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(Created page with "thumb|A wind turbine Wind power is a possible option for renewable energy. Wind turbines convert wind to electricity. <small>A lot of people incorrectly call wind turbines "windmills". But in fact windmills are a much older technology, which use the wind to mill grains ''mechanically'' (no electricity involved).</small> ==Intermittency== Wind power is even more intermittent than solar. There can be weeks where the wind blows strong{...")
 
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[[File:wind-turbine1.jpg|thumb|A wind turbine]]
[[File:Wind Turbines to the south of Stowford Cross - geograph.org.uk - 410831.jpg|thumb|Onshore wind (wind turbines on land)]]
[[File:Offshore wind farms photographed at the Port of Noshiro, at sunset 20220728.jpg|thumb|Offshore wind (stronger and somewhat less intermittent, on average)]]
[[Category:Energy sources]]
 
Wind power is a possible option for renewable [[energy]].
Wind power is a possible option for renewable [[energy]].


Wind turbines convert wind to electricity.
Wind turbines convert wind to electricity.


<small>A lot of people incorrectly call wind turbines "windmills". But in fact windmills are a much older technology, which use the wind to mill grains ''mechanically'' (no electricity involved).</small>
{{minor|Side note: A lot of people incorrectly call wind turbines "windmills". But in fact windmills are a much older technology, which use the wind to mill grains ''mechanically'' (no electricity involved).}}
 
{{considerations}}__NOTOC__ <!-- The above table replaces ''most'' of the table of contents. -->


==Intermittency==
==Intermittency==
{{sum|Needs [[energy storage]]}}
Wind power is even more intermittent than [[solar]]. There can be months where the wind blows strongly, and months where it barely blows at all. Also, wind turbines can't function when the wind blows ''too'' hard.
{{p2|[suitable wind speeds]|
Most wind turbines can only generate power when wind speeds are between '''3.5 m/s''' and '''25 m/s'''.
<ref>DASH, Meteorologically Defined Limits to Reduction in the Variability of Outputs from a Coupled Wind Farm System in the Central US [Online], Available: http://dash.harvard.edu/bitstream/handle/1/10981611/Meteorologically%20defined%20limits%20to%20reduction%20in%20the%20variability%20of%20outputs%20from%20a%20coupled%20wind%20farm%20system%20in%20the%20Central%20US_1.pdf?sequence=6</ref>
{{x|Power is proportional to the cube of the wind speed.}}
When the wind speed is ''too high'', the wind turbine has to switch itself off completely{{x|maybe with the right innovations, it could just dissipate ''excess'' power instead of shutting off completely? {{rn}} }} to prevent damage to the electronics and gearbox. Without this feature, some wind turbines have even been known to catch fire.
}}
This intermittency usually gets "filled in" with [[natural gas]] power plants, but that's not good enough if we want to phase out [[fossil fuels]].
{{minor|Having multiple wind farms might ''somewhat'' reduce the intermittency. But in practice, this doesn't seem to help much.<ref>David JC McKay, Sustainable energy - without the hot air [Online], Available: http://www.inference.phy.cam.ac.uk/withouthotair/c26/page_187.shtml</ref>}}
Scaling up [[energy storage]] is already a challenge, even for solar which only needs about a day's worth of energy storage in general. Wind might need several weeks worth{{x|i.e. could easily need 40 times more battery capacity for the same ''average'' energy consumption rate}}.
Wind energy is probably best stored via [[hydrogen gas]], which doesn't have a ''fixed capacity'' the way batteries do. {{x|A battery can only store a fixed amount of energy at any given time. But hydrogen could be produced and stockpiled if necessary (as long as [[hydrogen gas/safety|safety]] concerns are addressed). Hydrogen production units (electrolyzers) still have a fixed ''power'' rating: There's a limit to how much hydrogen can be produced ''per unit of time''.}}
==Geography==
{{sum|Limitation}}


Wind power is even more intermittent than [[solar]]. There can be weeks where the wind blows strong{{x|although if it blows ''too'' strong, power also can't be generated - more on this later}}, and weeks where it barely blows at all.
The best places for wind turbines [[/Geography|aren't usually near where people live]]. In most cases, the distance is far enough that power lines wouldn't even be viable. {{qn}}


