Given its status as the world’s first rechargeable all-electric tug, operating with virtually no engine noise, it seems appropriate that the high tech Zero- Emissions Electric Tug (ZeeTug), Gisas Power, which operates on 100 per cent green energy, has slipped quietly into service with little in the way of fanfare in Turkey’s port of Tuzla, near Istanbul.
When Turkish shipbuilding and port services company Gisas was looking to renew its tug fleet, it requested four environmentally- friendly harbour tugs. However, the tight operating conditions the tugs would face made a hybrid solution impractical given the constraints on the vessels’ dimensions.
Designer and builder Navtek Naval Technologies therefore took up the challenge and started work on what ended up as the ZeeTug, a fully electric and rechargeable tug that offers the flexibility of being able to manoeuvre precisely and delivering a powerful bollard pull.
The resulting Gisas Power has an LOA of 18.7m with a breadth of 6.7m and a draft of 3.5m. Despite its small size, the tug delivered 32 tonnes of bollard pull in testing – against a design brief of 30 tonnes – and achieves 10 knots.
The performance comes from a 1,500kWh Corvus Orca energy storage system (ESS) from Corvus Energy. This battery provides power for two 925kW Siemens propulsion motors driving a conventional propulsion system through ABB thrusters to two 1,800mm diameter nickel-aluminium-bronze five-blade propellers, turning at 300rev/min in fixed pitch Kort nozzles.
The new tug carries Türk Loydu classification, with notifications including +1A5 K50 TUG+M Li-BATTERY specifically for an electric tug.
Recharging of the Corvus Orca ESS is carried out overnight via shoreside connection – while the quick charge station developed by Navtek as part of the ZeeTug concept means the vessel’s battery can be charged in just one hour. A full charge generally provides Gisas Power with enough capacity to carry out a full day’s harbour towing duties, even allowing for the highly varied nature of tug work.
The batteries themselves, with an expected service life of 10 years, are located in fore and aft battery rooms, and kept safe thanks to a cooling system for a constant, optimum temperature. On the main deck, above the forward battery room, are the quarters for a crew of four, comprising two twin cabins, a shared WC and shower, a mess room/rest area, galley, store room and pantry.
The electronics package in the wheelhouse includes a Sperry Marine radar, while an autopilot, GMDSS, GPS, gyro, chart plotter and VHF are all from Simrad. On deck, in addition to 117.5m2 of deck space, is a single SWL 320kN winch.
Introducing totally new technology such as the ZeeTug is inevitably more expensive up front than using existing products. However, Gisas Power’s operating costs will be 85 per cent lower than conventional tugs. Also, with three further vessels scheduled to join the Gisas fleet, the quartet will save the operator around US$1.7m in combined operating costs over a five-year period. Additionally, of course, there are the environmental benefits: Gisas Power is expected to reduce CO2 emissions by 210 tonnes and NOX emissions by nine tonnes each year.
While the ZeeTug-30, as the series is referred to, was Navtek’s response to a specific set of client requirements, it is also ready to develop variants with bollard pulls ranging from 5 to 75 tonnes. Whatever the size and power of future ZeeTugs, Navtek offers a simple solution: “No noise. No emissions. Just efficient operation.”