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Carnot Engines Redefining Heavy-Duty Power for a Decarbonized Future

The Challenge: How to replace the Diesel Engine?

At Carnot we are taking on the biggest challenge of our age; decarbonizing heavy-duty power and how to replace diesel engines. 

Hard-to-abate sectors — from shipping to long-haul road transport to remote power generation — face the biggest challenge in reaching net zero. Traditional internal combustion engine and especially diesel engines, waste much of their fuel energy as heat, and many cannot operate effectively on next-generation low-carbon fuels like hydrogen or ammonia.

Decarbonizing heavy-duty power requires technology that combines exceptional fuel efficiency with full fuel flexibility, without compromising on performance, reliability, or cost-effectiveness.

Carnot Engines – The World’s most efficient, multi-fuel engine

At Carnot Engines, we are developing the world’s most efficient engines. Conventional engines operate around 35% efficiency, where a Carnot Engine can operate at over 70% break thermal efficiency. By doubling fuel efficient, we half fuel consumption, delivering enormous cost savings to our customers.

A Carnot Engine can also work on any fuel, and switch anytime. A Carnot Engine can run on:

  • Hydrogen
  • Ammonia
  • Methanol
  • HVO/Biofuels
  • Biogas
  • LNG
  • Diesel

Our design targets >70% brake thermal efficiency — more than double the efficiency of many conventional diesel engines. By operating at higher temperatures and eliminating most cooling losses, Carnot Engines aim to dramatically reduce fuel consumption and slash greenhouse gas emissions across the toughest sectors.

Applications Across Multiple Sectors

Our technology is built for the hardest jobs in the most demanding environments:

  • Maritime power — main propulsion and auxiliary power units (APUs) for ships

  • Heavy-duty road transport — trucks, buses, and specialist vehicles

  • Off-grid and industrial power generation — remote mining, construction, and backup systems

These sectors demand high reliability, long service life, and global maintainability — our engines are being engineered to meet or exceed these benchmarks.

Driving Maritime Decarbonization

Shipping accounts for nearly 3% of global CO₂ emissions, and international regulations are tightening fast. Carnot Engines is working with leading shipping companies to demonstrate hydrogen and ammonia-fuelled engines in real-world maritime environments.

Upcoming trials include:

  • Hydrogen-powered auxiliary engine testing aboard a commercial vessel

  • Hydrogen Engines for Shipping with the UK’s first hydrogen auxiliary engine sea trials 

  • Ammonia-fuelled APU retrofit projects for improved efficiency and emissions reduction

  • Ammonia Marine Engines and Auxiliary power units 
  • Fuel-Flexible high efficiency engines
  • Decarbonised Port Power

Designed for the Net-Zero Transition

Our approach solves three critical barriers to decarbonizing heavy-duty power:

  1. Fuel flexibility — switch between low-carbon fuels as supply chains develop

  2. High efficiency — reduced fuel use means lower emissions and operating costs

  3. Modular scalability — from smaller APUs to MW-scale maritime powerplants

This combination allows operators to begin cutting emissions now while staying adaptable for future fuels and standards.

Carnot is leading a consortium which has successfully won a £2.1m grant to decarbonise maritime power using Ammonia fuel.

This grant, part of the Clean Maritime Demonstration Competition delivered by Innovate UK, will develop a novel liquid Ammonia engine concept, delivering unrivalled efficiency whilst eliminating emissions from maritime power. We will be targeting heavy-duty maritime power applications, including Main Engines, onboard Auxiliary Power Units (APUs) and Shoreside Power for cold ironing.

At the heart of the system is Carnot’s high temperature engine technology capable of achieving 70% break thermal efficiency, twice what can be achieved with modern state of the art engines. By doubling the efficiency, fuel consumption is halved thus providing considerable cost savings for operators and providing valuable economic incentives to decarbonise.

Utilising liquid Ammonia fuel offers the benefits of decarbonised fuel and high energy density but without the challenges and energy losses associated with cryogenic hydrogen storage. Ammonia is however a more challenging fuel to use in a combustion context, due to its lower reactivity and slower combustion speeds. Conventional engines solve this issue by blending ammonia with fossil fuels, thus persisting with harmful emissions.

Carnot Engines utilise a hydrogen & ammonia fuel blend, utilising Ammonia Cracker technology from Transformational Energy, continuously converting ammonia into hydrogen to improve performance and deliver a decarbonised dual fuel engine.

The University of Southampton are employing comprehensive physics-based 3D-Computational Fluid Dynamics modelling to simulate mixing, ignition and combustion characteristics which will then be validated at Brunel University London, utilising their state-of-the-art optical chamber.

Throughout the project, our industry partners Carisbrooke Shipping and OS Energy, will provide operational data, integration insight and analysis to understand the implementation and benefits of ammonia fuel technology can provide to a vessel operator.

The project will conclude with a bench demonstrator to validate the feasibility of a high-efficiency ammonia engine for heavy-duty marine power.

 

This project is part of the Clean Maritime Demonstration Competition Round 4 (CMDC4), funded by the UK Department for Transport (DfT) and delivered by Innovate UK. CMDC4 is part of the Department’s UK Shipping Office for Reducing Emissions (UK SHORE) programme, a £206m initiative focused on developing the technology necessary to decarbonise the UK domestic maritime sector.