- Wind turbine installation
Obviously, the wind turbine should be installed as close as possible to the battery to reduce power losses in the cables. But the problem is that there may not be too much wind near where the battery is installed. Therefore, a compromise must be made.
In order to optimize the output power from the wind turbine, its installation height should be 2 times the height of its nearby buildings. According to experience, the distance from the wind turbine to the obstacle in the downwind direction should not be less than 10 times the height of the obstacle, and 20 times the height of the obstacle is the first choice, as shown in Figure 1.
Considering the effects of vegetation growth, a suitable site may not be suitable after 2 years. Land slopes can lead to increased wind speeds near that slope, so these advantages need to be taken advantage of. In general, gentle slopes increase wind speeds, but steep slopes create turbulence, as shown in Figure 2.
To determine whether a site is suitable for installing wind turbines, it is necessary to know the long-term wind volume of the site. However, the method of using wind measurement equipment takes too long, and the actual situation may require to know as soon as possible whether the location is suitable for setting up wind turbines, so local data should be used as much as possible. Wind speed data from nearby weather stations is very useful, but also go to your local airport, weather bureau, soil conservation department (they may have surface wind data). Once data is available for a few locations in the site area, reference data from any of these agencies can be used as a baseline to extrapolate local long-term wind data.
Directional wind speed data for selected locations are recorded over a short period of time, such as a month, and compared to weather station data over the same period. If the data measured in the field for the month exceeds the data recorded by the weather station for that month, then the wind resource in that area is almost certainly more than the location of the weather station at any time.
Note: Anemometers are not affected by wind direction or turbulence when measuring average wind speed, but wind turbines must be affected by these factors. Special attention should be paid to the vegetation, landscape features of the site to be sited, and any planned nearby structures, as these may be the culprits in blocking winds and causing turbulence.
While average wind speed is important in the siting of wind turbines, the quality of the wind is equally important. If the degree of wind fluctuation is large, it can be regarded as unsuitable for installing wind turbines as if there is no wind. The wind turbine should be set at a height where there is no turbulence. As a way to determine if turbulence is present, fly a kite with crepe paper (or use a helium-inflated balloon if local conditions do not permit kite flying, or if kite flying skills are not ideal). If the crepe paper sticks out straight from the line side, there may be no turbulence at this height, which will help determine the wind turbine placement height.
- Tower height
Another determinant of wind turbine siting is tower height. For economic reasons, the tower construction height should be as low as possible, but also the fact that the higher the height above the ground, the higher the wind speed is. After wind turbine selection and site selection, tower height becomes a key factor in determining the success of a wind power system.
As shown in Figure 3, although the wind speed at 12m is only 50% higher than that at 1.5m, the wind energy at 12m is 350% more than that at 1.5m. If the wind turbine runs beyond the cut-out speed, this excess energy is useless. The benefit of a tall tower is that it has a higher number of hours of rated wind per year than a low tower. High towers are difficult and costly to build, and require a larger area to clear the surrounding area for wiring and lifting towers to maintain wind turbines. Cost/benefit values also need to be considered when making decisions.
- Maintenance of wind turbines
The moving parts of wind turbines and generators require regular maintenance, especially to ensure that bearings and gearboxes are well lubricated. Before attempting to lower the wind turbine for maintenance, activate all mechanical or electrical braking systems. Note that self-excited alternators cannot be electrically braked. If the wind turbine cannot be stopped, do not attempt to start repairs, just wait for the wind to stop.
All nuts and bolts should be retightened (to manufacturer’s specifications), paying particular attention to the rotor assembly. Replaced nylon lock nuts cannot be reused. Check for transmission oil leaks. Replace any leaking oil seals and fill with oil specified by the manufacturer.
If there are cables on the tower, check whether they are twisted, pulled or broken, and the parts in question should be replaced. If the cable is tapped with the palm of the hand, it should oscillate; if the cable is loose, re-tighten it to the manufacturer’s specification. The AC motor runs at a fixed speed. Check whether the mechanical brake is effective. If the wind turbine runs beyond the design speed, it will cause the generator to heat up and burn out.
Wind turbine blades, especially the “leading edge” of wind turbine blades, should be regularly inspected to ensure there are no cracks or debris, as these can cause the wind turbine to lose balance. Some blades are tapered at the front end and should be replaced regularly. Any cracks and debris can cause unnecessary wear on the bearing and cause vibration, which can cause the nut to loosen.