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As the world pays more and more attention to clean energy and sustainable development, solid oxide fuel cells (Solid Oxide Fuel Cells), as an efficient and environmentally friendly energy conversion technology, are gradually becoming a shining star in the future energy field.
This article aims to deeply analyze the working principle, technical characteristics, market application and development prospects of solid oxide fuel cells.
What is a solid oxide fuel cell?
Solid oxide fuel cell (SOFC) is a third-generation fuel cell. It is a fully solid-state chemical power generation device that directly converts chemical energy stored in fuel and oxidant into electrical energy in an efficient and environmentally friendly manner at medium and high temperatures. It is generally believed that it will be widely used in the future, just like proton exchange membrane fuel cells (PEMFC).
Composition of solid oxide fuel cells
Solid oxide fuel cells are composed of anode and cathode, electrolyte, connector and sealing material.
The main function of the electrode is to provide a reaction site for the electrochemical reaction and conduct the electrons generated (or required) by the electrochemical reaction, the main function of the electrolyte is to conduct oxygen ions or protons, the main function of the connector is to connect the single cells to achieve high power output and isolate the direct reaction between air and fuel, the sealing material is to separate and seal the fuel and air in their respective process areas.
Working principle of solid oxide fuel cells
The cathode of the Solid Oxide Fuel Cell reduces oxygen from the air into oxygen ions. These ions can diffuse to the battery anode through the solid oxide electrolyte and then oxidize the fuel through an electrochemical reaction. The reaction releases byproduct water and two electrons, which do work through the external circuit, powering the anode battery, and return to the cathode to repeat the cycle.
Such devices can also be used for solid oxide water electrolysis (SOEC), which is based on the principle of electrolyzing water under external voltage and high temperature to produce H2 and O2, converting electrical energy and thermal energy into chemical energy. Solid Oxide Fuel Cell devices have high operating temperatures, long industrial chains, and high engineering and technical difficulties, and are typical "high threshold" technologies. In addition, these systems can integrate with a battery circuit to store excess energy and provide more flexible energy management.
Advantages of solid oxide fuel cells
Compared with other fuel cells, solid oxide fuel cells have the following advantages:
①Solid Oxide Fuel Cell uses solid oxide as electrolyte and has a fully solid structure, so it is corrosion-free, leak-free, highly safe, and can be designed as a single unit.
②Solid Oxide Fuel Cell has a high operating temperature (600~1000℃). At this temperature, the electrode reacts quickly and does not require the use of precious metals such as Pt as electrode catalysts.
③High power generation efficiency, not limited by the Carnot cycle, and high fuel utilization rate. High-quality waste heat can continue to generate electricity and can also achieve cogeneration of heat and power, with an energy utilization rate of up to 80%~90%.
④The fuel has a wide range of applications. Due to the high operating temperature, it can directly use fuels from fossil energy such as natural gas, liquefied petroleum gas, and coal gasification gas, as well as fuels from biomass such as ethanol, biogas, and biomass gasification gas. It can also use methanol, ammonia, and other renewable fuels obtained by reacting "green hydrogen" with CO2 in the future.
Application scenarios of solid oxide fuel cells
Based on the above characteristics, Solid Oxide Fuel Cell has broad application prospects. The specific application scenarios are as follows.
Small household cogeneration system
Small Solid Oxide Fuel Cell household cogeneration system can provide electricity and hot water for family residences, and has obvious advantages in energy conservation and emission reduction as well as peak load shifting of electricity.
Distributed power generation
Solid Oxide Fuel Cell has high power generation efficiency, no noise, no pollution emissions, and flexible power range adjustment. It can provide fuel cell systems with power from hundreds of kW to tens of MW, which is particularly suitable as a backup power supply for distributed power generation or data centers.
Transportation field
Solid Oxide Fuel Cell has also been promoted and applied as an auxiliary or power source for vehicles, ships, drones and other tools. In 2016, Nissan released the world's first car powered by Solid Oxide Fuel Cell. The fuel of Solid Oxide Fuel Cell is bioethanol, and the cruising range can exceed 600km.
Large power stations
Large-scale coal gasification fuel cell power generation technology (IGFC) with near-zero CO2 emissions is a power generation system that combines integrated coal gasification combined cycle power generation (IGCC) with high-temperature solid oxide fuel cells or MCFCs. It has higher power generation efficiency and low CO2 capture cost, and is a fundamentally revolutionary technology for coal-fired power generation.
Reverse electrolysis to produce hydrogen
Solid Oxide Fuel Cell can generate electricity when it is running forward, and can achieve electrolysis when it is running reversely, which is a solid oxide electrolysis cell (SOEC). SOEC can produce hydrogen by electrolyzing water, storing the wasted electricity that does not match the load in hydrogen, and the electrolysis efficiency is as high as 85% to 95%, which is much higher than other electrolysis technologies.
Key scientific and technological issues that need to be solved in solid oxide fuel cells
Although Solid Oxide Fuel Cell has a very broad application prospect, there are still some key scientific and technological issues that need to be solved urgently. In terms of basic research, the thermomechanical instability of key materials in Solid Oxide Fuel Cell should be overcome, especially the cracking, stratification and damage of batteries during thermal cycles.
In addition, in order to protect Solid Oxide Fuel Cell components, the heating rate is relatively slow, resulting in a long start-stop time. In the future, the research and development of key materials in Solid Oxide Fuel Cell should be accelerated. In terms of application, most of Solid Oxide Fuel Cell is currently concentrated in small-scale energy supply systems, combined heat, power and cooling systems, etc., while research on large-scale energy storage systems, including the integration of battery isolator, is still in the stage of verifying its feasibility.
In addition, the parameter configuration in the energy storage system, such as current density, operating pressure, operating temperature, system thermal integration, and battery connector design, should be fully optimized. Finally, there has been no systematic research on the life of Solid Oxide Fuel Cell, which is also a key breakthrough direction.
Conclusion
Solid oxide fuel cells are the leaders in the future energy field. Their high efficiency, environmental protection and multi-field application characteristics undoubtedly provide us with a new energy solution. With the continuous advancement of technology and the gradual reduction of costs, solid oxide fuel cells are expected to be applied in a wider range of fields and contribute to the sustainable development of human society.
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