After the completion of the turbine commissioning and extended autonomous running, the HS1000 was retrieved in January 2013. This was completed using the Olympic Zeus, a DP offshore construction vessel.
During the onshore inspection of the turbine in spring 2013, the seabed cable layout was modified. The revised arrangement incorporated a new dry-mate connector and additional 210m umbilical. This was achieved using a novel technique of two moored multicats, avoiding the high costs of DP vessels and extensive cabling equipment.
The second half of the summer involved the preparation, load-out and re-installation of the HS1000. The innovative technique utilised the Green Marine GM700 gantry barge, this moves away from the very high costs and volatility of the DP heavy lift vessel market.
The loadout required a mobile heavy lift crane to reposition the turbine for the mounting of the final blade and to position it on the seabed frame. Once the turbine was resting on the seabed the GM700 could then position itself over the top and lift the turbine from the seabed frame.
The GM700 was towed to site with the aft tow multicat holding the turbine pigtail cable. The two vessels were moored on site using a six-point mooring spread. The export cable was lifted to the deck of the multicat for the dry-mate connection; this allowed completion of full turbine systems checks prior to installation.
The pigtail cable support buoyancy was removed, and the GM700 was then used to lower the turbine to the substructure. This lift frame cameras confirmed positioning and the turbine was set down into its saddle.