The Nitrogen Engine: Ricardo spins out company to commercialize game-changing engine tech


In the UK, Ricardo has unveiled its CryoPower engine technology and points towards a potential saving of approximately 30 percent in CO2 emissions and 20 percent in operating fuel costs for heavy-duty trucks and in stationary distributed power generation systems.

That translates into potential operator savings of approximately $12,500 per year for each vehicle, or $250,000) per MW in a distributed power generation application. Huge.

The technology has been the subject of active R&D by Ricardo for approximately ten years and  now Simon Brewster has been tapped as CEO of a spin-out company, Dolphin N2 Ltd. to take forward to full system demonstration, pilot applications and industrialization. The company is vested with all CryoPower assets and Ricardo will have a minority shareholding. They’re on the hunt for investors for the majority stake.

The technology edge

Here are the two keys to the technology.

First, the Ricardo CryoPower split-cycle engine is based on the use of a separate induction and compression cylinder from that used for combustion and exhaust. This enables recovery of otherwise wasted exhaust heat to the working gas after the end of compression. Markedly improving thermal efficiency.

Second, air compression 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 utilizes 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.

The technology problem

The commercial vehicles industry expends considerable resources upon the achievement of incremental improvements to conventional powertrain technology, seeking improvements in operating range, payload, cost and emissions. But even if all currently known refinements and technologies are deployed on current state of the art truck diesel powertrains, there remains an effective fuel efficiency limit beyond which further gains become prohibitively expensive and impractical. With regulators worldwide seeking further improvements in fuel efficiency and reduced CO2 for this ubiquitous heavy-duty vehicle type, a new solution is needed.

As Dolphin N2 CEO Simon Brewster observed, “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.

Why not just electrify heavy-duty trucks?

Heavy-duty trucks are an essential element of the transportation mix of modern industrialized society. While trucks used in local deliveries or in drayage applications such as in port complexes and distribution hubs, may be amenable to powertrain electrification and hybridization, such CO2 saving opportunities are far more limited for long distance, heavy freight applications. The key challenges in this respect arise from the cost, mass and package envelope required for high capacity battery systems, which can limit payload and/or range. While battery electric solutions are thus potentially very attractive for shorter haul applications or where payload space is not at a premium, the conventional four-stroke diesel engine remains – almost universally – the power plant of choice for heavy-duty, long-haul trucks.

Sourcing the nitrogen

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. It is thus readily available. For commercial reasons, this production process already tends to be operated so as to maximize the use of ‘wrong time’, 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.

The Bottom Line

It’s early days, investment is being sourced to bring this technology to market. Having noted that — it’ certainly one of the most interesting technologies we’ve seen for heavy-duty trucking and distributed power generation. And we wonder if there’s an application for heavy duty marine including military — where fuel savings extend range, and time between re-fuels during operations. That makes for better warfighting capability and a more credible naval deterrent.