SAMSØ ferry power system

SAMSØ ferry power system maintains ecological requirements of one of the wonders of the world

Flexible, intelligent and safe power conversion UPS system meets both the environmental and power needs for transport between island and the mainland

Background

There are concerns that the environment we live in is increasingly polluted. That is why more and more actions are undertaken for its protection. In the marine industry, to reduce the potential for pollution, ship owners frequently require drive systems fuelled by LNG (liquid natural gas), designed to lower emissions of harmful substances into the atmosphere.

Denmark does not possess fossil fuels and since the 1970s they have been researching more ecological solutions. In fact Samsø became the symbol of a new energy policy and it is often called "the ecological wonder of the world" as it is the first Danish island to use 100% renewable energy and consequently has a CO2 emissions rating of zero.

In order to preserve its ecological status Samsø authorities issued a call for tenders for building an ecological ferry boat that would connect the island with the mainland. The Remontowa Shipyard, which was awarded the tender, built the EU's first gas-powered car-passenger ferry. For those ferries on which energy used in the main propulsion system and other systems is generated by LNG, the emission of harmful nitric oxides (NOx) is lower by 90%. Emissions of particulate matter (soot) and carbon dioxide (CO2) are also reduced by around 20% in comparison to ferries with diesel engines.

The ferry is designed for all-yearround transportation between Samsø and mainland. It can carry 600 passengers and 160 cars in a single trip.

Challenge

To reduce CO2 emissions during the time that the ferry is moored at the harbour, the generators powering the vessel's electrical system are stopped. The challenge is how to provide power for the vessel's electrical system, whose rated frequency is different from the rated frequency of the land electrical and power system, while the generators are not operating. Additionally, the solution needed to ensure bi-directional power flow, depending on whether the vessel is powered from the land or from its own generators.

Solution

To make it possible to 'power down' the generators during the vessel's time in harbour, an Eaton Power Xpert 9395 Marine UPS frequency converter was applied. The 275 kVA 9395 was used as a power converter to connect the power generation system based on land (operating at 50 Hz) with the vessel's power system (operating at 60 Hz). The 9395 converter also had to enable changing the direction of power flow depending on the system's status, i.e. if the system's batteries were approaching depletion then the 9395 could facilitate a seamless transition to power from the shore-based generation and vice versa.

It offers three-phase input and output, a small footprint, Hot Sync™ paralleling capability up to five redundant systems and Advanced Battery Management technology to extend battery service life, plus it has many communication options.

At harbour, the converter's input supply is 50 Hz, while the generated output power is 60 Hz. While the ferry is at sea, the direction of the power flow is changed, the converter is powered with 60 Hz supply and the output frequency is 50 Hz. This solution was put in place using a control system based on the Eaton EC4P PLC programmable controller.

Results

In order to meet the specific environmental and ecological requirements of the customer, Eaton provided an innovative reversible converter system that meets the specific requirements of both ship-to-shore and shore-to-ship power. Alongside this energy efficient solution, the EC4P PLC programmable controller enables simple configuration of the system depending on the power flow's direction in the installation.