Porsche Engineering is accelerating into the hydrogen space as it explores future powertrain solutions covering hybrids, electric and more efficient combustion engines.

From its six-month research, the German luxury carmaker is confident it can develop a clean, economical and sporty hydrogen engine, across the board.

Work is currently proceeding on hydrogen engines worldwide, predominantly focusing on commercial vehicles with a relatively low specific output of around 50kW per litre of displacement.

Vincenzo Bevilacqua, Senior Expert Engine Simulation at Porsche Engineering, said, “For the passenger car sector, this is insufficient. We have therefore developed a hydrogen combustion engine that aims to match the power and torque of current high-performance gasoline engines as a concept study. At the same time, we also had the objective of achieving low fuel consumption and keeping emissions at the same level as ambient air.”

The starting point for the study was an existing 4.4-litre eight-cylinder gasoline engine – or rather, its digital data set, since it conducted the entire study virtually using engine performance simulations.

Modifications to the engine model included a higher compression ratio and combustion adapted to hydrogen, but most importantly, a new turbocharging system.

“For clean combustion of hydrogen, the turbochargers have to, on the one hand, provide around twice as much air mass as they do in gasoline engines,” added Bevilacqua.

“On the other hand, however, the lower exhaust gas temperatures result in a lack of energy for their propulsion on the exhaust side. This discrepancy cannot be resolved with conventional turbochargers.”

Porsche Engineering has therefore examined four alternative, particularly powerful turbocharging concepts, some of which come from the motorsport arena. All systems consist of several electrically assisted turbochargers, some of them combined with additional control valves in the air system or electrically driven compressors.

Bevilacqua said in the benchmark studies, each turbocharging system showed specific advantages and disadvantages.

“The choice of the right concept is therefore highly dependent on the requirements profile of the hydrogen engine in question,” he said.

“For the engine study concerned, the development team selected a turbocharging system with back-to-back compressors. The special feature of this design is the coaxial arrangement of two compressor stages, which are driven by the turbine or the supporting electric motor using a common shaft. The process air flows through the first compressor, is cooled in the intercooler and then recompressed in the second stage.”

Hydrogen engine ‘on par’ with original gasoline unit

With an output of around 440kW, the hydrogen engine is on par with the original gasoline unit.

In order to better assess the performance of the powertrain, Porsche Engineering tested it in a luxury-segment reference vehicle with a relatively high total weight of 2,650kg on the Nürburgring Nordschleife – albeit entirely virtually: the drive was carried out using what is known as a digital twin, i.e. a computer-based representation of the real vehicle.

With a lap time of eight minutes and 20 seconds, the vehicle demonstrated high potential with regard to driving dynamics. Due to its chemical composition, neither hydrocarbons nor carbon monoxide are released during hydrogen combustion, and nor do particulates play a role either.

In terms of optimising emissions by the hydrogen engine, the experts at Porsche Engineering therefore concentrated on nitrogen oxides. In extensive optimisation rounds, they adapted the engine’s operating strategy for the cleanest possible combustion. Their approach was to keep the level of raw emissions low by means of extremely lean and therefore colder combustion, making it possible to dispense with an exhaust aftertreatment system.

Matthias Böger, Specialist Engineer Engine Simulation at Porsche Engineering, said as it turned out, the nitrogen oxide emissions are well below the limits set by the Euro 7 standard currently under discussion and are close to zero over the entire engine map.

In order to better contextualise the results of the emissions tests, he draws a comparison with the Air Quality Index, which is used by government authorities and other institutions as a benchmark for assessing the level of air pollution. In general, a concentration of up to around 40 micrograms of nitrogen oxide per cubic metre is equated with good air quality.

“The hydrogen engine’s emissions are below this limit. Operating it therefore has no significant impact on the environment,” said Böger.

Same-level emissions as ambient air

In addition to its barely measurable emissions, the hydrogen engine offers high efficiency in the WLTP measurement cycle as well as in customer-relevant cycles thanks to its lean combustion.

“We have thereby fulfilled our self-imposed project goal: the development of a clean, economical and sporty hydrogen engine, across the board,” Bevilacqua concludes.

“The cost of a hydrogen powertrain in series production could be comparable to that of a gasoline engine. Although the turbocharger system and a number of mechanical components of the hydrogen engine are more complex and therefore more expensive, there is no need for the exhaust gas aftertreatment required for the gasoline engine under Euro 7.

The Porsche Engineering team was able to carry out all tests virtually and efficiently. The established simulation process provided the foundations, along with the company’s extensive experience in modelling and calculation. “It took us only six months from the initial idea to the completion of the study. That included fundamental work such as creating new simulation models that take into account the different chemical and physical properties of hydrogen compared to gasoline.”

The hydrogen engine is unlikely to enter production in its current form, but that wasn’t the goal of the project anyway. Instead, the focus was on examining the technical potential of the alternative drive technology and expanding the capabilities of existing engineering tools.

“The study allowed us to gain valuable insights with regard to the development of high-performance hydrogen engines and add models and methods specifically for hydrogen to our virtual simulation methodology,” said Bevilacqua. “With this know-how, we are ready to efficiently handle future customer projects.”

Pros and cons of hydrogen-powered cars

Axel Rücker, Program Manager Hydrogen Fuel Cell at the BMW Group, which is also active in the hydrogen space, outlines the benefits and drawbacks of hydrogen fuel cell cars. Production and sales of a BMW hydrogen fuel cell vehicle could begin as early as 2025.

Currently, the biggest shortcoming of hydrogen fuel cell cars is the sparsity of options for refuelling. A hydrogen engine is refuelled at special fuel pumps, which in the future will probably find their way into ordinary service stations. As things stand, however, there are still very few refuelling stations for hydrogen-powered cars.

“We have a chicken and egg problem with hydrogen fuel cell technology,” said Rücker. “As long as the network of refuelling stations for hydrogen-powered cars is so thin, the low demand from customers will not allow for profitable mass production of fuel cell vehicles. And as long as there are hardly any hydrogen cars on the roads, the operators will only hesitantly expand their refueling station network.”

In order to promote the expansion of refuelling infrastructure there, vehicle manufacturers like BMW have joined forces with hydrogen producers and filling station operators in the Clean Energy Partnership initiative, which plans to expand the hydrogen fuelling station network to 130 stations by 2022.

That would allow the operation of about 60,000 hydrogen cars on Germany’s roads. The next target, with a corresponding increase in fuel cell vehicles, will be 400 stations by 2025. More fuelling stations are also needed in neighbouring countries to actually make it possible to travel outside Germany via FCEV.

H2 View’s Hydrogen in India – Snap Summit

With the launch of its national hydrogen strategy in recent weeks and growing interest in India’s bold ambitions to de-leverage from traditional fossil fuel-based energy, H2 View stages a Snap Summit to address the country’s path forward in hydrogen.

India plans to manufacture five million tonnes of green hydrogen per annum by 2030 and not just meet its own climate objectives but become a production and export hub for the clean fuel.

Some sources question a lack of detail over the wider ecosystem while others still point to the country’s reliance on coal power. Yet, the world’s third-largest energy consuming country is already embracing renewable energy, its solar power sector is moving forward, and data suggests coal’s hold over India’s power sector is steadily loosening. The grid is already evolving.

The question is, how can a renewable energy powerhouse fast-track to true sustainability with green hydrogen? Join H2 View and a programme of global hydrogen leaders to unlock answers and insights for the short, medium, and long-term future in India. Want to learn more? Click here.