Hydrogen Train Retrofit offer: Latvia Leads the Way
A Latvian-led European consortium is proving that retrofitting diesel trains with a hydrogen–battery hybrid costs roughly 13 times less than buying new zero-emission stock. Riga Technical University's independent validation work puts Latvian engineering at the centre of a fix that could reach thousands of ageing diesel trains across the EU.
INNOVATIONSNEWS
HydrogenLatvia
8/13/20263 min read
Most of Europe's rail decarbonisation conversation is about buying new trains. Fair enough — zero-emission rolling stock is the end state everyone wants. But new trains take years to design, certify and deliver, and railway operators are sitting on fleets of diesel units that still have a decade or two of useful life left in them. That's the gap a Latvian company just stepped into, and Riga Technical University is now the scientist checking its homework.
A Latvian company doing the engineering, not just watching from the sidelines
The project is called HYBUHTRAIN — HYdrogen engine Battery plUg-in Hybrid TRAIN — and it's been approved through EIT Urban Mobility's Strategic Innovation Open Call. The lead partner is DIGAS, a Latvian company that already holds a distinction worth noting: it built Europe's first certified gas-fuel locomotive. HYBUHTRAIN builds directly on DIGAS's earlier HYIPTRAIN project, which developed and certified a hydrogen internal combustion engine (H2-ICE) retrofit kit for a passenger train operated by SKPL in Poland.
This isn't a one-off. DIGAS has also signed with Iarnród Éireann, Ireland's national rail operator, to retrofit a diesel freight locomotive using the same hydrogen-combustion approach, with additional Latvian public co-funding alongside EIT Urban Mobility. Two countries, two fleets, one Latvian engineering team doing the retrofitting. That looks like a pattern, not a coincidence.
DIGAS (Latvia) — leads technology development and commercialisation
Mikroluch (Ukraine) — develops the hybrid train's control systems
SKPL (Poland) — provides the train and the operating environment
Rzeszów municipality (Poland) — drives public engagement
Riga Technical University (Latvia) — delivers independent scientific validation
Retrofit economics that make the business case straightforward
Here's the number that should get any railway operator's attention: modernising one diesel train with the hydrogen–battery hybrid kit is expected to cost roughly €0.9 million. A new zero-emission train costs around 13 times that. When the choice is between waiting a decade for capital budgets to catch up with fleet-renewal plans, or retrofitting an asset that's already on the books, the retrofit math wins almost every time.
The HYBUHTRAIN project has 18 months to take the technology from TRL 6 to TRL 9 — from validated prototype to full certification — including a three-month passenger trial before commercial rollout. That's a genuinely short runway for a rail technology, and it's only possible because the team isn't starting from zero: it's building on a retrofit kit that's already been engineered and certified once.
Multiply that math across Europe and the opportunity gets serious: there are thousands of diesel trains built between 2000 and 2021 still running across six EU countries — trains structurally similar enough to be candidates for the same kind of retrofit.
Less hydrogen, more range, zero emissions at the platform
The technical trick is pairing the existing hydrogen engine with a modular battery pack and an energy management system. The batteries capture energy during braking and top up overnight, which is estimated to cut hydrogen consumption by 20–35% compared with hydrogen alone. The upside isn't just fuel savings — it also means stronger short-term power output than the old diesel engine delivered, a longer range between refuelling, and fully emission-free running through stations and city centres, which matters as much for public health as it does for the climate numbers.
DIGAS expects each retrofitted train to avoid roughly 200–230 tonnes of CO₂ a year, alongside a cut of more than 95% in nitrogen oxide and particulate emissions — the pollutants that actually affect air quality where people are standing on the platform.
Riga Technical University's widening role in hydrogen validation
RTU's job in HYBUHTRAIN is independent scientific validation — measuring real-world emissions (CO₂, NOₓ, particulates) once the train is running, and assessing how scalable, economically viable and publicly beneficial the retrofit approach actually is. That's not a symbolic role. It's the kind of third-party verification that gives railway operators and regulators the confidence to move from pilot to procurement.
It also fits a broader pattern. RTU already coordinates EIT Community Hub Latvia, the country's official gateway into the EIT innovation network, helping Latvian companies, researchers and students plug into European funding and partnerships. Add its work on hydrogen electrolysis, hydrogen-adapted gas infrastructure, and a newly announced hydrogen centre of excellence for zero-emission aviation with Fokker Next Gen, and a picture emerges of a university becoming a genuine technical backbone for Latvia's wider hydrogen ecosystem — not just a validator on one railway project, but a partner the whole sector can lean on.
What it means for rail north of the Baltic
Latvia doesn't have to import this playbook — it's writing it. A Latvian company leading the engineering, a Latvian university providing the independent science, and an EU funding mechanism backing both: that's a template Baltic hydrogen ecosystem stakeholders can point to when the conversation turns to where regional rail operators start, if replacing entire diesel fleets isn't realistic on any near-term budget.
The HYBUHTRAIN target train, an SKPL CD 810 series unit in Poland, is a useful reminder that the closest markets for this kind of retrofit aren't far away. If it works there, the case for looking at it here writes itself.