Contributing to a carbon-neutral society by enhancing the efficiency of distributed power sources for industrial applications
Hitachi has developed a next-generation solid oxide fuel cell (SOFC)*1 technology that outputs high power at low temperatures, contributing to a sustainable society. This technology applies the expertise that Hitachi has cultivated in semiconductor development to construct each fuel cell layer from separately-manageable partitioned cells. Since the performance of each cell can be evaluated, defective cells can be identified and eliminated in advance, which reduces overall failure risk and ensures high reliability. In addition, the thickness of the electrolyte layer,*2 a key element in power generation, has been uniformly reduced to improve power density. As a result, the SOFC’s operating temperature can be lowered from the conventional 700°C to 519°C, while the SOFC still delivers high power density exceeding 1 W/cm2 with high reliability. Accordingly, this technology is anticipated to reduce the number of thermal insulation components required and lower costs, while offering broad application potential in industrial and portable power sources, including factory in-house generation and disaster-response emergency supplies. Going forward, Hitachi will work together with partner companies and auxiliary equipment manufacturers to implement this technology on a societal level in order to contribute to the realization of a carbon-neutral society.
Figure 1. Prototype of Hitachi’s next-generation SOFC that achieves high output and low-temperature operation
*1 Solid oxide fuel cell (SOFC): A fuel cell that utilizes a ceramic solid electrolyte to achieve highly efficient power generation.
*2 Electrolyte layer: A key element of the SOFC that conducts ions while insulating electrons, enabling power generation.
Background of the technology and related challenges
There is a growing demand for renewable energy and high-efficiency distributed power sources in line with the global trend toward carbon neutrality. SOFCs are a highly efficient power generation technology offering versatility and compatibility with a wide range of fuels, including hydrogen, ammonia, and biofuels, and are attracting growing attention as a promising solution for achieving a carbon-neutral society. However, conventional SOFCs require high operating temperatures of approximately 700°C, which necessitates longer start-up time and the use of many thick thermal insulation components, thus restricting their scope of application. Although thin-film electrolyte layers are being explored as a means of reducing operating temperatures, the reliability of such technologies remains a hurdle. Overcoming these challenges therefore holds the key to the widespread application of SOFCs and the realization of an energy-efficient and sustainable energy society.
Technologies and solutions developed to address these challenges
Hitachi has developed a SOFC technology that delivers high power density at low temperatures, with a high degree of reliability.
The main features of this technology are outlined below.
1. Cell partitioning and partition management technology that delivers high reliability
Utilizing cell partitioning and partition management technology, Hitachi’s engineers created an array of small cells. This technology makes it possible to identify cells that show signs of failure and remove defective cells, enhancing overall reliability. As a result, high reliability can be maintained even with a thin electrolyte layer. This technology also provides considerable benefits in increasing yield in the SOFC manufacturing process.
2. Electrolyte layer thickness uniformity technology that supports high-output power generation
By ensuring the uniform thickness of the electrolyte layer, electron leakage current*3, which tends to occur in sections where the film is thinner, has been reduced. This has enabled a reduction in the SOFC operating temperature to 519°C while achieving a high power density exceeding 1 W/cm2. The lower operating temperature also allows for shorter start-up time and a reduction in the number of thermal insulation components needed, which broadens the application scope of SOFCs and contributes to improved energy efficiency. The lower operating temperature is also expected to lead to higher SOFC reliability and longer service life.
*3 Leakage current: The leakage of electrons due to local loss of insulation in the solid electrolyte layer caused by uneven film thickness.
Future outlook
Hitachi will continue to pursue research and development of SOFCs capable of delivering even greater performance, such as higher output at lower temperatures. Hitachi will also work with partner companies and auxiliary equipment manufacturers to develop diverse applications for SOFCs, such as distributed power sources for industrial applications and portable power sources, in order to contribute to the realization of a carbon-neutral society.
Hitachi also plans to present parts of this research at SOFC-XIX (The 19th International Symposium on Solid Oxide Fuel Cells) to be held in Stockholm, Sweden, from July 13 to 18, 2025.
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