Getting more with less? Why repowering onshore wind farms does not always lead to more wind power generation -- a German case study

TL;DR

This study analyzes how regional land restrictions in Germany limit the benefits of repowering old wind turbines, showing that such restrictions can significantly reduce potential energy gains from repowering.

Contribution

It introduces a detailed, regionally differentiated methodology to assess onshore wind repowering potential considering land eligibility constraints.

Findings

Repowering could decrease capacity and energy yield by about 40%.

Half of existing turbines are in restricted areas due to new land use policies.

Distance to urban areas is the most influential exclusion criterion.

Abstract

The best wind locations are nowadays often occupied by old, less efficient and relatively small wind turbines. Many of them will soon reach the end of their operating lifetime, or lose financial support. Therefore, repowering comes to the fore. However, social acceptance and land use restrictions have been under constant change since the initial expansions, which makes less area available for new turbines, even on existing sites. For the example of Germany, this study assesses the repowering potential for onshore wind energy in high detail, on the basis of regionally differentiated land eligibility criteria. The results show that under the given regional criteria, repowering will decrease both operating capacity and annual energy yield by roughly 40\,\% compared to the status quo. This is because around half of the wind turbines are currently located in restricted areas, given newly enacted exclusion criteria. Sensitivity analyses on the exclusion criteria show that the minimum distance to discontinuous urban fabric is the most sensitive criterion in determining the number of turbines that can be repowered. As regulations on this can vary substantially across different regions, the location-specific methodology chosen here can assess the repowering potential more realistically than existing approaches.