DYNA JOURNAL ENGINEERING

However, the world's wind turbine stock continues to grow. It is currently estimated that there is a world "population" of some 350,000 machines, of which 12,000 are already offshore. With the best onshore possibilities already covered and in search of better yields, the market is turning to offshore, which, with the aim of a transition to fully renewable generation, could require some 200,000 more machines in the medium term and, above all, looking for the largest possible sizes. The promoters of these farms have exerted strong pressure on manufacturers to reduce prices, improve guarantees and penalise delivery times, which has caused crises in several of them.
But there is also a hidden problem that has come to light in an article published in the Harvard Business Review under the title The Long-Term Costs of Wind Turbines: the costs involved in the maintenance of the wind turbine during its useful life are not properly taken into account when calculating the cost of the energy produced and, even less so, what is involved in the retirement and recycling of obsolete machines due to replacement or disappearance after that useful life, estimated at between 25 and 40 years. We are all paying in energy bills for what is needed to phase out nuclear power plants when it is decided to cease operation, but all praise for wind energy without taking into account that they will also come to an end and, whether it is maintenance or whether it is decided to replace or phase them out, there is a cost to be taken into account.
The authors compare the situation to the beginning and rise of the oil wells in the US, which number in the thousands, and for which no consideration was ever given to disposal and environmental conditioning when they were depleted. They believe that we risk the abandonment of thousands of obsolete wind turbines on the land and seascape in a future in which we have done without them. In addition, they have calculated that, if maintenance and decommissioning costs are taken into account, the race towards ever larger wind turbine sizes does not make sense and they set an optimal blade size between 70 and 80 m in length.
In conclusion, and considering in the offshore case that the distance to the coast has a significant influence on these costs, they calculate that, for example, in a wind farm 35 km from the coast, four turbines with 75 m blades are preferable to three turbines with 90 m blades, with both proposals generating the same amount of energy.