Dr. Lars Schernikau, energy economist and commodity trader, Switzerland/Singapore, https://www.linkedin.com/in/larsschernikau/
It is time to talk about “Capacity Factors”
In electricity generation, capacity factor, utilization, and load factor are not the same.
A lot of confusion exists in the press and certainly in politics, and even amongst “energy experts”, about using the term “capacity factor”. It may be excused, since the distinction made in this article became only relevant with the penetration of variable “renewable” energy, such as wind and solar, in our energy systems.
- Worldwide average solar natural capacity factor (CF) reaches about ~11-13%. Best locations in California, Australia, South Africa, Sahara may have above 25%, but are rare. (see www.globalsolaratlas.info, setting direct normal solar irradiance)
- Worldwide average wind natural capacity factors (CF) reach about ~21-24%. Best off-shore locations in Northern Europe may reach above 40%. Most of Asia and Africa have hardly any usable wind and the average CF would be below 15%, except for small areas on parts of the coasts of South Africa and Vietnam. (see www.globalwindatlas.info, setting mean power density)
Natural capacity factors in Europe tend to be higher for wind than for solar. Wind installations in Northern Europe may reach an average of over 30% (higher for more expensive offshore, lower onshore), but less than 15% in India and less than 8% in Indonesia. Average, and the emphasis is on average, annual solar PV capacity factors reach around ~10-11% in Germany, ~17% in Spain, ~25% in California, and may reach 14-19% in India, but they reach less than 15% in Indonesia’s populated areas. Carbajales-Dale et al. 2014 confirm higher capacity factors for wind than for solar; they estimate global average wind capacity factors to be around 21-24% and solar around 11-13% (see figure above).
The figure further below illustrates a two week period in May 2022 (when I wrote this chapter of our book on capacity factors), where the average wind capacity factor reached only ~5% for ALL German wind installations (on- and offshore).
To avoid confusion, I try to use “natural capacity factor” in my writing wherever possible
- The “natural capacity factor (CF)” is the % of the maximum possible output of the “power plant” (coal, gas, nuclear, solar, wind, hydro, etc), achieved under the natural conditions of the site, assuming no operational or technological failures or outages.
- I define “utilization” is the % of the power plant’s workable capacity used on average over the year, which is only reduced because of technological, operational, economical outages or curtailments… completely independent of the CF
- The “net load factor” – in my definition – is then the product of natural capacity factor x utilization
Thus, when we speak of the natural capacity factor, we are only referring to the nature-derived capacity factor, not the technological or operationally driven “utilization” (often referred to as uptime, plant load factor, or PLF). In other words, when technology fails, or a power plant is turned off on purpose, this will reduce the utilization but not the natural capacity factor.
As mentioned, the natural capacity factor is due to the site, not the solar PV installation. Thus, even a perfect PV material still needs to deal with natural capacity factors with an annual average of 10-25%, not counting for other losses from conditioning, transmission, balancing, or storing highly intermittent sources of electricity (Schernikau and Smith 2021).
The press has mentioned several times that coal or gas have capacity factors of 60% or less on average. This is at best misleading, more likely knowingly wrong for political reasons. However, such a number is not the nature-derived capacity factor; it is the utilization which declines with higher penetration of wind and solar, and contributes to electricity system cost increases.
Utilization never should and cannot be compared to natural capacity factors, they are very distinct. Conventional power plants have near 100% natural capacity factors, but their operational and technological utilization often falls significantly below 90%, also but not only because of the priority given to wind and solar in the system. Because of their high CF, the net-load factor is only slightly lower than utilization for a convention power plant.
Because utilization of wind and solar is often near 100%, their net-load factor is often only slightly lower than their natural capacity factor.
Needless to say, the natural capacity factor of wind and solar (even for hydro, because of natural river flows) cannot be predicted or guaranteed for any given time frame. The natural capacity factor can be estimated on an annual basis but still varies widely even annually (see Europe in 2021) and is very erratic, sometimes for days and weeks reaching near 0% for wind and solar, even in top locations.
Thus, natural capacity factors worldwide are a direct result of the location of the wind or solar installation; they do not in any way depend on and cannot be influenced by the technology employed. The last point is important… no technological advances can change the natural availability of wind, solar, or river flows and therefore influence the natural capacity factor for a given installation. Technology CAN and WILL improve how much usable electricity you get out of the natural input product (wind, solar, river flow, gas, coal, uranium, etc)… this is called conversion efficiency and their limits are discussed further below.
