A UK airport trial has generated new operational evidence that could help the global aviation industry understand how hydrogen-powered ground equipment can be introduced safely and practically, and what is needed to support wider adoption.
The study, led by Exeter Airport, Cranfield University and ULEMCo, tested a dual-fuel hydrogen–diesel ground power unit over multiple days in winter operating conditions.
A new Cranfield University report finds that the equipment performed safely and reliably, delivered measurable reductions in diesel use and carbon emissions, and required little change for the ground teams operating it.
The findings also provide insights into where dual-fuel hydrogen technology may be most effective, suggesting that its greatest benefits could be achieved in equipment used continuously or for longer operating cycles.
The Winter Operations HyGPU project follows the groundbreaking Zero Carbon Turn trial at Exeter Airport in April 2025, which achieved several UK firsts when three different hydrogen-powered technologies supported the live turnaround of a TUI Boeing 737.
Delivered by Exeter Airport, Cranfield University and ULEMCo, with funding and support from the Connected Places Catapult and regulatory oversight from the UK Civil Aviation Authority, the latest project contributes practical evidence to the development of hydrogen infrastructure, operational procedures, safety frameworks and future investment decisions across the aviation sector.
Across eight operational days, the equipment completed 15 tests lasting a total of almost six hours. It consumed 7.41kg of green hydrogen, displacing an estimated 24.23 litres of diesel and avoiding approximately 63.9kg of carbon dioxide emissions.
No safety incidents or significant operational problems were reported. Airport ground crew also found little practical difference between operating the converted equipment and using a conventional diesel GPU.
The report estimates that converting all seven of Exeter Airport’s existing GPUs to the same dual-fuel system could potentially save more than 11,000 litres of diesel and approximately 35 tonnes of carbon dioxide equivalent each year.
Dr Thomas Budd, Associate Professor of Airport Decarbonisation at Cranfield University and author of the report, said: “This trial has taken us another step beyond a one-off demonstration and given us valuable operational evidence about how dual-fuel hydrogen equipment performs in winter conditions.
“The results show that the equipment can operate safely and deliver measurable reductions in diesel consumption and carbon emissions, with very little change required from the people using it.
“Although this remains a relatively modest dataset, it strengthens the evidence available to airports, regulators and equipment manufacturers as they consider where hydrogen can make the greatest contribution to decarbonisation.”
The report found no clear evidence that lower ambient temperatures, which ranged from 4°C to 14°C during the tests, directly affected the GPU’s technical performance.
However, the findings indicate that periods of inactivity, including overnight cold starts, may delay the point at which the equipment begins using hydrogen. This is because the dual-fuel unit starts on diesel and only introduces hydrogen after its engine reaches the required operating temperature.
The report says longer trials and a larger dataset would be needed to confirm the relationship between inactivity, temperature and performance.
The findings suggest dual-fuel technology may offer the greatest benefit for airport equipment used continuously or for longer periods. Equipment used for short, intermittent tasks may be better suited to other zero-emission technologies.
Stephen Wiltshire, Managing Director of Exeter Airport, which is part of the Regional & City Airports group, said: “The original Zero Carbon Turn project proved that different types of hydrogen-powered ground equipment could work together safely in a live airport environment. This latest study delivers on our commitment to build on that by testing the technology over a longer period and in more representative winter conditions.
“The new report gives us a much clearer indication of the potential operational and environmental benefits. It shows that converting existing equipment could provide airports with a practical way to reduce emissions while the infrastructure for fully zero-emission technologies continues to develop.
“Regional airports like Exeter are well placed to support trials of this kind, and we are proud that the evidence generated here is contributing to the wider development of hydrogen aviation in the UK.”
Amanda Lyne, Managing Director, ULEMCo, which conducted the conversion of the GPU to run on dual-fuel, said: “This study has given us insights into the operational benefits, working conditions and deployment implications of our dual fuel upgrade solution on the specific GPU, particularly in such a controlled safety environment, and has provided invaluable information for our wider plans for offering a range of solutions for ground support equipment decarbonisation.”
Supporting the UK’s hydrogen aviation roadmap
The project forms part of a much wider programme of work to understand how hydrogen could be introduced safely across the UK aviation sector.
The CAA’s Hydrogen Challenge has brought the regulator together with industry and academia to examine hydrogen-powered aircraft, engines, airport operations and supporting infrastructure. Eleven projects have contributed evidence to help identify safety considerations and potential gaps in existing regulation.
Together with the findings from the Challenge, the CAA has published a hydrogen roadmap setting out how it intends to support the scaling of hydrogen operations for small aircraft towards 2035.
The work undertaken at Exeter Airport has contributed practical evidence about the safe use of hydrogen in ground operations and the preparations airports may need to make before hydrogen-powered aircraft enter regular commercial service.
The Winter Operations HyGPU project was supported through the CAA’s Hydrogen Challenge Sandbox, which allows innovators to work closely with the regulator while maintaining high standards of safety, with funding from the Connected Places Catapult.
Arthy Ravichandran, Aviation and Maritime Director at Connected Places Catapult said: “Operational trials are essential to understanding both the opportunities and practical challenges associated with new transport technologies.
“This project has generated valuable evidence about the performance, operational requirements and potential emissions benefits of dual-fuel hydrogen equipment. It will help airports and the wider aviation sector make informed decisions about the role hydrogen could play in the transition to net zero.”
Building on the Zero Carbon Turn project
The Zero Carbon Turn trial at Exeter Airport in April 2025 brought together a hydrogen internal-combustion aircraft tug, a hydrogen fuel-cell baggage tractor and a dual-fuel hydrogen–diesel GPU during the turnaround of a TUI Boeing 737.
The project achieved a number of UK firsts, including:
- The first concurrent use of multiple pieces of different hydrogen-fuelled equipment at a UK airport.
- The first use of a hydrogen-fuelled GPU to power a commercial aircraft in the UK.
- The first use of a hydrogen-fuelled aircraft tug with a commercial passenger aircraft in the UK.
- The first use of dual-fuel hydrogen–diesel equipment at an airport.
- The first use of green hydrogen produced from renewable energy at a UK airport.
The first Cranfield University report into the project called for hydrogen technology to be tested for longer periods and under a broader range of operational conditions. The Winter Operations HyGPU trial was developed directly in response to that recommendation.
The latest report identifies three priorities for further research: longer trials as part of normal day-to-day airport operations; the development of higher-volume hydrogen storage and semi-permanent refuelling facilities; and scalable on-site testing of hydrogen fuel purity.
Dr Budd added: “The next stage must be to move from limited trials towards longer-term use as part of business-as-usual airport operations. That will allow the sector to expand the evidence base, develop the necessary infrastructure and build the operational knowledge and skills required to support hydrogen-powered aviation in the future.”
Download the Winter Operations HyGPU technical report here: https://www.cranfield.ac.uk/centres/centre-for-air-transport-management
