Wind turbine cleaning without working at height: why the drone replaces the rope
Spain closed 2024 with 22,486 wind turbines installed. Every one of them needs blade, tower and nacelle maintenance, and until recently that meant one thing: a person hanging off a rope tens of metres up.
Spain closed 2024 with 22,486 wind turbines installed, across 1,416 wind farms and 31,679 MW of capacity, according to the 2025 yearbook of the Spanish Wind Energy Association.1 Every one of those machines needs periodic maintenance of blades, tower and nacelle. And until very recently that meant one thing: a person hanging off a rope tens of metres above the ground.
Rope access, described plainly
Cleaning a wind turbine with ropes is slow by design. A technician certified for work at height reaches the nacelle, abseils down the blade or the tower and covers the surface section by section. When one side is done, they reposition and repeat. For a full clean covering blades, tower and nacelle, the job takes four to five days per machine.
The turbine is down for that time. Not because the contractor decides so, but because you cannot leave someone suspended from a blade with the rotor turning.
The real cost of that week is not just the specialist day rate. It is:
- The production the machine does not generate while it is down.
- The logistics of rigging and de-rigging the access, which at awkward sites can be half the job.
- The safety exposure inherent to any work at that height, with everything it brings in contractor coordination, health and safety paperwork and liability.
Why many sites go unwashed
Here is the part that rarely gets said. A significant share of the Spanish fleet has gone years without a proper clean, and it is not because nobody cares about the condition of the machines.
It is that once cleaning means taking a turbine offline for most of a week and rigging a work at height operation, it stops behaving like routine maintenance and starts behaving like a capital decision. It competes against other budget lines, it rises to a higher approval level and, very often, it slips to next season. And the one after that.
What the drone changes is not the quality of the clean. It is the arithmetic you have to defend to get it approved.
The alternative: cleaning from the ground
A cleaning drone works from the ground, fed by hose from the equipment below, with an accredited pilot who never leaves the site. Removing physical access to the machine has two direct consequences.
Nobody works at height. No operative climbs the turbine. The risk attached to rope access is not mitigated with more procedure: it leaves the process, because the process no longer contains it.
One working day per turbine, against four to five with rope access. Downtime goes from days to hours. That time reduction is what translates into 75-80 % lower cost and lost production compared with rope access: no extended day rates for personnel certified at height, and no machine standing idle for most of a week.
What does not change
It is worth being straight about the limits, because an O&M manager will find them anyway.
The machine still has to stop. During the intervention the turbine is held in maintenance position, with yaw and pitch controlled by the site. The difference is that the stop lasts one day.
Wind still decides. Drone work depends on a weather window, exactly as rope access does. The final date is confirmed the week before based on the forecast, and sometimes the calendar has to move.
Permits take time. Flying a drone around a wind farm requires aviation authorisation, and that takes around 3 weeks from confirmed order before anyone can fly. At Eolinet we handle that filing ourselves, but the lead time is real and has to be planned for.
What this means for an ageing fleet
With 22,486 machines installed in Spain and much of that fleet accumulating operating years, the question in front of every O&M team is not whether to clean. It is by what method, and at what operational and safety cost.
Rope access remains technically valid. But choosing it is now an explicit decision: accepting four to five days of downtime per machine and bringing work at height onto the site. With an alternative available, that decision has to be justified.
1 Asociación Empresarial Eólica, Anuario Eólico 2025 (year-end 2024 data, published June 2025). View the yearbook.