Cut-in speed is the speed at which the windmill starts to generate power, rated speed is the speed at which it makes maximum power, shutdown speed is the speed above which the furling mechanism can't operate or has no more effect, which causes the machine the shut down (anything above rated speed is essentially wasted), finally survivable speed is the speed which will not cause damage to the machine.
If the wind speeds are increasing that's mixed news because you will make more power between cut-in and rated, but given that the top end will likely also increase and that wind power is v^3 the destructive force of that top-end you might lose the machine entirely, only a very small relative speed increase could make things go from survivable to catastrophic.
This is because all of these speeds given above are designed in to the system when it is conceived and the survivable wind speed is not something that you can easily modify once a machine has been built.
So mixed blessing, unless it is only in the mid-range and the top-end is unchanged.
Shutdown speed comes in two forms - steady speed, the speed at which the prop will be feathered, which typically comes with prevailing winds around the 65-75mph mark, and gust speed which is dealt with via brakes. Enough gusts will trigger a stop and feathering too.
When the odd one catches fire, it's failed to feather or brake correctly.
However, if you can count on increased wind speeds you can build equivalent power windmills with smaller sails. Thus increasing the number of them you can put per square mile while keeping them out of each other's vortices...
That depends greatly on the distribution of the speeds. If the baseline goes up then yes, you can do with smaller rotors. But if it is gusty or disturbs the laminar flow because vortices will carry further then it may very much upset existing wind power installations.
Spacing of machines is a pretty tricky balance and if the wind patterns start changing in unpredictable ways that will be a very hard thing to design for. You may end up playing it safe and under-powering the windfarm or go for maximum power generation and end up with a number of machines switched off (or worse case: damaged) for longer periods of time. Steady windspeed (narrow distribution) is the biggest single factor in wind installation efficiency.
That's why some of the earliest wind parks were set up where there was a constant source of wind with a relatively constant speed.
> Spacing of machines is a pretty tricky balance and if the wind patterns start changing in unpredictable ways that will be a very hard thing to design for.
It sounds like you do have confident experience of modern wind farm specification and design.
I read that wind turbines are commonly built now with relatively over sized blades because after decades of development designers have greater confidence in their gust survivability and control mechanisms, and larger blades raise cut in speeds making better use of the most expensive part - the generator.
With your experience in these matters, can you say what percentage of modern wind turbine installations have been seriously damaged by being under specified to unpredictable wind conditions ? And very roughly what level of increased damage we might be talking about here from potential change in wind patterns.
That is not necessarily true, it depends on the allowed degree of pitch and the shape of the first 1/3rd of the blade which tends to generate the torque required to get the machine going because it is generally coarser pitched than the rest of the blade.
Once it is running you can just about ignore that first 1/3rd or even the first 2/3rds of the blade, the bulk of the power is generated by the outer 1/3rd.
> what percentage of modern wind turbine installations have been seriously damaged by being under specified to unpredictable wind conditions ?
Very few turbines have seen damage from overspeed or direct wind damage to the nacelle or the tower, for now this is a non-issue but if there is a structural change in wind dynamics then for sure there will be a price to pay, either in terms of machines ending up shut down more frequently, longevity issues or breakdowns.
> And very roughly what level of increased damage we might be talking about here from potential change in wind patterns.
That all depends on the magnitude of the change.
Suffice to say that wind power is generally installed for 20-30 year life-span of the Turbines, after that they become un-economical to operate both due to increased maintenance costs, wear on the main structural components and the blades themselves (the bending stresses eventually weaken the blades) as well as technical developments making the more modern machines much more economical to operate than aging ones. So as long as the changes do not happen on a timescalle smaller than that the effects will likely be limited, if they happen (much) faster then there could be a real problem.
Gusty and turbulent airflow has a further detrimental effect on lifespan.
> > and larger blades raise cut in speeds
> That is not necessarily true, it depends on the allowed degree of pitch ...
I think you are correcting a different matter here. Blade diameter in practice dominates the amount of power a which turbine can be designed to generate at lower windspeeds, aerodynamic design choices have to work with whatever diameter is provided. Increasing diameter involves significant expense and the entire reason it is payed is to raise cut in / raise generation at lower speeds / increase capacity factor.
