The petrol-powered element of the e-POWER hybrid system by Nissan will go beyond 40% thermal efficiency.
Nissan have been a leader in electrification for many years. They were amongst the first mass market manufacturers to introduce an all-electric option with the 1st gen LEAF. Their e-POWER hybrid system is also available in more and more models. Today they announce that this hybrid system is about to get a little more efficient.
Some background into thermal efficiency
As great as petrol engines are for mobility, they’re not very efficient. In a typical petrol engine, only about 1/3 of the energy stored in fuels is converted into useful kinetic energy that moves the car. The remaining 2/3 of energy is converted to heat, vibrations and emissions. In recent years, engineers have managed to increase this ‘thermal efficiency’ to about 40%, however, this is only on a few engines. Now Nissan says that they’re about to break the industry standards once again by approaching 50% thermal efficiency.
New e-Power petrol engines with STARC
To get to this incredibly high thermal efficiency, Nissan used a concept called ‘STARC’, which stands for: Strong, Tumble, and Appropriately stretched Robust ignition Channel. Their 40 minutes long technical presentation breaks this down, skip to the 19th minute for the start of the thermal efficiency discussion.
In brief, STARC:
- strengthens in-cylinder flow of air-fuel mixture
- more reliably burns a more diluted air-fuel mixture at high compression ratio
Add to this the fact that e-POWER does not use the petrol engine to drive the wheels. This allows for the petrol motor to run at an optimal range of speed and load as a generator. At this optimal speed and load, the engineers have been able to achieve the following thermal efficiency levels;
- 43% using exhaust gas recirculation dilution method
- 46% using lean combustion
- 50% at fixed RPM and load + waste heat recovery technology
We’re not sure when they’ll deploy these new technologies, but the next generation of e-POWER might be a good guess.
About e-POWER
Nissan’s e-POWER system utilizes an on-board gasoline engine to provide electrical energy to the e-powertrain battery pack. Nissan’s latest approach to engine development has raised the bar to world-leading levels, accelerating past the current auto industry average range of 40% thermal efficiency, making it possible to even further reduce vehicle CO2 emissions.
A dedicated approach towards enhanced efficiency
Conventional internal combustion engine (ICE) vehicles demand power and performance from an engine under a wide range of speeds (RPMs) and loads. This fundamental requirement means conventional engines cannot perform at their optimal efficiency at all times. However, Nissan’s e-POWER system utilizes an on-board engine as a dedicated electricity generator for the system’s e-powertrain. Operation of the engine is limited to its most efficient range, appropriately managing the engine’s electricity generation and the amount of electricity stored in the battery.
With this dedicated approach, and the evolution of battery technology and energy management techniques, Nissan has been able to improve thermal efficiency beyond current levels. Development of the next generation e-POWER system continues this path of efficiency through Nissan’s design and development of an engine exclusively for e-POWER.
The Nissan e-POWER System
e-POWER was first introduced in Japan in 2016 with the Nissan Note. At its core is the same 100% electric motor-driven technology used in the Nissan LEAF to deliver instant torque, power, efficiency and excitement. The system is comprised of a gasoline engine with a power generator, inverter, battery and electric motor.
Unlike a conventional hybrid system, e-POWER enables exclusive use of the on-board engine for electrical generation by separating the engine’s output and the driving force at the wheels.
