Kubota Engine High on HVO, Hydrogen and Hybrids

Kotaro Shiozaki details the engine maker’s diversified path to carbon neutrality.

Kubota is billing hybrid powertrains as a potential long-term solution. This P1 hybrid provides brief periods of motor assist when high output is required. (SAE/Ryan Gehm)

As part of its path to carbon neutrality, Kubota Engine engineers have developed a new 3.8-liter hydrogen engine that was introduced at CONEXPO 2023 in Las Vegas. The 4-cylinder spark-ignited engine employs port fuel-injection and provides 85 kW (114 hp), which is the output required for a 45-kVA generator, the company notes.

Kotaro Shiozaki, PR manager, Industrial Engine at Kubota Corp., stands next to the hydrogen engine at CONEXPO 2023. (SAE/Ryan Gehm)

Kotaro Shiozaki, PR manager, Industrial Engine at Kubota Corp., said that hybrid powertrains also are an effective solution for reducing CO2 from industrial engines, and he’s confident they will be more than just an interim solution. Kubota displayed three hybrid solutions: a P0 micro-hybrid that will be available later this year, a P1 hybrid that provides brief periods of motor assist when high output is required and a P2 hybrid engine scheduled for production in 2025 that offers electric-motor drive.

All Kubota diesel engines in Europe are approved to use paraffin-based fuels — gas to liquid (GTL) and hydrotreated vegetable oil (HVO) fuels — that comply with European standard EN15940. The company announced that HVO now is approved for use in its diesel engines in the U.S., enabling a CO2 emissions reduction of up to 90% with no engine modifications, Shiozaki said. He spoke with SAE Media in Las Vegas about these technologies and discussed Kubota’s plans to bring them to market.

Tell me about Kubota’s hydrogen engine.

This is really based on what we have today from the spark-ignited engines. Achievability of the [hydrogen] engine is not so difficult, I would say. The most concern is twofold: one is the procurement of a hydrogen infrastructure and the second is emissions regulations. The regulation is based on the type of fuel — today we don’t have regulations for the hydrogen, that’s why we cannot sell this product in the market yet. So once those two aspects are solved, then we believe we’ll be ready.

[While SAE Media was talking with Shiozaki, California Air Resources Board (CARB) reps came to check out the hydrogen engine.] You can actually witness that they are trying to understand what we can do. And then we are [encouraging] them to set up the regulations. We need to have the regulations.

The majority of the components for Kubota's hydrogen engine are existing (in blue); the new components for hydrogen are silver. (SAE/Ryan Gehm)
Though hydrogen is cleaner, there still are emissions.

NOx. NOx can be handled with the SCR [selective catalytic reduction], which is already available. We have a variety of options. Again, back to the applications, if you have X amount of NOx allowed then we can fit whatever we have today. I believe aftertreatment systems will be involved, but maybe less than with diesel because it doesn’t emit CO2 and almost no particles (PM).

Are you testing your hydrogen engine in the real world?
The P2 hybrid engine, which is scheduled for production in 2025, offers electric-motor drive. (SAE/Ryan Gehm)

Most of the development is happening within Kubota in Japan. Another part of the development needs to be coworking with the machine manufacturers. When it comes to matching between the applications, it’s local. So, if the customer is located in the U.S., we have a U.S. resource to help the customer to match up the engine to the application.

What applications are you targeting?

This past September we made an announcement with Denyo, a leading genset company in Japan. We believe the genset [an engine-generator combination] can be a good application to start with hydrogen engines. The genset does not move around; it could sit on-site so we can have a big fuel tank nearby. And then maybe next is tractors or excavators.

What is your outlook for hydrogen engines?
Kubota’s P0 micro-hybrid engine will be available later this year and can run on HVO fuel. (SAE/Ryan Gehm)

It’s up to the applications, but we believe this will be a good alternative solution to replace diesels. It will probably take five to eight or maybe 10 years. Again, back to how soon the infrastructure will be ready.

Are hybrids a good interim solution?

Yes, interim and also permanent. These engines are covering the use of HVO, which is already carbon-neutral. So, if customers or the owner of the machine are able to procure HVOs, then they are done with carbon-neutral. In that case, I’d say it’s a permanent solution. In some countries like Scandinavian, HVO is already popular. For commercial use, they can procure it. In the U.S., I think it’s starting up. You can’t buy it at a gas station around the corner, but if you’re in the commercial business, then you can have [an avenue] to procure it.

What are Kubota’s plans for future diesel development?

We are still working on it — on new combustion and injection technologies. As you see, the base technology of hybrid or hydrogen is based on diesel [and SI] technologies. Whatever we are improving with the diesel engines can be transferred to the hybrid or the hydrogen engines, so there’s no reason for us to stop doing the research on diesel.