How can marine engineers assess and improve the energy efficiency of existing ships?

1 Baseline and benchmark

The first step in assessing and improving the energy efficiency of existing ships is to establish a baseline and a benchmark. A baseline is the current or historical energy performance of a ship, expressed in terms of indicators such as energy efficiency operational indicator (EEOI), energy efficiency design index (EEDI), or specific fuel oil consumption (SFOC). A benchmark is a reference value or a target for energy performance, based on best practices, standards, or regulations. By comparing the baseline and the benchmark, you can identify the gaps and opportunities for improvement, and set realistic and achievable goals.

2 Data collection and analysis

The next step is to collect and analyze data on the energy consumption and performance of the ship, using various sources and methods. Data can be obtained from onboard measurements, such as fuel meters, flow meters, power meters, speed logs, and engine parameters, or from external sources, such as weather data, voyage reports, and ship certificates. Data can be analyzed using software tools, such as ship energy efficiency management plans (SEEMP), energy management systems (EMS), or energy audit tools, that can help you calculate, monitor, and visualize key energy indicators, and identify patterns, trends, and anomalies.

3 Energy audit and diagnosis

The third step is to conduct an energy audit and diagnosis of the ship, using the data collected and analyzed in the previous step. An energy audit is a systematic process of inspecting, testing, and evaluating the energy flows and uses of the ship, and identifying the sources of energy losses, inefficiencies, and wastage. An energy diagnosis is a comprehensive assessment of the energy performance of the ship, and the potential for improvement, based on the findings of the energy audit. An energy audit and diagnosis can help you prioritize the most effective and feasible energy-saving measures, and estimate their costs and benefits.

4 Energy-saving measures and technologies

The fourth step is to implement the energy-saving measures and technologies that have been identified and prioritized in the energy audit and diagnosis. Energy-saving measures and technologies can be classified into two categories: operational and technical. Operational measures are related to the management and optimization of the ship's operation, such as speed optimization, trim optimization, weather routing, voyage planning, and crew training. Technical measures are related to the modification or installation of the ship's equipment or systems, such as hull coating, propeller polishing, engine tuning, waste heat recovery, or renewable energy sources.

5 Monitoring and verification

The fifth step is to monitor and verify the results and impacts of the energy-saving measures and technologies that have been implemented. Monitoring and verification are essential to ensure that the expected energy performance improvements are achieved and maintained, and to evaluate the actual costs and benefits of the interventions. Monitoring and verification can be done using the same data sources and methods as in the data collection and analysis step, but with a focus on comparing the post-implementation performance with the pre-implementation baseline and benchmark.

6 Continuous improvement

The final step is to pursue continuous improvement of the energy efficiency of the ship, by applying a cyclical and iterative approach that repeats the previous steps on a regular basis. Continuous improvement is based on the principle of plan-do-check-act (PDCA), which involves planning the energy efficiency objectives and actions, implementing them, checking the results and feedback, and acting on the lessons learned and opportunities for further improvement. Continuous improvement can help you adapt to changing conditions and requirements, and maintain a high level of energy performance over time.

7 Here’s what else to consider

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