> Suffice to say that wind power is generally installed for 20-30 year life-span
Not in recent years. 15 year contracts for windfarms are the current norm. I've read this often while following industry news and it can be observed from querying the different times [1]
> after that they become un-economical to operate both due to increased maintenance costs
Its not known to be the case that they'll become uneconomical. It may just be more economical to upgrade them, there is uncertainty involved which is the manufacturers bet.
Its a great commercial advantage of wind farms (and solar) that they can be relatively quickly online and make a profit on investment in 15 years rather than seeking 30 or 40 or 50 year supply contracts as some competing technologies do because of higher construction costs.
I don't believe its a term in general use in the industry (of large wind turbines). Since "survivable" means "might survive" - that's not a very useful engineering target. Wind turbines have to be rated to reliably withstand specific gust speeds, so talk of certain speeds being "survivable" should be non-technical.
Afaik modern turbines are specified to reliably withstand an "extreme 50 year gust" estimated by their locales "Wind Class" [1] Some headroom is likely as with all large constuctions, building, bridges.. The matter of what stronger gust speeds might be survivable by the majority of installations is not specified.
It is surprising to me that windmills seem to have such a large structural headroom with this "50 year gust". Farms of windmills around me of 1000's of units have had zero collapses. When your business is offshore wind farms, why not remove all the headroom, make the structure far cheaper and lighter, and aim for say 25% of windmills to collapse around 30 years? The cheaper capital costs will surely pay for increased decommissioning costs of collapsed windmills and loss of production 30 years later after compounded cost of capital.
Heh, well maybe - adopt an Elon Musk development strategy : "Failure is an option here. If things are not failing, you are not innovating enough." it more than works for his projects, but if you're competing for policy support and you happen to get your 20 year gusts this year it looks really bad, even if a low percentage of turbines actually caught them from a bad direction and happen to need new blades.
Also with offshore windfarms, the big extra expense is in installing the towers and cabling. They are getting significant subsidy to be built for 15 year power purchase contracts, but once those towers and cables are built the farm can remain very valuable at the end of the contract, if refurbishment is required it could be remarkably cheap especially with a fleet of specialized ships to it carry out, some of which are already at work putting them up.
Did they call it something else? It's the concept that matters, not the exact phrasing. Every structure, windmill or otherwise, has a wind speed at which it will break apart, possibly even if not rotating. It seems important to know what that speed is.
It is a very important figure and it works its way into many of the design details of the turbine as well as the tower and the foundation, if it was called something else I'd like to know what it was called as well as what kind of role GP had in the industry.
The wind energy industry gives this sort of thing a lot of thought. I think it says more about the GPs exposure to particular literature and theory than it does about the industry as a whole, also, whatever companie(s) they worked for may have simply used different terminology, it would be interesting to know what term they did use rather than to extrapolate large and unsupported conclusions from a comment like this.
The problem with wind is it's uneven distribution across hours and days.
Because wind usually often weak and below rated speed, you need to build extra capacity to get enough electricity in normal days. When there is enough capacity, the price goes to zero or negative during days when windmills work close to rated speed, then increases dramatically when there is no wind. If wind power generates profits only when there is wind but not enough to saturate the demand, profitability suffers. Energy storage increases the price and is unsolved in large scale. Bigger smarter grids over large areas and solar compensate to some degree.
Am I the only one who thinks this is all good, in fact?
The push for extra capacity and small scale distributed energy storage increases redundancy / eliminates large single points of failure. Whereas the status quo is a huge power plant serving a city and when a blackout/brownout occurs, it's darkness and blinking lights and chaos all over.
Yeah it costs some money to get there. Cheapest isn't always the best.
Also, I feel like a large distributed network of smaller generators & storage solutions is going to foster innovation in a way that one huge power plant that stands for decades cannot.
> The push for extra capacity and small scale distributed energy storage increases redundancy / eliminates large single points of failure. Whereas the status quo is a huge power plant serving a city and when a blackout/brownout occurs, it's darkness and blinking lights and chaos all over.
