Optimus Pråm - Semi-submersible wind farm installation vessel for Blekinge Offshore

Rapport, 2014

In Sweden the government is investing lots of resources in order to meet the energy need with clean and renewable alternatives. Since wind is an unlimited source of energy the exploitations of wind farms is of great interest. This report describes a conceptual design of an innovative offshore wind turbine installation vessel for inland sea conditions, with highest possible energy efficiency and environmental friendly performance in every detail. The customer, Blekinge Offshore, main requirement is to receive a concept with an as low installation cost as possible. The final concept Optimus Pråm includes one installation vessel, which is a semi-submersible barge, and one support vessel that supply the installation vessel with power and propulsion. The power is distributed from the support vessel to the installation vessel through a power cable. The installation vessel will be self-propelled during the installation phase using electrical motors and thrusters. The installation vessel shall be able to handle gravity foundations and fully assembled wind turbines, transported vertically to the installation site. Foundations and windmills will be fully assembled in Karlshamn port before transit to site. During transit the installation and support vessel are connected to each other in all motions except pitch. This almost total fixed connection makes the two vessels acts like one, which gives the joint vessel excellent manoeuvrability. When installing foundations, the installation vessel and the support vessel disconnect. The installation vessel places the foundation at the planned location by ballasting until the foundation has reached the seabed. After de-ballasting the installation vessel and support vessel connects again and transit back to the harbour. When installing wind turbines the two vessels are kept connected and makes highly accurate positioning for the installation possible