limitations : Energy production takes place according to the wind and not the demand. In the case of autonomous installations, it is, therefore, necessary to resort to storage or to double the facility by a diesel generator, which increases the cost. In the case of grid coupling, wind turbines can never represent a reduced percentage of conventional plants because they are the ones that ensure the stability of the frequency.
In addition to the many benefits it shares with other renewable sources of energy, the exploitation of wind energy has a number of distinct advantages.
- Wind energy is flexible and can be perfectly adapted to the capital available as well as the energy needs. There is, therefore, no superfluous investment. This modularity also makes it possible to keep most of the installation in operation when a part is defective.
- The running costs are quite limited given the high level of reliability and the relative simplicity of the technologies implemented.
- The cost price of a wind turbine will probably decrease in the coming years due to economies of scale that can be realized in their manufacture.
- Technically advanced, wind turbines are profitable in well-winded areas.
- The period of high productivity, often in winter with stronger winds, is the time of year when energy demand is highest.
- Problems related to small networks
- The issue of wind energy, pointed out by most specialists, is the inconstancy of the power supplied. When this power is less than the load capacity of the network, a complementary power source is required (for example, a diesel generator). When this energy exceeds the load capacity of the net, it lacks the intervention of a control system to maintain constant frequency and voltage. The complexity of solving these technical constraints has led most companies to neglect, until now, wind energy for small networks.
When the power supplied by the wind turbine is less than the load capacity of the system, the problem is solved quite easily by using a diesel generator that operates in parallel with the wind turbine. In this case, the diesel group must be able to react very quickly to compensate for variations in wind power.
On the other hand, when the power of the wind exceeds the power required by the network, several solutions have experimented.
- The derivation of the excess energy of the aerogenerator in a load shedding. Several experiments have been performed with a computer-controlled load shedding load, but the additional costs and the long reaction time of these systems have hindered their application.
- Storage of excess power from the wind turbine. Storage in batteries has often been tried, but its additional cost and critical technology for AC-DC-AC conversion make this approach unacceptable for networks of 100 to 1,000 kW. Means of flywheels also achieved the storage of power peaks due to gusts of wind. In combination with load shedding loads, this solution can be considered for small networks, but again, the additional costs and maintenance reduce the economic viability of these solutions.
- The instantaneous adaptation of the power output of the wind farm with the network load. The first approach to this solution is the subdivision of the wind farm’s capacity into a multitude of small wind turbines, which can be connected or disconnected to adapt as well as possible to the network load. This solution has been tried in different situations and proved its technical feasibility. Its disadvantage is its complexity and cost. In most cases, the kWh produced from small wind turbines is substantially more expensive than that provided by giant wind turbines. Also, this approach always leads to sudden fluctuations in frequency and voltage when switching on a new wind turbine. Its start draws power from the grid at a time when demand for energy is increasing. The second approach of this solution is the action on the aerodynamic efficiency of the aerogenerator. This can be achieved by changing the pitch of the propeller blades. For this solution to be possible, the control system must react quickly enough.
The effects on the landscape
The most controversial environmental issue associated with wind farms is their visual intrusion and the impact they have on the scene. Turbines are a striking vertical presence in the landscape, particularly in rural areas where the wind potential is often most significant. Evaluating this impact is often difficult because it is a subjective opinion. The design of the wind farms and the type of landscapes in which they are inserted are apparently of great importance. It should also be known that people’s perception of a wind farm is not only determined by the physical parameters of a landscape, but also by their attitude towards pollution problems. Some studies in Europe and the USA have shown that in the majority of people, the perception of wind energy as a clean and renewable source of energy exceeds the visual impact. However, the design of wind farms must be designed to reduce this visual effect. Factors to consider are the careful choice of location, color, and shape.
The noise emitted by wind turbines can be classified into two categories that the human ear perceives differently. First, there is the noise produced by the passage of air in the propeller, and secondly, there is the noise generated by the rotation of mechanical elements such as gearboxes and generators. The first sound is a rhythmic hiss. Although this is usually the loudest of the two noise categories when measured in decibels, it is the least disturbing and the least subject to complaints, as opposed to the sharp squeak of the second source. The impact of noise is easily minimized by judicious choice of wind turbine location relative to topographic features and proximity to dwellings. Experience shows that sound does is not excessive when homes are located more than 300 meters from the nearest turbine.