CELT4Wind

CELT4Wind: electrothermal cables for offshore wind

The CELT4Wind project aims to contribute to the necessary cost reduction by targeting the very significant investment savings that can be made in the farm’s export cable. This cable has very high thermal inertia, meaning that it can take several days or even months to reach its maximum permitted temperature (which is the limiting factor for energy transmission), even when its nominal current is applied.

Some Transmission System Operators (TSOs), who are now responsible for the electrothermal management of this cable in an increasing number of countries, have begun to consider exploiting this phenomenon, which makes it possible to maximize electricity production with a constant electrical infrastructure. In recent years, some of these network operators have allowed offshore wind farm operators to design their wind farms with a higher capacity than can be transmitted by their export cable in steady state. These farms only operate at full power for a fraction of the time: thus, the temperature of the cable rises slowly, due to the phenomenon of thermal inertia, during the period of full-load production, while remaining below its maximum authorized temperature, as full load is only maintained temporarily. This “undersizing” of the cable can therefore lead to very significant investment savings. However, exploiting the thermal inertia of export cables poses many scientific and technical challenges.

Optimized, real-time electrothermal management by a TSO of a cable connected to a wind farm whose production is controlled by a farm manager requires dialogue between these two players, the basis for which has yet to be defined in terms of the type and temporal precision of the information exchanged. Indeed, relevant operating conditions, which can be achieved by offshore wind farm managers, must be specified by the TSO in the context of offshore wind farm tenders. This is the challenge that the CELT4Wind project aims to address. It aims to address this obstacle from a necessarily multi-stakeholder perspective, involving a TSO (RTE), an offshore wind farm developer/operator (WPD), and an offshore test site manager (SEMREV). This project must also be multidisciplinary and therefore brings together researchers from the fields of electrical engineering and thermal engineering (SATIE and IREENA).

It is based on four pillars:

•  the generation of offshore wind power generation datasets (provided by RTE) based on historical wind meteorological data representative of conditions on the French Channel/Atlantic coast, which can be cross-referenced with actual measured data (provided by WPD);
• the development of electrothermal models of offshore cables combining accuracy and calculation times compatible with real-time constraints;
• the development of an electrothermal management module that takes into account uncertainties, particularly those related to electricity production forecasts;
• the drafting of recommendations for technical specifications to be included in future calls for tenders for offshore wind farms.