Since the easy locations have already been “used up”, one can expect average natural capacity factors to decline over time… contrary to what Net-Zero plans assume (see International Energy Agency (IEA), McKinsey & Company, or International Renewable Energy Agency (IRENA)).
- For a photovoltaic (PV) park, the natural capacity factor CF depends entirely on the intensity and duration of the sunlight, which is affected by seasonality and cloudiness, day and night, and the ability to maintain the PV panel surface’s transparency, e.g., dust in the Sahara or snow in winters.
- Wind farms’ natural capacity factors depend on the site’s wind speed distribution and the saturation speed of the wind turbine. The CF of a wind turbine is determined by the number of hours per year in which the wind farm operates at or above the saturation wind speed (Smith and Schernikau 2022). If the design wind saturation speed is set low, e.g., 4-5 m/s, the wind farm produces little energy, even for high capacity factors. Typically, wind saturation speeds are 12-15 m/s.
It now becomes obvious why the installed capacity needs to be much larger for wind and solar than for dispatchable power such as nuclear, coal, gas, or hydro. This significant relative increase in energy generation capacity to produce the same available, but unpredictable, energy output is coupled with a significantly higher raw material input and energy input factor for variable “renewable” energy which must be offset from any fuel savings.
#Germany is a good example: Total installed power capacity more than doubled in the past 20 years, essentially all consisting of wind and solar (see figure below)
- Wind and solar installed capacity is now above 125GW, more than 150% higher than peak power demand in Germany of around 80GW
- Germany’ conventional installed power capacity consisting of coal, gas, and nuclear still barely matches peak power demand
- With all this capacity addition in Germany, wind and solar made up less than 30% of total electricity generation in 2021 and about 5% of total energy consumption
The low natural capacity factor of wind and solar installations – without any doubt – is one of the key reasons for their low net-energy efficiency (https://dx.doi.org/10.2139/ssrn.4000800).
On Conversion Efficiency
Below figure summarizes energy conversion efficiencies for wind and solar and the laws they follow. Conversion efficiency measures the ratio between the useful output of an energy conversion machine and the input, in energy terms, thus after accounting for capacity factor.
For more Details please see our book “The Unpopular Truth… about Electricity and the future of Energy” (on Amazon)… or www.unpopular-truth.com
This article can also be accessed at
The other issue is the diversion of capital to wind and solar deterring construction of nuclear, gas, or coal power. No ons seems to have worked out a way to charge weather dependent sources, wind, solar, and hydro for the required backup.
‘No on[e] seems to have worked out a way to charge weather dependent sources, wind, solar, and hydro for the required backup.’
It would be straightforward if all supply (quantity and price) had to be bid in to the the day ahead market to be dispatched AND all suppliers were held responsible for non-performance by having to purchase energy in the real time market. In other words, no subsidies, just like competing against like.
That’s pretty much the same idea I came up for leveling the playing field between non-dispatchable and dispatchable generation. This would strongly encourage PV farms and wind farms to have some sort of local energy storage as well as investing in peaking plants.
It would also make sense for the market to be designed to match need, so that there would be bids for baseload energy (eg, bids to supply x units for a given y hours – y would likely be in the 8-24 range maybe even many days), separately from the usual minutes-ahead bids.
That’s how it worked before ‘renewable’ energy. Base load nuclear and coal plants would bid low in the auction to ensure they were dispatched 24/7, since they would likely receive the higher clearing price awarded to the ‘marginal’ generator for each hour. Unfortunately, renewables basically undermined the economics of these base load units because of politically driven subsidies and mandates that the former be dispatched whenever available but not penalized when not available.
Presumably the cost pass-through provisions in contracts, where the rate payers have to pay for spot market energy when wind/solar is not capable should encourage some construction of spot market resources but cannot guarantee the needed capacity. A person needs to figure out the needed margin and then finance dispatchable sources only to supply that margin. But of course the problem is the needed margin might be 100%.
Wyoming imposes a $1/MWhr wind energy tax on energy exported out of state, but this is meant only to replace some lost mineral severance tax when wind replaces coal and is a pittance anyway. No one is contemplating how to finance dispatchable backup because they don’t understand the need.
Our PSC appears to believe that we can run a reliable grid with 80% wind/solar penetration while simultaneously believing they should never allow the construction again of any plant that releases CO2.
