Zero-emission Dearman engine runs alongside diesel to reduce emissions in urban traffic
A “revolutionary” hybrid bus that runs on both diesel and liquid nitrogen has completed a rigorous series of trials at the Horiba MIRA proving ground as one of the companies behind it says that it is a step closer to being used on public roads.
The bus – called CE Power – is the world’s first to be powered by liquid nitrogen and it has a high-efficiency, zero-emission Dearman engine alongside a conventional diesel power unit.
It has been built by engineers at Horiba MIRA as part of an Innovate UK consortium.
Improved efficiency
“The Dearman Engine has the potential to significantly improve the efficiency of buses,” says Dearman Commercial Director David Sanders.
“It can provide a cost-effective alternative to other emerging zero-emission technologies whose environmental performance is often offset by complexity and cost.
“This successful trial could be the first step towards rolling out a British innovation to the streets of the UK, and around the world.”
Cutting out diesel
When driving at 20mph or below, the liquid nitrogen – which is stored in a low-pressure insulated cylinder – is warmed to the point of boiling. It creates enough pressure to drive the multi-cylinder Dearman Engine and when 20mph is exceeded, the diesel engine engages.
Testing at Horiba MIRA included an engineered drive cycle to simulate a standard bus route with a variety of stops, says Dearman. A hybrid propulsion system is used, and Dearman adds that it will allow the bus to produce no nitrogen oxides or carbon dioxide at low speeds.
The consortium behind the bus says that refuelling liquid nitrogen takes “a matter of minutes.” Air Products has developed an on-vehicle cryogenic system specifically for the CE Power. After being stored at low pressure it is moved to high-pressure cylinders for use in the Dearman engine.
