Wind Power Analysis Using Non-Standard Statistical Models

Niall McCoy

School of Electrical Systems Engineering

Prof Jonathan Blackledge

15th February 2013

Introduction Name:

Niall McCoy. Qualifications:

Degree in Electrical Engineering 2008 (DIT); Degree in Energy Management 2010 (DIT); Chartered & Professional Engineer 2012 (EI).

Company & Position: Electrical Engineer of Wind Prospect Group, based in Carrickmines, Co

Dublin. Roles & responsibilities:

International Project Management & Electrical Design. Academic Works:

Commenced Part-Time PhD with DIT October 2011; Published one academic paper to date in December 2012 in association

with Prof Jonathan Blackledge;“Analysis of Wind Velocity and the Quantification of Wind Turbulence in Rural and Urban Environments using the Levy Index and Fractal

Dimension - 2012” 2

Agenda Project Background Research Methodologies Current Industry Standards The Urban vs Rural Resource Next Steps

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Project Background Project Background Research Methodologies Current Industry Standards The Urban vs Rural Resource Next Steps

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Why is Wind Energy Analysis Important?

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Currently circa 2,158MW of installed wind generation on the system.

Current energy demand of 35,532GWh¹.

Target of 40% system demand to be via renewable energy by 2020, 35% of which to be wind.

Resulting in a requirement of circa 39,852GWh (SD in 2020)² where 35% must be sourced from wind generation.

Applying capacity factors of 0.31, the required installed capacity for wind generation by 2020 is 5,178MW¹.

Le Tene Maps 2013 ¹ EirGrid 2013² Wind Prospect 2013

Why is Wind Energy Analysis Important?Main reason – Wind Farm Development & Financial Risk; Wind farm developments require capital investment to be developed; Financial return is directly linked to the wind speeds at the site; Financial risk is amplified in the energy prediction due to the

relationship between turbine output and wind speed; To avoid financial disadvantages, uncertainties must be minimised in:

Wind resource assessment Power curve performance (Turbine output at specific wind

speed) Turbine availability

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What has Financial Risk to do with Wind Energy Analysis?

To have confidence in an investment, you need confidence in the wind resource and associated studies;

Wind studies are performed to understand that return on your investment;

All current wind studies carry a degree of uncertainty and potential for error. All stages of the wind study aim to minimise uncertainty, resulting in a “best guess”;

Therefore the Aim of the Project Design a more accurate model of wind energy analysis with reduced errors; Provide a reduced risk profile to investors; Increase funding access to wind projects and increase wind energy

penetration on the Irish system.

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Research Methodologies Project Background Research Methodologies Current Industry Standards The Urban vs Rural Resource Next Steps

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Non-Standard Statistical Models In order to find a more accurate forecasting model for wind energy at a

potential wind farm location are number of equations have been looked at; Non-Gaussian model for simulating wind velocity data; Levy distribution for the statistical characteristics of wind velocity; Thus, deriving a stochastic fractional diffusion equation for the wind velocity as a function of

time whose solution is characterised by the Levy index;

Eventually deriving both to establish Levy index using Betz law to understand the energy output of a specific turbine.

http://eleceng.dit.ie/blackledge/index.php?uid=516&page=publications

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Betz’s Law – Windpower.de 1999 Illustration of Betz’s Law – Windpower.de 1999

Current Industry Standards Project Background Research Methodologies Current Industry Standards The Urban vs Rural Resource Next Steps

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Current Measurement Systems

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WTG Measurement SystemMet Tower Measurement System

NRG System 2010 Vestas 2013

Power Law vs Log Law Profiles

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• Power law profile:

– α = wind shear coefficient

• Log law profile

– Requires knowledge of u* and z0

– Both must be estimated

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1

2

1

h

h

U

U

0* z

h1

u

U

Data Sources & Sets Fully calibrated industry standard anemometers; 10 minute average data set from 80m metrological mast, with cup

anemometers located at heights of, 50m, 65m, 80m & 82.5m;

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The Urban vs Rural Resource Project Background Research Methodologies Current Industry Standards The Urban vs Rural Resource Next Steps

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The Urban vs Rural Resource

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– u(z) denotes the wind speed at height z– u*friction velocity– κ the Von Karman constant– z height above the earth’s surface– d displacement height– z0 height above the earth’s surface roughness

Mertens 2006

The Urban vs Rural Resource

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Main Aim of the paper;

To quantify rural and urban areas in terms of the Levy index using data generated from industry standard sources;The emphasise is based on a theoretical basis, where;

gamma= 1 for 'perfect' urban area (i.e. full diffusion)

and = 2 for 'perfect' rural area (i.e. perfect laminar flow).

In practice, 'perfect' never exists but the differences in gamma for the two environments appears to reflect the hypothesis.Greenspec 2011

Non-Gaussian results of the Urban & Rural Wind Resource

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Project SOLU WDIT ICLT KING DKITUrban Location Newport Waterford Limerick Cavan DundalkCo-Ordinates

X 503732 659727 553282 679051 704775Y 571087 610694 564665 766272 806261

Qmean 1.4918 1.4628 1.4640 1.4590 1.4110 Project RABR KNLR DUNM CRIG DROMRural Location Mayo Wexford Louth Tyrone LimerickCo-Ordinates

X 511370 706819 695381 628938 549251Y 794745 657023 785030 868785 645517

Qmean 1.4607 1.4721 1.5235 1.4836 1.4929

Levy index using data generated from industry standard sources

Five rural and five urban sites were analysed through determination of the Levy index over a period of 12 months.

The Table show that, bar one anomaly, the trend is that the mean values of the Levy index for the rural sites is consistently higher in comparison to the mean values of the same index for the urban sites.

Resulting in the urban-to-rural ratio of 0.9832.

Urban vs Rural the Conclusion In conclusion, it can be stated that the wind resource in the urban

environment is curtailed due to the influencing factors such a surface roughness, turbulence intensity, etc...

When a direct comparison is drawn between the urban and rural wind resources at selected location across Ireland and the UK, using similar reference heights, fully calibrated equipment and stochastic models to define the results. It is evident that the rural resource is generally of a higher energy yield when compared to the urban resource.

For the full paper see - http://users.jyu.fi/~timoh/isast2012.pdfhttp://www.isastorganization.org/index.html

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Next Steps Project Background Research Methodologies Current Industry Standards The Urban vs Rural Resource Next Steps

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Next Steps Detailed look at developing a non-Gaussian based energy yield

platform model and possibly CFD software; Challenge current industry energy analysis model accuracy, such as

Wind Pro & WaSP, with newly development model/software; Introduce more complex influences, such as specific types of

surface roughness, turbulence intensity, etc..;

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Wind Pro & WaSP model Conceptual Non-Gaussian CFD Model

Q&A

Any Questions?

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