Command economies with administered prices are something of a multi-layered lie. As the real costs are impossible to determine, given subsidies and purchase requirements, it will never go well.
Cost pass-through provisions only punish the consumer. Unreliables need to be held to the delivery price, regardless of the cost they incur because of a sudden high-pressure dome coming in or a 3-day cloud cover.
Couldnt agree more. We have covered this in http://www.unpopular-truth.com
“The nameplate farce”:
There should be financial penalties for wind and solar power plants inability to deliver at least 90% of their permitted nameplate ratings on an ANNUAL basis, like their backup competitors of coal, natural gas, and nuclear power plants that provide continuous uninterruptable electricity.
Subsidies for wind and solar power plants are based on “nameplate ratings”, thus they should be penalized when they cannot deliver what they have been permitted for.
Practically every windmill or solar panel requires a backup from coal, natural gas, or nuclear, thus understanding electricity generation’s true cost is paramount to choosing and prioritizing our future electricity generating systems.
I would delete “practically.”
When designing for renewable generation you need to account for worst case (those 2 weeks in April/May) when the capacity dropped to 5% avg. You would need a system that contains 20 times the amount of capacity needed to ensure 100% availability to meet demand. But that average is just that, average, with periods of almost 10% capacity followed by periods of zero% capacity and during those hours of zero% capacity even 100 times capacity produces NIL so Battery Back-up is necessary.
Batteries capable of meeting demand for hours and able to recharge as quickly.
You not only need sufficient battery back-up to fill in the daily energy dearth but sufficient overcapacity to ensure your battery is fully recharged for tomorrow’s weather induced inadequacy
You don’t need batteries because thermal plant backup is less costly than batteries, and for grid reliability considerations is needed anyways…
But “They” want to eliminate any CO2 producing energy source (Zero Emissions by 2040) so traditional thermal is out and batteries will be required.
Well [channeling Burgess Meredith], they can ‘wish in one hand and crap in the other, and see which one gets filled first.
Just reading Schernikau (et al)’s ebook. What strikes me as a more important issue is the EROEI of renewables, which if implemented to the extent of zero carbon (to an EROEI of 2 to 4), would force our current civilization (which needs a minimum of 10 just to maintain what we have) back to pre-industrial standard of living! How can we in a sane frame of mind even be contemplating this as an option?
thanks… the concept of eROI is also discussed in our academic paper available at Elsevier’s SSRN https://dx.doi.org/10.2139/ssrn.4000800
if you like YouTube, here is a short summary from Asia’s Sage Talks: https://youtu.be/k_uBiHoIZIw
the book puts it all into perspective… happy to receive feedback, also if you find mistakes…
Indeed, ‘ ”Energy returned on invested”, EROI (often also called ERoEI), is the most important parameter as it describes the overall life-cycle efficiency of a power supply technique, independent from temporary economical fluctuations or politically motivated influence distorting the perception of the real proportions ‘.
Solar PV in Northern Europe (for instance) is a net energy sink.
These factors are highly optimistic. They exclude system requirements. They are determined on the basis of natural capacity factors not potential utilisation or net load factor in a dispatchable network that needs to operate reliably.
Take at look at how much has been invested in “renewables”, to produce a tiny fraction of global energy production. Now use that money to buy coal and that coal will produce a lot more energy than the “renewables” for a lot longer. At best “renewables” are a fuel replacement and that is how they should be evaluated- can they save enough fuel to justify their total system cost?
I have an off-grid power supply that supplies a daily load that ranges from 2kWh to 3kWh. The system operates at 37S and achieves net load factor of 3.8%. It has averaged 99.7% availability over more than 10 years now. In thermal coal of the day it cost 120 tonne. So embodies the equivalent of 1GWh thermal capacity.or 400MWh of electricity from efficient conversion.
So the solar battery averages 930kWh per year. For my system to return the energy it embodies in its purchase requires an operating life of 400MWh/930kWh.equals 430 years.
China has price control on its thermal coal production of CNY700/tonne. That is a huge subsidy for their manufacturing compared with global spot price for coal. It has enabled than to dominate energy intensive industries but also under values the energy embodied in the stuff they make.
“Renewables” are unsustainable because they actually take more energy to make than they can ever deliver. It is an illusion based on China subsidising coal and people not understanding power system requirements.
