I’ve written extensively about the misuse of wind turbine power ratings and why the term “capacity factor” should not be used.[1] In short, don’t use it. There are much better descriptors of wind turbine performance.
Many of the outlandish claims made by “inventors” rely on the improper use of power ratings and capacity factors. It’s easy for unscrupulous promoters to hoodwink the public, the media, and even some engineers with the sleight of hand that “power ratings” and “capacity factors” makes possible.
I explain all of this—and more–in Chapter 8, Silent Wind Revolution, of my book Wind Energy for the Rest of Us.[2]
The expression “Silent Wind Revolution” was coined by my colleague Bernard Chabot. It succinctly captures how a subtle change in design approach has led to a radical transformation of wind turbines and their place in the utility network. It’s not sexy. It doesn’t garner banner headlines in the tech press, but it has profound ramifications on how and where wind energy is used.
There are several articles by me, Bernard Chabot, and others scattered across my web site that discuss these and related topics. I’ve tried to pull them altogether here.
Generator Ratings & Capacity Factors: Why You Should Avoid Them (2006)
- Generator Size and Swept Area
- Generator Size and Rated Power
- Measures of Wind Turbine Performance
- Examples of Actual Specific Yields at Sample Sites
- Installed Cost
Technical Comparators: Swept Area preferred over Rated Power by Geoff Henderson, Windflow (2011)
- What is a Wind Turbine?
- Generator Ratings
- Swept Area Trumps Generator Ratings
- Metrics of Productivity
- Measures of Relative Swept Area
- Historical Abuse of Power Ratings
- Wind Turbine Design and Wind Regimes
- Specific Capacity/Area and Capacity Factor
- Why All This is Important
Specific Rated Capacity of Wind Turbines in the 1980s—listing several dozen wind turbine manufactured in the 1980s and their power ratings. Some of these ratings are outrageous as I’ve remarked elsewhere. (2013)
DyoCore and Why the Rating of Small Turbines Remains a Black Art (2011)
- Background
- Responsibility
- Power Ratings
- Gipe’s Standard Power Rating
- DyoCore’s Rating
- Energy Estimates Out of This World
- Solution to the Rating Black Art
Wind Power Silent Revolution: New Wind Turbines for Light Wind Sites by Bernard Chabot (2013)
Wind Power USA: A (silent) revolution in the wind sector by Bernard Chabot (2015)
New IEC3A Wind Turbines: Bright Strategic and Economic Perspectives for Onshore Wind in Medium to Low Wind Speed Areas by Bernard Chabot
Wind Power USA: A (silent) revolution in the wind sector—a presentation packed with detail by Bernard Chabot 2015.
How the Silent Wind Power Revolution May Contribute to the Danish Energy and Climate Plan by Bernard Chabot 2015.
The Silent Wind Revolution: Increasing the Opportunity for Distributed Wind—a presentation by Paul Gipe before the Distributed Wind Energy Association in Washington, DC February 28, 2017.
Wind’s Silent Revolution Grows in Germany with More High Specific Area Turbines (2017)
[1] The term capacity factor is used primarily in North America. A similar term, plant factor, is used in Great Britain, and the related term, full-load hours, is used elsewhere in Europe.
[2] “Silent Wind Revolution,” in Wind Energy for the Rest of Us: A Comprehensive Guide to Wind Power and How to Use It, by Paul Gipe (Bakersfield, California: Wind-works.org, 2016), 191–202. https://wind-works.org/wp-content/uploads/2023/12/Chapter-8-Silent-Wind-Revolution-Pages-191-202-from-Wind-Energy-Final-PagesLR.pdf.
