Wind Turbine Capacity: 50% is the New Normal

July 30, 2012


Anyone who hangs around in the comments section of sites covering wind energy knows one thing — clean energy haters love to talk about wind turbine capacity factor. In particular, they love to chant the now quite untrue claim that wind turbines have a capacity factor of 20-30%.

If you’re not familiar with capacity factor, it is how much electricity a power plant actually produces compared to how much it would produce if it operated at full nameplate capacity 100% of the time.

No power plant operates at 100% capacity factor. NREL’s new Transparent Cost Database shows the following capacity factors:

  • natural gas combustion turbines — Minimum: 10%; Median: 80%; Maximum: 93%
  • natural gas combined cycle — Minimum: 40%; Median: 84.6%; Maximum: 93%
  • coal, pulverized & scrubbed — Minimum: 80%; Median: 84.6%; Maximum: 93%
  • nuclear — Minimum: 85%; Median: 90%; Maximum: 90.24%
  • biopower — Minimum: 75%; Median: 84%; Maximum: 85%
  • hydropower — Minimum: 35%; Median: 50%; Maximum: 93.2%
  • enhanced geothermal — Minimum: 80%; Median: 90%; Maximum: 95%
  • solar PV – Minimum: 16%; Median: 21%; Maximum: 28%
  • offshore wind – Minimum: 27%; Median: 43%; Maximum: 54%
  • onshore wind – Minimum: 24%; Median: 40.35%; Maximum: 50.6%

Where Does Capacity Factor Fit Into Things?

Now, before moving on to the focus of this article, here’s one more thing to note:

Clean energy haters love to talk about capacity factor because it’s clearly a metric wind, solar, and hydro don’t win at (though, geothermal and biopower actually do very well). However, capacity factor by itself is really not that important. What’s important is the total cost of producing electricity. In the energy field, levelized cost of energy (LCOE) is one of the most important metrics. This is “an estimate of total electricity cost including payback of initial investment and operating costs,” as NREL writes.

Capacity factor plays a role in LCOE, of course, but so does free fuel (i.e. wind and sunshine). (In a perfect market, LCOE should also include the cost of pollution, which is not the case at all in the US today.)

Even without the cost of pollution figured in, if you look at NREL’s LCOE tab, onshore wind energy has a median of $0.05/kWh. The only energy source that beats that is hydropower ($0.03).

So, the point is, onshore wind energy is already essentially the cheapest option for new electricity (new hydro is not so cheap — that low figure is based on very old dams), even with NREL’s median capacity factor of 40.35%.


Technology Changes

Wind power is still a relatively new electricity option. The technology is still improving, becoming more and more efficient. And, as a part of that, there has been what is essentially a breakthrough in net capacity factor of various turbines in just the last 2 years.

Chris Varrone of Riverview Consulting, a friend of ours and true expert in this arena, recently noted in an email to me that this is due to a “proliferation of ’stretch rotor’ machines like the GE 100-1.6MW and the V100-1.8MW and V112-3.0MW…. such machines can often hit 50% capacity factor onshore.”

In other words, new wind turbines are regularly hitting 50% capacity factor, much better than that antiquated 20-30% clean energy haters love to throw around!

More from Chris: “this contrasts with low 30s for the last generation of rotors (e.g., V80-2.0MW) — it is changing the game.”

NREL’s minimum of 24% is old news, old technology. Even turbines in the 30s are old technology now. And the median is being brought down by these older turbines.

New wind turbines are more efficient. And, thus, new wind power is even cheaper. It is now at an all-time low, in fact.

One more note from Chris: “LCOE has declined by 33-45% in the past 3 years in the US!”

10 Responses to “Wind Turbine Capacity: 50% is the New Normal”

  1. [...] is how much electricity a power plant actually produces compared to … … Read more: Wind Turbine Capacity: 50% is the New Normal « Climate Denial … ← Wyoming Seeks California, Colorado Wind Power Buyers | Wyoming [...]

  2. skeptictmac57 Says:

    I love these kind of stories to help balance the “there’s nothing we can do!!!” attitude that comes from both sides.
    I have my Trapit feed set to ‘trap’ stories about all types of alternative energy, and it is like a firehose of information flooding in everyday.Many of these new ideas won’t pan out,but the depth and breadth of research and actual application of these technologies is quite astounding.
    There is not only something we CAN do,but we ARE doing it.

  3. kap55 Says:

    well …

    The increased capacity factor of recent turbines is really more due to a (large rotor)/(small generator) arrangement — the “stretch rotor” you describe. In the old days if you were to build a rotor that large, you would also go to a larger generator to capture more high-end wind. Essentially the large rotor de-rates in higher windspeeds, letting more energy pass through uncaptured.

