Offshore wind farms are important contributors to reaching renewable energy and climate targets. However, their location offshore requires subsea transmission cables to bring the generated electricity to shore. At long distances, Direct Current transmission is commonly applied, but requires costly converter stations. Thus, to cut costs, there is industry interest in applying Alternating Current (AC) transmission also for longer distances, though implying higher electrical losses.
Innovation: EARTO Member SINTEF developed an innovative method to minimise such electrical losses by a system that controls the voltage depending on the offshore wind energy production. The voltage can be controlled through the transformers at each end of the cable, and their optimised operation can be precalculated and specified in a look-up table as a function of the wind farm output power to minimize the electrical losses in the long AC transmission cable.
Impact Expected: This innovation represents a significant improvement relative to current industry practice. For a case of a large offshore wind farm connected 200 km from shore with AC cables, the innovation reduces the annual losses with one percentage-point compared to the case of operating the cables at nominal voltage as per industry standard. This improves the economics of far-offshore wind farms and can result in their further deployment.