Germany had to curtail a quarter of offshore wind output in the first quarter

In the first three months of this year, around a quarter of the output from German offshore wind farms was curtailed due to transmission grid constraints. Around 3% of onshore wind output and just under 2% of solar output were also curtailed. The information was reported by the international news service Clean Energy Wire.  

The need to curtail electricity generation from renewable energy sources has been a long-standing problem in Germany. The reason is the slow expansion of the transmission grid, which is lagging behind the pace of construction, particularly of wind farms, which are generally located in northern Germany.

According to recently published information, the amount of electricity that German renewable energy sources could feed into the grid had to be significantly curtailed in the first quarter of this year. This was particularly true of offshore wind farms, whose output was curtailed by around a quarter.

"The bottleneck for offshore wind farms is the area between Lower Saxony and North Rhine-Westphalia," Clean Energy Wire reported, adding that the problems are unlikely to end before 2027, when a new transmission line in the area is scheduled to come into operation.

California faces a similar problem with solar

The slow expansion of transmission grids compared with the development of wind and solar farms is not an issue confined to Germany. For example, the US state of California, which ranks among the leading states in the country for renewable energy development (particularly solar power), has seen a sharp increase in curtailed electricity generation from these sources over the past two years.

The most significant curtailment in California occurs in spring, when solar generation is high and demand is relatively low after winter and before the start of summer, when electricity demand rises as air conditioning is used intensively. For this reason, curtailment mainly affects solar power plants. Solar accounted for 95% of curtailed generation last year and 94% in the first seven months of this year.

Curtailment is generally caused by one of two situations: either low electricity demand or, in most cases, limited transmission capacity. In the past, electricity grids were generally not designed to handle the sudden output fluctuations of intermittent sources.