# Moving Towards Large(r) Rotors Is that a good idea?

## Presentation on theme: "Moving Towards Large(r) Rotors Is that a good idea?"— Presentation transcript:

Moving Towards Large(r) Rotors Is that a good idea?
P. K. Chaviaropoulos, CRES H.J.M. Beurskens, SET Analysis S.G. Voutsinas, NTUA EWEA 2013 Conference Vienna, 4-7 February

Motivation Sway 10 MW Turbine V164-8.0 MW SeaTitan 10 MW
Upwind/NREL/DOWEC UpScaled to 10 MW SeaTitan 10 MW (HTS generator) Siemens 6 MW Offshore WT Alstom Haliade 150-6MW

Motivation Large Multi MW Offshore commercial turbines with
Higher Tip Speed (~90m/s) Large Diameter Concept 10 MW designs with Even Higher Tip Speed (~100m/s) Even Larger Diameter High Tip Speed -> High TSR-> Lower Solidity -> Thicker airfoils Higher Diameter-> Higher Loads for OPT Cpmax HOW DOES THAT WORK ?

Quantification with BEM Theory
All Functions of a, λ, x Ref: Peter Jamieson, Innovation in Wind Turbine Design, A John Wiley & Sons, Ltd., Publication, ISBN , 2011

Low Induction Rotors (LIRs)
Conventional Design For given Ro and λ Maximize CP(λ,a) New, R is a design variable Maximize {[CP(λ,a).R2]/[CP0(λ0,a0).R02]} Constrained by [CM(0)(λ,a).R3]/[CM0(0)(λ0,a0).R03]=1 Or Maximize { CP(λ,a)/ CM(0)(λ,a)2/3} RIGHT: Plots of non-dimensional coefficients, candidates for blade optimization, versus axial induction coefficient a. Application for Β=3, k=100 and λ=8.85 (providing the maximum CP value = for the selected B and k combination).

Low Induction Rotors (LIRs)

Low Induction Rotors (LIRs)

Low Induction Rotors (LIRs)
Characteristic properties of rotors with the same root bending moment designed for different values of the axial induction factor. Plots are presented for the rotor diameter (D), the power production at design wind speed P (Vdes), the levelized rotor cost (LCE) and the annual energy production AnEP. All properties are divided by their corresponding reference values (a=1/3)

LIRs in Large Wind Farms
Capacity factor and wake losses per turbine in a 10X10 offshore wind farm for 8D spacing. Red dots address the initial turbines (highly loaded) and blue squares the less loaded turbines. The dashed red and the blue line correspond to the wind farm mean values. The less loaded turbines increase the wind farm capacity factor by nearly 6%. This comes partly (3%) from the increased annual production of the larger diameter turbine and partly (another 3% roughly) from the reduction of the wake losses due to the lower axial induction and, therefore, thrust coefficients of the larger rotors.

LIRs in Large Wind Farms
Annual energy production of a 10X10 offshore wind farm as a function of turbines spacing (x times Diameter). Red dots address the initial turbines (highly loaded) and blue squares the less loaded turbines. The 6% gain in annual energy production is more or less flat and independent from the turbine spacing. Evidently, this is very much connected to the accuracy of wake calculation in multi-raw offshore wind farms with engineering models, like the one used.