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Tuesday, July 23, 2019 

Dutch system integrators RH Marine and Bakker Sliedrecht have succeeded in incorporating a flywheel in a hybrid marine power plant.

The battery lifetime prediction was previously implemented into the ship's fuel-saving Energy Management System (EMS). The innovation reduces the installed battery capacity but increases lifetime. This has a positive result, in that the Total Cost of Ownership (TCO) decreases, while the reduced fuel consumption remains intact.

Product Manager Hybrid, Despoina Mitropoulou of RH Marine and Electrical System Design Manager, Jan-Kees de Ronde of Bakker Sliedrecht presented the research paper Optimizing the performance of a hybrid power plant with EMS including a flywheel at the International Conference of Smart & Green Technology, SMATECH.

In a continuously developing maritime industry, the demands on fuel consumption and greenhouse gas reduction are becoming stricter. To meet this changing demand, more and more ships are investigating various energy sources besides diesel propulsion, such as batteries and flywheels. In such systems, with multiple energy sources, energy management becomes crucial.

RH Marine developed its own Rhodium Energy Management System (EMS), using a self-learning artificial intelligence algorithm that automatically distributes the power demand over the available diesel generators and batteries. Data analysis shows that on seagoing ferries, the EMS saves fuel up to 12%, and 11% on superyachts. Putting battery shore charging in the mix further reduces fuel consumption on ferries by 38%.

In order to optimise the total performance of a ship, RH Marine and Bakker Sliedrecht further optimise the TCO by incorporating a flywheel on a diesel generator-battery hybrid power plant. The first step closer to minimizing TCO, achieved by incorporating battery lifetime prediction and power consumption forecasting in EMS. In the presented paper, the impact on a hybrid power plant with an EMS of a flywheel implementation for a cutter suction dredger study-case was described.

Using a simulation for a hybrid superyacht, Mitropoulou and de Ronde demonstrated that battery lifetime can be extended by adapting the optimisation algorithm to carefully include lifetime determining quantities, like the state of charge (SOC) and the magnitude of charging and discharging currents, thus optimising the TCO. Additionally, for a ferry with a forecasted load demonstrated that adapting the algorithm to include forecasting of the power consumption can improve the desired operation. Finally, for the load profile of a hybrid cutter suction dredger, implementing a flywheel can have a major impact on TCO minimisation.

Flywheels have excellent peak-shaving qualities for mitigating power peaks taking place in very short time frames without being penalised in operational lifetime. So with this study case on such a load profile, it is expected, that adding a flywheel would improve the grid stability and the power fluctuations on the battery for these type of vessels while maintaining the lifetime and the installed capacity.

However, it did also show that optimising battery lifetime can lead to undesirable generator start-stop cycles. "We are adjusting our control algorithm in achieving a balance between multiple goals, for moving towards global optimization,” said Mitropoulou.

"The most important of our findings, is that with this sophisticated EMS and the implementation of a flywheel, we are one step closer towards optimising the Total Costs of Ownership and changing demand for green energy sources” , said de Ronde.

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