Unfortunately most systems are "anti-islanding"; if they lose a link or go outside parameters, they shut down. A brownout is rarely because the nearest plant has gone down and more likely due to a transmission system fault.
The problem is, existing market mechanisms for power don't work well for this.
A wind operator will face a low energy price when wind is overproducing; but society needs wind to be significantly overprovisioned to avoid burning carbon.
> The push for extra capacity and small scale distributed energy storage
Storage is really hard. We don't know how to meaningfully do it yet. Maybe concentrated/thermal solar power will deliver it. Maybe power->gas->power will. Batteries are at best a small stopgap.
Further, the net result is that we have less grid stability, because we have variable loads and lots of non-dispatchable generation. The loading on transmission is fairly unpredictable, too.
> but society needs wind to be significantly overprovisioned to avoid burning carbon.
Should be "...overprovisioned in order to completely avoid burning any carbon relying on wind power alone"
> Storage is really hard. We don't know how to meaningfully do it yet.
This is plainly misunderstood. Storage can already be bought, currently costs between 165 and 305 $/MWh [1]. And the price reliably drops as there is more demand and development in it. There is no huge demand for storage yet. Long term storage can actually take the form of carbon neutral fuels and use existing thermelectric plants to generate when required. No "maybe" about that, its existing commercial tech.
If your main goal is to get a more distributed power grid, it's great.
If your main goal is to decarbonize our grid before climate change wrecks civilization, then anything that makes that more expensive is bad. We're way behind in that race already.
We're planning on building a number of new windmills today. So long as potential future increases in wind speed are taken into account in their construction, this would be a straight benefit.
Assuming those future wind increases materialize yes. But if they don't then you're going to end up with a less efficient set-up. Windmill efficiency is a notoriously hard problem and any kind of up front assumptions have immediate efficiency risks associated with them.
Nice to know I haven’t been imagining things! In 20 years of flying it’s really seemed to me like I’ve had way more high-surface-wind days (which I’ve arbitrarily defined as >20 kts) than when I started. It used to be a rarity and now it’s well over half the days of the year.
I know there’s a lot of local variation, but even with that in mind it’s been noticeable.
There was also a sci-fi movie I watched as a kid that is set in a post-apocalpytic earth in which a constant wind belt around the earth that people 'sail' to get around. Does anyone remember?
I understand the need for a study to quantify it, but I don't understand how the increase itself can even be called a finding ?
I thought it completely obvious that there is more energy in the global "climate system", so everything is amplified. When the sun heat is increased on two surfaces with different heat capacities and albedos, the temperature difference between them is increased, thus the pressure difference, thus the wind.
Not mysterious. This is perfectly in line with expected science.
Climate is a huge chaotic system, akin to how Jupiter's Great Red Spot persists as a chaotic phenomenon. It's impossible to predict in detail, but follows some general principles we can depend on, and the generalization 'wind speeds are increasing' is one of those principles.
As we increase the energy of the overall system (by heating it), the range of weather behavior grows more extreme and more chaotic. Pretty sure this has at least as good a claim on observed wind speeds increasing, as any ocean pattern.
So the range of behavior will expand (higher peak speeds) and the rapidity with which the weather can change will also expand (is expanding). That poses dangers but if you can capture and store the energy it also gives opportunities: the danger is simply that expanded storms will smash our civilization, but the opportunity is that sufficiently sturdy generating equipment can harvest a LOT of power in a big hurry. Our ability to expend energy (even in so catastrophic a way as thermonuclear war) is NOTHING to the power of heating climate. We only think it is a certain way because we're used to seeing it that way.
There effectively is no such thing as the 'thousand year' storm anymore. It becomes commonplace, and design has to take on challenges like the million or billion year storm… as calculated under last century's conditions. Because that's how chaos works: small increases in total energy can give rise to increasingly spectacular chaotic flows.
One thing about it, it's fairly likely that any particular extreme will blow over more quickly. It all becomes a challenge of 'survive what climate threw at you during this 48 or 72 hours' and it'll likely change very aggressively again, perhaps to something a lot more survivable. You prepare for weather events like they are 'shock and awe' military assaults, no matter where you are in the world, because that's how it increasingly is. Wind speed is only one part of it, but it's certainly a significant part for unprotected humans and human structures.
