continuum wind flow model booklet

8/10/2019 Continuum Wind Flow Model Booklet

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Wind Flow Model

Intuitive.Accurate.

Affordable.


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Wind Flow Model

All met sites used simutaneously to form site-calibrated models

The only commercially available wind flow model that is capable of usingmore than one met site.

Only two required inputs Topo XYZ data and Met TAB files.

No expert knowledge required The site-calibration is automatically started when the TAB files are

imported.

All model parameters and results are exportable to .CSV Not ablack boxsoftware

Generates estimates of wind speed and gross AEPat turbinesites or map nodes.

Can specift any area or grid resolution for map generation. No limit on number of turbine power cuves.


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...At A GlancePerforms a Round Robinanalysiswhere subsets ofmet sites are used toestimate the wind speed atexcluded met sites.

Every subset combination of

met sites are found using N-1,

N-2 and N-3 met sites and

models are created for each

combination Determines how the estimate

uncertainty changes as mets are

added

Tests the robustness of the

model

Analyzes met data and

generates model in minutes Quick to provide turbine

estimates and wind speed maps

Forms uncertainty estimatesand produces P90/P99estima

of wind speed and AEP Only commercially available wind flow model that generates unce

tainty estimates.


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Theory & ApplicationContinuum In a Nutshell

Continuum (patent pending) is an exposure-based wind

flow model that utilizes all available met sites

simultaneously to generate four site-calibrated models.

Each model has a different radius of investigation (used to

calculate the exposure) which range from 4000 to 10,000

m. The four site-calibrated models are used to form

estimates of the wind speed and gross annual energy

production (AEP) at the turbine sites and/or at map nodes.

Between each pair of met sites and from each met site to

every turbine site and/or map node, a path of nodes is

created where there is a small change in the exposure and

elevation from one node to the next. Based on the wind

direction and the terrain complexity at each node, the

model coefficients are determined from the model

relationships and the wind speed is calculated along thepath of nodes as the upwind and downwind exposure

changes from the met site to the turbine or map node.

What is exposure?

Exposure is defined as a weighted average of

the elevation difference between a given point

and the surrounding terrain within a given

radius of investigation weighted by the inverse

distance.

How is wind speed estimated?

Continuum uses a two-parameter linear relations

that describes the change in wind speed with ch

in the upwind and downwind terrain. There are

coefficients, m and m , which describe the senDW UW


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What do the model coefficients represent?

The model coefficients describe how sensitive the

wind speed is to changes in the upwind or downwind

terrain exposure.

As derived from Navier-

Stokes conservation of

momentum equation, if

wind is flowing downhill,the model coefficient is:

CRIT

CRIT

If wind is flowing uphill,

the model coefficient is:

If UWUW then and the wind

decelerates.

Model coefficients are a function of gravity, g, and the

vertical pressure gradient force ( ) which is related to

atmospheric stability. They are also a function of the

velocity flow field which is related to terrain

complexity. They are defined in log-log relationshipas a function of P10 Exposurewhich is a measure of

terrain complexityand site-calibrated log-log

relationships are found for each wind direction sector.

of the wind speed to changes in the downwind (DW) and

upwind (UW) exposure.

If the wind speed is known at Site 1 then the wind speed

at Site 2 can be estimated by analyzing the differences in

the UW and DW terrain from Site 1 to Site 2 in each wind

direction sector.


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Why is a path of nodes created?

Since theterrain complexity can vary across a project

area and since the model coefficientsare a function of

terrain complexity, the wind speeds are calculated in a

stepwise fashion.

Between each pair of met sitesand from each met site to

every turbine or map node, a path of nodes with a gradual

change in terrain complexityis found. The model

coefficients are determined at each node based on the

site-calibrated log-log relationships and the wind speed is

calculated along the path of nodes.

How are the models site-calibrated?Once the met sites are imported, Continuum finds a path of

nodes between each pair of met sitesand cross-predicts

the wind speedusing the default log-log relationships.

Then using a self-learning algorithm, the log-log

relationships are varied and the met cross-predictions are

regenerated. The log-log relationships that yield the

minimum met cross- prediction errorare found and these

form the site-calibrated model.


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Case Study: Five Met Sites at Moderately

Complex Site in North Dakota

The topo data and met TAB files were entered

into Continuum and the four site-calibratedmodels were found. The met site cross-prediction

error is summarized in the table to the right.

The wind speed at each met site was estimated

using the Continuum model and the comparison

between the actual and estimated wind speed are

shown in the two plots below. The RMS error of

the wind speed estimate was 0.026 m/s (or

0.31%).

Site - Calibrated Model Results

Radius of

Investigation,m

Met Cross -

Prediction RMSError

4000 0.64%

6000 0.47%

8000 0.57%

10000 0.37%

~50 km

Validation


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To test the robustnessof the model, the Round Robin analysiswas run

where subsets of the met sites are used to form a model and predict the

wind speed at the excluded met sites. The results are shown in the plots to

the right.

When two mets were used, the RMS error of the wind speed estimates was

0.107 m/s (or 1.21%). As more mets were added to the model, the wind speed

estimate error reduced and, with four mets used in the model, the RMS error

of the estimates dropped to 0.043 m/s (or 0.49%).

Num Mets

RMS

Error, m/s

RMS

Error, %

2 0.107 1.21%

3 0.071 0.80%

4 0.043 0.49%

5 0.026 0.31%


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Whats new in 1.1?Uses local SQLdatabase to store calculated values

Keeps file size small and manageableeven with several large, high-res wind speed or AEP maps

Continuously savesto database as WS or AEP map is generated If Windows reboots or Continuum is accidentally closed, all calculations are safe and retrieved from the database

when the map generation is restarted.

Searches stored data for previously calculated data to help speed up map generation.

Generates site-calibratedmodels on a sectorwise-basis

Model coefficients vary as a

function of wind direction to bettermodel sectorwise variations in

mean atmospheric stability

Accepts and exports eitherUTM coordinates orLat/Long in TAB files andturbine imports/exports

Accepts any topo dataresolution


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Pricing & Contac

$US 4000 for a single user license and one-year of free customer support.

$US 500 annual fee for customer support after first year

Contact:

Liz Walls, Co-Founder, Engineering | [email protected]

Email Liz for a free 5-day trial (5 unique days) of Continu

Visit our website at www.cancalia.com

continuum wind flow model booklet

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