Dolphin N2 and the CryoPower Engine
Dolphin N2 Ltd is a spin-out of renowned engineering services, manufacturing and consultancy company Ricardo plc, formed to commercialise the revolutionary CryoPower engine technology. CryoPower directly mitigates the sustained growth of oil demand in commercial sectors, competing head-on with batteries and fuel cells in terms of air quality and energy efficiency and with significant cost advantage.
What does CryoPower do?
CryoPower is an internal combustion engine, with all that implies in terms of low cost and ease of manufacture, that aims to compete with zeroemission drivetrains. It targets longhaul trucks (where zero-emission technology is least easy to apply), 0.5-50MW distributed power generation (an area seeing rapid growth to reinforce electricity grids and balance out intermittent renewables), and mixed-mode rail. It can potentially do this with the efficiency of the largest power stations, and air quality somewhere between the toughest Californian SULEV standard, and zero-impact (meaning emissions can’t be detected or are cleaner than the surrounding air). There are in fact two versions of the technology: ThermoPower is a simplified system offering most of the air quality benefits and efficiency advantage versus advanced diesel engines in research; CryoPower delivers ultimate efficiency and air quality by addition of Liquid Nitrogen or Air to its internal processes.
How does CryoPower work?
CryoPower and ThermoPower are Recuperated Split Cycle Engines. The revolutionary step is to separate the “cold” and “hot” parts of the traditional internal combustion engine. A first set of cylinders draw in air and compresses it – in the CryoPower version, Liquid Nitrogen is injected to keep this process cool for maximum efficiency; the simpler ThermoPower omits it. Then the compressed air passes through a recuperator, where the engine’s exhaust heats it up – saving fuel which normally has to do this. The air now passes to the second, hot cylinder set, which are thoroughly insulated – infeasible in a normal ICE where the same cylinder handles hot and cold processes. These cylinders host the combustion and expansion events, which produce power; they are bigger than the compressor cylinders (again impossible in a standard engine) because that is most efficient. As a final twist, the hot air passing into these combustion cylinders does so at the speed of sound, leading to extraordinary mixing with the fuel, and a unique “cool combustion” regime. The very low level of emissions, especially NOx and Particulates, can be reduced to at least SULEV and potentially lower using known “SCR” (Urea-based) after-treatment.
Is it futureproof?
It is tempting to see any ICE as a “transition technology”. However, combustible fuels remain by far the most energy-dense in comparison to batteries or fuel cells / hydrogen; they can be manufactured sustainably from bio-mass or synthesised. The CryoPower combustion system has been demonstrated on Diesel and Natural Gas, and it is potentially compatible with napthas, ethanol, hythane and hydrogen. The Liquid Nitrogen is already sustainable, as air-separation is a major player in electricity “demand-side management”; as use of renewables rise, it has been shown to be an attractive way of balancing the grid.
How well validated is the technology?
Split-cycle engines are known technology, and recuperation is commonplace in industrial gas turbines. It is the specific combination of these, plus liquid nitrogen, that is innovative. Ricardo’s work on recuperated split cycle engines started in 1992 in a project with the UK energy utility National Power, leading to two demonstrator units. The CryoPower system itself has been validated using a single cylinder Titan engine with recuperator (the “hot half”), to study low emissions behaviour; the industry-standard WAVE virtual-engine system has been used to predict power and efficiency, using realistic scenarios for sources of energy loss validated by Ricardo’s extensive knowledge of ICE technology. Specific rig tests are being used to study critical aspects such as liquid nitrogen injection and the fast-acting intake valves. Use of liquid nitrogen in vehicle and mobile applications is well known, with four companies offering it for truck refrigeration; refuelling is straightforward and similar to Liquified Natural Gas.
What is the business case?
The business case for the technology is based on much lower CapEx than low emission alternatives, and a rapid payback versus conventional (usually Diesel) technology. On-cost for the ThermoPower engine is estimated at around +20% vs conventional Diesel, with a fuel saving of 10% giving payback in a year or less; for CryoPower, capital cost is estimated at around 50% of the cost of a commercial Diesel engine; fuel cost savings of up to 20% per year will again give a rapid payback on the extra cost.
What are the plans for development?
In Phase 1, we will develop the engine to a full demonstrator over the next 21 months, using funding raised now and a £4.8m InnovateUK grant already won. For Phase 2 we will then raise further funds for application-specific prototypes and industrialisation. From this point we expect the route to market to be a combination of lower volume manufacture by Dolphin N2 plus licensing in higher volume sectors where this is appropriate.