Although there may be more total energy in the atmosphere, the polar regions are warming faster than the tropics. This would seem to decrease the temperature gradient as a function of latitude and slow convection. It must be that average wind speeds are mainly determined by the vertical temperature gradient as a function of altitude?
> As we increase the energy of the overall system (by heating it), the range of weather behavior grows more extreme and more chaotic.
As I understand it, atmospheric water content is a huge factor. Greenhouse forcing from CO2/CH4 increases water content. And increased water content leads to increased greenhouse forcing.
Plus lots more heat energy available when some of that water condenses. Sort of like a steam engine.
Nothing we do directly compares. For instance, the waste heat from coal plants is insignificant compared to the energies in the atmosphere. Same with any other energy scales we can reach with our technology. The climate emergency is happening because we made a blanket to capture the energy of the sun on a planetary scale, not because we directly added heat to the atmosphere by burning stuff.
Studies are finding waste heat from thermo-electric plants may not be insignificant. In this study [1] "energy consumption" is a shorthand for all human heat emissions from combustion engines, industrial processes and thermo-electric plant generation / consumption, etc. A large portion of human heat release can be attributed to thermo-electric generation. Electricity consumption accounts for 18% of energy use, with generation around 30% efficient that means coal,gas and oil power stations account for somewhere around half of global fossil fuel burn. [2]
From: Nature - A new global gridded anthropogenic heat flux dataset with high spatial resolution and long-term time series (2019) [1]
> For example, Zhang et al.5 found that energy consumption could lead to increases in winter and autumn temperatures of up to 1 °C in the mid- and high latitudes across North America and Eurasia. Ichinose et al.1 found that the maximum anthropogenic heat flux (AHF) in central Tokyo, Japan, was as high as 1,590 W/m2 in winter, resulting in warming to a maximum of 2.5 °C. Moreover, anthropogenic heat can affect wind speed because it reduces the stability of the boundary layer and enhances vertical mixing. In view of the effects of anthropogenic heat on climate at local and continental scales and the increasing consumption of energy worldwide, the potential significance of anthropogenic heat as it relates to global climate change over a long-term period should be further studied using techniques such as global climate models.
There is a little bit of climate change feedback by getting more power from windmills, because that means, roughly speaking, we can shut down more carbon-spewing plants.
Compared to the amount of power in the weather system what we puny humans can do it insignificant. A typical wind turbine causes a slow-down behind it but that's only in the layer that windmill sits in. Given that the atmosphere's active airmass extends many 100's of time above the height of the highest windmills and windmills will only ever cover a very small fraction of the surface area of the planet their effect is negligible.
Yes. Anything we can do is a millionth of the size of the flowing climate, its temperatures and airmasses. It becomes a heck of a potential power source, but nothing we do with windmills is going to have the least effect on it.
I think even if we manage to make the best of the situation, weld still be economically worse off, because of all the harbour cities which will be reclaimed by the sea and all the lost land mass
it's not odd if you think about what that law is saying. The wind turbine extracts kinetic energy from the wind. If it could extract 100% of the kinetic energy, then the air would simply stop. So incoming air would "pile-up" after the turbine (since it has v=0).
Since that is impossible, the air must have some speed after crossing the turbine to make space for the incoming air. The details of that law are simply, how much can you slow it down?
I think the odd part is the weirdly specific integer ratio with large-ish numbers. You expect numbers like 1/2 and maybe 3/4 in fundamental laws, but 16/27 earns a double-take.
Global warming -> increased in wind speeds -> massive boom in windmill construction -> extracting energy out of the wind causes slower wind speeds -> Saves the planet from global warming.
Kind of thinking the same thing, I once did a back of the napkin estimate of the amount of energy entering the system just from global warming. Even if we could use it effectively it completely dwarfs the amount of energy we use globally. It really is astounding how little our current energy needs are in the grand scheme of things.
>>> Princeton University scholar Timothy Searchinger, one of the study's authors, says researchers expect wind speed to continue to increase, he says, which has multiple positive effects.
It is good news, because it means that the return on wind investments is a little better, rather than getting worse as climate change happens. That is, it's a (very small) means of negative feedback: as climate change happens, non-carbon intensive wind gets a little better instead of a little worse.
