When it comes to the environmental costs of transporting manufactured and agricultural goods we typically think of the fuel expended by large freighters. One associated cost that is less visible to us is the costs of guiding and maneuvering the vessel into the harbor and the assigned berth by a tugboat. A typical tugboat includes tankage for 10,000 to 30,000 gallons of fuel if intended for local ship-assist work, and up to 100,000 or more gallons if the tug is intended for coastal or offshore towing.
The technology group Wärtsilä is seeking to reduce the fuel consumption and related GHG emissions. The Finnish firm has signed a memorandum of understanding with Petrocity, the parent company of the new port facility being built in the Brazilian city of São Mateus-ES, to develop a harbor tug design. The prime consideration is to maximize the ecological operational sustainability of the vessel since the environmental demands of the new port are among the most stringent in the world. For this reason, the design will be based on the recently launched Wärtsilä HYTug, which features hybrid propulsion and energy storage using batteries.
The Wärtsilä HYTug emphasises environmental sustainability, operational efficiency, and lower fuel consumption than is possible with conventional tug designs. The fully integrated hybrid power module combines engines, a lithium-ion energy storage system, and power electronics optimized to work together through a newly developed energy management system. The design marks a new frontier in marine hybrid propulsion.
The fuel efficiency of this design has the added benefit of reducing exhaust emission levels. Additionally, when operating in ‘green’ mode, the Wärtsilä HYTug will produce little if any visible exhaust since the load is being picked up by the batteries. At the same time, the noise level of the tug will be notably reduced.
The Wärtsilä HYTug is expected to change the landscape of the tugboat market as battery usage significantly increases environmental sustainability and operational efficiency. At the same time it should greatly reduce operating costs.
“This will be the first of many others in a huge logistics project which aims at the regional integration of the Espirito Santo, Minas Gerais and Bahia states. It represents a definitive guarantee of the interiorization of the economy in the north of Espírito Santo,” says Mr José Roberto, CEO of Petrocity.
The new hybrid vessel features a very distinctive outlook while providing the power and maneuverability for practical tug operations. The overall design has been optimized for low hull resistance, high towing and escort performance, efficient sea-keeping, crew safety and comfort, as well as for easy maintenance.
According to Wärtsilä Marine Sales Manager Mario Barbosa, “while the tugs are designed according to an operational profile for each vessel, they will essentially be on “green” electrical mode when leaving and returning to the terminal, with main engines off and when the load is light. When the tug is on Bollard pull mode (full power required), the batteries supply extra power to the propulsion system.”
The tug’s batteries can be recharged by onshore solar panels, as the vessels will have onshore connection capability and the tugs will be operating in a sunny climate. According to Barbosa, Petrocity is already evaluating the potential for solar charging.