An environmentally sustainable energy management strategy for marine hybrid propulsion

Integrating electric technologies, such as battery energy storage systems and electric propulsion, has become an appealing option for reducing fuel consumption and emissions in the transportation sector, making these technologies increasingly popular for research and industrial application in the maritime sector. In addition, hydrogen is a promising technology for reducing emissions, although hydrogen production technologies significantly influence the overall impact of hydrogen-powered systems. This paper proposes an optimization-based strategy to minimize the environmental impact of a hybrid propulsion system over a given load profile, while furthermore considering the environmental impact resulting from the hydrogen production chain. The propulsion system includes diesel generators, hydrogen-powered fuel cells, batteries, and electric motors; mathematical models and assumptions are discussed in detail. The paper applies the proposed strategy, and compares different hybrid solutions considering equivalent CO2 emissions, discussing a test case applied to a short-range ferry operating in a marine protected area, an area particularly sensitive to the problem of atmospheric emissions. The results demonstrate that the proposed strategy can reduce greenhouse gas emissions by up to 73% compared to a conventional mechanical propulsion system.