This is often repeated, and is incorrect. life cycle analysis of wind turbines suggests that the carbon and energy pay off is anywhere from 1/2 to 2 years, after which point, the turbine is a net win compared to fossil fuels sources. In this context, life cycle analysis includes all of the embedded energy used to manufacture and operate the wind turbine. See, for example, https://www.ourenergypolicy.org/wp-content/uploads/2014/06/t...
There is absolutely nothing wrong with putting up a renewable energy source using hydrocarbons if alternative sources of materials and transportation are not available.
If it were up to you then we'd all wait until renewable energy would be able to produce all of those goodies and move them around but then it would never happen in the first place.
This is called a transition. You could make the same arguments for electric vehicles and they'd be just as broken.
For those interested in actual analyses of the lifecycle emissions from various energy generation types, NREL has a fantastic review of the literature here:
While you’re numbers are wildly off base, that post represents a critical misunderstanding of what’s involved.
Using hydrocarbons to make stuff has zero direct impact on climate. CO2 requires carbon to end up in the air not turbines.
PS: Global annual electricity demand is ~21,000TWh. 25% of that is 5,250 TWh. A 5 MW turbine at 40% average output produces 5 * 0.4 * 24 * 365 = 17,520 MWh so you want 300,000 of them.
I was referring to his comment ‘The wind turbine hydrocarbon based lubricants industry is fast growing.’ Talking about this as if it was a significant issue is completely failing to understand what’s involved.
Anyway, it depends on what you’re doing, if your for example using coal to add carbon to iron to make steal the it ends up in the steel. If you’re burning it to make heat then it ends up in the air.
The average CO2 intensity for the steel industry is 1.9 tons of CO2 per ton of steel produced. Taking into consideration the global steel production of more than 1,3 billion tons, the steel industry produces over two billion tons of CO2.
That’s ~5% of global emissions per year, though looking at a number per decade and comparing it to a number per year is rather big difference.
I think with steel you can guesstimate about 4-5kwh per kg. The energy has to come from somewhere. Right now it comes from coal and nat gas.
Reducing the carbon intensity of steel and also concrete production are things that being worked on. Companies in those industries aren't willing to be martyrs but unlike fossil fuel companies they aren't hostile either.
I'm suspicious of some of your numbers. For example, what does this line mean: "The rotor’s mass of such a turbine is ~20 metric tonnes. (About 75 million metric tonnes of oil)"
Where does the oil come in, and why is the ratio 3.25 million to one?
Sure, wind turbines are large structures that take energy to build. But they are mostly made from steel, one of the most recycled materials. Glass is equally well recyclable. And you make wind turbines once and they need little resources for the rest of their lifespan. Currently their lifespan is 20-25 years, but as the technology matures and new turbines stop being massive improvements over older designs that lifespan will go up. For comparison a coal plant lasts about 40-50 years, and is also a massive heap of steel and concrete.
500M tonnes of steel over 10 years is ~3% of the worldwide steel production, for some context.
It would be more helpful to know how much carbon an average turbine "costs" and how long an average turbine lasts and how much electricity it produces.
I think most people are aware it costs a lot of carbon to make anything, windmills being no exception.
You sound like you might know some of the specifics, so I'm hoping you could inform us further.
- Cut-in speed
- rated speed
- shutdown speed
- survivable speed
Cut-in speed is the speed at which the windmill starts to generate power, rated speed is the speed at which it makes maximum power, shutdown speed is the speed above which the furling mechanism can't operate or has no more effect, which causes the machine the shut down (anything above rated speed is essentially wasted), finally survivable speed is the speed which will not cause damage to the machine.
If the wind speeds are increasing that's mixed news because you will make more power between cut-in and rated, but given that the top end will likely also increase and that wind power is v^3 the destructive force of that top-end you might lose the machine entirely, only a very small relative speed increase could make things go from survivable to catastrophic.
This is because all of these speeds given above are designed in to the system when it is conceived and the survivable wind speed is not something that you can easily modify once a machine has been built.
So mixed blessing, unless it is only in the mid-range and the top-end is unchanged.