New fuel for revolutionary ICE: liquid nitrogen

The Ricardo CryoPower concept is a potentially game-changing engine technology that aims to substantially increase fuel efficiency while reducing operating costs and CO2 emissions in heavy-duty applications. Its effectiveness and the critical enabling technologies has now been proven, according to owner Dolphin N2 Ltd, paving the way for a full system demonstration and subsequent pilot applications and industrialisation. Initial research suggests that distributed generation and long haul trucks would be ideal applications for the technology.

The underlying technology has been the subject of active R&D by Ricardo for approximately ten years and has demonstrated the potential to reduce operating fuel costs and fuel usage by, respectively, 20 % and 30 % in comparison with today’s heavy-duty engines, after allowing for the financial and energy costs of the liquid nitrogen used by the new engine in addition to its fuel. In addition, by virtue of its entirely new approach to combustion, CryoPower offers the potential for significant reductions in engine-out emissions without compromising efficiency.

Redefining the combustion engine

The CryoPower split-cycle engine concept completely redefines the processes of internal combustion, says its maker, resulting in significantly improved internal thermal efficiency compared to the best conventional engines available. It achieves it by separating the four processes of the standard internal combustion engine. Induction and compression take place in one cylinder, while combustion and exhaust take place in another.

This separation enables the recovery of otherwise wasted exhaust heat to the working gas after compression in complete. The compression process is carried out isothermally, cooled via the injection of a small amount of liquid nitrogen. The liquid nitrogen is thus both a coolant and an additional energy vector, which offsets some of the fuel requirement.

The combustion process utilises either renewable or traditional fuels, liquid or gaseous, and delivers heat energy back to the chilled and compressed intake air. Its most important benefit, however, is to enable otherwise unachievable improvements in fuel economy, reduced CO2 and other emissions through improved internal thermal efficiency. 

Liquid nitrogen as an energy vector

CryoPower requires liquid nitrogen to operate, with a usage and refilling requirement broadly in line with that of the fuel used to power the vehicle. Liquified nitrogen is already routinely produced in electrically powered air separation units by the industrial gases industry, both directly and as a by-product of the production of liquid oxygen from air and is therefore readily available. For commercial reasons, this production process already tends to be operated so as to maximise the use of cheaper rate energy, and it would be comparatively straightforward to develop an expanded supply chain for liquid nitrogen based on both on this and on intermittent renewable sources. Using liquid nitrogen generated in this way as an energy vector in CryoPower engines for trucks would therefore offer arguably one of the most effective pathways by which renewable energy could be deployed in long-haul, heavy freight road-based transportation.

Business aspects

A spin-out company, Dolphin N2 Ltd, has been created to own all CryoPower IPR and assets, and it intends to push on with the development of the technology. “CryoPower is a potentially game- changing, commercially and environmentally attractive technology whose time really has come,” commented Simon Brewster, CEO of Dolphin N2 Ltd. “The development of the conventional heavy-duty engine is reaching the point of diminishing returns with regard to fuel efficiency and CO2; to go significantly beyond the current state of the art requires a completely new approach. CryoPower offers a step-change improvement in both fuel efficiency and operating fuel cost, and the prior development of its crucial enabling technologies has significantly reduced development risk. It does, however, require further significant investment to take it forward to full system demonstration, pilot applications and industrialisation. For these reasons, Dolphin N2, an entity independent of Ricardo, has been formed. The company will be vested with all CryoPower assets and IPR, and Ricardo will acquire a minority shareholding. We are now seeking further investors to join us in taking this exciting concept forwards towards commercial development.”