A Hybrid Tug

Caterpillar Marine and Istanbul, Turkey-based Sanmar Shipyards will cooperate on a tugboat that incorporates a hydraulic hybrid propulsion system.

The Cat Marine Advanced Variable Drive (AVD) is a patented system leveraging Caterpillar’s extensive experience with integrated power systems technology. Sanmar is the largest tug builder in Turkey and has more than 40 years of experience in the tug building industry.

The Sanmar hydraulic hybrid tug will be a Robert Allan Ltd. designed RAmparts 2400SX harbour tug (Sanmar’s Bogacay series), incorporating an integrated Caterpillar AVD system.

The AVD system provides significant improvements in both fuel efficiency and vessel performance through a fully integrated hydro-mechanical propulsion system, the company said.

“Different from a typical power take in (PTI) solution, the AVD incorporates a planetary gear set allowing seamless clutch engagement of main engines, auxiliary engines, or both to provide a scalable power installation to meet any customer need in terms of maximum vessel speed, power, or bollard pull,” said Nathan Kelly, Caterpillar Marine product definition engineer. “This also allows propeller speed independent of engine speed so optimal engine efficiency can be achieved leading to fuel savings of 15-20%. Basically, all the benefits of a variable speed diesel electric propulsion (DEP) system at a fraction of the cost and size.”

The AVD system is also flexible and can accommodate multiple configurations,  auxiliary engines can be utilized to accommodate low load or transit operations greatly extending time to overhaul and reducing service costs on main engines. Electric motors can be used instead of hydraulics if required. Diesel engines can be substituted by natural gas engines because the AVD system provides superior vessel performance regardless of engine load acceptance, the company said. Main engines can also be downsized with supplemental power provided via auxiliary engines or generators if electric motors are used.

“This strategic development between Sanmar and Caterpillar will provide a highly optimized, lower-cost alternative to conventional electric hybrid systems with similar benefits regarding improved performance, lower noise, and lower emissions,” said Ali Gürün, Director of Projects, Sanmar Shipyards.

The Sanmar hydraulic hybrid tug will incorporate an integrated Caterpillar AVD system of 3512 main engines, a C32 auxiliary engine, Caterpillar MTA 627 fixed pitch tug thrusters, and bridge controls. It will carry Fifi 1 designation with 70 tonnes bollard pull and will be supported by Turkish Caterpillar dealer Borusan Makina. The AVD system will also include a fully integrated controls system with customizable operating modes and display panels at the bridge. Compared to a conventional tug with equivalent bollard pull, the Return on Investment (ROI) is estimated at three years or less based on projected fuel and operating cost savings, the company said.