undertaken by two major companies, ERC (Energy Research Corporation) (now FuelCellEnergyInc.) And M-CPower. They built MCFC reactors in different ways. Both companies have reached the on-site demonstration stage: in 1996, ERC has conducted a demonstration test of a 2MW MCFC power plant in Santa Clara, California, and is looking for a site for a 3MW plant test. ERC's MCFC fuel cell can be reformed without gas inside the battery, without the need for a separate reformer. According to the test results, ERC redesigned the battery and changed the battery to a 250 kW single-cell stack instead of the original 125 kW stack. This allowed 3MW MCFC to be installed on a 0.1 acre site, thereby reducing investment costs. ERC expects to provide a 3MW unit at an equipment cost of $ 1200 / kW. This is close to the $ 1000 / kW of equipment cost for a small gas turbine power plant. However, the efficiency of small gas power generation is only 30%, and there are problems with exhaust emissions and noise. At the same time, the US company M-CPower has conducted a 250kW unit test at the Naval Air Station in San Diego, California, and plans to test and improve the 75kW unit at the same location. M-CPower is developing a 500kW module and plans to start production in 2002.

Japan s research on MCFC began in 1981 with the Moonlight Plan and turned to focus after 1991. The annual cost of fuel cells was 1.2-1.5 billion US dollars. In 1990, the government added an additional 200 million U.S. dollars to MCFC the study. The power of the battery stack was 1 kW in 1984 and 10 kW in 1986. Japan studies both internal conversion and external conversion technologies. In 1991, a 30kW class indirect internal conversion MCFC was commissioned. 50-100kW test run in 1992. In 1994, Hitachi and Ishikawa Island Harima Heavy Industries completed two 100 kW, 1 m ² electrode areas and pressurized external reforming MCFC. In addition, the 1MW external reforming MCFC manufactured by the Chubu Electric Power Company is being installed in the Kawagoe thermal power plant. When natural gas is used as the fuel, the thermoelectric efficiency is expected to be greater than 45% and the operating life to be greater than 5000h. The internal reforming 30kW MCFC developed by Mitsubishi Electric and the United States ERC has run for 10,000 hours. Sanyo has also developed a 30kW internal reforming MCFC. Ishikawa Island Harima has the world's largest area of MCFC fuel cell stacks, and the test life has reached 13,000 hours. In order to promote the development and research of MCFC, Japan established the MCFC Research Association in 1987, which is responsible for research on fuel cell stack operation, power plant peripheral equipment and system technology. It has united 14 units to become the main research and development force in Japan.

In Europe, a Joule plan was formulated as early as 1989. The goal is to build a "second-generation" power plant with low environmental pollution, decentralized installation and 200MW power, including three types of MCFC, SOFC and PEMFC. It will assign tasks to Countries. MCFC studies are mainly conducted in the Netherlands, Italy, Germany, Denmark and Spain. The study of MCFC in the Netherlands has begun in 1986. In 11989, a 1kW-class battery stack was developed. In 1992, tests were performed on 10kW-class external conversion and 1kW-class internal conversion battery stacks. In 1995, coal-based gas and natural gas were used as fuel. Commissioning of two 250kW systems. Italy began to implement the MCFC national research plan in 1986, and developed 50-100kW battery stacks from 1992 to 1994. Ansodo and IFC in Italy signed an agreement on MCFC technology. A set of single-cell (area 1m2) automated production equipment has been installed. The production capacity is 2-3MW, which can be expanded to 6-9MW. German MBB company completed the research and development of 10kW-class external conversion technology in 1992. With the assistance of ERC, it conducted manufacturing and operation tests of 100kW-class and 250kW-class battery stacks from 1992 to 1994. MBB now has the world's largest 280kW battery pack.

Data show that MCFC has unique advantages over other fuel cells:

a. Higher power generation efficiency than PAFC;

b. Do not need expensive platinum as catalyst, low manufacturing cost;

c. Can use CO as fuel;

d. Due to the MCFC operating temperature of 600-1000 ° C, the exhaust gas can be used for heating or combined with steam turbines for power generation. If cogeneration is used, the efficiency can be increased to 80%;

e. Compared with several small and medium power generation methods, when the load index is greater than 45%, the MCFC power generation system has the lowest cost. Compared with PAFC, although the initial investment of MCFC is high, the fuel cost of PAFC is much higher than MCFC. When the power generation system is small and medium-scale decentralized, the economics of MCFC are more prominent;

f. MCFC has a simpler structure than PAFC.

Solid oxide fuel cell (SOFC)

SOFC consists of an electrolyte that energizes oxygen ions with ceramics such as yttria-stabilized zirconia (YSZ), and a fuel and air electrode that energizes electrons with a porous material. Oxygen in the air is oxidized at the air electrode / electrolyte interface. Under the action of the oxygen difference between air and fuel, it moves to the fuel electrode side in the electrolyte. At the fuel electrode electrolyte interface, it reacts with hydrogen or carbon monoxide in the fuel to generate water. Vapor or carbon dioxide, emitting electrons. The electrons pass through the external circuit and return to the air pole again, at this time generating electricity.

The characteristics of SOFC are as follows:

Due to the high-temperature operation (600-1000 ° C), by setting the bottom surface cycle, it is possible to obtain high-efficiency power generation with an efficiency of more than 60%.

Since oxygen ions move in the electrolyte, CO and coal gas can also be used as fuel.

