The task of an EMS is to optimize the operation based on a specific goal or goals, having as a primary goal the minimisation of fuel consumption, and as a result the exhaust pollution reduction. Implementing an EMS in a hybrid ferry, including diesel generators and batteries has led to a considerable reduction of fuel consumption, of even up to 38%. A further objective of the EMS is to optimize the total cost of ownership (TCO), i.e. the lifetime, wear and tear, and maintenance requirements of the complete power plant equipment.
As a first step the battery lifetime is incorporated in the controller. This is realised by carefully observing battery lifetime determining quantities, like state of charge (SOC) and magnitude of charging- and discharging currents. The latter can be additionally improved by the application of a flywheel which leads to a better grid stability, taking up high powers, which is a limiting factor for the batteries. Unlike the batteries, a flywheel is a long-lasting device that can offer many years of reliable performance and implementation in combination with batteries, can lead to an even more long-lasting battery lifetime.
The paper describes how the above has been integrated into the EMS and demonstrates the fuel consumption reduction operational results. In addition showing simulation results of how controlling the battery usage maximizes the battery lifetime and how the application of a flywheel further improves the performance of a diesel generator-battery hybrid power
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