Performance Evaluation of Dynamic HV Cables with AL Conductors for Floating Offshore Wind Turbines
Presented at the EERA DeepWind 2020, 15th-1th January of 2020, Tronheim, Norway.
FLOTAN is a collaborative project funded by EU Research and Innovation programme Horizon 2020, under the Grant Agreement nº 815289. It is composed of 17 partners from 8 different European countries and has recently started (April 2019). The main objective of FLOTANT is to develop the conceptual and basic engineering, including performance tests of the mooring and anchoring systems and the dynamic cable to improve cost-efficiency, increased flexibility and robustness to a hybrid concrete-plastic floating structure implemented for Deep Water Wind Farms (DWWF).
According to WindEurope report, offshore wind is expected to produce 7% to 11% of the EU’s electricity demand by 2030, as offshore wind energy could have an average cost of 54 €/MWh in the most favourable locations. Energy produced from turbines in deep waters could meet the EU’s electricity consumption four times over, according to estimates from WindEurope. In consequence, encouraging the development and deployment of offshore wind in deep waters is a key strategic issue for the EU. With floating solutions, wind power can expand into new deep-water areas, often further from shore, opening vast new areas and markets currently unavailable for offshore wind. However, many elements of an offshore wind farm become more expensive as depth increases: mooring, anchoring and dynamic cables are the most obvious. Far-shore sites also pose additional challenges for installation, and O&M manoeuvres.
The cost of the mooring system is a growing part of the whole foundation costs as depth increases. Traditional mooring solutions, based exclusively on chains, are not a satisfactory solution, due to the high weight associated with long tethers and the lack of flexibility in the very likely case of excursions of the structure, due to currents and/or changes in the wind. The speed and off-set of these excursions can be important in the case of deep-water moorings, giving place to very important stresses in the rigid chains to counteract the inertia of the structure. Innovations in mooring components and anchoring systems to reduce loads and actively control and minimise excursions are required.
New challenges arise in DWWF for electrical transmission, as the power cable must be able to accommodate all movement and loading from the ocean in relation to the platform, as well as its own weight, and therefore has different performance specifications from the cable used in shallow-water wind farms. Advances in light weight dynamic cables are needed to reduce loads and achieve reliable and cost-effective export systems in FOW farms. Cost reductions should be achieved through optimisation of the whole energy export system, including the dynamic cable, the inter-array cabling, the floating offshore substation and the export lines.
Other aspects as installation and O&M strategies in DWWF should be optimised, boosting port-based pre-assembly and installation, removing the need for expensive heavy-lift installation vessels that would increase the investment needed as distance to shore is higher. Optimal marine management and predictive O&M strategies will enable the reduction of major repair costs, hence minimising the number of marine operations.
FLOTANT Innovative solutions will be designed to be deployed in water depths from 100m to 600m, optimizing the LCOE of the floating solution (85-95 €/MWh by 2030). Prototypes testing of this offshore wind floating platform and its associated mooring, anchoring and dynamic cable systems are foreseen in relevant environment and real sea conditions within the scope of the project. Moreover, the assessment and optimisation of the construction, installation and decommissioning techniques will also contribute to bring down the current cost of offshore wind energy, as well as, increasing its deployment. An expected 60% reduction in CAPEX and 55% in the OPEX by 2030, will be directly motivated by FLOTANT novel developments and additional reductions due to external technology improvements. In addition, environmental, social and socio-economic impacts will be assessed, increasing social acceptance of FOW in deep waters.