engineering an optimal wind farm stjepan mahulja ewem rotor design : aerodynamics s132545, 4312600...

Engineering an Optimal Wind Farm

Stjepan MahuljaEWEMRotor Design: Aerodynamicss132545, 4312600

30th September 2015

SUPERVISORS:

Gunner Chr. Larsen (DTU)

Ali Elham (TU DELFT)

COMMITTEE:

Gerard J.W. Van Bussel (TU DELFT)

Michiel Zaaijer (TU DELFT)

DTU Wind Energy, Technical University of Denmark2

WFLO FRAMEWORK

The thesis structure

• Special project – Literature study – Exploration of the topic

• Thesis– WFLO using surrogate models

SURROGATE MODELING OPTIMISATION PLATFORM

COST MODEL

WFLOSURROGATE MODELING

LAYOUT OPTIMISATION… …


Plan for today

1. Introduction– Wind farm planning– Wind Farm Layout Optimisation Problem -> How to engineer an optimal wind farm?

• Consequences of the wake field• Design variables, objective function

2. Surrogate modeling – Introduction to surrogate modeling (+ SUMO)– Building a DWM surrogate model

3. Wind Farm Layout Optimisation– Design variables -> optimisation strategies– Example: Middelgrunden

4. Conclusions


LAYOUT OPTIMISATION… …


How to plan a wind farm?


LAYOUT OPTIMISATION ……


Wind Farm

PERFORMANCE

CO

STS

Site Layout O&M

Turbines

Count

Position

Availability or accessibility

Component degradation

Wind conditions

Turbulence characteristics

Mean wind speed distribution

Wind direction distribution

Loads

Spacing

Orientation

Structure

SURROGATE MODELING

LAYOUT OPTIMISATION …WFLO…


Wind Farm Layout Optimisation Problem (WFLOP)

“determining locations of where the turbines should be placed in order to maximize the financial value of the wind farm”

InvestmentPositive cash flow -> ElectricityNegative cash flow -> O&M Financial Balance

SURROGATE MODELING



Investment Power output Lifetime equivalent loading

Turbines + foundation Estimate for AEP Fatigue driven degradation of components

Cable grid Price of electricity O&M costs

SIMULATIONS

SHORTHEST DISTANCE

ALGORITHM

COST MODEL- design- analysis

-grade

OPTIMISATION strategy (module) remains...

SURROGATE MODELING



SIMULATIONS

SHORTHEST DISTANCE

ALGORITHM

COST MODEL

OPTIMISATION

- AEROELASTIC SIMULATIONS OF EACH WT IN THE FARM

- SHORTEST CABLING LAYOUT

- TRANSLATES AEP, LOADS AND CABLE LENGTH TO MONETARY UNITS (WEIGHTING)

- DETERMINES HOW THE TURBINES WILL BE SHIFTED

TRADITIONAL APPROACH

WIND FARM LAYOUT

SURROGATE MODELING



SIMULATIONS:Dynamic Wake Meandering model

• In-stationary wind field (as seen from 1 turbine)• Part of HAWC2• Simulation of 30min (takes approx. 30min of real time)

– For each wind speed (4..25 m/s -> 22)– For each wind direction (0..330° -> 12)– eg. 50 turbines -> 50 x 22 x 12 = 13200 simulations each layout

• parallel computing (550 CPUs) -> 24runs x 30min = 12h each func. eval– Genetic optimization – O(1000) func. eval.– Gradient based optimization - O(100) func. eval. 13200h = 550 days !!!

Optimistic estimate

SURROGATE MODELNeed for a

SURROGATE MODELING



SHORTHEST DISTANCE

ALGORITHM

COST MODEL OPTIMISATION

MODIFIED APPROACH

SURROGATE MODEL

SURROGATE MODELING

LAYOUT OPTIMISATION …

WIND FARM LAYOUT

WFLO…


WTSURROGATE

MODEL

Power Loads

sec1 sec1

sec2 sec2

sec3 sec3

… …

sect12 sect12

Spac Ang

sec1 5D 0°

sec2 3D 30°

sec3 ∞ -

… … ..

sect12 ∞ -

IN

OUT

Farm levelTurbine level

Secto

r level

COST MODELOPTIMISATION

SURROGATE MODELING



OPTIMISATION: Multi-fidelity strategy

GENETIC SEARCH GRADIENT BASED OPTIMISATION on a coarse grid in a continuous domain

- Implicitly finds the optimal number of turbines

- Primarily deals with balancing the costs

- Wake effects are optimised on coarse grid size with accuraccy of 2D

- Turbine count is constant

- Hardly any effect to the investment

- Depends of the initial solution

- Minimises the wake effect

SURROGATE MODELING



Surrogate modeling

• What is a surrogate model?• How to build a surrogate?