The Chinese price is $100/tonne which may look cheap against Appalachian coal, but very expensive against Powder River Basin.
Chinese domestic coal qualities do vary enormously between about 3,500kcal/kg (6,300Btu/lb) to over 6,000kcal/kg.
I think the vast majority of people have no idea what any of these terms mean. Many have no inkling that a huge wind turbine reaching over 200m has any limit to what power it can produce. So just adding more terms, eventhough they provide more precision to the discussion, will not generally make clear the deficiencies of so-called renewables to those for whom it must be made clear. At least must be made clear if we are ever to reach sensible decisions on policy and use of resources.
However, on those few instances where I have had a discussion on these points it has been frustrating to not be able to explain that the CF of a wind turbine will never reach more than, say, 15% in August is not a valid comparison with the 60%-90% CF of a coal fired plant. For coal plants in North America a 60% CF is general forced upon them by the cock-eyed energy auction practices or curtailment for purposes of making room on networks for wind/solar at their peak periods. A 90% CF is generally for reasons of plant turn-around, i.e. a couple of weeks time to do routine/scheduled maintenance on a tuurbine and boiler.
Right now in South Africa coal-plants are achieving CFs (or utilization in the spirit of this essay) of 60% or maybe less because of failure to perform regular turn-arounds, thefts of fuel and material, and sabotage — no way to run a utility.
From memory (about 20 years since I last was involved with Eskom) the average utilisation was not a whole lot higher in better days – simply because of the diurnal and seasonal variation of demand, and despite the baseload from aluminium smelting. Perhaps the difference now is that peak demands go unmet and stations are offline with frequent breakdowns due to inadequate maintenance.
Maybe a good time to wudabout fossil fuel “capacity factors”. Every new well, every new mine, is now less prospective than the last. This was masked by amazing commercial tech breakthroughs for years, but those days are over. The numbers simply don’t work anymore. 46 DS all you like, but in the juiciest shale oil play in the world, the Permian, the PDP SEC oil reserves now being booked will not be fully replaced this time next year. Why? Because, now that the drilled, uncompleted inventory left over from the pandemic is being eaten up, the boring old geological and petroleum engineering/economic realities have finally hit home. And since the Permian is the leading edge of CONUS oil production, we will effectively have CONUS Peak Oil starting next year.
Yes, no doubt the best green sites have already been spotted and/or developed. But green tech is on the upswing, and the sites, unlike oil and gas fields, do not have a resource that depletes.
Unless nuc resurges – along with enough long term storage that the locals agree to steward for tens of thousands of generations – your fossil fuels will only last an eyeblink in geologic time. After that, what else besides renewables will be available? Maybe we should actually plan ahead for a change.
“But green tech is on the upswing”
Where ? Link ?
“Where ? Link ?”
Dozens of ’em. But the ASME has no dog in the fight. In fact, they are the antitheses of the ideological poodles paraded here. And since many petroleum engineers are retrained mechanical engineers, they are a respected part of my cohort.
To see what an ideological poodle looks like BOB, just stand in front of your mirror and open your eyes.
Wind & solar acolytes (you) are pure ideologists, deniers of the the basic implausible numerics of physical real-world realities and practicalities.
Part time weather dependent CO2 free “Green Tech” will never be able to power a modern society without reliable back-up capable of covering 100% of demand requirements for days at a time.
We simply cannot control the whims of weather.
Peak oil was supposedly reached back in early
1970’s 1980’s 1990’sbut proved to be folly.
Your predicted peak oil near year will prove to be equally fallacious as methods will always be produced to release more unproven reserves and new plays yet to be discovered.
“Peak oil was supposedly reached back in early 1970’s 1980’s 1990’s but proved to be folly.”
Might want to check out the links. Let’s make a bet. Pioneer Natural Resources is the savviest Permian player, and will release their SEC PDP oil reserves for 2022 soon. This time next year, let’s compare those from 2022 to 2023. Yes, I know I’m giving away the store, because any 2023 non drill bit CAPEX – acquisitions, increased non op buy ins, etc. – will artificially bias the comparison of interest your way. But I’m cool with that.
The bet? If they go up, I will declare in a post here, “Living with genital herpes has made me a better human being”. If not then you.
Bookmark the post and man up?
