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PLUG: Power Generation During Loading and Unloading

Examples of the simulation

The project studies possibilities for electricity exchange between LNG tankers and harbour. In order to make the study more specific, the study uses Snøhvit project in Northern Norway, which is Europe's first export facility for liquefied natural gas (LNG), as an example and reference point.

The Snøhvit project will use natural gas from the Snøhvit, Albatross and Askeladd fields in the Barents Sea for production of LNG at processing facility on Melkøya Island outside Hammerfest in Northern Norway. The regular operation of the facility was initially planned to start in October-November 2007 and will result in approximately 50-60 LNG shipments by special carriers to markets in Europe and the USA per year.

To perform the simulations and calculations, some information from the user/carrier is necessary. This input data is divided into five categories:

  • Generator data: availability of the vessels’ electricity production and costs of the generation
  • Energy demand data: the vessel’s own electricity demand during a call
  • Contract data: prices from the day ahead or other electricity markets
  • Distribution network tariff data: costs of the network services for both export and import of electricity
  • Emission data: emissions from the vessel’s generation, compared with emissions in the port of call

For each category, data is displayed and can be edited in a separate window (user interface). These windows can be reached from the main window where the simulation is displayed.

In order to study interaction between the spot market and a vessel, several simulations have been made, based on historical electricity prices for 2006. The sample simulation example, shown in following figure uses electricity spot prices from the 9th of January of 2006, where it was a very high price variation during a day. The simulation is related to an LNG boat with three auxiliary generators with different capacity and generation price.  Duration of the call is 19 hours.


Connection between the vessel and the local electricity network is established at 03:00. From 03:00 until 05:00 the electricity spot prices ashore are lower then the generation costs, so the vessel imports electricity from the net. After hour 6 the spot prices start to raise and access the own generation costs. The vessel starts Generator 1 with the lowest generation costs in order to cover the own consumption. The further raising of the electricity price leads to activation of all three generators. The generators start to supply electricity to the vessel and simultaneously export the residual capacity to the local net. This lasts until hour 20, when the spot prices start to fall again. The vessel accordingly deactivates Generator 3 with the highest production costs at hour 20 and stops export of electricity at hour 21.

The simulations have shown that an efficient operation in the spot market environment requires a frequent decision making and regular developing of generation schedules based on day-ahead electricity spot prices. The main conclusion, which can be derived from the simulation examples that the generation schedules are going to be influenced a lot by the price development ashore and likely to have a strong variation even within a fairly short time frame.