Auxiliary systems optimization

Optimising auxiliary systems to vessel specific operational profiles can lead to significantly reduced energy consumption. Auxiliary systems are often designed to support engines and other primary systems at extreme ambient conditions, or 100% load, which rarely occur. For the majority of the time these systems experience supporting primary engines and systems at loads from 80% and down, and with the era of slow steaming, the auxiliary systems typically support engines and systems at loads below 50%.

Operating over a prolonged time at lower loads can induce accelerated wear and can increase the need, cost, energy consumption and complexity of maintenance.

Applicability and assumptions

Auxiliary systems optimization is applicable for all vessels with auxiliary systems, regardless of ship type and age. The measure includes full or partial assessment of the energy consumption and production in the vessel auxiliary systems. Through simulation and optimization potential to save energy and fuel can be revealed via

• speed control of pumps and fans
• control strategies of cooling water systems
• replacement of heat exchangers, new more efficient heat exchangers
• adjusted room ventilation, and better control strategies
• redesign of piping and instruments
• smarter utilization of heat recovery from the high-temperature and exhaust gas systems
• smarter sensor and power management systems controlling distribution and consumption of auxiliary energy
• others

Auxiliary systems optimization can represent a wide range of measures, but the key message is that there exists large potential in saving energy consumed by the vessels auxiliary systems. The cost and reduction potential estimate of this measure is highly dependent on whether the case is a newbuild or retrofit, design points distance to actual operational points, complexity in auxiliary system design, etc.

Cost of implementation

The cost of implementation is estimated to $10,500 – $210,000 (USD), spanning from simpler improvement to control of cooling water systems to partial redesign of piping system for cooling and steam, including smart energy automation systems.

Reduction potential

The reduction potential is estimated to 1 – 2% of total ship fuel consumption. Note that this reduction potential estimate is highly dependent on whether the case is a newbuild or retrofit, the design point’s distance to actual operational points, complexity in auxiliary system design, etc.

Other References

1. DNV GL Energy efficiency finder / Holistic approach to finding applicable energy efficiency measures to a specific vessel type.
2. Dere, K., et al. (2019) ‘Load optimization of central cooling system pumps of a container ship for the slow steaming conditions to enhance the energy efficiency’