# Wind Turbine Technology Trends
## 3 Discussion
### Onshore Wind Turbine Development
#### 3.1.5 Repowering a Wind Farm  
The capacity of about 38 GW of onshore wind farms in Europe will reach the end of their normal life of 25 years (i.e., 20 years) by 2025 [30]. When they reach the end of the useful life for which they have been granted an operating license, there are three options: extending the useful life, for which new operating licenses must be obtained, decommissioning, or restoring the capacity (repowering). Repowering a wind farm involves replacing old wind turbines with more powerful and efficient new models. Regeneration on average doubles wind farm capacity and triples electricity production. Repowering is particularly effective and important because the oldest (and least efficient) wind farms in Europe are located in places with the best wind conditions, as the first wind farms were built there. State-of-the-art turbines in these locations can produce much more electricity than the existing wind farms. According to the available data, some large repowering projects are already taking place. One such example is the Windplan Groen project in the Dutch province of Flevoland. In this area, there used to be 98 wind turbines with a total capacity of 168 MW. They are now being replaced by 90 new, more efficient wind turbines. This will increase the capacity of the wind farm to about 500 MW, enough to supply the entire province with electricity. Half of the wind turbines are built by Vestas, including 37 V162-6.2 MW EnVentus wind turbines and eight V126-3.45 MW turbines. The main features of the V162-6.2 turbine are: rotor diameter 162 m, swept area 20,612 m\({}^{2}\), hub height 166 m. Cut-in wind speed is 3 m/s and cut-out wind speed 25 m/s. The carbon footprint is 6.1 g CO2e/kWh and the recycling rate is 88%. At the same time, these are the most powerful turbines in the Netherlands [30]. The other turbines in the project will be supplied by Nordex and General Electric (GE). The wind farm in Malpica (Spain), underwent an even larger rebuild. The number of turbines decreased from 69 to 7, but the electricity production doubled [30]. Repowering can thus be a very effective measure. However, less than 10% of decommissioned wind turbines are currently being repowered. Slow and complex authorization processes and changing laws discourage operators. Instead, most onshore wind farms that reach 25 (or 20) years of operation receive a license to extend their operation. Another option is to stop operating wind farms, dismantle them, and recycle them. While concrete and steel can be easily recycled, the composites that make up the rotor blades pose a problem. This problem has been studied by [PERSON] et al. [31], [PERSON] et al. [32], and [PERSON] et al. [33]. It should be noted that 9.4 GW of capacity is expected to be decommissioned and retired in Europe over the next five years. Article 16 of the Renewable Energy Directive requires EU member states to issue permits for new renewable energy projects within 2 years and for repowering within 1 year (this does not take into account deadlines for completing environmental impact assessmentsor deadlines for resolving legal disputes). Unfortunately, most countries do not adhere to these deadlines. The procedure for issuing permits is too slow and complicated, and the reasons for this are mainly:  
* Regulations are complex. There are more and more spatial planning restrictions (e.g., minimum distances from residential buildings, height restrictions for buildings, etc.). Moreover, regulations differ not only from one Member State to another, but also between different regions within the same Member State. * Unnecessary bureaucracy. Procedures are slow because too many administrative bodies are involved at national, regional and local levels. This multiplies the number of applications utilities must make and the number of procedures that must be strictly followed, increasing costs to utilities and the time it takes to resolve problems.