Best area or location for installing reference meteo mast to monitor performance of an operating wind farm

[Windlinus]

Hello colleagues, please could you suggest me how to identify the best location area to install the reference meteo station to monitor and calibrate the wind speed for an operating wind farm? Could you suggest a guideline document, or a report containing a list of requirements to be followed to define this area in the vicinity of the turbine installation locations? Thank a lot in advance for your kind support!

[Morten]

I can think of two related problems:

• The recommendation for WAsP AEP predictions, before the windfarm construction, is to select a reference mast position, which is as representative as possible, e.g. with a ruggedness index close to the average RIX number of the turbines. 
• Another problem is verification of power performance after wind farm construction, where the IEC 61400-12-1 specifies a procedure for power curve verification. For this, the manufacturer and wind farm operator agrees on test turbine and mast position, where the terrain is not too complex, and only applies data from a sector where measurement are not disturbed by wake effects. WAT can help with the IEC 61400-12-1 terrain assessments.

However, your application seems different. I am not sure that I understand what you mean by calibrating the wind speed, but you probably need a reliable wind signal for a wind farm in operation, perhaps with curtailments and other complicating factors. I do not think that there is a standard for this, and the solution may on the application. Things to consider: 

• Are there significant terrain effects? 
• Is it possible to estimate speedup effects by flow model or measurements?
• Should you avoid wake effects, e.g. by installing multiple reference masts for winds from different directions? 

[Windlinus]

Dear Morten,

Thank you very much for your precious suggestions!

I should have to fullfill both power curve verification and monitoring the performance of the plant after construction too.

I have selected a point which satisfy the following requirements:

1. Terrain with a RIX equal to the mean of RIX at Turbines locations;

2. Point in baricentric position respect to locations of the four wind farm's turbine;

3. Use of a single station installed at the same distance from the farest turbines.

In your opinion, taking into account that the farest and closest locations of turbines are respectevely 1400 m and 600 m from the point selected as wind farm meteo mast, is it allowable to use the same station also for IEC61400-12-1 procedure using as turbine test the closest one at a distance of 600 m? How much is the maximum distance between plant's test turbine and the meteo station to check power curve?

Thanks again, Lino

[Morten]

Hi Lino, 

The IEC61400-12-1 standard states that the ideal distance between the reference mast and the tested turbine is 2.5 times the rotor diameter, 2.5D. I believe this is a compromise between good correlation between the free wind at mast and turbine site and reasonably low effect of flow blockage by the operating turbine. The standard also specify the allowable range to be 2-4D, so unless your turbine is very big, 600m will be a little too far. 

Sorry for the delay, by mistake I did not subscribe to this topic.

Cheers, Morten 

[Windlinus]

Hello Morten,

thanks a lot for your kind reply.

May be i could succeed because the distance between the mast and the closest turbine is 557 m, with planned turbines having a rotor diameter equal to 155 m.

The IEC61400-12-1 procedure for power curve calibration is, in this case, applyable for only one of the four turbines.

I will see if the customer wishes to apply the IEC procedure for all four turbines of the plant, requesting the installation of a second dedicated station.

In your experience, can it be sufficient to limit the test to a representative turbine, if the plant is not very large?

Best, Lino

.

[Morten]

Hi Lino, 

I lack personal experience with this, but I assume that typical applications for the IEC61400-12-1 power curve test are

1. A turbine manufacturer needs to verify turbine performance in order to help customers predicting the production and economical viability of a wind energy project. These measurements are often made at a special test station in nearly flat terrain. 
2. A wind-farm developer and manufacturer agrees to verify the power-curve at a new wind farm and the manufacturer guarantees to compensate the developer if the tested turbine is seriously underperforming. I do not know how the parties agrees which turbine to use, but I assume that they want to avoid wake affects and too complex terrain, and it will be practical to test one representative turbine only. To avoid legal dispute, it is probably wise to make this contract long before wind farm construction and hire a neutral consultant for power-curve tests according to IEC standards.

[Windlinus]

Hi Morten,

thanks a lot again for your kind reply. It's all clear!

Best regards and have a nice evening,

Lino