Who owns the wind?
Wind is neither superfluous nor simply ‘there’. Nor is it merely moving air from which energy can be extracted at will.
Wind is generated by solar radiation, temperature differences and the resulting air-pressure gradients. It transports heat and water vapour across continents and oceans, drives weather processes and influences ocean waves and near-surface ocean currents.
Wind is the atmosphere’s transport system.
Anyone who extracts energy from the wind is therefore not merely using a supposedly unlimited resource. They are also interfering with a system that plays a major role in determining weather, the water cycle and climate.
Wind power extracts energy from the atmosphere
In the case of a single wind turbine, this interference is spatially limited. In large wind farms, however, the wake effects overlap. If numerous wind farms are constructed within the same prevailing wind corridors, the question of cumulative and large-scale effects inevitably arises.
Impact on water transport
Wind turbines are typically erected in locations where strong and persistent air currents prevail. A simplified model calculation for a Vestas V172-7.2 MW illustrates the potential scale of this impact.
Assumptions
- Rotor diameter: 172 m
- Rotor-swept area: approximately 23,200 m²
- Wind speed upstream of the turbine: 14 m/s
- Wind speed in the wake: 7 m/s
- Water vapour content of the air: 15 g/m³
The assumed difference in wind speed gives:
23,200 m² × 7 m/s = 162,400 m³/s
At 15 g of water vapour per cubic metre of air, this corresponds to a reduction in the horizontal moisture flux of:
162,400 m³/s × 15 g/m³ = 2,436 kg/s
Mathematically, this equates to:
- 146 tonnes per minute,
- 8,770 tonnes per hour,
- around 210,000 tonnes per day.
This amount of water does not disappear from the atmosphere. However, the calculation illustrates the order of magnitude by which the horizontal transport of moisture across the rotor-swept area is initially reduced.
The airflow is slowed, disturbed and partially diverted. Whether the moisture transport subsequently returns to its original level, where such compensation takes place and what consequences arise when the wake effects of many turbines overlap have by no means been conclusively established.
For a wind farm comprising 20 turbines, the calculated change in moisture flux already amounts to several million tonnes of water vapour per day.
A taboo in the energy debate?
There is intense debate about CO₂. By contrast, there is hardly any discussion of the extraction of kinetic energy from the atmosphere.
Yet the fundamental process is undisputed:
Energy extracted from an air current and converted into electricity is no longer available within that current as directed kinetic energy.
The question, therefore, is not whether wind turbines affect the atmosphere. They demonstrably do.
The crucial questions are:
- How far do the wake effects extend?
- How do large wind farms alter moisture transport?
- What happens when the effects of many wind farms overlap?
- Can this cause precipitation zones to shift?
- What are the consequences for evaporation, soil moisture and temperature?
- Is there a limit to the amount of energy that can be extracted from regional wind systems?
The fact that these important questions are neither widely discussed nor adequately investigated, despite the massive expansion of wind power, is problematic from both a scientific and an energy-policy perspective.
Wind turbines in Europe’s western wind belt
A large proportion of Europe’s wind turbines are located within the temperate Ferrel cell. It is precisely here that the prevailing westerly circulation transports moist Atlantic air across Europe.
Consequently, energy extraction is concentrated, of all places, within a circulation system that is crucial to the distribution of heat and moisture across Europe.
Copernicus identifies Europe as the fastest-warming continent. At the same time, a particularly large number of wind turbines have been erected across the continent.
This does not in itself prove a causal link. However, the spatial and temporal correlation provides sufficient reason to investigate the possible connection with an open mind.
- Where are the large-scale comparative analyses for Europe—one scenario including the expansion of wind power and one without it?
- Where are the long-term studies on moisture transport, evaporation, cloud formation and precipitation?
Until these questions have been answered convincingly, no one can seriously claim that the massive expansion of wind power has no impact on the climate.
Possible consequences: logical, not ideological
‘Renewable’ does not mean consequence-free
The term ‘renewable energy’ is physically misleading. Energy is neither generated nor renewed; it is converted.
In wind power generation, kinetic energy is extracted from a real air current. However, that air current already fulfils a natural function: it transports energy, heat and moisture.
The atmosphere continually generates new air currents. However, this does not mean that every localised and temporary extraction of energy is immediately compensated for without consequences.
A forest can regrow, yet it cannot be used indefinitely. Wind, too, is constantly replenished—but this does not mean that its use has no impact or consequences.
Possible consequences
Large-scale wind energy use can, in principle, contribute to the following changes:
- slowing and shortening the reach of air currents
- changes in horizontal moisture transport
- increased vertical mixing
- altered temperature and moisture profiles
- shifts in cloud and precipitation patterns
- changes in evaporation and soil moisture
- regional warming or cooling effects
Some of these effects have already been demonstrated through measurements and modelling. Their extent, intensity and cumulative significance remain subject to considerable debate.
This is no reason to sound the all-clear. It is a reason for much more intensive research..
Conclusion
Wind is not a free resource. It is an indispensable component of the climate system.
Wind turbines deliberately interfere with atmospheric flows by slowing them down and extracting kinetic energy from them. At the same time, they alter turbulence, mixing and the transport of heat and moisture.
The crucial question is therefore not merely:
How much electricity can we generate from wind?
But rather:
Are we entitled to extract energy from the atmosphere—and, if so, how much—without significantly altering its natural transport and balancing functions?
These questions were not adequately answered before the massive expansion of wind power began. Continuing to ignore them would not be an expression of responsible climate policy, but rather an extremely costly experiment involving a system on which weather, water and life directly depend.
