The XeroPoint Hybrid system configures the most effective power and propulsion options to meet the needs of the vessel’s operation. The multiple system configurations also provide redundancy by offering alternate sources of power to the vessel.

With only the diesel engine providing power, the electric motor acts as a shaft-driven generator providing power to meet the vessels hotel loads. Auxiliary generators and optional electrical storage provide power for propulsion through the electric motor during electric or diesel-electric modes of operation.

The XeroPoint Hybrid energy management system offers four modes of propulsion:

• Electric only: Power provided from electrical storage (i.e., batteries).

• Diesel-electric: Power provided from auxiliary engines.

• Mechanical: Power provided directly from main engines.

• Mechanical-electric: Power provided from main engines and the motor-generator.

Results from the UC Riverside study comparing conventional and hybrid tugs. Click to enlarge.

A 2010 study by a team from UC Riverside for the California Air Resources Board (ARB) compared the hybrid tug, Carolyn Dorothy (using the ZeroPoint hybrid system) to her conventional sister tug, Alta June. The study found a 73% reduction in PM, 51% reduction in NO_x and 27% reduction in CO₂. Significant improvements are also seen in performance, control and noise levels. The new Cat Powered Marine Hybrid System is currently available for order through the Cat Dealer network.

The Cat Powered Marine Hybrid System is currently being utilized in the global tug and salvage market. The RT Adriaan, a hybrid tug built by Kotug, features 3x Cat 3512 marine engines as well as the new hybrid system. Kotug has elected to install the system on two new tugs currently under construction at the DAMEN shipyard. Two more hybrid ready tugs are currently under construction at CHEOY LEE Shipyard.

The Cat Marine Hybrid System optimizes the use of currently available components and operates diesel engines at peak efficiency. For customers, this means significant reductions in owning and operating costs, with decreased fuel consumption and maximized reliability. With the Cat hybrid system, vessels have the potential to increase operating efficiencies as well as meet or exceed increasingly stringent environmental requirements. The system is completely customizable to specific customer specifications and can provide payback periods in less than 5 years in many instances, according to Caterpillar.

Although the projects up to now have exclusively been in tug boats, we are confident that other applications, such as pleasure craft or offshore, will also find this an attractive proposition. Essentially any vessel that sees duty cycle benefit would also benefit from a hybrid solution. For yacht applications, the hybrid system is able to help the vessel silently maneuver in and out of harbors. For offshore oil and gas applications, the hybrid system provides ample safety benefits in areas of hazardous conditions by being able to operate on purely electrical power.

—Michael Braun, Caterpillar Marine Power Systems tug and salvage segment manager