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Turbines: how old is too old?

Some anti-wind campaigners claim that wind turbine performance more than halves after 15 years, whereas manufacturers assert that units can last almost twice as long (or more). So what’s the real story? PES went in search of some answers…

The Renewable Energy Foundation (REF) has made the surprising assertion that the performance of wind farms declines rapidly with age. A study carried out by Professor Gordon Hughes for the REF in 2012 suggested that:

“The rate of decline in performance is greatest for offshore installations in Denmark, with a fall from load factors of over 40% at ages 0 and 1 to less than 15% by at ages 9 and 10. Onshore installations in the UK show a more rapid rate of decline – 0.9 percentage points per year over the first 10 years of operation – than is the case for Denmark, though the normalised Danish performance curve lies below the UK curve for the first four years. For the UK the normalised load factor falls to just over 15% at age 10 and to 11% at age 15. With such low load factors it seems likely that many wind farms will be re-powered – i.e. the turbines will be replaced – once they reach the age of 10 or at most 15.”

To put this in everyday English, the study is saying that a 15 year old onshore wind farm will typically produce less than half its initial output of electricity.
Furthermore, the study states that: “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.”

Few people in the industry would demur from a conclusion that wind farms very gradually lose output but hardly any would accept the finding that electricity generation falls at anything like the rate stated above.


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