Why not add in some hypotheticals. Let’s add in all acreage that the Biden admin has not allowed to be drilled in the Gulf. Then add in all the acreage that the Biden admin has not allowed to be drilled on the North Slope. Then add in all the acreage not allowed to be drilled offshore California. All the acreage not allowed to be drilled offshore on the East Coast. yadda, yadda, yadda. Peak oil is a fantasy because peak oil is price dependent. Get the price up to a couple of hundred dollars per bbl and see how many reserves are added. I wonder how many P reserves Pioneer could add if the price per bbl jumped to $200/bbl?
Opening up new areas also potentially adds low cost reserves that were not previously permitted for access (e.g.ANWR), especially now that the hard work has been done on things like techniques for use in the Arctic.
All of your “acreage” is mostly worth free. It’s unprospective goat pasture. But I do agree that at least some of it should have been offered. That would show you how much of it would have gone begging, a la the current acreage that the producers are not developing. And since there is a historic “gamblers ruin” bias to overbid on new lease boni, the gubmint would have benefitted. Of course the “successful” bidders would have then – typically – tried for royalty reduction, and delays on drilling obligations, but Biden would then tell them to kick rocks. As he should.
“Peak oil is a fantasy because peak oil is price dependent.”
Half right. Peak Oil is price dependent. And OPEX dependent. And CAPEX dependent. And ultimate economic recovery dependent. And production schedule dependent. And diminishing well candidate quality dependent. And competitive drainage and frac hit dependent. And so on. In other words, Peak Oil is “dependent” on every input into every SEC reserves incremental economic analysis that is used to calculate different reserve classes. It’s how those reserves are calculated.
In practice, PDP – proved, developed, producing – is all that matters. The rest is the stuff of dreams.
This is why we are indeed into Permian – and thereby CONUS – Peak Oil, next year. The numbers from all of these inputs simply don’t work anymore. Candidate quality is inexorably down. Service costs are up and will correlate with product prices from now on. We petroleum engineers have utterly failed to economically solve the increasingly serious problem of frac hits. And there are less Ben Dover regulators – at least at the federal level – than ever.
So, yes, Peak Oil “is price dependent’. But it’s only a wishful “fantasy” inside of your eyeballs…
Lots of whiny deflections so far, but no one with the nads to take my bet. This channels 2016. Then, I made the same bet in many fora, on Trump being elected. I was dead wrong then, but since no one had the goodies to take my bet, I didn’t have to make the humiliating claim. BTW, as part of the bet, the loser will not weasel out of the post in other posts.
But so far, the expected All Hat and Belt Buckle non response….
What Capitalism does best is plan better than any commie apparatchik will ever do. Take your five year plans and sell them to the Germans. When the real money invests on the expectation of a commercially competitive RAROC it will be on the basis that fossil fuels are arguably no longer the best solution available. Anything else is just taking money off poor people.
“Green tech” is 100% DEPENDENT ON FOSSIL FUELS FOR ITS EXISTENCE.
“Green tech” REQUIRES 100% BACKUP since it is intermittent, unpredictable, unreliable, and inconsistent.
The US alone has HUNDREDS OF YEARS worth of coal to use even if we produced 100% of our electricity with it.
Nobody “needs” so-called “green tech,” which is not green (and is much more environmentally destructive than fossil fuels), CANNOT provide the energy needed by a modern civilization, and is a net energy sink as opposed to a source. In short, a non-solution to an imaginary “problem.”
No matter how many engineering explantations there are, nothing seems to penetrate the net zero true believers minds. And so far they have also gaslighted real world examples like Texas ERCOT Feb 2021. Will not end well in places like New England, UK, and Germany.
Good article. Good comment elsewhere here from Kevin Kilty that most folks have no idea what all this means.
I find it highly disturbing, from my free-market, free-enterprise orientation, to recognize that the current managed/regulated market in the U.S. is FAR WORSE than a public monopoly. Why? Because the regulators allow and ENCOURAGE power from wind and solar to be injected whenever it is being produced with no responsibility to provide anything at all when it is calm or dark. And they are getting paid a premium in the form of tax incentives or pricing schemes (e.g. NY value stack component called “environmental value” – a $0.031/kWh fixed amount) regardless of reliability. It pains me to say this, but better to go back to a single publicly accountable entity with full responsibility for cost control, reliable generation and delivery, and investment optimization. The politically captive regulators are the core problem, having been directed to act on the unsound attribution of climate harm from GHGs and the unsound fears of nuclear power.
