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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 £3m grant to decarbonise the largest source of in-port greenhouse gas emissions with a novel Cold Ironing Solution.

When in Port, most vessels use diesel generators to power onboard operations. Globally, this produces around 35Mt of CO2e generated per year and accounts for roughly 60% of total port emissions. This project aims to eliminate these emissions by providing highly efficient, shoreside power to replace the need for diesel generators. 

The end-to-end system starts with a Solar PV system, utilising technology and hosted by our partners at Cranfield University.

 This provides power directly to the vessel when at birth, but during periods where supply exceeds demand, electricity is fed into a high-efficiency power management architecture provided by project partner HyWaves. HyWaves’ technology massively simplifies the architecture needed to operate Electrolysers to produce green hydrogen from solar power, delivering both an efficiency improvement and cost reduction.

Hydrogen is stored using low-cost, high-density MOF technology from Rux Energy. This stage is critical in providing long-term, cost-effective energy storage, managing seasonal and operational variations.

High efficiency Carnot Engines will then use Hydrogen fuel to provide on demand power. Shoreside generators will be connected to vessels whilst moored in port. Clean Air Power, a supplier of specialist injectors and valves for alternative fuels, will provide High Pressure Hydrogen Injection (HPHITM) technology to control the flow of hydrogen into the Carnot engine. This method of providing shore-to-ship power is known as Cold Ironing. 

The Manufacturing Technology Centre, the UK’s centre of excellence for manufacturing technologies, is providing expertise guiding the critical path to engine development and providing design for manufacture insight, optimised for additive manufacturing processes. This will then be tested at Brunel University London. Throughout this phase, Carisbrooke Shipping will provide the critical insight from a vessel operators perspective, including implications on regulations and operational requirements.

The project revolves around Freeport East, assisting with outreach and engagement with ports operators, shipping lines and the Trust Port, Harwich Haven Authority. Freeport East, CEO Steve Beel comments: “We are delighted to be part of this ground-breaking consortium looking at fresh approaches to greening the maritime sector, which brings together leading hydrogen innovators from across the UK”. 

Swanbarton and Brunel University are collaborating to develop the Energy Vector Analyser (EVA). EVA will help ports understand their current energy landscape and facilitate future planning. By evaluating a wide range of potential fuel, generation, and storage options, EVA seeks to minimise investment risks associated with unviable or obsolete technologies, thus avoiding stranded assets. This tool will enable ports to identify viable aspects of the hydrogen lifecycle within their full energy system enabling informed investment and ensuring they can offer future services like shore power, despite existing infrastructure and geographical constraints.

The entire project will then have the regulatory and certification oversight provided by Bureau Veritas.

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.