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ULEMCo and Revolve demonstrate 45% thermal efficiency for 100% hydrogen engine

ULEMCo and its R&D partner Revolve Technologies have demonstrated thermal efficiencies of 45% in engine control strategies for a 100% hydrogen-fueled engine being developed for the Mega Low Emissions (MLE) truck demonstrator unveiled earlier this year. (Earlier post.)

The 100% hydrogen engine runs stably at air/fuel ratios in excess of 300:1.


This milestone performance shows that it is possible to go well beyond previously reported energy efficiency results for hydrogen combustion, at the same time as achieving immeasurable NOx levels, according to ULEMCo. The company says that the results point to the realistic prospect of zero emission trucks running on 100% hydrogen in the relatively short term.

ULEMCO’s approach of adapting existing diesel engine designs to run on hydrogen-diesel dual fuel has provided substantial learning on the opportunity for zero-emission engines. This ultimately provides routes to the much quicker adoption of hydrogen in heavy duty applications than alternative approaches, which are still many years away from cost effective commercial availability, the company suggests.

A recent report from the Department for Business, Energy and Industrial Strategy (BEIS)-sponsored Committee on Climate Change (CCC) on the future role of hydrogen in a low carbon economy referred to hydrogen in vehicles as potentially playing an important role for heavy-duty vehicles (e.g. buses, trains and lorries).

Similar conclusions were reached for longer-range journeys in lighter vehicles, where the need to store and carry large amounts of energy is greater.

The report acknowledges that although overall well-to-wheel efficiencies are less for hydrogen than for battery EV, the latter’s negative impact on payload means that according to the report he aim should therefore be to move HGVs to zero-carbon energy (i.e. electricity and/or hydrogen) where feasible by 2050.

As a hydrogen vehicle can be refueled quickly, fleet operators can also plan for similar numbers of vehicles to their current operation, rather than needing to increase fleet size to cover lengthy charging times for EVs.

These excellent results represent engine efficiency levels very similar to those seen with some fuel cell technologies. Combining these results with our knowledge of how to ensure that the engine can operate over a wide performance curve—and with industrial grade hydrogen—gives us confidence in this approach. Vehicle operators, particularly in heavy duty applications, will have a truly cost effective option for very low carbon and zero emission driving in the future.

—Amanda Lyne, Managing Director at ULEMCo



As I recall, the chief problem with hydrogen combustion engines hasn't been efficiency, but low power density; hydrogen displaces quite a bit of air and the requirement for excess air to limit combustion temperatures and NOx only exacerbates it.

Perhaps this engine runs in pure diesel mode when power is required, using H2 as a flame-speed enhancer?


Why on earth burn H2 in an engine rather than using a fuel cell - should be much higher efficiency?


A hybrid or PHEV version would increase efficiency to over 50% (reference Mercedes Benz F1 Hybrid Engine). This would add increased performance as well, though with additional weight and complexity. Note: Cummins already has plug-in hybrid electric powertrains -
The added benefit of this system is the dual fuel capability that a pure fuel cell system would not have, particularly since there are still few H2 fueling facilities. If Zero emissions are a requirement, e.g. urban areas and the economics make sense then this might be a solution.

Roger Pham

>>>>>>"...the chief problem with hydrogen combustion engines hasn't been efficiency, but low power density."

Correct. However, this can be overcome by strong electric hybridization. With the advent of strong electric power train and low-cost batteries, we can have bigger battery pack to provide acceleration power and generation of braking energy. So, the engine is there mainly to provide base-load power.

The use of turbocharging will further alleviate the low power density, best for trucks which must require extended high power for climbing long grades. The low exhaust temperature will allow turbochargers to be cheap and durable.


and what is the "well to wheel" efficiency?


Use fuel cells, eliminate the NOx from combustion smog.


With low-cost batteries and an electric powertrain, you wouldn't need hydrogen, much less hydrogen fueled ICEs.

I still like the idea of hydrogen fuel cells powering aircraft in cruise mode and hydrogen fueled turbines for aircraft climb out mode. Use hydrogen in unique applications where you need clean power, .i.e., container ships, etc. It's not needed where EVs will do the job.

Roger Pham

>>>>>>>"With low-cost batteries and an electric powertrain, you wouldn't need hydrogen, .."

But you will still have Hydrogen made from grid-excess Solar and Wind energy from Springs and Falls that you'll have to do something with it. Might as well use those in vehicles as high-value transportation fuel instead of as substitution for low-value natural gas or coal in power generation.

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