The weather factor in portfolio diversification and asset management – a Vaisala study.
The year of 2015 has undoubtedly been one of challenge for many U.S. wind project operators. In terms of performance, the first quarter was one of the lowest on record for large portions of the country with some areas seeing wind speeds up to 50% below average.
Reports of low production both at individual projects and even across entire grid systems, such as California and Texas, captured a lot of attention and raised a great deal of concern for utilities and project owners, a number of whom reported expected shortfalls in quarterly and annual wind production.
Since then, the industry as a whole has turned much attention to the science of weather and climate to gain a better understanding of variability for setting more accurate performance expectations and managing anomalies across portfolios of variable generation assets.
Wind trends of Q1 and Q2 2015
The extreme low wind event experienced in the U.S. the first quarter of the year had a clear and direct impact on wind performance. The reductions in generation were most visible across grid systems with high wind penetration.
In the first quarter of the year, wind production in southern California fell to just 64% of 2014 levels, recovering somewhat in the second quarter to 80% of 2014 levels. Texas wind production was 93% of 2014 levels over the first half of the year. However, it is important to bear in mind that year-over-year nameplate wind capacity increased in Texas by 10%, meaning actual production was much lower in 2015 than in 2014 given the number of plants in operation.
The low wind anomaly of the first quarter was caused by a large blocking high pressure system over much of the West. This pushed the polar jet stream further north compared to last year, keeping storms and strong winds from passing over the western U.S., driving them instead through central Canada and several border states.
While the low wind event of Q1 severely hampered projects in many areas of North America, less pronounced deviations, such as those ranging from +/-20% of the long-term average, occur frequently. For example, in Europe’s first quarter of the year there were strong positive anomalies up to 20% of above normal across most Mediterranean countries, the United Kingdom, and Scandinavia. The following quarter Scandinavia and the United Kingdom remained above normal while winds were up to 5% below the long-term average in the Mediterranean.
Key weather patterns
