Estimating Wind Speed – SJ1 Renewables Ltd

TECHNOLOGIES >> INSIGHTS >> ESTIMATING HEAD

Estimating Wind Speed

Nature of The Surrounding Nature

The nature of the surrounding landscape will have features which act to slow down the wind. This is effectively the friction of the land’s surface which varies according to the land coverage. Landscape features, from relatively smooth surfaces such as freshly mown grass, through to meadows, bushes, tress and dense woodland, will have the effect of slowing down the wind and in the case of the large objects such as trees, woodlands and houses, will affect the wind speed over considerable distances.

These effects are accounted for by applying correcting factors to the Annual Mean Wind Speed (AMWS). These factors are expressed as a ‘terrain category’, and apply equally to both natural and manmade land coverage. Considered over a distance 1 km from the turbine(s) Microgeneration Certification Scheme (MCS) provides five categories used to estimate how obstacles surrounding a site slow the wind down. The category used for this site is highlighted below:

MCS installation guidance good siting practice applies to all sites.

Find Annual Average

To find an estimated AMWS for your proposed site you will need a grid reference number. Click here for our simple guide on how to obtain this.

Database

The NOABL database provides a good idea of the wind at a site and gives us the annual mean wind speed.

This database requires the land range coordinates; these are the grid references that are formatted with two letters at the start followed by 6 numerical digits.

Write down your grid reference and space it so that you have the two letters and then the numbers are split into 2 even groups of digits.

Then leave out the number on the end of each block of numbers, shown in red in the below example:

The NOABL database gives the long term average and there a few things to think about in regards to results for your site:

This average (mean) speed is based on the 1km grid square that you fall into. This means there will be a difference in average speed within the grid square, i.e. if you are on a hill your wind speed will be higher, or alternatively if you are on a valley floor, it will be lower.
Factors are applied because wind will slow down as it passes over obstacles, whether they are nearby and over longer distances.
The wind speed is not measured at your site, it is calculated and could overestimate as easily as underestimate.

Results

FOR THE 1KM GRID SQUARE 379 502 (NY7902)

You can see a list of terrain categories and information on the nature of the surrounding site by following this link.

Variation from NOABL

An example of where the data may vary is in Hebenbridge, a land of steep valleys, the wind speed is given as 3.5 m/s, deemed too low for useful power. Wind measurements on the top of the hills were recorded as 5.2 m/s.

Speak to us today if you need any assistance estimating your wind speed.

NOABL Database Archive

This database was originally commissioned by BERR in 1996 and generated at the Hadley Center. This data was collected between 1975 and 1985 and was used to calculate the estimates. The original source for this database was taken down, however, there is an archived version with academic paper references. We used this data overlayed onto a map in 2017.

Get in touch with us

Let’s change the way we think about and use power; one embedded generator at a time!