Significant multidecadal variability in German wind energy generation

Jan Wohland,Nour Eddine Omrani,Noel Keenlyside,Dirk Witthaut

doi:10.5194/wes-4-515-2019

Abstract

Abstract. Wind energy has seen large deployment and substantial cost reductions over the last decades. Further ambitious upscaling is urgently needed to keep the goals of the Paris Agreement within reach. While the variability in wind power generation poses a challenge to grid integration, much progress in quantifying, understanding and managing it has been made over the last years. Despite this progress, relevant modes of variability in energy generation have been overlooked. Based on long-term reanalyses of the 20th century, we demonstrate that multidecadal wind variability has significant impact on wind energy generation in Germany. These modes of variability can not be detected in modern reanalyses that are typically used for energy applications because modern reanalyses are too short (around 40 years of data). We show that energy generation over a 20-year wind park lifetime varies by around ±5 % and the summer-to-winter ratio varies by around ±15 %. Moreover, ERA-Interim-based annual and winter generations are biased high as the period 1979–2010 overlaps with a multidecadal maximum of wind energy generation. The induced variations in wind park lifetime revenues are on the order of 10 % with direct implications for profitability. Our results suggest rethinking energy system design as an ongoing and dynamic process. Revenues and seasonalities change on a multidecadal timescale, and so does the optimum energy system layout.

Highlights

We find ERA20C and coupled atmosphere–ocean 20th century reanalysis (CERA20C) to feature statistically highly significant trends
There is no significant trend in 20CR. The existence of these trends comes as no surprise given strong long-term trends in (C)ERA20C surface wind speeds over large parts of the world (Wohland et al, 2019)
This connection to a physical pattern of climate variability suggests that the peak is not a statistical artifact, despite its low statistical significance

Summary

Introduction

Onshore wind energy outperforms all other types of power generation in terms of levelized costs of electricity (IEA/IRENA, 2017). This economic development, in conjunction with the necessity to eliminate carbon emissions from the electricity sector in the decades (Schleussner et al, 2016; Rogelj et al, 2015), will most certainly lead to substantial investments in wind energy. The current German market design privileges renewables over conventional generators via a guaranteed feed-in, and wind park operators are compensated for congestion-related curtailment. This implies that there is no market incentive for planners to increase the systemfriendliness of their wind parks. In particular in cases where a trade-off has to be made between total energy generation and system-friendliness, planners and investors will likely prefer the former over the latter

Objectives

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Results

Conclusion