The intermittent nature of wind and the speed restructions on wind turbines means that the load factor of wind farms is low to begin with (about 20 -25% for on-shore units and about 35-40% for off-shore units). But this is only when they are new. They seem to age very rapidly. This study of UK on-shore plants and Danish on-shore and off-shore plants shows that
- Wind farms age rapidly with on-shore plants declining in performance by about one-third in 10 years and off-shore plants declining by over 60% in 10 years, and
- The economic life of a wind farm is, at best, around 15 years and not the 25 years considered “normal” for a power plant
The Renewable Energy Foundation [1] today published a new study, The Performance of Wind Farms in the United Kingdom and Denmark,[2] showing that the economic life of onshore wind turbines is between 10 and 15 years, not the 20 to 25 years projected by the wind industry itself, and used for government projections.
The work has been conducted by one of the UK’s leading energy & environmental economists, Professor Gordon Hughes of the University of Edinburgh[3], and has been anonymously peer-reviewed. This groundbreaking study applies rigorous statistical analysis to years of actual wind farm performance data from wind farms in both the UK and in Denmark.
The full report is available here.
The Executive Summary states.
1. Onshore wind turbines represent a relatively mature technology, which ought to have achieved a satisfactory level of reliability in operation as plants age. Unfortunately, detailed analysis of the relationship between age and performance gives a rather different picture for both the United Kingdom and Denmark with a significant decline in the average load factor of onshore wind farms adjusted for wind availability as they get older. An even more dramatic decline is observed for offshore wind farms in Denmark, but this may be a reflection of the immaturity of the technology.
2. The study has used data on the monthly output of wind farms in the UK and Denmark reported under regulatory arrangements and schemes for subsidising renewable energy. Normalised age-performance curves have been estimated using standard statistical techniques which allow for differences between sites and over time in wind resources and other factors.
3. The normalised load factor for UK onshore wind farms declines from a peak of about 24% at age 1 to 15% at age 10 and 11% at age 15. The decline in the normalised load factor for Danish onshore wind farms is slower but still significant with a fall from a peak of 22% to 18% at age 15. On the other hand for offshore wind farms in Denmark the normalised load factor falls from 39% at age 0 to 15% at age 10. The reasons for the observed declines in normalised load factors cannot be fully assessed using the data available but outages due to mechanical breakdowns appear to be a contributory factor.
4. Analysis of site-specific performance reveals that the average normalised load factor of new UK onshore wind farms at age 1 (the peak year of operation) declined significantly from 2000 to 2011. In addition, larger wind farms have systematically worse performance than smaller wind farms. Adjusted for age and wind availability the overall performance of wind farms in the UK has deteriorated markedly since the beginning of the century.
5. These findings have important implications for policy towards wind generation in the UK. First, they suggest that the subsidy regime is extremely generous if investment in new wind farms is profitable despite the decline in performance due to age and over time. Second, meeting the UK Government’s targets for wind generation will require a much higher level of wind capacity – and, thus, capital investment – than current projections imply. Third, the structure of contracts offered to wind generators under the proposed reform of the electricity market should be modified since few wind farms will operate for more than 12–15 years.
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