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Wind Turbine Net Capacity Factor
-- 50% the New Normal?

by Zachary Shahan
Clean Technica, July 27, 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:
Capacity Factors for various Power Plants
Source Minimum Median Maximum
Natural Gas combustion turbines 10% 80% 93%
Natural Gas combined cycle 40% 84.6% 93%
Coal, pulverized & scrubbed 80% 84.6% 93%
Nuclear 85% 90% 90.24%
Biopower 75% 84% 85%
Hydropower 35% 50% 93.2%
Enhanced Geothermal 80% 90% 95%
Solar PV 16% 21% 28%
Offshore Wind 27% 43% 54%
Onshore Wind 24% 40.35% 50.5%

(bluefish notes: Capacity Factor of four Lower Snake River dams is 34.3% = 1050 aMWH / (3 x 810 + 630 MW))

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%.

But. . .

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!"

Next Time You're in a Conversation with a Wind Energy Hater

What are the takeaway points?

Zachary Shahan
Wind Turbine Net Capacity Factor -- 50% the New Normal?
Clean Technica, July 27, 2012

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