Estimation of Wind Energy Production - Revision history

Ranisha at 12:30, 29 August 2014

2014-08-29T12:30:32Z

Show changes

Ranisha: /* Calculation of uncertainties in energy yield for a specific wind turbine */

2014-08-12T12:46:11Z

Calculation of uncertainties in energy yield for a specific wind turbine

Ranisha at 12:45, 12 August 2014

2014-08-12T12:45:25Z

Show changes

Ranisha: /* Further Information */

2014-08-01T09:20:06Z

Further Information

Wiki Gardener at 14:45, 16 June 2014

2014-06-16T14:45:25Z

Show changes

Katharina Wiedemann at 13:38, 15 April 2013

2013-04-15T13:38:28Z

Katharina Wiedemann at 12:28, 15 April 2013

2013-04-15T12:28:34Z

Show changes

Katharina Wiedemann at 13:47, 15 May 2012

2012-05-15T13:47:49Z

Show changes

Katharina Wiedemann at 13:46, 15 May 2012

2012-05-15T13:46:52Z

Nils Marscheider at 12:16, 28 August 2011

2011-08-28T12:16:57Z

@@ Line 256: / Line 256: @@
 [[Estimation of Wind Energy Production#Overview|Go to Top]]
-=== Calculation of uncertainties in energy yield for a specific wind turbine<br/> ===
 The transformation of the wind speed related uncertainties into the energy related uncertainty by appropriately reducing the wind speed at hub height leads to the following results:
@@ Line 302: / Line 303: @@
 [[Estimation of Wind Energy Production#Overview|Go to Top]]
 = Further Information =

@@ Line 296: / Line 296: @@
 <br/>
 == Further Information ==
 *[[Portal:Wind|Wind Portal on energypedia]]
 <br/>
 == References<br/> ==

