Wind power

Wind turbines

Wind power is a possible option for renewable energy.

Wind turbines convert wind to electricity.

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

#Intermittency	Needs energy storage
#Geography	Major limitation
#Rare earth magnets	[RESEARCH needed]
#Cement	Not a significant problem
#EROI	Manageable
#Land use	Manageable
#Noise	[RESEARCH needed]
#Recyclability	[RESEARCH needed]

Intermittency

Wind power is even more intermittent than solar. There can be weeks where the wind blows strongly(...)( although if it blows too strongly, power also can't be generated - more on this later ), and weeks 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.

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.

Maybe wind energy could be stored via hydrogen, 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. ) This has its own challenges.

Geography

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 wind/hydrogen (as described above) is the main solution. 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

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

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

Compared to burning gasoline(...)( for the same amount of energy per unit of time ), a wind turbine's cement footprint "pays itself off" in just under 20 days.

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

EROI

Energy return on investment: 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

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 could provide enough space for wind turbines to meet global energy demands.^{[QUANTIFICATION needed on a separate page]}

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

Noise

This section has not been filled in yet.

Recyclability

This section has not been filled in yet.