Carrying out of measurements of wind potential
In the past few years, we have seen an increase in the involvement of serious investors in wind power. This is facilitated by the development of public incentives in many countries and the dynamic progress of technologies that are aimed at ensuring a high level of profitability of the wind energy sector.
But it is obvious that in wind energy, with its direct dependence on the wind potential, the utilization factor of the installed capacity (CURTD is the most important indicator of the efficiency in the electric power industry) is traditionally low, and usually is 20-40%.
To a large extent, this coefficient will depend on the correct choice of sites for the placement of wind power plants.
Thus, to calculate the economic efficiency of the project and make a decision on financing, the investor needs a preliminary calculation of economic indicators. Just making measurements of the wind parameters to determine the location of the most rational placement of the wind farm, and help to provide the most realistic forecast.
In all countries wishing to develop wind energy, complex studies of potential areas are conducted: the wind directions, its speed, as well as changes in temperature, humidity and air pressure are analyzed.
For a detailed assessment of the wind energy potential in a particular locality, representative long-term (at least one year) measurements are required. This task is met by the installation of meteorological measuring systems. At the mast, with a height of 60 – 150 meters, a number of measuring sensors are installed:
● wind speed (anemometers);
● wind direction (weather vanes);
● air temperature (thermometers);
● humidity (hygrometers);
● Atmospheric pressure (barometers);
● and other sensors for a particular facility (for example, heated sensors in cold climates).
All devices have a channel for continuously transmitting data to a single database, where special software processes the measurements.
Of course, the main object of the study is the wind speed, so at many altitudes the mast is installed by numerous anemometers. In this case, the correct choice of anemometers is important, because high accuracy and objectivity of the results of data collection is required.
In wind power, anemometers are used which, depending on the method of measurement and type, can be mechanical (cup or wing type of wind resistance) or ultrasonic (acoustic).
Cup anemometers have proven themselves as reliable and proven sensors, and in accordance with international standards are recognized as the most suitable for wind measurement. Cup anemometers are able to measure exclusively the horizontal component of the wind vector, it also serves to generate energy when running a wind turbine.
Vane anemometers, just like cups, measure the horizontal component of the wind, but they have a built-in weather vane. Despite the obvious advantage in using one device for measuring two quantities at the same time, the presence of a wind vane leads to rocking in the wind, which distorts the measured values. There are wing anemometers capable of measuring the vertical component of the wind.
Ultrasound anemometers, unlike cups, are able to determine, regardless of wind direction, all components of wind speed (wind vector). Ultrasound anemometers are rarely used for long-term measurements due to greater susceptibility of sensors, due to the increased complexity of the design.
In modern approaches to measuring the wind potential, in addition to mast meteorological stations, radar systems such as SODAR, using remote acoustic methods for measuring wind parameters, and systems of the LIDAR type, in which measurements are made by laser radiation, are used.
The SODAR (Sonic Detecting And Ranging) measuring system is a remote acoustic measurement method.
The characteristics of the “wind profile at different heights” are the most important characteristics that determine the height of the wind generator rotor and the set of components for a specific wind power plant.
As a rule, the best efficiency is achieved by taking into account the optimal height of the rotor of the wind generator, which helps to reduce the cost of investments and increase the planned profit.
With this method of measurement, focused sound pulses are emitted into the atmosphere. One part of the sound pulses is reflected by the atmosphere and comes back. Based on the measured time interval, during which the sound pulses are returned, as well as the frequency offset of the pulses, the wind speed and direction are calculated. Such a remote measuring system is mobile and can be installed in hard-to-reach places.
With the help of a three-dimensional measurement system, it becomes possible to determine not only the wind profile up to a height of 200 m, but also to determine the direction of the air currents.
The LIDAR (Light Detection And Ranging) measuring system is the solution in measuring the wind profile at high altitudes. With the help of laser radiation, it is possible to measure wind parameters up to a height of several hundred meters, not only up to the height of the rotor placement of the wind farm, but also to its upper blade level. Such measurements make it possible to avoid miscalculations when planning and calculating the efficiency of the installation.
This laser-optical method of measurement allows us to cover the entire site of the planned location of the installation and determine the existing turbulence.
Inaccuracies in the measurement of wind potential can have a huge impact on the generation of electricity, and as a result, on the return of invested funds. In comparison with the cost of building wind farms, the cost of monitoring wind is negligible. The use of a full wind monitoring complex will allow to give the best estimate of wind conditions and determine the suitability of the site for the subsequent construction of a wind farm.
The installation of modern wind generators at carefully researched sites allows today to invest confidently in wind energy.