• In application to WFLO, what is needed?

SURROGATE MODELING



- Substitution of the true response of some computationally expensive or technically demanding system

• Needs to be cheap to build and cheap to use• Good enough


SURROGATE MODELING

WFLO…


- Approximation based on known function values

• Locations of sampling points are chosen


SURROGATE MODELING

WFLO…


How is it done?

SEQUENTIAL MODELING- Initial samples– Fit a model– Measure the model– Exploit the model / Explore the domain– New samples

• Fit a model• Measure the model• Exploit the model / Explore the domain• New samples• CONVERGENCE

2. PARALLEL COMPUTING

1. EXPERIMENTAL SET-UP

3. COORDINATION


SURROGATE MODELING

WFLO…

DTU Wind Energy, Technical University of Denmark17LAYOUT

OPTIMISATION …SURROGATE MODELING

WFLO…


results• 3 inputs• 7 outputs• 1051 sampling points (+ 421 for validation)• Accuracy of 5% (MRE)• RBF gives best results


SURROGATE MODELING

WFLO…

Coarse ”one-shot” surrogate -> study -> Sequential design surrogate


Layout optimisation in practice

• Middelgrunden Wind Farm – ORIGINAL: 20x2MW -> SCALED: 20x5MW


SURROGATE MODELING

WFLO…



WFLO…

CONVEXITY

2ND STAGE

- 53 TURBINES- AEP INCREASE BY 150%- NPV INCREASE BY 100%

WAKE LOSS INCREASES, BUT EVENS OUT

1ST STAGE

- CAPACITY FACTOR IS INCREASED BY 4%, BUT TOTALLY REDUCED BY 2%- NPV INCREASES BY 134%



WFLO…


OPTIMAL design


SURROGATE MODELING

WFLO…



WFLO…


Conclusions

• Framework makes sense– Surrrogate models are necessary– Multi-fidelity optimisation is prefered

• Surrogate requires tune-up

• Financial aspects fo a wind farm need to be taken into account (weighting!)


LAYOUT OPTIMISATION

… ……


Thank you


COST MODEL:Objective function

• Has to consider all parameters describing the wind farm (performance + costs)• DVs:

– Number of turbines– Turbine positions

• LCoE (not considering market conditions) -> may not be optimal in from economic POV

• NPV


LAYOUT OPTIMISATION

… …WFLOSURROGATE MODELING

LAYOUT OPTIMISATION

… ……


SHORTHEST DISTANCE ALGORITHM:Cable grid design

• Cable accounts for approx. 5% of the total cost• Prim’s and Kruskal’s algorithms• function written in MATLAB• run on layout at the end of each iteration (not considered as DV) -> part of COST MODEL


LAYOUT OPTIMISATION

… ……


Turbine mapping in the genetic algorithm


LAYOUT OPTIMISATION

… ……


3. In a form of regression/interpolation


LAYOUT OPTIMISATION


LAYOUT OPTIMISATION

… ……


Sequential modeling


SURROGATE MODELING

WFLO… WFLOSURROGATE MODELING

LAYOUT OPTIMISATION

… ……


RBF

Rational

Kriging

RBF

RationalKriging

Qu

alit

y

ENSAMBLE

Domain

Dom

ain

Surrogate model types:

HETEROGENETIC


LAYOUT OPTIMISATION


LAYOUT OPTIMISATION

… ……

DTU Wind Energy, Technical University of Denmark32 WFLOSURROGATE MODELING

LAYOUT OPTIMISATION


LAYOUT OPTIMISATION

… ……


Optimisation


LAYOUT OPTIMISATION


LAYOUT OPTIMISATION

… ……

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