@@ Line 1: / Line 1: @@
-= Overview =
+== Overview ==
 The calculation of the wind resources on-site and the corresponding energy production are based on the [[Assessing Wind Potentials|assessment of wind potentials]] by anemometric measurement. The wind data is processed by software packages to calculate the expected wind energy yield for the proposed site<ref>The contents of this article have been prepared by the project team of the feasibility study of the Ethiopian wind park Ashegoda, conducted by the Deutsche Gesellschaft für internationale Zusammenarbeit (GIZ) in cooperation with the Austrian development agency and Lahmeyer international. Originally the contents have been published as: GTZ (2006) Feasibility Study for Wind Park Development in Ethiopia and Capacity Building - Ashegoda Wind Park Site), retrieved 11.7.2011 [[http://www.gtz.de/de/dokumente/en-feasibility-study-wind-park-ashegoda-2006.pdf]]</ref>.
 == Meteorology<br/> ==
@@ Line 18: / Line 18: @@
 ==== WindPro<br/> ====
 The WindPRO philosophy is object orientated projecting. A wind park project consists of a number of objects, whereby the wind turbines are key elements. Objects are: wind turbines, wind monitoring stations, local obstacles etc. Some of the objects directly determine the wind energy, others focus on the environmental aspects and yet some others can also influence the feasibility of the project. The characteristics of the objects are combined with the terrain data such as the surface roughness maps and the height level contour lines and serve as basic input data for the energy calculations with WAsP, which is the WindPRO integrated meteorological simulation model<ref>EMDinternational (2010) WindPro users manual, retrieved 26.7.2011 [[http://help.emd.dk/knowledgebase/content/WindPRO2.7/03-UK_WindPRO2.7_ENERGY.pdf]]</ref>.
 ==== WAsP<br/> ====
@@ Line 44: / Line 44: @@
 === Roughness ===
 For the model simulations the roughness classification for the surface in close proximity to the wind farm site is derived from topographical maps, data obtained during site visits as well as aerial photos of the region. A basic description of the roughness classes is given in the following (roughness length is a second roughness description unit), it has to be noted that the roughness class is a defined value which can not be measured directly. The roughness length describes the height where the wind speed in a logarithmic wind profile is becoming zero; the coarser the surface, the higher the roughness length.
 {| cellspacing="1" cellpadding="1" border="1" align="center" style="width: 600px"
@@ Line 101: / Line 101: @@
 <br/>
 As an example for a roughness description the map of Ashegoda site is presented in the following Figure 3.
 [[File:Roughness Description of Ashegoda wind park site.jpg|frame|center|180px|Figure 3: Roughness map for Ashegoda wind park site in Ethiopia]]
@@ Line 115: / Line 115: @@
 The wind gradients for the twelve wind distribution sectors describe the wind speed at different heights for all wind directions diveded in sectors of 30°. An example for a calculated wind profile (increase of the wind speed with height) for the main wind direction of this site (sector south-southeast) is displayed in Figure 4.
 [[File:Wind profile of Ashegoda wind park site.jpg|frame|right|180px|Figure 4:Wind profile of Ashegoda wind park site (main wind direction south-southeast)]]Combining considerations of terrain and roughness, the wind profile for the area of each individual wind turbine is then calculated by WAsP. The extrapolation from 40 m measuring height to 60 m hub height can be considered as reasonable but a further increase of the wind speed for hub heights of 80 m and more is not stringent as the power law is not suitable for height extrapolations over this range.
 <br/>
@@ Line 190: / Line 190: @@
 The reliability of the WAsP calculation is highly dependent on the quality of the input parameters of which wind data is the most important one. The collection and processing of wind date is subject to several uncertainties.
 *Anemometer calibration<br/>Anemometers should be calibrated in order to secure that the measured wind speed equals the actual wind speed.
 *Anemometer characteristics<br/>Describes the uncertainty of the quality the anemometer detects the wind flow and processes the values to digital data.
 *Mounting error<br/>The anemometer has to be vertically mounted. The uncertainty describes the effect if this is not done properly.
 *Data recording<br/>Describes the uncertainties related to processing and storage of the data provided by the anemometer and the wind vane in the data logger.
 *Terrain description<br/>Describes the uncertainty of the influence of the terrain to the measurement. Inclined wind flow and strong turbulence can not be measured accurately by a cup anemometer.
 *Long term correlation<br/>The data used for the long term correlation as well as the MCP-Process includes uncertainties;
 To calculate the total uncertainty all single uncertainties can be considered as stochastically independent and the commonly used way of estimating the joint uncertainty of independent (un-correlated) uncertainties is to calculate the RMS value.
 ==== Uncertainties of the Power Curve ====
@@ Line 204: / Line 204: @@
 The uncertainty of the power curve is, assuming the power performance of the turbine as independent of the energy deviation due to wind uncertainties, connected to the uncertainties of the energy yield by the following equation:
 &#x5B;&#x5B;File:&#x5D;&#x5D;
 The turbine supplier usually gives a guarantee of 95 % of the energy values, which leads to an uncertainty to the predicted figures of 5 %; the actual guarantee value has to be negotiated with the manufacturer, the uncertainty can be adapted accordingly. This figure has been taken for every wind turbine type as it is sufficiently conservative for both calculated and measured power curves.
@@ Line 257: / Line 257: @@
 Gross annual energy describes the energy yield as calculated and net annual energy the energy yield considering the losses and uncertainties.
 Besides the uncertainties for wind conditions and power curve, the losses for electricity transmission (e.g. 2,8 %) and reduced availability of the turbines (e.g. 95 %) have also to be considered as constant factors, reducing the estimated energy yield.
 == Further Information ==
@@ Line 265: / Line 265: @@
+*
+<br/>
 == References<br/> ==

