The primary problem in building a wind farm is site selection. The site selection requirements for wind farms are very strict. Usually, the following points need to be considered:
(1) Choose a place with abundant wind resources, the annual average wind speed is above 6m/s, and the wind direction is stable, and measure data such as wind speed, wind direction and wind speed along the height, such as hourly wind speed and wind direction data. After measuring for more than one year, the wind speed frequency distribution and wind direction rose diagram are calculated to estimate the annual power generation of the wind turbines in the field and determine the layout of the wind power generators in the field. Wind resources directly affect the amount of wind power and thus the cost of electric power generation. Under the same conditions, a wind farm with an average annual wind speed of 6m/s has a power generation cost that is about 14% higher than that of a wind farm with a wind speed of 7.5m/s, and nearly 30% higher than that of a wind farm with a wind speed of 8m/s.
(2) Detailed assessment of the topography and obstacles in the field, the surface roughness, the distribution of trees and surrounding buildings in the field will affect the power generation of the wind farm;
Whether there are bird migration routes or bird migration destinations and the composition of power grids in the construction area.
(3) The wind farm should choose a place close to the road, which is convenient for the transportation and installation of wind power equipment, which can not only reduce the cost, but also facilitate the travel of the staff. At the same time, wind farms should also choose places close to the local power grid, which can facilitate access to the power grid and reduce costs.
(4) To measure and make statistics on other meteorological data affecting the power and safe and reliable operation of wind turbines in the field, such as temperature, atmospheric pressure, humidity, and the possibility and frequency of occurrence of typhoons, lightning, sandstorms, earthquakes, floods, landslides, etc., and the length of freezing time; For offshore wind power, seawater salt spray should be assessed.
(5) Wind turbines have development value only if their annual utilization time is higher than 2000h; they have good development value if their annual utilization time is higher than 2500h; and they are excellent wind farms if their annual utilization time is higher than 3000h.
(6) In today’s society, many things cannot be successfully completed without the support and cooperation of the government, and the construction of wind farms is particularly prominent in this regard. Government support will have a very important impact on the construction and development of wind farms.
(7) When the wind turbine is running, the noise from the gearbox and generator, as well as the noise generated by the air swept by the blades of the wind rotor, will cause dissatisfaction among residents. Therefore, the location of the wind farm should not be too close to the residential area.
It is necessary to point out that compared with onshore wind farms, the construction of offshore wind farms is more technically difficult, and the generated energy needs to be transmitted by laying submarine cables. The main advantages of offshore wind farms are that they do not occupy valuable land resources, are basically unaffected by topography, have higher wind speeds, more abundant wind energy resources, larger single-unit capacity of wind turbines, and higher annual utilization hours.
After the site selection is completed, it should be the design and construction of the wind farm. When designing the construction plan of a wind farm, the layout of the units within it should be considered based on the maximum power generation per unit cost. If the distance between the generator sets is too close, the upper wind turbines will have a larger wake effect on the lower wind turbines, resulting in a reduction in the power generation of the downwind wind turbines. At the same time, due to the combined action of turbulence and wake, wind turbines will be damaged prematurely and service life will be reduced. A large number of experimental studies have shown that in order to reduce the influence of the wake effect, when the wind turbines are arranged in an array on a flat ground, the distance (line spacing) between the front and rear of the wind turbine along the main wind and phoenix direction should be 8~10 times the diameter of the wind turbine rotor, the distance between the left and right of the wind turbine (column distance) should be 2 to 3 times the diameter of the wind turbine rotor.
In addition, when building a wind farm, the local topography should be considered. On the one hand, try to avoid areas such as mountains and forests that have a greater impact on wind speed. When the wind turbine is installed in a relatively flat area, with the installation site as the center, there should be no obvious obstacles in the circle with a radius of 0.5~1km (small wind turbines can be reduced to 0.4km), if there are hills and woods, it should be handled as shown in Figure 1. On the other hand, when the airflow passes through the platform or mountain, it forms a flow around the flow. When there is an acceleration zone and a pro-current, the wind turbine should be installed in the area with the highest wind speed, and remember not to install it in the pro-current zone.
35Figure 1 – Installation distance between wind turbine and hills and woods