Alfa Laval has introduced Hukka-5, a next-generation exhaust gas steam boiler designed to improve waste heat recovery and energy efficiency on cruise ships and passenger ferries.
Unveiled at SMM 2026 in Hamburg, the Hukka-5 uses an inverted downward natural circulation configuration to recover heat from engine exhaust gases while keeping the boiler’s footprint compact. The system is available immediately for project orders.
Downward natural circulation improves heat recovery
Exhaust gas steam boilers using natural circulation are widely used on cruise vessels because they can operate without circulation pumps, using the physical movement of water within the boiler.
Alfa Laval’s Hukka-5 applies the principle in a downward-flow configuration. The arrangement creates counter-current flow conditions within the restricted space typically available in ship funnels and is intended to reduce the overall footprint of the exhaust gas boiler.
The configuration is also designed to reduce the risk of flow instability in evaporative circuits when exhaust gas temperatures fluctuate. This can be particularly relevant for vessels operating on alternative fuels, where exhaust conditions can vary.
The boiler is targeted at four-stroke engine applications, particularly cruise ships and passenger ferries that make frequent port calls.
“Our previous state-of-the-art WHR boiler, Aalborg XWi, set the standard for natural circulation on cruise vessels. Now, as the need for greater waste heat recovery grows, we are introducing the Hukka-5 and taking energy efficiency to the next level. Since every square meter matter on cruise ships, the new innovative inverted natural circulation design recovers more waste heat without increasing the footprint”, says Matti Takasuo, General Manager for BD & Sales for Power, Offshore & Cruise business line, Alfa Laval.
Modular configuration for cruise and ferry applications
The Hukka-5 has been developed with a modular architecture that allows configurations to be adapted to individual vessel requirements. The system can integrate electrical steam generation without requiring additional pressure vessels or auxiliary or fired boilers.
According to Alfa Laval, this configuration can support steam production during port stays when shore power is available.
The boiler can also be configured with multi-stage heat recovery options and an optional condensing cold-end design. These configurations are intended to increase the amount of usable energy recovered from exhaust gases and improve overall installation efficiency.
A vertical steam drum is provided as standard, allowing greater flexibility in equipment layout and removing requirements related to the vessel’s orientation during installation.
Compatibility with alternative fuels
Hukka-5 forms part of Alfa Laval’s Hukka range of exhaust gas steam boilers, alongside Hukka-8. The product range is designed for engines and gas turbines operating on a range of fuels, including methanol and hydrogen.
The ability to operate with engines using alternative fuels is increasingly relevant as shipowners evaluate different pathways for reducing emissions while maintaining vessel performance.
By recovering exhaust heat for onboard steam generation, the Hukka-5 is designed to reduce the amount of additional fuel required for steam production. This can contribute to lower fuel consumption and CO₂ emissions, depending on vessel configuration and operating profile.
Alfa Laval’s waste heat recovery installations
Alfa Laval said it has completed more than 1,300 waste heat recovery boiler installations for cruise ships and passenger ferries since 2000. The company also reports hundreds of land-based installations across more than 100 countries.
According to the company, its installed waste heat recovery systems collectively reduce CO₂ emissions by more than 10 million tonnes annually.
The Hukka-5 is now available for project orders, positioning it as a waste heat recovery option for new and future cruise vessel and passenger ferry projects.