@@ Line 103: / Line 103: @@
 [[Image:Roughness Description of Ashegoda wind park site.jpg|frame|center|Figure 3: Roughness map for Ashegoda wind park site in Ethiopia]]
-=== Wind Shear  ===
+=== Wind Shear ===
-In many [[Assessing wind potentials|assessments of the wind potential]] the upper anemometers of the wind measurement are installed at a height of 40 m above ground while the hub height of modern wind turbines today often reaches heights between 55 m and 60 m above ground level. To estimate the wind regime at hub height of the wind turbines (the WAsP model simplifies the wind speed distribution over the rotor as concentrated to the hub height) the wind speed is extrapolated according to the following formula:
+In many [[Assessing_Wind_Potentials|assessments of the wind potential]] the upper anemometers of the wind measurement are installed at a height of 40 m above ground while the hub height of modern wind turbines today often reaches heights between 55 m and 60 m above ground level. To estimate the wind regime at hub height of the wind turbines (the WAsP model simplifies the wind speed distribution over the rotor as concentrated to the hub height) the wind speed is extrapolated according to the following formula:
-<math>v_{new}=v_{old} \cdot (\frac{h_{new}}{h_{old}})^\gamma</math>
+[[File:]]
-Whereas&nbsp;<math>\gamma</math> is the Power Law Exponent or Wind Gradient which is depending on the roughness of the terrain, the thermical lamination of the atmosphere, the wind speed itself and the height above ground. The exponent must be calculated sectorwise for the wind park site. This can be done by the WindPro-Software package from the measured wind data at the heights of 10 m a.g.l. respectively 40 m a.g.l..
+Whereas&nbsp;<span class="texhtml">γ</span> is the Power Law Exponent or Wind Gradient which is depending on the roughness of the terrain, the thermical lamination of the atmosphere, the wind speed itself and the height above ground. The exponent must be calculated sectorwise for the wind park site. This can be done by the WindPro-Software package from the measured wind data at the heights of 10 m a.g.l. respectively 40 m a.g.l..
 The wind gradients for the twelve wind distribution sectors describe the wind speed at different heights for all wind directions diveded in sectors of 30°. An example for a calculated wind profile (increase of the wind speed with height) for the main wind direction of this site (sector south-southeast) is displayed in Figure 4.
 === Wind Turbine Parameters  ===

← Older revision		Revision as of 12:16, 28 August 2011
Line 1:		Line 1:
−	The calculation of the wind resources on-site and the corresponding energy production are based on the [[Assessing wind potentials\|assessment of wind potentials]] by anemometric measurement. The wind data is processed by software packages to calculate the expected wind energy yield for the proposed site<ref>The contents of this article have been prepared by the project team of the feasibility study of the Ethiopian wind park Ashegoda, conducted by the Deutsche Gesellschaft für internationale Zusammenarbeit (GIZ) in cooperation with the Austrian development agency and Lahmeyer international. Originally the contents have been published as: GTZ (2006) Feasibility Study for Wind Park ~~DevelopmentfckLRin~~ Ethiopia and Capacity Building - Ashegoda Wind Park Site), retrieved 11.7.2011 [[http://www.gtz.de/de/dokumente/en-feasibility-study-wind-park-ashegoda-2006.pdf]]</ref>. <br>	+	The calculation of the wind resources on-site and the corresponding energy production are based on the [[Assessing wind potentials\|assessment of wind potentials]] by anemometric measurement. The wind data is processed by software packages to calculate the expected wind energy yield for the proposed site<ref>The contents of this article have been prepared by the project team of the feasibility study of the Ethiopian wind park Ashegoda, conducted by the Deutsche Gesellschaft für internationale Zusammenarbeit (GIZ) in cooperation with the Austrian development agency and Lahmeyer international. Originally the contents have been published as: GTZ (2006) Feasibility Study for Wind Park Development in Ethiopia and Capacity Building - Ashegoda Wind Park Site), retrieved 11.7.2011 [[http://www.gtz.de/de/dokumente/en-feasibility-study-wind-park-ashegoda-2006.pdf]]</ref>. <br>

	== Meteorology <br> ==		== Meteorology <br> ==