The information on wind speeds and directions have been obtained from NASA Langley Research Center Atmospheric Science Data Center. It is based on average monthly wind conditions taken from satellite measurements taken over a ten year period between July 1983 and June 1993. The measurements are taken at approximately 40 mile intervals across the entire surface of the Earth.
In some countries and regions, there are more accurate databases available that use ground measuring data rather than satellite-based data. These are typically based on a much higher density of readings. However, these databases are not universally available. Ground measurements, where they exist, can also take into account topology factors such as hills, valleys and surface conditions. These are not taken into account with satellite measurements.
Despite these limitations, the NASA dataset has the benefit of covering the entire globe and is based over a longer time period than most other tests. It also samples wind speeds at multiple heights - 50 metres, 100 metres and 150 metres - which provides a greater overall view of atmospheric conditions which in itself allows the data to be fine tuned, and allow the wind speed at other heights to be estimated with a much greater level of accuracy. Consequently, it is widely regarded as being good enough for providing an initial evaluation to test the viability of a renewable energy system. More accurate (and costly) measurements, usually involving a full site survey, can then be carried out to confirm the findings of the initial assessment and to carry out any fine tuning that may be required.
The wind turbine performance estimator takes the average wind speed conditions and calculates the efficiency of the wind turbine selected. This is calculated by assessing the total amount of power available from the wind for a given wind-speed and using this information to work back to the actual power created based on the rotor size. There are a number of assumptions that have been made in order to provide these figures:
The 'Example Turbines' pull down list is based on a cross-section of different wind turbines using information supplied by the manufacturers. For example, to provide the information on a 2kW wind turbine, specification sheets for three different turbines were evaluated and the average data for all three were used to provide the data for the example turbine. Consequently, the power curve shown in the power generation chart will vary slightly from specific manufacturer derived figures.
There are various reasons why the power curve will vary between turbines from different manufacturers:
All renewable energy systems are site specific and only general information can be provided using online resources alone. The calculator is designed to provide an indication of the likely performance of a renewable energy system that has been installed in an optimal location by professionals. This calculator is not a substitute for a full site survey and can only be used as a rough indicator to the performance for a specific wind turbine.
The calculations also only take into account average wind speed - there is no analysis of the peaks and troughs of wind production. The amount of power available from the wind is a cube of the wind speed, so as the wind increases in speed, the amount of power available increases significantly faster. Conversely, when wind speed drops below average, the reduction in available power is comparatively small. You can see this in the power generation chart where the power generated by the turbine increases about ten-fold from 5m/s to 11m/s.
Consequently, if you have a wind pattern where the wind is blowing at its average rate for half the time, blowing 2m/s harder for 25% of the time and in a lull for the rest of the time, you will actually achieve higher energy generation levels than if the wind was a constant speed for the entire time.
The content of these calculators are for your general information and use only. Neither we or any third parties provide any warranty or guarantee as to the accuracy, performance, completeness or suitability of the information found or offered on this calculator for any particular purpose. You acknowledge that such information may contain inaccuracies or errors and we expressly exclude liability for any such inaccuracies or errors to the fullest extent permitted by law.
Your use of any information or materials on this website is entirely at your own risk, for which we shall not be liable. It shall be your own responsibility to ensure that any the information provided with this calculator meets your specific requirements.