In the past few years we have seen an increase in attraction of serious investors to the wind energy. This was made possible thanks to the development of government incentives in many countries and dynamic progress of the technology aimed at ensuring high level of profitability of wind power sector.
At the same time, it is clear that in wind energy, with its direct dependence on wind potential, the installed capacity utilization factor (ICUF is the key performance indicator in the electrical energy industry) is traditionally low, and is typically 20-40%.
This factor will largely depend on the proper selection of sites for wind power installations.
Thus, an investor needs a preliminary calculation of economic indicators in order to calculate economic efficiency of the project and decide whether to finance it or not. It is measurement of wind parameters with the aim to select the most rational site for a wind farm that will help to provide the most realistic forecast.
Integrated studies of potential sites are conducted in all the countries willing to develop the wind power: analysis of wind direction, its speed, as well as changes in temperature, humidity and air pressure.
A detailed assessment of wind energy potential in a certain area requires long (not less than one year) representative measurements. This task can be solved by installing meteorological measuring systems. A number of measuring sensors are installed on the mast with the height of 60-150 m:
● wind speed sensors (anemometers);
● wind direction sensors (vanes);
● air-temperature sensors (thermometers);
● humidity sensors (hygrometers);
● atmospheric pressure sensors (barometers);
● and other sensors for a certain object (e.g., heated sensors for cold weather).
All devices have a channel transmiting continuously received data into a single database, where special software processes the measurement results.
The main object of study is, of course, the wind speed, that is why numerous anemometers are installed at different heights of the mast. It is important to select the right anemometers because high accuracy and objectivity of the results of data collection are required.
Anemometers used in wind energy, depending on the method of measurement and type, can be mechanical (cup or vane type of wind resistance) or ultrasonic (acoustic).
Cup anemometers have proven themselves to be reliable and approved sensors, and in accordance with international standards, they are recognized as the most suitable for wind measurement. Cup anemometers can measure only the horizontal component of the wind vector, which is used to generate energy in the wind turbine.
Vane anemometers, as well as cup ones, measure the horizontal component of the wind, but they have a built-in vane. Despite the obvious advantage of using one device for measuring of two values, the presence of a weather vane leads to swinging in the wind, distorting the measured values. There are vane anemometers taht are capable of measuring the vertical component of the wind.
Ultrasonic anemometers, unlike cup ones, can measure all the components of wind speed (wind vector) regardless of wind direction. Ultrasonic anemometers are rarely used for long-term measurements because of the greater sensitivity of sensors, due to the increased complexity of the design.
Modern approaches to the measurement of wind potential, besides mast meteorological stations, make use of locator systems of the type SODAR, using remote acoustic method of measuring the wind parameters, and systems of the type LIDAR, where measurements are made using laser radiation.
The measuring system SODAR (Sonic Detecting And Ranging) represents a remote acoustic method of measuring.
Characteristics of the “wind profile at different heights” are the most important characteristics determining the elevation of the wind turbine rotor and a set of components for a particular wind power installation.
As a rule, the maximum efficiency is achieved by taking into account the optimal elevation of the wind turbine rotor, thereby reducing the cost of investment and increasing the target profit.
During this method of measuring, focused sound impulses are emitted into the atmosphere. One part of the sound impulse is reflected back by the atmosphere and returns. Based on the measured period of time, during which the sound impulses return, and the impulse frequency shift, wind speed and direction are calculated. This remote measuring system is mobile and can be installed in hard-to-reach places.
With the help of three-dimensional measurement system, it is possible to determine not only the wind profile up to a height of 200 m, but also to set the direction of the air currents.
The measuring system LIDAR (Light Detection And Ranging) is a solution in the measurement of the wind profile at high altitudes. By means of laser radiation it is possible to measure the wind parameters up to a height of several hundred meters, not only to the height of the wind turbine rotor, but also to the upper level of its blade. Such measurements allow to avoid mistakes in the planning and calculation of the efficiency of the installation.
This laser-optical measurement method allows to cover the whole area of the planned site for the installation and determine the existing turbulence.
Inaccurate measurements of wind potential could have a huge impact on the generation of electricity and, as a result, on the return on investments. Compared with the cost of the construction of wind turbines, the cost of wind monitoring is insignificant. The use of a full range of wind monitoring will allow to give the best estimate of the wind conditions and determine the suitability of the site for the future construction of a wind farm.
Installation of modern wind generators on the well-examined sites allows for confident investments in the wind energy.