And as we know from previous articles on this site the problem of limited supply of rare earth metal’s eventually will come into play. We will quickly reach “peak rare earth metal” and all the economic ramifications as renewable hardware and storage manufacturing inputs become more scarce.
Good point. Lithium batteries, for example, are notoriously hard to economically recycle. We’re already approaching CONUS Peak Oil (see comment with d.t.’s but no rebuts as of 10:22m CST https://wattsupwiththat.com/2022/12/27/it-is-time-to-talk-about-capacity-factors/#comment-3656459), so we need to extend peak rare earth as long as possible.
Roger that. Its a tough situation. I agree Bob . Especially when you factor in 3rd world transition into to first world fossil fuel demand. I too believe we will rapidly consume the remaining fuel in the ground and faster than some think.
In a way I do agree with you but not in the way you might define agree…
Any country that has access to FF sources within their borders should not be barred from using it. It probably shouldn’t be exported to places that have no domestic sources though. Places without it should embrace alternate energy sources and perhaps actively seek to develop them
Yeah, like nuclear?
We’ll reach “peak rare Earth metal” for real long before we hit “peak oil.”
It’s those German figures that stick in my mind:
Renews are good for 150% of peak demand yet that turns into 30% electricity and 5% of total energy
Could they, could anyone apart Boris Johnson, have organised a bigger fail if they tried?
Something is very badly wrong here.
very very wrong
yes, every time I look at those figures from my home country Gemrany, I get really scared about other countries, especially in Asia, trying to copy this… especially in countries that dont have any wind, and less sun than Spain
Why are they pushing for building still more wind and solar? Because the numbers add up to needing perhaps 600% capacity factor of peak demand; 150% is certainly not going to make it. Of course that still won’t account for the times actual capacity factor is 5% rather than the yearly average %, nor what to do with the 500% excessive generation on those rare times that the potential capacity factor becomes reality.
They could build 6,000% of demand, and it still wouldn’t be enough.
When the wind isn’t blowing, NONE of [insert overbuild percentage of demand here] are producing anything – you still essentially need 100% backup.
None of it makes sense until they invent the magic batteries.
A magnitude better performance at a magnitude lower cost.
As noted, the German renewable installs are equal to 200% of average grid load while reliable generation is less.
Here in Alberta, we 1.4x average grid load of installed reliable generation which is still just barely enough but soon won’t be. We have 4.7gw of wind and solar which produced nothing during the recent cold spell where we had grid alerts, because most new generation built is crap.
Every announcement of a new solar or wind project seems to be accompanied by a claim like “the new plant will have a capacity of X MW, enough to power YY thousand homes.” They should say enough to power the homes for 15% or 25% of the time. Solar can power 0 homes at night and wind 0 homes when the wind goes away. And, no, storage does not change this since the original claim is made based on dividing the nameplate capacity by the average home usage. The claim also ignores the issue of weather dependent wind and solar producing power in excess of demand at times and having to curtail production.
If you have to be dishonest in your representation of your product to sell it your product is crap.
According to the tallies, Australia has enough wind power to power three times the existing number of houses. But it managed to supply a good proportion of the houses on August the 23rd in 2021 between 2pm and 5pm. We can only be thankful that there was gas and coal generation for the rest of the time. And to power the houses, commercial building and industry (what’s left of it) as required rather than a couple of fleeting hours.
The underlined portions of these two statements from the article seem contradictory to me.
and . . .
The Betz limit is a feature of extracting energy from a fluid stream. The saturation speed of the turbine is an engineered limit.
Wind power is a function of the wind speed cubed. So the available power rises rapidly with wind speed. The Betz limit limits extraction to 16/27 of the available wind power. But the mechanical and electrical design limits the maximum power that can be extracted.
For example, a turbine sweeping 15,000m^2 (blades around 70m long) With windspeed of 10m/s would have 15MW of wind power in the swept stream. The Betz limit means that the maximum that can be extracted is 8.9MW. So lets say the unit has a combined mechanical and electrical efficiency of 60% to give rated power output of 5.3MW.
Now take the design design wind speed (saturation speed) is a little under 10m/s so the mechanical electrical rating was set at 5MW. These are expensive parts and you want to get the maximum average energy from them for a particular site.
When the wind gets up to 15m/s the swept stream power is now 50.6MW. However the machine can only able to extract 5MW. because that is the engineering design limit. The control system of the turbine would alter the pitch of the turbine to maintain the 5MW limit. As wind speed increases, there is a point when the blades have to be fully feathered and brakes applied to prevent the turbine from destroying itself.
