Porsche has very well defined its electrification goals: by 2030 they want 80% of their sales to be electric cars. And if they have proposed it, they will most likely achieve it. However, the German firm is developing different propulsion solutions for its cars in parallel, including hydrogen combustion engines as a less polluting alternative to conventional fuels and synthetic fuels (e-fuels), which Porsche is also committed to.
The engine division Porsche Engineering is investigating the possibilities of hydrogen, not with a fuel cell but in internal combustion engines. The company explores the potential of hydrogen as an alternative to gasoline, maintaining a high level of performance -as it could not be otherwise- but reducing emissions as much as possible. Of course, for now Porsche has carried it out virtually.
The starting point of the study was a V8 gasoline engine, turbocharged and with 4.4 liters of displacement already existing, suitable modified. To be more precise, Porsche has not taken the engine physically but rather its digital dataset, conducting the entire study virtually using computer simulations. Modifications to the engine include a higher compression ratio, hydrogen-adapted combustion and a new turbocharging system.
For a clean combustion of hydrogen, turbos have to provide about twice the mass of air than in gasoline engines, since hydrogen is very little dense. It is not the only technical difficulty, since the lower temperatures of the exhaust gases cause a lack of energy for their propulsion on the exhaust side. This means that the same system as in turbo gasoline engines cannot be applied. Porsche has studied four alternative concepts, of which one has been chosen for the final virtual model.
In the case of the chosen engine, the development team opted for a system with electric turbo and compressors in parallel. The distinctive feature of this design is the coaxial arrangement of two compressor stages, which are driven by the turbine or by the supporting electric motor via a common shaft. Air flows through the first compressor, is cooled in the intercooler and then it is compressed again in the second stage. The result is an engine with 598 hp and very low emissions. According to Porsche, the emissions of nitrogen oxides are “well below” the limits set by the Euro 7 standard that is currently being discussed.
But the engine could not just stay within the theoretical parameters, and that is why Porsche has carried out simulations on the Nürburgring Nordschleife circuit with a car weighing 2,650 kg (everything points to a Cayenne). Virtual, let’s not forget. The result has been a lap time of 8 minutes and 20 seconds. To put it in context, the fastest version of the Cayenne, the Cayenne Turbo GT, managed to do a lap of 7:38.925 last year.
A very low-polluting engine but “unlikely” to reach production
Porsche has calculated that nitrogen oxide emissions from this engine are less than 40 micrograms of nitrogen oxides (NOx) per cubic meter of air, a concentration that government authorities and other institutions consider to be within the limits of good quality air. To achieve the cleanest combustion possible, the combustion is extremely lean. In addition, due to the chemical composition of the reaction, in the combustion of hydrogen, hydrocarbons or carbon monoxide are not released, nor are particles.
Porsche says that the cost of a hydrogen combustion engine could be comparable to that of a gasoline engine. The electric turbo system is more complex and more expensive, and in addition several specific mechanical components are added for adaptation to hydrogen, but it compensates by not having to install the necessary exhaust gas after-treatment system in a gasoline engine to comply. Euro 7 regulations.
Although everything seems to be advantages, according to Porsche Hydrogen engine ‘unlikely’ to enter production in its current form, and in fact that was never the goal of the project. The objective was to examine the technical potential of the technology and gain insights into the development of high-performance hydrogen engines. If the European Union ends up vetoing synthetic fuels, who knows if Porsche will end up changing its focus from e-fuels to hydrogen for certain models and competition.
