HyEkoTank project proposes the design, development, approval and demonstration of a 2.4 MW hydrogen fuel cell system.  The technology will be developed by a consortium of 10 partners who are experts in the field and demonstrated by retrofitting a 18600 DWT tanker, EK Stream, under operation at 3 different journeys from Porvoo in the Baltic Sea. The main challenges that need to be resolved concern the development of a cost-efficient fuel cell system specifically designed for maritime applications and suitable to retrofit existing vessels, as well as the assessment and creation of hydrogen infrastructure and logistics for vessel refueling in ports, as well as safe hydrogen storage and handling. We aim at approving the HyEkoTank technology to deploy it for any type of vessel and operation, while demonstrating the expected environmental impacts: 55% GHG reduction during voyage, 100% reduction in port, and 62% total reduction yearly. The project will take the technology from TRL 4/5 to TRL 8.