"Gas engines provide a route towards a net zero powertrain solution"
The increasingly stringent exhaust emission limits for diesel engines represent a major challenge especially for the manufacturers of large engines. ATZ heavyduty spoke with Simon Edwards, Global Director Technology, and Andy Skipton-Carter, Head of Business Development in Europe for Commercial Vehicle and Off-Highway, of Ricardo about how these challenges can be met.
ATZ heavyduty_What is your vision of a powertrain split for truck and then off-road vehicles in 2025 and 2030?
Skipton-Carter_It’s quite difficult to answer, because it’s a fleet average number and therefore about proportions of technologies. I think, even by 2025 there will be a small number of battery electric vehicles in the fleet.
Edwards_Drawing a picture of 2030 all the light-duty commercial vehicle and at least half the medium-duty applications will be battery electric in some way. And let’s say up to a quarter of the heavy-duty applications you could see with some alternative powertrain technology. The other side of the equation is that a majority of the other powertrains will be heavily hybridized. So, by 2030, almost every powertrain will have some sort of electrical variation. You may have some ZEV capability set even on some parts of the heavy-duty applications.
Skipton-Carter_Well, it’s required for the legislation and everyone’s developing electric up to medium-duty trucks. The challenge is to sell them and make them economical for the customers. You won’t meet the legislation unless your customers buy the products. I think that is a very big challenge for the OEMs and for the industry.
If you would swap to gas engines, would that be a way to handle the challenges?
Edwards_The potential is there. And it’s a potential of using your existing hardware concepts and converting the engine. The second point is, as soon as you’re running an internal combustion engine in heavy-duty applications, but with a spark plug, then, especially if you start running it lean, you’ve also got a very good stepping stone to converting those engines to running on pure hydrogen. Because of that chain, I think that gas engines provide today and, measurably from what we’ve seen on the test beds, in the future for 2030 and beyond, a route to go towards a completely net zero powertrain solution, while still retaining some of our existing architectures. They also bring in an infrastructure based on hydrogen.
Skipton-Carter_If you‘re going to use liquefied gas or liquefied hydrogen you can use direct injection and you can store it on the vehicle. That is a route that we should not ignore. The next point is whether you do generate a synthetic drop-in fuel of some description. But that is a completely different route that we have to discuss and talk about the economics of it. Ideally, as a society we must do that because we could well do with a drop-in solution for all of the vehicle part that we still have running around even by 2030. Generally there is a lot of interest in hydrogen at the moment, and not just in its application in fuel cells, but also for its use in internal combustion engines. Given the current costs of fuel cells and the timeline for them to become cost-effective, there is a potential opportunity to burn hydrogen in an internal combustion engine, probably as an interim solution. It's not quite as efficient as burning it in a fuel cell but we develop lots of lean combustion technologies, which can apply to gas and to hydrogen.
So the loss of range when using hydrogen is not a crucial thing?
Skipton-Carter_If you want a zero CO2 tank-to-wheel solution, then your choices are either synthetic fuel, or hydrogen, or electricity. And clearly there are issues with a large battery pack for a long-haul truck in terms of its mass and cost. And so it has a range impact.
Edwards_If the vehicles themselves are more efficient, then maybe you don't have a loss of range. And even if you do, then it comes down to the refueling time brackets compared to the recharging time, which is why I think the hydrogen is also looking promising.
Skipton-Carter_You also have to accept that at some point in the future you are not going to be able to use conventional diesel. Of course you can make synthetic diesel, but the more steps you take to build a longer molecule out of hydrogen and CO2 the more energy that takes. A synthetic diesel is going to be very expensive because of the electrical input that you need, green electricity, and also the process it takes. So, it will be inherently more expensive than hydrogen. You're going to have to look at the economics of all of those things, and it's a complicated calculation.
Better fuel qualities would help as well, wouldn’t they?
Edwards_Better fuel qualities could help, yes. It’s well known that EGR systems are also at risk of fouling and blocking for example. But if you can model the accumulation of the soot inside the EGR system, you’ve got a better way to optimize it and get out those last little bits of percentage gains from EGR systems.
Skipton-Carter_That’s another topic in terms of the simulation methods and the virtual engineering which is developing very fast now in order to optimize the engine, but one key tool for that is the use of simulation to really optimize and fine tune the design of the engine and its features. So that’s something that in its own way will be directly contributing to CO2 emissions reduction.
Edwards_You’re right we haven’t really talked about disruptors on the process side. We can analyze everything, we can get more data now and understand the problem better, but actually, I think some of the things we’re not building into the equations at the moment are our ability to simulate everything much more effectively to get out the last bits of optimization, and maybe sneak towards the targets that we have. Whether in the end the targets are enough is another question.
Skipton-Carter_The same on calibration. You can do more offline calibration of the engine, which means you can more quickly get to a more optimized solution. And again, I think that, particularly in off-highway, where there is often a different calibration for all the different applications, by doing more of that offline you can get to a more optimized solution. And that’s optimized in terms of fuel consumption and performance, but also regarding emissions in general. These virtual processes do enable some of these important greenhouse gas reductions.
But regarding the backward compatibilities, synthetic fuel would be a big enabler…
Skipton-Carter_Indeed, regarding the existing fleet. But then, if you're going to do something about aviation, then naturally you'd think that that would be the priority for a liquid fuel and then it becomes about how much can you produce and where do we want to use it? All those things are unknowns. But, yes, you could certainly imagine that it would be a priority for aviation over other areas and if there‘s capacity also others can have it too.
What about stage 2 biofuels in your sector?
Edwards_Not necessarily for the on-highway activities, but increasingly for the stationary power generation aspects. Yes, we are looking at other ideas that convert whatever you want to call it, bio waste, in one way or another to generating, in some sort of possible combustion engine through a fuel based process, then, electricity.
Skipton-Carter_We've been involved in a tractor program recently for Case New Holland. Their philosophy is that the farmer produces his own fuel, bio gas. They're already doing it in some places around the world. The principle of turning waste into fuel is an existing technology and I think it will become more prevalent in the future. The question really is, how much of the demand can be met by that. The gas is already being produced in the UK, for example, and at the moment put into the natural gas grid because there's a big government incentive – the farmers get paid a lot of money. You need quite a lot of equipment but the farmers tend to come together, doing it on a reasonably large scale.
How does electrification change the maintenance costs of a commercial vehicle?
Skipton-Carter_I think they are generally lower. I guess there's always the question about the battery and how long it lasts, or if you have to change the battery after a certain period. And clearly that's a big cost at some point in the future. But the OEMs are offering reasonably robust guarantees on that.
Edwards_I think that reflects what we're seeing also in terms of some of the investigations we're looking at, when you've still got a traditional combustion engine integrated into a large hybrid powertrain. You get different issues with the engine, whether it's there because of stop-start with the oil intervals, or even then with coolant and with fuel qualities over time, as well. So some of the investigations, especially on the light-duty side, that we're doing now are related to what happens when we restart the engine after six months, nine months or a year, because the duty cycle has never been seen before.
You can read more on the subject in the interview with Simon Edwards and Andy Skipton-Carter in ATZ heavyduty worldwide 1-2020.