The new Nénuphar concept is an absolute game changer on the floating wind turbine offshore market with 2 contrarotative turbines on one floater: the TWINFLOAT.
Boasting more than 5MW power coefficient, this machine will be ready to be traded from 2021 onwards with unbeatable competitiveness in the renewable energies sector.
This disposition will considerably increase each wind turbines and the whole farms performance. While keeping all the previously described assets, those contrarotative wind turbines can reach and go beyond 5 MW thanks to a doubled rotor swept area.
A performance increase for each wind turbine
The Nénuphar contrarotative wind turbine boasts better aerodynamic performances than usual horizontal axis wind turbines.
When you come close to a wind turbines rotor, you can see an air stream expansion: part of the air bypasses the wind turbine, which reduces the available amount of wind and therefore the energy you can make out of it. The problem is the same both for horizontal and vertical axis wind turbines.
However the Nénuphar wind turbine stands out in terms of performance: the two combined contrarotative wind turbines, with appropriate spacing between the rotor, generate between 10 and 20% power coefficient increase (wind-electricity conversion yield) thanks to the creation of a forced stream between the two wind turbines.
An improvement of performances at wind farm level
The Nénuphar concept also boosts energy production at farm level. In a wind farm, most wind turbines are placed in the wake of the first row where the wind has a lower speed. Operation losses generated by the wake effect represent substantial random losses that can reach 12% of the Annual Energy Production.
Traditional horizontal axis wind turbines generate a regular swirl whose regularity limits those exchanges with the environment that allow wind speed recovery.
To the opposite, the Nénuphar vertical axis wind turbines generate an extremely irregular wake characterised by a multiplicity of exchanges with the environment, which allows to retrieve full wind speed on a short distance, to quasi eliminate wake losses, and hence to increase wind resources row after row.
This rapid wind speed recovery allows to increase the Nénuphar wind farm density. The last wind turbines rows still capture lots of wind energy, which is not the case for traditional horizontal axis wind farms. By removing the wake effect, the Nénuphar wind turbine achieves an at least 10 to 20% increase on a farms Annual Energy Performance.
A sizeable CAPEX (Capital Expenditure) decrease
With a contrarotative arrangement, each rotors thrusts partially cancel each other because of their slanted orientation. Because the gravity center is also lower than that of usual wind turbines, the heeling moment is very much reduced. Moreover, because vertical axes turbines can tolerate larger moves than horizontal axis turbines, the dimension constraints on the floater are clearly reduced, which directly impacts the CAPEX.