Having multiple wind farms might ''somewhat'' reduce the intermittency. But in practice, this doesn't seem to help much.
This might not be an issue if hydrogen (as described above) is the main solution for the [[energy storage]]. Instead of power lines, the wind turbines would generate [[hydrogen gas]] which would be [[transportation of hydrogen gas|transported]] and used for [[energy]] elsewhere.
<ref>David JC McKay, Sustainable energy - without the hot air [Online], Available: http://www.inference.phy.cam.ac.uk/withouthotair/c26/page_187.shtml</ref>


Scaling up [[energy storage]] is already a challenge, even for solar which usually only needs a day's worth of energy storage. Wind might need several weeks worth.
We'd need to estimate the full [[EROI]] of such a system, to make sure it's [[Term:viable|viable]].{{rn}}


Maybe wind power could be stored via [[green hydrogen]], which doesn't have a ''fixed capacity'' the way batteries do. {{x|A battery can only store a fixed amount of energy at any given time. But hydrogen could be produced and stockpiled if necessary (as long as [[hydrogen gas/safety|safety]] concerns are addressed). Hydrogen production units (electrolyzers) still have a fixed ''power'' rating: There's a limit to how much hydrogen can be produced ''per unit of time''.}} This still comes with other [[green hydrogen|challenges]].
==Rare earth magnets==
{{sum|Probably reasonable{{rn}} }}


==Suitable wind speeds==
To build a wind turbine{{x|specifically, the ''dynamo'' component which converts spinning motion into electricity}}requires either:
Most wind turbines can only generate power when wind speeds are between '''3.5 m/s''' and '''25 m/s'''.
* ''strong magnets'', made with rare earth metals{{qn}}
<ref>DASH, Meteorologically Defined Limits to Reduction in the Variability of Outputs from a Coupled Wind Farm System in the Central US [Online], Available: http://dash.harvard.edu/bitstream/handle/1/10981611/Meteorologically%20defined%20limits%20to%20reduction%20in%20the%20variability%20of%20outputs%20from%20a%20coupled%20wind%20farm%20system%20in%20the%20Central%20US_1.pdf?sequence=6</ref>
* or a complex gearbox, which requires maintenance{{qn| - labor}}and isn't suited for offshore wind.
{{x|Power is proportional to the cube of the wind speed.}} When the wind speed is ''too high'', the wind turbine has to switch itself off completely{{x|maybe with the right innovations, it could just dissipate ''excess'' power instead of shutting off completely? If so, we should write a page about it.}} to prevent damage.
 
{{pn|This section needs more research to determine which rare metals are needed, in what quantities, and whether there would be enough global [[mineral reserves]] to scale up wind power enough to replace fossil fuels or not.}}
<!-- TALK:
Consider citing the following study:
 
Increase in demand for critical materials under IEA Net-Zero Emission by 2050 scenario - Yanan Liang †* , René Kleijn † , Ester van der Voet † - † Institute of Environmental Sciences (CML), Leiden University, 2333 CC, Leiden, the Netherlands - Corresponding author: y.liang@cml.leidenuniv.nl
 
and cross-reference it with USGS data on rare-earth mineral reserves. Seems that even a "net zero by 2050" scenario would use only a very small fraction of mineral reserves - and that most of that is actually for electric car motors, not wind turbines.
-->
 
==Cement==
{{sum|Reasonable}}
 
The footing of a wind turbine requires a lot of concrete - a potential concern because cement production releases CO<sub>2</sub>. However, it turns out that the amount of CO<sub>2</sub> is '''not''' very significant:
 
