Dutch system integrators RH Marine and Bakker Sliedrecht have managed to include a flywheel on a dredger’s hybrid power plant. The innovation allows for a reduced installed battery capacity, while increasing the batteries’ operational life.

Battery lifetime prediction was previously implemented into the ship’s fuel-saving Energy Management System (EMS). The optimisation of the vessel’s hybrid power plant including a flywheel reduces operational costs as well as Total Cost of Ownership (TCO). 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.

Self-learning Artificial Intelligence Algorithm

When using multiple energy sources, such as batteries and flywheels, energy management becomes crucial. RH Marine developed its 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 most optimally. Analysed data shows that on seagoing ferries, the EMS saves fuel up to twelve per cent, and eleven per cent on superyachts. Putting battery shore charging in the mix even reduces fuel consumption on ferries with 38 per cent.

Study into Incorporating a Flywheel

To optimise a ship’s total performance, RH Marine and Bakker Sliedrecht incorporated a flywheel on a diesel generator-battery hybrid power plant. In the paper, the impact on a hybrid power plant with an EMS of a flywheel implementation for a cutter suction dredger study-case is described.

Using a simulation for the hybrid super yacht, 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, a ferry with a forecasted load demonstrated that adapting the algorithm to include forecasting of the power consumption can improve the desired operation. 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. From the study, it is expected that adding a flywheel would improve the grid stability and the power fluctuations on the battery for a cutter suction dredger while maintaining the lifetime and installed capacity.

One Step Closer

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 optimisation,’ says 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, says De Ronde.

Picture: Despoina Mitropoulou and Jan-Kees de Ronde presenting their research at the International Conference of Smart & Green Technology, SMATECH.