Power inverters – essential core element of the Siharbor system

The core element of this shore side power supply system Siharbor is the Siplink system developed by Siemens (Siemens Multifunctional Powerlink), in which two converters are connected together back-to-back by a DC link and are each connected to one power grid. In this way, the system can not only feed an isolated network from a distribution network but can adapt power grids with different parameters and connect them. Both these capabilities are used in the Siharbor solution as a means of linking the ship’s on-board system to the local power supply network. The shore side voltage and the voltage of the on-board system are adapted via suitable transformers which are included in the overall concept. These elements are also an important safety factor, because they isolate the galvanic connection between shoreside and on-board supply systems. This prevents surge voltages of the kind typically caused by lighting striking an overhead power line from reaching the on-board system. Normally the ship’s structure forms a Faraday cage that protects the on-board supply system against lighting strikes. The potential risk of surge voltages in the ship’s on-board system caused by the cable to the shoreside connection is averted by the double power transformation.

For using the Siemens solution both the harbor and the ship must be equipped for the shoreside power supply, or adapted according to requirements. The decisive factor for an onshore electricity supply is the uninterrupted changeover to the shoreside system. A “blackout” would not be acceptable.

In order to meet the requirements for connection of a shoreside power supply on both sides (ship and shore) Siemens has created the possibility of synchronizing the onshore power supply from both sides. The diesel generators for the on-board supply can then be shut down and the complete on-board network can be supplied in an environmentally friendly way from the shore-based power supply. The required connector systems are currently in the process of being standardized.

The Siharbor concept offers an additional interesting possibility for ship-owners, namely a ship-relevant data communication system. That is a matter of a software module that not only records and archives power consumption while the ship is berthed in port but also forwards the total power consumption of the ship to the ship-owner immediately per data transmission via the Internet for settling the electricity costs.

Siharbor is based on standardized, proven components produced on a large scale which have been employed in industry for many years. The degree of automation and the cable feed must be analyzed on a case by case basis. There are circumstances that require bringing the cable from land to the ship or the complete opposite. The decisive situation here is whether the ship recognizes its berth as a permanent shoreside power supply or whether the ship is confronted with a whole lot of different unfamiliar dockside facilities and power supply systems. In every application the handling of the cable on land or on-board ship must be defined and set down unambiguously. Here again, the different vessel types play an important role.

The cable feed – crucial key to success

Under these constraints the cable feed system of the shoreside power supply is the key to success. The cable from the transformer substation is first routed in underground duct systems to the quayside. Cable feed systems designed specially for the purpose then provide the shore-to-ship link. Compensation for the rise and fall of the tide is also taken into account here.

Siemens has developed cable feed systems that cover the tidal range for all different types of ship. The different power requirement for every type of ship is used as the basis and taken into account when developing the system. This can be consistent with a power demand of approximately one to 16 megawatts. As far as frequency and voltage are concerned, this is standardized internationally to 50 Hz/10 kilovolts and 60 Hz and 11/6.6 kilovolts. About 70 percent of national grids worldwide operate at 50 Hz and 30 percent at 60 Hz, whereas with ships it is precisely the other way round.

Siemens implemented the first project with the Siplink system in a maritime area in 2000 at the Flender shipyard in Lübeck where a 1-MVA medium voltage back-to-back link was designed and installed for supplying electrical power from the 50-Hz shipyard grid to ships while under construction. Siplink was also used here to test the on-board generators and to feed back power into the shipyard grid when the generators are running. A controlled exchange of active power takes place in both directions under these circumstances, what is known as “interconnected operation”. In this case the system improves the stability of the network and optimizes the load flow in the shipyard and on-board power grids.

Siemens is currently delivering the first commercial shore side power supply for ships in Germany on behalf of the Lübeck municipal utilities on the Nordland dock. This is the first venture to be undertaken as part of the “New Hansa” project. Under the lead management of the Lübeck municipal utilities, New Hansa has finally been established as a joint project of the countries bordering the Baltic, namely Germany, Finland, Sweden, Denmark and Poland, with the signing of a “Memorandum of Understanding”. The object is to formulate a coordinated policy for the Baltic cities with regard to the environmental criteria of air quality, noise, waste and waste water. The project has also been supported by the European Commission in Brussels.

Hansa city Lübeck – a model for the whole Baltic

The first consumer of environment-compatible electricity from a shoreside power supply at the Nordland dock in Lübeck is the Finnish ferry line Transatlantic. The client of the shipping company cruising the transatlantic lines to Lübeck, the integrated paper, packaging and forest products company Stora Enso, is performing a pilot function here as part of the New Hansa project. Starting in June 2008, the three paper ferries Transpaper, Transpulp and Transtimber, will be able to make use of a shoreside power supply at the destination ports with their 400V/50Hz on-board systems.

For the Hansa city Lübeck a clean solution for ship’s smog is also of great interest because otherwise it stands to lose the spa status of its famous district Travemünde which was granted in 1957 and was called into question for the first time by air quality inspectors in the mid-1990s. Uwe Döring, European Minister of the State of Schleswig-Holstein has therefore held out the promise of financial assistance for the municipal utilities. With the commissioning of the connection in Lübeck Siemens has a complete reference in North Germany for a shoreside power supply system for ships relating to medium voltage side plug-in connection and frequency adaption. In the interests of our environment and most important of all in the interests of the people living in seaports it is to be hoped that this example will be followed, and not only on the Baltic.