The world’s first hybrid bus powered by liquid nitrogen (N2) has completed a rigorous series of trials to bring it another step closer to the road.

The hybrid vehicle, dubbed CE Power, runs on both diesel and liquid N2. It features a high-efficiency Dearman Engine alongside a conventional diesel engine.

The alternative propulsion system addresses urban air pollution challenges by reducing emissions during acceleration after stopping. The zero emission Dearman Engine enables the bus to frequently stop, unload and pull away from a bus stop without expelling damaging pollutants.

Whilst driving below 20 miles-per-hour, the liquid N2 – stored in a low pressure insulated cylinder – is heated to boiling point, creating enough pressure to drive the multi-cylinder Dearman engine. Once the bus reaches 20 miles-per-hour, the diesel engine takes over.

Jon Trembley, Head of Cryogenic Technology at Air Products, explained the technology behind the development, stating, “The innovative system was developed to store cryogenic N2 liquid at low pressure, then pressurise and store in high pressure cylinders for use in the Dearman engine. This stored pressure is then used to provide the rapid reaction pressure responses required.”

“The development of an on-vehicle cryogenic system was a notable achievement to come from the project.”

”A bus that runs on ‘thin air’ represents a significant breakthrough”

David Sanders, Commercial Director, Dearman

CE Power was built by engineers at HORIBA MIRA as part of an Innovate UK consortium. The trials were completed at HORIBA MIRA’s facilities in Nuneaton near Birmingham and included components and full system testing along with an engineered drive cycle to simulate a standard bus route.

David Sanders, Commercial Director at UK-based Dearman, highlighted, “As the UK wrestles with dangerous levels of urban air pollution, a bus that runs on ‘thin air’ represents a significant breakthrough.”

He went on to explain that the Dearman Engine could significantly improve the efficiency of both buses and HGVs, reduce fuel consumption and slash pollution. “This successful trial could be the first step towards rolling out a British innovation to the streets of the UK and around the world,” Sanders added.

Martin Watkinson, Technical Lead on the project at HORIBA MIRA, continued, “The completion of these trials paves the way for the use of liquid N2 more widely in the automotive sector and takes the UK one step closer to stamping out harmful emissions for good.”