A consortium of UK companies is developing a hybrid bus powered by liquid nitrogen and diesel. It aims to provide a cost-effective transport solution with a substantially reduced carbon footprint.
The project, named CE Power, is co-ordinated by Innovate UK and is funded by the Department for Business, Innovation and Skills. Contributors to the project include Horiba MIRA, Dearman, Air Products, The Manufacturing Technology Centre, Productiv, CENEX and the Transport Research Laboratory.
CE Power uses a liquid nitrogen expansion engine during acceleration from rest and at speeds below 20mph. In diesel-powered buses, this is where NOx and CO2 emissions are relatively high. The stopping and starting of the liquid nitrogen bus, at speeds under 20mph, produces zero emissions.
The liquid nitrogen is stored in a low-pressure insulated cylinder and is warmed to the point of evaporation which creates sufficient pressure to drive the multi-cylinder Dearman engine. Once the bus reaches 20mph, the diesel engine takes over.
Liquid nitrogen gives a longer life than an electric hybrid system, allows for local production and easy refueling. Batteries, which power many of the UK’s electric hybrids, require changing several times over the lifetime of the bus, whereas the liquid nitrogen system will last the lifetime of the bus.
Liquid nitrogen can be produced locally without the need for neodymium or lithium both of which are used by motors and batteries and sourced from overseas. Furthermore, refueling liquid nitrogen can take 10-15 minutes, enabling the bus to return to the road quickly.
Horiba MIRA’s role in the project includes systems integration, vehicle dynamics modelling and overall vehicle control, ensuring the liquid nitrogen system operates seamlessly and safely with the diesel engine.
Derek Charters, Technical Lead at Horiba MIRA, said, ”This project is a first for liquid nitrogen use in hybrid buses. Liquid nitrogen is a fascinating energy source as it can be created worldwide from many renewable sources, meaning its carbon footprint is minimal. With the UK looking to continue to reduce its reliance on carbon fuels from overseas, and the search for lower emissions buses, this project takes the UK one step closer to achieving this goal.”
The project is expected to be finished by 2016.