    It would be just as accurate to call this arrangement a “small generator” setup as it would to call it a “stretch rotor”. I assume the reason for this is economics.

  4. otter17 Says:

    The industry is still in its toddler years, but learning new abilities every day and competing with the established industries.

  5. franbarlow Says:

    Declaration: I’m a very strong supporter of clean energy solutions and of course the IPCC-led consensus on climate science. I’m from Australia and am always thrilled when progress is made in low human footprint energy solutions. This sounds like great news.

    That said, it seems that one of the key reasons for the CF-based objections to intermittent sources such as wind is low dispatchability. The objection runs that even if on average wind power is producing 40% of nameplate, since we can’t say when with confidence that will be or match it to actual load then redundant but more dispatchable power must be on standby not merely to match actual load but to meet LOLP requirements on the grid (since current fluctuations can damage transmission equipment. The need to maintain redundant capacity to cover potential capacity variance means that the effective cost of integration of intermittent/low dispatchable capacity should include the cost of the extra redundant capacity or overbuild. In the case of wind, where one would need complementary wind regimes (i.e. reticulation over a large set of unconnected wind regimes) that should include supplemental grid connection costs.

    As the usual redundant capacity for wind is gas, it follows, so the argument runs, that wind displaces gas rather than coal so the marginal savings in GHGs is to that extent diminished and the abatement cost per tCO2e rises.

    Due to the intersection of these debates with the broader cultural resistance to conversion from fossil hydrocarbon energy to non-polluting energy, there is a great deal of half truth in these claims, and personally, I’d like to see these claims examined in some detail. There are days here in Australia when the wind over large parts of Southern Australia is becalmed all at once and where SA (which now has impressive wind capacity for a single state) has to rely on gas or other energy imported from the Eastern grid. Some data does suggest though that wind is abating new coal builds and assisting in the closure of one of our older plants — Playford B, so perhaps these becalments are anomalous. It would be good to know though.


    PS: Congrats on your fabulous “climate crocks” series on YouTube!

  6. One always has the dilemma of comparing unlike things. As noted, for wind, capacity factor could mean a smaller generator or a bigger rotor. It could also mean a blade feathering scheme or furling scheme that limits maximum power. Wind power increases as velocity cubed, so limiting maximum output misses a lot of energy. So why limit it? The only reasons are to reduce stress or because the grid cannot handle excess capacity. Capacity factor is a matter of choice and economic expediency, not a figure of merit. The best choice has the best cost of operation and return on investment and other desirables. The real problems with wind are not that there is not enough, or that it’s to intermittent, rather that when it’s very windy, there is more than enough. Think of it like ocean waves. If you wade into the ocean, the waves may cover your waist all the time, your chest part of the time, and your head occasionally. A wind turbine could be rated the same way. Incidentally, we should probably be referring to wind farms, not wind turbines, because the output of wind farms is what matters. Grid operators know that wind can always be relied on for a level of power if it is from farms distributed across many miles. Likewise, even though gas fired plants could operate most of the time, they are not used that way, and are used for peaking. That makes their actual on time low and their cost high. As has been noted, power from some sources cannot be throttled and cannot be turned on or off quickly. Peaking power, throttle ability, maintenance downtime, transmission, and fuel costs all drive power generation costs. Grid reliability can also be improved with local micro grids and local generation.y

  7. Franbarlow- Here is one source that debunks the high price of wind backup myth:

    In his calculations, Mr. Zycher claims that backup capacity is needed for 3-4.5% of the nameplate capacity of wind energy added to the grid, based on analysis done by the California grid operator. In addition, the DOE tables cited by Mr. Zycher indicate the cost of that backup natural gas capacity would be $648-984 per kilowatt of gas capacity.
    Taking those numbers at face value, multiplying 4.5% by the $984/kw backup cost indicates that the cost of backup capacity would add a mere $44.28 to the cost of each installed kilowatt of wind energy, adding just over 2% to the cost of wind energy, not the 250% that he claims. Thus, Mr. Zycher’s assumed cost for backup is wrong by a factor of at least 100. Even if drastically higher assumptions are used for the quantity of backup capacity needed and for the capital and operating cost of those reserves, the added cost for wind energy is still far less than a tenth of what Mr. Zycher claims it is.

    Clean Technica (

  8. [...] rate of renewables [credit: Ren 21]Furthermore, the reliability of renewables has improved, with better capacity factors now being recorded and crucially, the installation and running costs have been falling. Indeed its [...]

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