Since all the constituent materials of the battery body are solid, there is no evaporation and flow of the electrolyte. In addition, the fuel electrode and air electrode were not corroded. l The operating temperature is high, and internal modification such as methane can be performed.

Compared with other fuel cells, the power generation system is simple, and it can be expected to develop from equipment with relatively small capacity to large-scale equipment, which has a wide range of applications.

In the field of fixed power stations, SOFC has obvious advantages over PEMFC. SOFC rarely requires fuel treatment. Internal reforming, internal thermal integration, and internal manifolds make the system design simpler. Moreover, SOFC, gas turbines, and other equipment can easily perform high-efficiency cogeneration. The picture below shows the world's first SOFC and gas turbine hybrid power station developed by Siemens-Westinghouse. It was installed at the University of California in May 2000 with a power of 220kW and a power generation efficiency of 58%. The future SOFC / gas turbine power generation efficiency will reach 60-70%.

The so-called third-generation fuel cell is being actively researched and developed, and it is one of the emerging new power generation methods. The United States is the first country in the world to study SOFC, and the role of Westinghouse Electric Company in the United States is particularly important. It has now become the most authoritative organization in SOFC research. As early as 1962, Westinghouse Electric Co., Ltd. used methane as a fuel to obtain current on the SOFC test device, and pointed out that hydrocarbon fuels must complete the two basic processes of catalytic conversion and electrochemical reaction of the fuel in the SOFC, laying the foundation for the development of SOFC The foundation. In the following 10 years, the company collaborated with the OCR organization to connect 400 small cylindrical ZrO ₂ -CaO electrolytes to trial production of 100W batteries, but this form was not convenient for large-scale power generation applications. After the 1980s, in order to open up new energy sources and ease the energy crisis caused by the shortage of petroleum resources, SOFC research has flourished. Westinghouse Electric Corporation applied electrochemical vapor deposition technology to the preparation of SOFC electrolytes and electrode films, which reduced the thickness of the electrolyte layer to the micron level and significantly improved the performance of the battery. This opened a new page in SOFC research. In the mid-to-late 1980s, it started to develop high-power SOFC cell stacks. In 1986, a 400W tubular SOFC battery pack was successfully run in Tennessee.

The fuel cell

In addition, some other US departments also have certain strengths in SOFC. PPMF, located in Pittsburgh, is an important production base for the commercialization of SOFC technology. It has complete SOFC battery component processing, battery assembly, and battery quality testing equipment. It is currently the world's largest SOFC technology research and development center. In 1990, the center produced a 20kW class SOFC device for the United States DOE. The device uses pipeline gas as fuel and has been in continuous operation for more than 1,700 hours. At the same time, the center also provided two sets of 25kW-class SOFC test devices for Tokyo and Osaka Gas Corporation and Kansai Electric Power Company, one of which is a combined heat and power plant. In addition, the Argon National Laboratory in the United States has also researched and developed a laminated corrugated plate type SOFC cell stack, and developed a casting method and a rolling method suitable for the molding of such structural materials. The battery energy density is significantly improved, which is a more promising SOFC structure. In Japan, SOFC research is part of the Moonlight Project. As early as 1972, the Institute of Electronic Comprehensive Technology began to study SOFC technology, and later joined the research and development ranks of the "Moonlight Project". In 1986, it developed a 500W round tube SOFC battery stack and formed a 1.2kW power generation device. Tokyo Electric Power Corporation and Mitsubishi Heavy Industries started to develop round tube SOFC devices in December 1986, and obtained single cells with an output power of 35W. When the current density was 200mA / cm2, the battery voltage was 0.78V, and the fuel utilization rate reached 58%. . In July 1987, the power supply development company cooperated with these two companies to develop a 1kW round tube SOFC battery stack, which was continuously tested for 1000 hours with a maximum output power of 1.3kW. Kansai Electric Power Company, Tokyo Gas Company, and Osaka Gas Company have introduced 3kW and 2.5kW round tube SOFC battery stacks from Westinghouse Electric Company in the United States for testing, and obtained satisfactory results. Since 1989, Tokyo Gas Company has also started to develop large-area flat-type SOFC devices. In June 1992, it completed a 100W flat-type SOFC device with an effective area of 400 cm ² . At present, the flat SOFC power developed by Fuji and Sanyo has reached the kilowatt level. In addition, Chubu Electric Power Co., Ltd. has cooperated with Mitsubishi Heavy Industries to research and comprehensively evaluate the laminated corrugated plate SOFC system since 1990, and has developed a 406W test device, which has an effective single cell area of 131 cm ² .

As early as the 1970s in Europe, the Central Research Institute of Heidelberg, Germany, developed a SOFC power generation device with a circular tube or semi-circular tube electrolyte structure, which has a good single cell performance. In the late 1980s, under the influence of the United States and Japan, the European Community actively promoted the commercialization of SOFC in Europe. Germany's Siemens, DomierGmbH, and ABB Research are committed to developing kilowatt-level flat-plate SOFC power plants. Siemens also cooperated with the Dutch Energy Center (ECN) to develop open-cell SOFC single cells with an effective electrode area of 67 cm2. ABB research company developed an improved flat-type kilowatt SOFC power generation device in 1993. This battery has a metal bipolar structure and has been tested at 800 ° C with good results. It is currently being considered to be made into a 25-100kW class SOFC power generation system for home or commercial applications.