A new engine burns liquid ammonia at 70% efficiency—matching the best diesel engines—while producing zero carbon emissions. The HEAT-HD project tackles a core problem for shipping: ammonia is a promising zero-carbon fuel, but it is difficult to ignite and burns poorly in conventional engines. The team combines four technologies to solve this: a heat-insulated engine that wastes no fuel energy on cooling, high-pressure direct injection, a turbulent jet ignition system for ultra-lean combustion, and on-board cracking of a small fraction of ammonia into hydrogen to act as a pilot flame. If successful, the engine could replace diesel generators and propulsion systems on vessels up to 10 megawatts, cutting greenhouse gas emissions from a sector that currently accounts for nearly 3% of global CO₂. The project is a lab-based feasibility study, not a sea trial—it will model combustion physics, validate results in optical chambers, and run a single engine test. End users Carisbrooke and OS Energy will assess how the technology might integrate into real ship operations and supply chains.
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HEAT-HD is a game-changing high-temperature liquid-ammonia (LNH3) powered engine technology with 70% BTE. Targeting marine propulsion systems and Auxiliary Power Units (APUs) and shore-side power generation units up to 10MW. LNH3 has clear economic and operational benefits for maritime applications as it offers the energy storage density and true zero emission property of liquid hydrogen without the parasitic losses associated with storing cryogenic liquids. Ammonia technology is specifically targeting the heavy-duty marine sector. HPDI injector technology will enable a new generation of high-efficiency LNH3 engines that offer lower emissions than comparable port-fuelled engines. HEAT-HD will develop a novel LNH3 fuel system and engine concept combining four unique technologies together to tackle critical challenges of using LNH3 as a fuel, a clear step-change from current SOTA NH3 ICE technologies for marine applications. The four unique technologies included and their advantages are: 1. High-temperature (thermally insulated) Carnot engine with key components manufactured from high temperature resistant materials able to withstand fuel combustion temperatures, eliminating the third of fuel-energy wasted to cooling systems 2. HPDI fuel injection strategy for improved performance and reduce in-cylinder emission and knock 3. Active pre-chamber TJI concept with multi-point ignition for ultra-lean combustion and cold-start operation. 4. Cracking of ammonia in-situ to provide the hydrogen pilot for the ammonia engine to achieve efficient combustion. The pre-chamber Turbulent Jet Ignition (TJI) concept will optimise secondary combustion, with small hydrogen consumption, cracked from ammonia in-situ. The project is a feasibility and lab-based demonstration study to assess the technical, economic and regulatory feasibility of using Carnot's technology to reduce GHG emissions using LNH3 as the primary fuel source. The project will develop and demonstrate a dual-fuel hydrogen-piloted fuel system with only ammonia stored, a proportion cracked to hydrogen, via the Transformational Energy (TE) SOFC Ammonia cracking technology, and will identify the design elements required to convert to this fuel-system. It will employ comprehensive physics-based modelling expertise from University of Southampton to simulate LNH3 engine combustion covering the four unique technologies, complemented by Brunel University's optical chambers to validate combustion dynamics, before targeting a Carnot engine test at the end of the project. Carnot will also engage with Carisbrooke and OS Energy (OSE) as end users to explore technology commercialisation via duty cycle data collection on board vessels, data analysis and exploration of potential system integration opportunities. HEAT-HD aims to break down one of the main barriers to ammonia being adopted as a marine fuel.
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