Return to Answer

###Summary of the changes

###Global impacts As far as we can tell it's unlikely that there would be global effects at any plausible levels of global deployment (let's say, up to terawatts of mean power, but below tens of terawatts). But a single row of turbines can be enough to cause very local effects, and those could be positive or negative.

###What happens to the wind's energy?

###What are the energy changes, and where?

###A quick romp through the literature

###Consequences and conclusions

Summary of the changes

Global impacts

As far as we can tell it's unlikely that there would be global effects at any plausible levels of global deployment (let's say, up to terawatts of mean power, but below tens of terawatts). But a single row of turbines can be enough to cause very local effects, and those could be positive or negative.

What happens to the wind's energy?

What are the energy changes, and where?

A quick romp through the literature

Consequences and conclusions

The full picture is more complicated. Whether switching from fossil/nuclear to wind would change patterns of energy service demand, and energy efficiency, is an open question, so there are plenty of ripple effects. But, putting those aside to simplify things, just switching from fossil/nuclear to wind wouldn't create new sinks for the low-grade heat: lighting would carry on getting used at the same time and place as it does at the moment. What would happen is that energy would be extracted from the wind in new places: at turbines, rather than further downwind where the energy would be dissipated by friction. The other thing that would change is that there would no longer be additional sources of low-grade heat at all those fossil and nuclear power stations. Now, they're pretty intense sources of heat: nuclear or coal plants typically push out 150% - 200% as much energy as local heat, as they do electricity. So that's a signicant input of heat into a local weather system, which would no longer be there when they're turned off because the electricity is being supplied from wind instead.

On top of what I've written above, we've also got a bunch of modelling in the literature. Now, this is largely a bunfight between different assumptions: pick the answer you want, and tune your assumptions accordingly. However, these papers are written by people with different axes to grind, so you'll find a range of possible outcomes, and you can decide for yourself which assumptions are more or less likely.

Wang & Prinn looked at potential long-term global impacts of multi-terawatt-scale installations and found that massive onshore wind turbines might cause some warming over land (though less than the coal & gas plants they would replace), and massive onshore wind turbines might cause some global cooling. The modelling was done by assuming the turbine interactions would behave like a generic increase in surface roughness; the other key assumption is that the loss of detail from meso-scale modelling did not significantly impact the results.

The full picture is more complicated. Whether switching from fossil/nuclear to wind would change patterns of energy service demand, and energy efficiency, is an open question, so there are plenty of ripple effects. But, putting those aside to simplify things, just switching from fossil/nuclear to wind wouldn't create new sinks for the low-grade heat: lighting would carry on getting used at the same time and place as it does at the moment. What would happen is that energy would be extracted from the wind in new places: at turbines, rather than further downwind where the energy would be dissipated by friction. The other thing that would change is that there would no longer be additional sources of low-grade heat at all those fossil and nuclear power stations. Now, they're pretty intense sources of heat: nuclear or coal plants typically push out 150% - 200% as much energy as local heat, as they do electricity. So that's a significant input of heat into a local weather system, which would no longer be there when they're turned off because the electricity is being supplied from wind instead.

On top of what I've written above, we've also got a bunch of modelling in the literature. Now, this is largely an argument between different assumptions: pick the answer you want, and tune your assumptions accordingly. However, these papers are written by people with different underlying positions, so you'll find a range of possible outcomes, and you can decide for yourself which assumptions are more or less likely.

Wang & Prinn looked at potential long-term global impacts of multi-terawatt-scale installations and found that massive onshore wind turbines might cause some warming over land (though less than the coal & gas plants they would replace), and massive offshore wind turbines might cause some global cooling. The modelling was done by assuming the turbine interactions would behave like a generic increase in surface roughness; the other key assumption is that the loss of detail from meso-scale modelling did not significantly impact the results.

Rooijmans' Masters' thesis (Universiteit Utrecht, 2004) looked at the impact of a huge (9000km²) offshore wind farm on patterns of rainfall, using a mesoscale circulation model, and found that the distribution of precipitation could change, with more rain at sea, and less onshore. That modelled windfarm would be about four times the size of the largest envisaged offshore wind farm.

Distributions of heat affect weather and climate. So, deploying lots of wind turbines can change local patterns of evaporation and rainfall. They can also change patterns of frost: the turbines increase the turbulence in the flow, close to the ground, reducing frosts: there are farms that deploy turbines in order to harness that frost-prevention.

Rooijmans' Masters' thesis (Universiteit Utrecht, 2004) looked at the impact of a huge (9 000 km²) offshore wind farm on patterns of rainfall, using a mesoscale circulation model, and found that the distribution of precipitation could change, with more rain at sea, and less onshore. That modelled windfarm would be about four times the size of the largest envisaged offshore wind farm.

Distributions of heat affect weather and climate. So, deploying lots of wind turbines can change local patterns of evaporation and rainfall. They can also change patterns of frost: the turbines increase the turbulence in the flow, close to the ground, reducing frosts: there are farms that deploy turbines in order to harness that frost-prevention: you can even (HT scruss) buy wind machines dedicated to producing that turbulence in no-wind conditions (these wind machines, ironically, are typically powered by fossil fuels).