SoftBank Corp.'s Research on High Energy Density
Battery Packs and High-power Generation Efficiency
Solar Cell Panels for HAPS Adopted by NEDO

SoftBank Corp. (“SoftBank”) announced its proposal entitled “Research and Development on High Energy Density Battery Pack and High Power Generation Efficiency Solar cell panel for HAPS” has been adopted for a feasibility study on solar panel and storage battery technologies as part of “Research and Development on Long-Term Navigation Technology for High-Altitude Unmanned Aircrafts,” in the research and development field “Development and Verification of Maritime Domain Awareness Technology Using High-Altitude Unmanned Aircraft” of Key and Advanced Technology R&D through Cross Community Collaboration Program, an open call by Japan's national research and development agency “New Energy and Industrial Technology Development Organization” (“NEDO”).

HAPS (High Altitude Platform Station) aircraft are operated in the stratosphere using power generated during the day by the solar cell panels mounted on the surface, and the power stored in the battery pack during the day serves as the battery power source during the night. Currently, long-term flight demonstrations are being conducted mainly in low-latitude regions, however, the higher the latitude, such as in Europe or Japan, the shorter the daylight hours in winter, which poses a challenge for long-term flights throughout the year. To solve these issues, it is important to reduce the aircraft weight, which affects power consumption, by reducing the weight of the battery packs and solar cell panels, which account for a significant ratio of the aircraft weight, as well as increase the power generation efficiency of solar cells.

To reduce the battery pack weight, it is necessary to investigate the performance of next-generation battery cells with high specific energy (Wh/kg), such as lithium metal batteries. Compared to lithium-ion batteries, weight and volume can be reduced using lithium metal batteries, and development of battery pack assembly technology is also necessary. In addition, to reduce the weight and increase the efficiency of the solar cell panel, it is important to develop new ultra-high conversion efficient and low-cost solar cells, fine tune the solar cells for the stratospheric environment, where the solar spectrum differs from that on the ground, and for extremely low temperatures. Making the solar panel materials thinner and lighter is also essential.

To realize long-term HAPS flights in high-latitude regions, such as Japan, and with the aim of achieving early practical applications of HAPS, SoftBank will conduct a feasibility study to identify development elements and goals to be achieved, and it will continue to focus on essential core technologies — research and development on battery packs and solar cell panels.

For details on the program and adopted research theme, please refer to this page. (in Japanese)
To learn more about SoftBank's HAPS initiatives, please visit this website.

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