<tab name="(see maths)">
{{dp
|<nowiki>concrete.density</nowiki>
|<nowiki>2400 kg/m^3</nowiki>
|<nowiki></nowiki>
|<nowiki>Dorf, Richard. Engineering Handbook. New York: CRC Press, 1996. "The density of normal concrete is 2400 kg/m^3 and the density of lightweight concrete is 1750 kg/m^3"</nowiki><br /><nowiki>
</nowiki><br /><nowiki>
McGraw-Hill Encyclopedia of Science and Technology. "Volume generally assumed for the density of hardened concrete is 150 lb/ft^3. (2400 kg/m^3)"</nowiki><br /><nowiki>
</nowiki><br /><nowiki>
Read more: https://hypertextbook.com/facts/1999/KatrinaJones.shtml</nowiki>
}}
{{dp
|<nowiki>wind.rq_concrete</nowiki>
|<nowiki>125 m^3 concrete.density / MW</nowiki>
|<nowiki>Concrete needed to build a wind turbine</nowiki>
|<nowiki>Concrete mass, per megawatt of capacity (peak power), not per megawatt of the average output.</nowiki><br /><nowiki>
</nowiki><br /><nowiki>
SUSTAINABLE CONCRETE FOR WIND TURBINE FOUNDATIONS www.bnl.gov › isd › documents </nowiki><br /><nowiki>
"Turbines in the 1 to 2 MW range typically use 130 to 240 m3 of concrete for the foundation"</nowiki>
}}
{{dp
|<nowiki>concrete.cement_by_mass</nowiki>
|<nowiki>15%</nowiki>
|<nowiki>How much of concrete is cement</nowiki>
|<nowiki>The rest is rocks & sand (aggregate material) and water. I don't think the rebar is counted here.</nowiki>
}}
{{dp
|<nowiki>cement.ghg_by_mass</nowiki>
|<nowiki>0.81 tonnes per ton</nowiki>
|<nowiki>CO2 emissions of cement</nowiki>
|<nowiki></nowiki>
}}
{{dp
|<nowiki>wind.capacity_factor</nowiki>
|<nowiki>35%</nowiki>
|<nowiki>Wind power: ratio: average output / peak power capacity</nowiki>
|<nowiki>"The capacity factor of a wind turbine is its average power output divided by its maximum power capability. On land, capacity factors range from 0.26 to 0.52. The average 2019 capacity factor for projects built between 2014 and 2018 was 41%. In the U.S., the fleetwide average capacity factor was 35%."</nowiki><br /><nowiki>
https://css.umich.edu/factsheets/wind-energy-factsheet</nowiki>
}}
{{dp
|<nowiki>gasoline.ghg_by_energy</nowiki>
|<nowiki>71.30 kg / million btu</nowiki>
|<nowiki>CO2 emissions of burning gasoline</nowiki>
|<nowiki>https://www.eia.gov/environment/emissions/co2_vol_mass.php</nowiki>
}}
{{calc
|<nowiki>wind.rq_concrete / wind.capacity_factor * concrete.cement_by_mass * cement.ghg_by_mass</nowiki>
|<nowiki>days gasoline.ghg_by_energy</nowiki>
}}
</tab>
 
A wind turbine's cement CO<sub>2</sub> footprint "pays itself off" in about 20 days, when you compare the wind power with the fossil fuels it would typically replace. {{x|Note that this equation compares [[Term:primary|primary]]-energy from wind (intermittent electricity) with [[Term:primary|primary]]-energy from gasoline (which is a sort of "average" fossil fuel in terms of carbon-per-energy; coal has a bit more carbon while natural gas has a bit less, but they're [[:File:fossil-fuels-ghg-by-energy.png|close enough]] for the purpose of this estimate). Additional energy losses in coal or natural gas power plants would mean that the wind turbine cement CO<sub>2</sub> pays itself off even sooner. }}
 
<small>This is pretty reasonable considering that a wind turbine's lifespan is about 20 ''years''.<ref>United States Environmental Protection Agency (EPA) - [https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P100IL8K.TXT Renewable Energy Fact Sheet: Wind Turbines - epa nepis]</ref></small>
 
==E.R.O.I.==
{{sum|Reasonable}}
[[Energy return on investment]] (EROI): About 19.
 
In other words: wind turbines, over their entire lifespan, produce about 19 times as much energy as it takes to make them.<ref>Hall, C., et al. (2013) EROI of different fuels and the implications for society. Energy Policy (64), 141-152.</ref> There would still need to be some [[fossil fuels]] invested into wind power to "get the ball rolling".
 
