GRID CONNECTION

All of described technologies operate with an electrical network connection. Therefore the off-shore technologies required also well developed internal grid. Unfortunately in most of cases the grid capacity is relatively low near coasts. Lack of connection availability is one of the fundamental barrier for marine technologies development.

Substations usually are installed on the nearest coast (excluding the Hub project – laid down). Generating devices are connected with substation by the LV or MV cable (e.g. 11kV). Cables consist of three isolated power copper cores (designed for an AC voltage), three copper signal/pilot trip cables and a 12-cores single-mod fibre-optic bundle and two layers of galvanised steel wire. Usually cables lay on the seabed and in short distance from the shore also housed in steel protectors. On the shore all cables terminal are connected to the 11kV breaker and to the bus bar. To retrieval a cable, the end of the each cable are capped by the heat-shrink caps and attached to the buoy. One of the marine technologies advantages is predictability in comparison with wind technologies. That virtue allow to eliminate expansive energy converters and to continuous generation.[35]

The Hub project is underwater substation located 16 km off the north coast of Cornwall, United Kingdom. It is some kind of socket for four types of wave energy converters which will deploy around (the first customer is the OPT). Total capacity equals 20MW (5MW for each technology) and operating on 11kV, however the Hub is prepared to the future upgrade to 50MW and operation voltage 33kV. The local grid is very strong due to in region is 400kV transmission electricity network. It is experimental project for the WEC technology testing and development. [30], [36], [39]

Measurements

The tidal and wave activity is easer to predict than the wind however the weather measures are also required. Generally for the SCADA system and for developers. Usually, the weather stations are located near to each test site. Stations are calibrated to national standards and obtains the following information with property frequency: (Fig. 33) [36]

Fig.33 Measurements. Own study based on [35]


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