Power grid developments to accommodate offshore wind

Wind turbines are moving further out to sea, and more floating wind farms are planned, which means power needs to travel further to the shore. Connecting large amounts of offshore wind energy to - often outdated - grids poses a huge challenge. Integrating offshore wind energy into the power system requires expansion and upgrades. Let’s examine some key challenges and developments.

One major challenge is dealing with Power Quality issues. Wind turbine switching and large variations in generation and consumption of energy can result in significant voltage fluctuations. When turbines are commissioned, voltage fluctuations in the distribution network must be kept within certain limits. IEC 61400-21 - the international standard for measurement and assessment of grid-connected wind turbines - recommends load-flow studies to assess the influence of wind turbines on steady-state voltages. IEC 61400-21 also defines power quality characteristics for wind turbines and suggests methods to assess the impact of wind turbines on grid power quality. Furthermore, the required converters and long cables introduce phenomena such as harmonic distortion and power losses. The new technologies and power electronics used are also often sensitive to voltage disturbances.

Different regions are facing different challenges and coming up with a variety of solutions. In several countries, national transmission operators are planning network rollouts and building lines to the turbines. In the U.K., transmission lines connecting wind farms are sold to independent operators. In the U.S., 30 GW of offshore wind parks are scheduled to be installed by the end of the decade. However, if federal agencies, states and grid operators do not develop transmission plans ready in time, capacity may largely remain underused.

Network developers and regulators have not only pointed out that growing pressure on the network will require grid renewal and a more integrated approach, but also that new (international) interconnections are needed to transmit power from where it’s generated to where it’s needed. According to the UN, “international electricity grid interconnection (…) can (…) improve energy security in the interconnected countries.” A study from Stanford University professor Mark Jacobson modelling energy grids powered by 100% wind, water and sunlight across Western Europe found that increased interconnection between countries would lower energy costs and improve grid stability. 

This challenge is stimulating new cooperation. In the North Seas Energy Cooperation (NSEC), for example, EU Member States, are working to develop offshore wind energy generation and transmission infrastructure. The British government, which wants to reach 40 GW of offshore wind by 2030, has studied a coordinated approach to building both offshore wind transmission and subsea cables to other countries. Britain's transmission grid operator found that integrated approach could save consumers 18%, or $8 billion, in CAPEX and OPEX by 2050. A multipurpose interconnector that would link future offshore wind farms in the waters off of both the U.K. and the Netherlands and provide up to 2 GW of power trading capacity is also being studied. In Denmark, the government plans to build energy islands that connect multiple wind farms.