Maybe there are some other wind turbine designs that have a better EROI. {{rn}}
 
==Land use==
{{sum|Reasonable}}
Per unit of energy, wind needs far more [[land]] than solar{{x|in terms of the spacing between the wind turbines; not in terms of the footing size of the turbines}}. However, wind turbines can coexist with farm land{{x|whether crop land or pasture}}, without interfering with [[crop yields]]. Crop land alone might provide enough space for enough wind turbines to meet global energy demands:
{{dp
|<nowiki>wind.rq_land</nowiki>
|<nowiki>34.5 hectares/MW</nowiki>
|<nowiki>Land requirements of wind power</nowiki>
|<nowiki>Important:</nowiki><br /><nowiki>
- This is per megawatt capacity (peak), not per average output.</nowiki><br /><nowiki>
- Stats can vary tremendously based on how windy the location is.</nowiki><br /><nowiki>
- This stat is based on 172 different wind projects scattered throughout the USA.</nowiki><br /><nowiki>
- Consider variance: (34.5 +/- 22.4) hectares/MW</nowiki><br /><nowiki>
- This is the total land use, including the spacing between turbines in a wind farm.</nowiki><br /><nowiki>
- This is much bigger than [wind.rq_land_disturbed] which is just the land directly impacted by constructing the turbine itself.</nowiki><br /><nowiki>
</nowiki><br /><nowiki>
Citation:</nowiki><br /><nowiki>
Land-Use Requirements Of Modern Wind Power Plants In The United States</nowiki><br /><nowiki>
(Paul Denholm, Maureen Hand, Maddalena Jackson, and Sean Ong)</nowiki><br /><nowiki>
Page 16</nowiki>
}}
{{dp
|<nowiki>energy.tfc</nowiki>
|<nowiki>9937.70 Mtoe/year</nowiki>
|<nowiki>Global energy usage - total final consumption (TFC)</nowiki>
|<nowiki>Includes: fuel (80.7%) + electricity (19.3%) AFTER it is generated.</nowiki><br /><nowiki>
</nowiki><br /><nowiki>
Does not include the fuel used in generating electricity. See [energy.tes] for that.</nowiki><br /><nowiki>
</nowiki><br /><nowiki>
Citation: "Key World Energy Statistics 2020" IEA</nowiki><br /><nowiki>
- Page 47 - Simplified energy balance table - World energy balance, 2018</nowiki>
}}
{{dp
|<nowiki>wind.capacity_factor</nowiki>
|<nowiki>35%</nowiki>
|<nowiki>Wind power: ratio: average output / peak power capacity</nowiki>
|<nowiki>"The capacity factor of a wind turbine is its average power output divided by its maximum power capability. On land, capacity factors range from 0.26 to 0.52. The average 2019 capacity factor for projects built between 2014 and 2018 was 41%. In the U.S., the fleetwide average capacity factor was 35%."</nowiki><br /><nowiki>
https://css.umich.edu/factsheets/wind-energy-factsheet</nowiki>
}}
{{dp
|<nowiki>crop_land</nowiki>
|<nowiki>15000000 km^2</nowiki>
|<nowiki>Agricultural land used for growing crops - global total</nowiki>
|<nowiki>https://ourworldindata.org/land-use</nowiki>
}}
<tab name="(see maths)">
{{calc
|energy.tfc / wind.capacity_factor * wind.rq_land
|% crop_land
|
|
|{{p2|[discussion needed]|~ <code>wind.rq_land</code> is based in the status quo of wind projects, which are probably on land that's more windy than average. If wind turbines were to be on ''average'' crop land, the energy productivity may be less. Then again, there's also pasture and barren land where wind turbines could be placed too, and there's also offshore wind.{{pbr}}~ If all countries were developed, we'd need more than just <code>energy.tfc</code> - but then again, we don't need to get all our energy from wind; [[rooftop solar]] also has a lot of productive potential.}}
}}
</tab>
There should be '''no need''' to destroy natural habitats to build wind farms.
 
==Noise==
{{sum|{{rn}} }}
{{empty}}
 
==Bird deaths==
{{sum|{{rn}} }}
{{empty}}
 
==Recyclability==
{{sum|{{rn}} }}
{{empty}}


==References==
==References==
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<!-- TODO:
<!-- TALK:
sections to add:
sections to add maybe:
* viability: how much land is suited, how it can coexist with agriculture, how much energy can be captured per unit of land
* designs: wind turbine types, with their pros and cons and pictures
* designs: wind turbine types, with their pros and cons and pictures
* something about rare-earth magnets{{qn}}
-->
-->
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