It is not unusual for wind turbines to shut down when a front passes to avoid being damaged. So a lot of the wind energy cannot be extracted.
Just like everything else the Marxists are finagling the only time people will listen is when a failure affects them.
Inadequate engineering has gone into the ‘wake’ and diversion affects of large wind farms. Wind flow is from high pressure to areas of low pressure down wind from the turbines. The low pressure demand for air will not be denied.
The partial damming effect of the wind farm creates a deficit of air volume which results in the low pressure cell then drawing a portion of wind from other directions (wind diverted into an end run around the wind farm). Apparently, the effect has been measured up to 100km downwind of the ‘farm’.
This diminishing return on wind as net zero ‘advances’ will mean the number of windmills needed is likely to be several hundred percent more than ‘experts’ have calculated.
Good points, except for one. NO wind turbines are “needed.”
Since they require 100% backup and are 100% dependent on fossil fuels for their existence anyway, we’re better off WITHOUT ANY.
Overthinking it. Capacity factor = actual energy delivered/Nameplate Capacity.
Don’t care if the asset was not producing because of planned maintenance, unplanned maintenance or political interference.
You should care; political interference is cynically applied to make worse-than-useless “renewables” look much better than they are, by suppressing the use of fossil fuel and nuclear assets.
it makes a big difference wha the reason is for not producing power… because weather you cannot control, planned maintenance, curtailment, political interference, you can control… this is exactly the main point.
OK, I will grant you that curtailment/political interference is a big deal, including pricing mechanisms that keep base-load-designed facilities from actually running at base load because this not only directly reduces their CF but also increases planned and unplanned maintenance.
All facilities have planned and unplanned outages. When you start with a planned ~50% outage (as for solar) and then add to that only being able to run at nameplate ~15% of the time, capacity factor gets pretty grim.
Here’s a thought: To help enforce net zero, why not require that all the equipment used to generate the electricity has to be manufactured using only renewable energy.
The problem with using capacity factor is that, as an engineer, it is not a viable metric from which to design a power system. Capacity factor is an average. I cannot design a system based on an average. I need to know what the minimum power that is possible to be generated over the life of the project. If it’s solar and/or wind the answer is “zero”. I have to design a system that will generate the necessary power when there is no wind and no sun. And it cannot be done with renewables. Unless there is an economical way to store power, then fossil fuel power or nuclear power are here to stay.
125 is only 56% more than 80…
Peak solar output across the installed capacity is unlikely to be more than 70-75% of nominal capacity. Of course, it tends to occur at times where demand is not at a winter rush hour peak level. The result is that by the time you add in the need for some inertia providing generation, solar output is already having to be curtailed in Germany.
you are right, apologies, it is about 150% of peak power, not “150% higher than peak power”. apologies
Look at the numbers. Pathetically low percentages across all metrics for unreliables. Let’s not even discuss batteries…
The calculations for wind can be a little more nuanced. The efficiency curve of a turbine in terms of converting the energy in the wind to useful power looks some thing like this
Efficiency at low wind speeds just above cut in speed is quite low, and rises to a plateau at about 75% of the theoretical Betz limit (which is 16/27ths) as output approaches generator capacity. Once that is reached, efficiency drops off because the energy in the wind continues to increase with the cube of wind speed, while generator output is capped until it reduces approaching cut out speed (and there maybe hysteresis around cut out with generation not restarting until wind speeds have dropped somewhat below cut out speed to avoid too much stop-start in gusty conditions).
This has to be mapped against the probability distribution of wind speeds for a particular location in order to derive an energy optimised design. There is a very good discussion of the factors involved at this link
(The whole tutorial is thoroughly worth going through if you want a good understanding of wind energy and wind turbines)
A further sophistication is to consider likely revenues rather than merely wind output. High wind output is almost certain to see lower market prices, and the possibility of curtailment or negative revenues. There may be more value in trying to improve the output efficiency at lower wind speeds. All has to be balanced against the cost of alternative design choices.
As capacity increases to be sufficient to create surpluses above demand on windy days curtailment comes to dominate the economics. More hours of surplus, and bigger surpluses in hours that were previously small surpluses mean that curtailment starts rising quadratically, and then becoming almost linear as windless hours add little to useful output, while windy hours are already surplus.