In the competitive world of Liquefied Natural Gas (LNG) shipping, efficiency and sustainability are not just aspirations; they are imperatives.
Success in this segment demands not only innovation but also the precision to navigate its complexities. For a forward-thinking operator employing a new MEGI vessel equipped with a Partial Reliquefaction System (PRS), the stakes were clear: every drop of LNG saved meant greater delivery volume, reduced environmental impact, and maximized voyage profitability.
Faced with the challenge of managing the complex interplay of vessel speed, reliquefaction, and vapor pressure, the charterer turned to Danelec’s Boil-Off Gas Optimization. Their mission? To fine-tune the vessel's operational setpoints, minimize LNG consumption, and ensure maximum cargo delivery, all while maximizing efficiency and sustainability across the voyage and meeting terminal requirements at arrival.
By the numbers
- LNG savings potential: ~90 MT by reducing gas consumption in the main engines and increasing reliquefaction
- AER reduction potential: ~0.52 g-CO2/t-nm
- Enhanced reliquefaction efficiency: increased PRS reliquefaction by ~9 MT/day
Why Danelec?
Danelec’s BOG Optimization solution integrates advanced machine learning, thermodynamic models, and real-time vessel data, enabling charterers and operators to optimize gas handling procedures and determine optimal operational setpoints.
The solution provides:
- Actionable recommendations tailored to vessel-specific systems and voyage goals
- Seamless integration with existing systems to support consistent decision-making.
- Real-time predictive insights that consider reliquefaction, consumption, and environmenal impacts on cargo condition and voyage outcomes
- High accuracy in predictions, with reliquefaction predictions accurate to within ~1 MT/day or ~4% on average, and total voyage BOG predictions within 5 MT/day or ~1% on average
- Environmental impact reduction, helping vessels meet decarbonization goals by reducing consumption and CO2 emissions
The platform facilitates collaboration between stakeholders, ensuring operational efficiency while maintaining compliance with pressure and temperature targets.
Our Solution Methodology
Using BOG Optimization, Danelec recommended the optimal shaft speed and cargo conditioning strategy to meet arrival targets. The prescribed shaft speed and engine mode were recommended using digital-twin machine-learning models to predict key parameters and voyage outcomes such as speed over ground (SOG), main engine gas consumption (MEGC), reliquefaction condensate flowrate, and cargo condition (temperature, pressure, and composition) based on forecasted weather data along the route.
- PRS system modeling indicated our recommended operation would maximize reliquefaction while meeting the required arrival time and pressure target
- Recommended operation: slow to ~49 RPM (13.6kts) to achieve the required arrival time, while maximizing system reliquefaction
Results
Operational Highlights:
- The vessel averaged ~49 RPM (13.6kts), aligning with BOG-Sim recommendations, but varied her shaft speed between 40–65 RPM over the course of the voyage
- This variability in shaft speed decreased the average PRS output and increased total gas consumption.
Key Metrics:
Additional Technical Insights
Reliquefaction Performance
The average reliquefaction observed over the voyage was 21.4 MT/day, compared to Danelec’s prediction of 22.3 MT/day based on the observed shaft speed and MEGC. These results demonstrate model prediction accuracy within ~1 MT/day, corresponding with only 4% variance, underscoring the high accuracy of Danelec’s models.
The voyage ranked as the third-best laden leg in reliquefaction efficiency since the implementation of Danelec BOG Optimization, showcasing above-average operational performance.
Predictive Accuracy
Predictions of the total cargo conditioning (consumption + reliquefaction) required to meet the arrival pressure target at the required arrival time were accurate within ~5 MT of LNG, with an RMSE error of 0.03°C for temperature and 0.7 kPa for pressure, further validating the precision of Danelec’s models.
This case highlights the value of consistent operation and predictive analytics in optimizing LNG consumption and improving environmental performance. Danelec’s BOG Optimization sets a new standard for efficiency, environmental responsibility, and operational excellence. For more information, contact sales@danelec.com.
