In the ever-evolving seascape of maritime regulations, the Energy Efficiency Existing Ship Index (EEXI) stands as a guiding star towards a more sustainable future. One of the critical tools in achieving EEXI compliance is the Engine Power Limiter (EPL).  In this article, we’ll dive into the significance of EPL, the challenges it poses, the available technology, and what marine engineers need to do to navigate these waters successfully.

The Essence of EPL

The Engine Power Limiter (EPL) is an integral part of a vessel’s propulsion system, designed to regulate engine power to meet the EEXI requirements. Its primary function is to limit the maximum engine power output to ensure compliance with the defined energy efficiency thresholds, ultimately reducing greenhouse gas emissions.

What is EPL and how does it work?

EPL is a system that limits the maximum engine power output in normal operating conditions, by adjusting the fuel index (the ratio between fuel flow and engine speed) with the aid of a fuel index limiter, a simple device on the ship’s engine control system. The fuel index limiter can be either mechanical or electronic, depending on the type of engine and control system.

Engine Power Limiter Source and Credit: MAN Energy Solutions

The EPL system can be overridden in emergency situations that require the use of additional power (reserve power), such as avoiding collision, maneuvering in adverse weather or responding to distress signals. The override function is activated by a switch on the bridge or in the engine room, and it triggers an alarm and a log record for reporting purposes.

The EPL system can be designed to limit either the actual engine power output or the shaft power output. The former option is suitable for ships with direct drive propulsion systems, while the latter option is suitable for ships with shaft generators or other devices that affect the power transmission from the engine to the propeller.

The level of power limitation is determined by the EEXI reduction factor, which depends on the ship type, size and age. The reduction factor ranges from 5% to 30%, meaning that the ship’s engine power must be reduced by that percentage from its original maximum continuous rating (MCR). For example, a bulk carrier built in 2010 with an MCR of 10 MW must limit its engine power to 7 MW (30% reduction) to comply with the EEXI.

Challenges on the Horizon

The main benefit of EPL is that it is a simple and cost-effective solution to achieve EEXI compliance, without requiring major modifications to the ship’s hull or propulsion system. EPL can be easily installed and retrofitted on existing ships, and it does not affect the engine’s operation under normal conditions (unless the power limit is reached).

Another benefit of EPL is that it reduces the ship’s fuel consumption and GHG emissions proportionally to the power reduction. By limiting the engine power, the ship’s speed is also reduced, which leads to lower resistance and propulsive power demand. According to some studies, a 10% decrease in speed can result in almost 30% reduction in fuel consumption and emissions.

However, implementing EPL systems presents a unique set of challenges:

• Engineering Complexity: Installing EPL systems can be technically complex, as they must be seamlessly integrated into the existing engine control systems.

• Data Precision: Accurate measurement and control of engine power are critical. Any discrepancies or inaccuracies in measurement could lead to non-compliance.

• Synchronization: Coordinating engine power with vessel speed and operational demands requires precise synchronization to avoid any adverse effects on vessel performance. EPL compromise the ship’s performance, safety and operability in certain situations that require high power or speed, such as heavy weather conditions, strong currents or tides, congested waterways or ports, or contractual obligations. Therefore, EPL should be used with caution and discretion, and always considering the prevailing circumstances and risks.

• Regulatory Adherence: Ensuring that the EPL system meets EEXI regulatory standards is essential, and this may require constant monitoring and adjustments. EPL it may not be sufficient or optimal for all ships or routes. Depending on the ship’s design characteristics, operational profile and trade pattern, other solutions may be more effective or efficient to improve the ship’s energy efficiency and reduce its emissions. For example, some ships may benefit more from hull optimization, propeller retrofitting, waste heat recovery or alternative fuels.

Technology on the Market

Several manufacturers and suppliers have developed and offered different products and solutions for EPL implementation. Some examples are:

• Kongsberg Maritime: The company provides a software functionality called EPL upgrade for its AutoChief 600 (and AutoChief C20) remote propulsion control systems with digital governor systems (DGS). The feature enables a vessel to limit its engine power when the pre-set value is reached.
  

  Engine Power Limiter by Wartsila

• Lloyd’s Register: The company has issued guidance notes for class approval of EPL and shaft power limitation (SHaPoLi) equipment, which include the requirements and procedures for the design, installation, testing and certification of such systems.
  

  Engine Power Limiter by MAN

• DNV: The company offers an advisory service called EEXI vibration pre-check, which assesses the potential impact of EPL on the engine’s vibration and torsional stress levels, and provides recommendations to avoid or mitigate any adverse effects.

What Marine Engineers Need to Do

Marine engineers play a crucial role in the implementation and operation of EPL systems. They are responsible for:

• System Assessment: Conduct a comprehensive assessment of the vessel’s current engine and propulsion systems to determine compatibility with EPL technology.

• Technology Selection: Collaborate with technology providers to select the most suitable EPL solution, ensuring it aligns with the vessel’s specific needs and EEXI compliance requirements.

• Integration: Installing and testing the EPL system according to the manufacturer’s instructions and the class society’s rules and regulations, ensuring its proper functioning and integration with the existing engine control system.

• Performance Monitoring: Operating and maintaining the EPL system in accordance with the operational manual and the best practices. Implement regular monitoring and data analysis to assess the system’s performance and make adjustments as needed to maintain compliance.

• Training: Ensure that the vessel’s crew is trained in operating and troubleshooting the EPL system effectively.

• Documentation: Overriding the EPL system when necessary, following the safety procedures and protocols, and documenting and justifying the reasons and duration of the override events. Maintain comprehensive records of all EPL-related activities, including installation, adjustments, and performance reports, for compliance verification.

In conclusion, EPL is a viable solution for EEXI compliance that can improve the ship’s energy efficiency and reduce its emissions by limiting its engine power. However, EPL also has some challenges and limitations that need to be carefully considered and addressed. Therefore, marine engineers should be well informed and prepared to deal with EPL systems, as they are key actors in their selection, installation, operation and maintenance. With the right measures in place, EPLs can be the key to navigating these new regulatory waters with confidence.