BMW, ZF supplier aims to convert diesels into hydrogen-fueled powerplants

Why socially?

The automotive industry, particularly in Europe, has made massive investments in diesel technology, ranging from the engines to the injection and control systems and more. All these investments – and most of the jobs connected to diesels – are at risk of extinction if we will go to battery-power only.

What are the biggest technical challenges in converting a diesel to burn hydrogen?

Hydrogen burns seven times faster than diesel, so you need to decrease the temperature in the combustion chamber. Water injection is a proven technology to do this, but a negative side effect is that this creates corrosion. Lubrication is another potential issue for an engine that tends to be very dry, so spray lubrication is the only solution. The engine itself only needs minor changes to the cylinder head. The injection and control systems also need to be reworked to handle hydrogen.

Is it more difficult to convert a gasoline engine into a hydrogen-burning powertrain?

Not really. The main issue is durability. Modern diesels are designed to last for 350,000 km while gasoline engines designed to last for about 250,000 km.

Punch Group plans to start producing hydrogen-fueled engines by 2024. What will be in the portfolio?

We are working on CO2-free solutions ranging in power from 80 kilowatt hours to 400 kWh (109 to 544 hp). At the top of the range, we are currently testing an evolution of the GM Duramax 6.6-liter V-8. (This unit was designed by the Turin center under GM. Punch has the rights to sell the hydrogen-powered variant of the engine worldwide, while the diesel version can be sold everywhere except the U.S.) Then we are working on a 500 cc combustion chamber that can accommodate several displacements, from  a 3.0-liter V-6 to a 2.0-liter I-4. We also have the ability to make a 1.5-liter three-cylinder, but it is not on our near-term plans.

Looking at Punch Group’s history, are you already targeting any potential diesel engine factories to add?

I cannot say anything specific, but you can easily imagine there will soon be plenty of “widow” diesel engine plants around Europe.

Why do you expect a top down spread of hydrogen-powered engines?

Mainly because of the limitation of the recharging infrastructure. By 2023-24, Europe should start to have in place a significant number of hydrogen stations on major highways. (The EU Green Deal proposes there should be hydrogen refueling stations every 150 km on Trans-European Transport Network corridors by 2030.) That will be enough for heavy trucks. Light commercial vehicles up to the size of a Ford Transit will follow.

And what about passenger cars?

Here the challenge is more on the package than on the technology. A car needs a tank capable of storing about 4 kg of hydrogen. While the weight of the tank is a fraction of a battery pack – about 50 kg versus several hundred kilograms for the batteries – the tank requires a space of approximately 100 liters. This is a significant packaging challenge if you want to house the tank in the trunk of a sedan. It’s even more problematic with hatchbacks. For passenger cars, we think the more promising solution is an electrified flywheel, which we call a Flybrid.

What is a Flybrid?

It is a mechanical flywheel that runs at speeds up to 42,000 rpm and gives kinetic energy recuperated while braking back to the wheels. The kinetic energy is used to reduce the engine load at start and when accelerating. We have a second application where a generator is connected to the flywheel to charge a small battery. Here the stored energy is given back to the vehicle using a motor inserted in the transmission, similar to what happens with full hybrids. We have been testing this solution in some taxis in London, where we have seen fuel consumption savings of about 34 percent. We have also tested the Flybrid on a Jaguar XF diesel, delivering a 22 percent reduction in fuel consumption.

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