Wind power

Onshore wind (wind turbines on land)

Offshore wind (stronger and somewhat less intermittent, on average)

Wind power is a possible option for renewable energy.

Wind turbines convert wind to electricity.

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).

Intermittency

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. [suitable wind speeds] Most wind turbines can only generate power when wind speeds are between 3.5 m/s and 25 m/s. (...)( 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(...)( maybe with the right innovations, it could just dissipate excess power instead of shutting off completely? ^{[RESEARCH needed]} ) 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.

Having multiple wind farms might somewhat reduce the intermittency. But in practice, this doesn't seem to help much.

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(...)( 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. (...)( 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 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

Limitation

The best places for wind turbines aren't usually near where people live. In most cases, the distance is far enough that power lines wouldn't even be viable. ^{[QUANTIFICATION needed]}

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 transported and used for energy elsewhere.

We'd need to estimate the full EROI of such a system, to make sure it's viable.^{[RESEARCH needed]}

Rare earth magnets

Probably reasonable^{[RESEARCH needed]}

To build a wind turbine(...)( specifically, the dynamo component which converts spinning motion into electricity )requires either:

• strong magnets, made with rare earth metals^{[QUANTIFICATION needed]}
• or a complex gearbox, which requires maintenance^{[QUANTIFICATION needed - labor]}and isn't suited for offshore wind.

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.

Cement

Reasonable

The footing of a wind turbine requires a lot of concrete - a potential concern because cement production releases CO₂. However, it turns out that the amount of CO₂ is not very significant:

(see maths)(see maths)

concrete.density

2400 kg/m^3

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"

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)"

Read more: https://hypertextbook.com/facts/1999/KatrinaJones.shtml

wind.rq_concrete

125 m^3 concrete.density / MW

Concrete needed to build a wind turbine

Concrete mass, per megawatt of capacity (peak power), not per megawatt of the average output.

SUSTAINABLE CONCRETE FOR WIND TURBINE FOUNDATIONS www.bnl.gov › isd › documents
"Turbines in the 1 to 2 MW range typically use 130 to 240 m3 of concrete for the foundation"

concrete.cement_by_mass

15%

How much of concrete is cement

The rest is rocks & sand (aggregate material) and water. I don't think the rebar is counted here.

cement.ghg_by_mass

0.81 tonnes per ton

CO2 emissions of cement

wind.capacity_factor

35%

Wind power: ratio: average output / peak power capacity

"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%."
https://css.umich.edu/factsheets/wind-energy-factsheet

gasoline.ghg_by_energy

71.30 kg / million btu

CO2 emissions of burning gasoline

https://www.eia.gov/environment/emissions/co2_vol_mass.php

wind.rq_concrete / wind.capacity_factor * concrete.cement_by_mass * cement.ghg_by_mass days gasoline.ghg_by_energy (calculation loading)

A wind turbine's cement CO₂ footprint "pays itself off" in about 20 days, when you compare the wind power with the fossil fuels it would typically replace. (...)( Note that this equation compares primary-energy from wind (intermittent electricity) with 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 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 CO₂ pays itself off even sooner. )

This is pretty reasonable considering that a wind turbine's lifespan is about 20 years.

E.R.O.I.

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. 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. ^{[RESEARCH needed]}

Land use

Reasonable

Per unit of energy, wind needs far more land than solar(...)( 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(...)( 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:

wind.rq_land

34.5 hectares/MW

Land requirements of wind power

Important:
- This is per megawatt capacity (peak), not per average output.
- Stats can vary tremendously based on how windy the location is.
- This stat is based on 172 different wind projects scattered throughout the USA.
- Consider variance: (34.5 +/- 22.4) hectares/MW
- This is the total land use, including the spacing between turbines in a wind farm.
- This is much bigger than [wind.rq_land_disturbed] which is just the land directly impacted by constructing the turbine itself.

Citation:
Land-Use Requirements Of Modern Wind Power Plants In The United States
(Paul Denholm, Maureen Hand, Maddalena Jackson, and Sean Ong)
Page 16

energy.tfc

9937.70 Mtoe/year

Global energy usage - total final consumption (TFC)

Includes: fuel (80.7%) + electricity (19.3%) AFTER it is generated.

Does not include the fuel used in generating electricity. See [energy.tes] for that.

Citation: "Key World Energy Statistics 2020" IEA
- Page 47 - Simplified energy balance table - World energy balance, 2018

wind.capacity_factor

35%

Wind power: ratio: average output / peak power capacity

"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%."
https://css.umich.edu/factsheets/wind-energy-factsheet

crop_land

15000000 km^2

Agricultural land used for growing crops - global total

https://ourworldindata.org/land-use

(see maths)(see maths)

energy.tfc / wind.capacity_factor * wind.rq_land % crop_land (calculation loading) [discussion needed]~ wind.rq_land 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. ~ If all countries were developed, we'd need more than just energy.tfc - but then again, we don't need to get all our energy from wind; rooftop solar also has a lot of productive potential.

There should be no need to destroy natural habitats to build wind farms.

Noise

^{[RESEARCH needed]}

This section has not been filled in yet.

Bird deaths

^{[RESEARCH needed]}

This section has not been filled in yet.

Recyclability

^{[RESEARCH needed]}

This section has not been filled in yet.