HY2FLY’s Prof. Dr.-Ing. Josef Kallo on hydrogen-electric propulsion
18/07/2025
Speaking ahead of his presentation, Prof. Dr.-Ing. Josef Kallo, co-Founder and CTO of H2FLY, shared insights into the company’s work on reshaping the future of flight through hydrogen-electric propulsion, a technology that promises to significantly extend the range of electric aircraft while reducing environmental impact.
Founded a decade ago, H2FLY focuses on the development and deployment of hydrogen fuel cell powertrain systems. “Since October 2024, I’ve taken on the CTO role, overseeing our advanced technologies and strategic partnerships,” Kallo said. “One of our main innovations is the H2F175 powertrain – not to be confused with Airbus’s H175. We’re exploring where we can deploy this technology, from hydrogen-electric eVTOLs to fixed-wing aircraft.”
Kallo brings a wealth of experience to the role, having worked at General Motors, the German Aerospace Centre, and currently conducting research at the Helmholtz Institute. He’s been instrumental in steering H2FLY to several industry milestones, including the world’s first piloted liquid hydrogen powered electric aircraft flight in 2023 and, more recently, the first hydrogen-fuelled eVTOL flight in collaboration with Joby Aviation.
According to Kallo, hydrogen-electric propulsion offers a major leap in efficiency over battery-electric alternatives. “Liquid hydrogen storage in an electric aircraft with fuel cell propulsion gives us six to ten times the range of battery-powered aircraft,” he explained. “That’s a huge differentiator in terms of scalability and practicality.”
Looking ahead, the company's top priorities are technical optimisation and system lightweighting. “Our goal over the next year is to improve, optimise and reduce the weight of the H2F175, so it can be eligible for a wider range of applications,” Kallo noted.
In his talk, Kallo plans to focus on two key themes: “First, hydrogen-electric aviation can fundamentally change how we travel, enabling fast, point-to-point connections between rural and urban areas, or city to city, with ranges of 650 to 900 kilometres,” he said. “Second, we must pair this technology with renewable energy sources like wind and solar to avoid further pollution in the transport sector.”
Kallo emphasises that hydrogen produced from renewables, rather than fossil fuels, is essential to achieving truly sustainable aviation. Compared to synthetic fuels, renewable hydrogen can be generated and used far more efficiently. Once stored on board, it is converted into electricity via a fuel cell, powering electric motors with only water and heat as by-products. This creates a highly efficient, low-emission energy chain from source to flight.
However, Kallo warns that renewable hydrogen production must scale significantly. “We need to increase production by a factor of 1,000 or more to meet aviation needs,” he said. “It’s technologically feasible, but we need society to prioritise clean energy over fossil fuels if we’re serious about cutting emissions.”
Kallo hopes to engage with a broad audience at the show, from students to experts, potential customers, and policymakers. “The Future Propulsion Forum offers both public and professional visibility. That’s why it’s important for us to be there.”
He also highlighted the challenges H2FLY has already overcome. “Our first major step was proving the full functionality of a hydrogen fuel cell-electric motor powertrain in flight,” he said. “The next is improving power and efficiency to meet the needs of future aircraft designs.”
Session: Hydrogen-electric aviation: Pioneering the next generation of flight
Date: 30th September 2025
Time: 2:20 - 2:50
Kallo brings a wealth of experience to the role, having worked at General Motors, the German Aerospace Centre, and currently conducting research at the Helmholtz Institute. He’s been instrumental in steering H2FLY to several industry milestones, including the world’s first piloted liquid hydrogen powered electric aircraft flight in 2023 and, more recently, the first hydrogen-fuelled eVTOL flight in collaboration with Joby Aviation.
According to Kallo, hydrogen-electric propulsion offers a major leap in efficiency over battery-electric alternatives. “Liquid hydrogen storage in an electric aircraft with fuel cell propulsion gives us six to ten times the range of battery-powered aircraft,” he explained. “That’s a huge differentiator in terms of scalability and practicality.”
Looking ahead, the company's top priorities are technical optimisation and system lightweighting. “Our goal over the next year is to improve, optimise and reduce the weight of the H2F175, so it can be eligible for a wider range of applications,” Kallo noted.
In his talk, Kallo plans to focus on two key themes: “First, hydrogen-electric aviation can fundamentally change how we travel, enabling fast, point-to-point connections between rural and urban areas, or city to city, with ranges of 650 to 900 kilometres,” he said. “Second, we must pair this technology with renewable energy sources like wind and solar to avoid further pollution in the transport sector.”
Kallo emphasises that hydrogen produced from renewables, rather than fossil fuels, is essential to achieving truly sustainable aviation. Compared to synthetic fuels, renewable hydrogen can be generated and used far more efficiently. Once stored on board, it is converted into electricity via a fuel cell, powering electric motors with only water and heat as by-products. This creates a highly efficient, low-emission energy chain from source to flight.
However, Kallo warns that renewable hydrogen production must scale significantly. “We need to increase production by a factor of 1,000 or more to meet aviation needs,” he said. “It’s technologically feasible, but we need society to prioritise clean energy over fossil fuels if we’re serious about cutting emissions.”
Kallo hopes to engage with a broad audience at the show, from students to experts, potential customers, and policymakers. “The Future Propulsion Forum offers both public and professional visibility. That’s why it’s important for us to be there.”
He also highlighted the challenges H2FLY has already overcome. “Our first major step was proving the full functionality of a hydrogen fuel cell-electric motor powertrain in flight,” he said. “The next is improving power and efficiency to meet the needs of future aircraft designs.”
Session: Hydrogen-electric aviation: Pioneering the next generation of flight
Date: 30th September 2025
Time: 2:20 - 2:50