Hybrid propulsion with a power take in (PTI) mode motor is the choice that Cintranaval Group, Schottel and Industrias Ferri took for their Smartug project. These companies are co-operating in a tug concept study to develop a tug design that combines harbour operations with some escort and deepsea towage operations.
During the initial part of the study, the partners considered different propulsion and engine systems for the operational, economic and environmental requirements from a tug. They decided a hybrid system with a PTI would be the optimal choice.
Two other propulsion configurations were considered during the project analysis. The partners investigated the use of diesel-mechanical systems with direct transmission and diesel-electric systems with two gensets and shared loads. However, the hybrid system with a PTI motor had clear benefits over these other two methods for the Smartug concept.
During the analysis of the propulsion alternatives, the rate of propulsion engines, working rate of engines, fuel consumption and the time between overhauls was investigated. The partnership chose a hybrid system because the working rate of the engines is closer to the optimum requirements while avoiding the low rates, and the working time of the engines was reduced increasing the time between overhauls.
Another reason for choosing a hybrid system was the order of magnitude of the predicted fuel savings and emission reductions. The Smartug partnership estimated that fuel savings could reach 16 per cent for the hybrid configuration compared with the base one. With all these positive attributes, the designers recommended the hybrid system with PTI to take forward into the Smartug design phase.
Cintranaval, Schottel and Industrias Ferri wanted to develop a state-of-the-art tugboat design that has a reduced environmental footprint, increased safety and lower operating costs. The tugboat design would also include the following aspects over existing designs:
- reduced fuel consumption
- increased safety of the crew and personnel working on board
- improved safety of the vessel against possible damage
- enhanced energy efficiency of the tugboat
- better comfort for the people that work on board
- increased performance of the tug compared with other vessels of the same size
- improved operating assistance provided to other vessels
- reduced operating costs and overhaul expenditure
- similar construction costs as conventional tugs of the same size and performance
The group considered market trends and asked European tug owners about their requirements from Smartug. From the results of these studies, the partnership concluded that a tugboat designed for harbour operations, but with deepsea towage capabilities was required. The vessel should have high manoeuvrability with escort capabilities and an external fire-fighting system. It should have a reduced crew and a bollard pull of around 80 tonnes. It would also have a standard operation time of about 1,500 hours a year. A base level operating profile was determined to consider the total required propulsion power and the optimal propulsion system.