Trends in performance factors of wind energy facilities
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Trends in performance factors of wind energy facilities Alberto Boretti1 · Stefania Castelletto2 Received: 12 March 2020 / Accepted: 16 September 2020 © Springer Nature Switzerland AG 2020
Abstract This communication discusses the two parameters recently emerged as key performance indicators of wind energy facilities, the mean capacity factor over a year, and the standard deviation of the capacity factor from a high-frequency sampling of 1 min or less (the annual mean does not change if the sampling interval of the statistical population is every month or every minute; the standard deviation does). Both parameters impact the levelised cost of electricity. They permit to quantify the energy production by the specific facility. They also permit to attribute grid energy storage costs to the specific facility. This manuscript shows that the annual mean capacity factors of wind energy facilities are not improving in the U.S. with the year of completion. The average of the annual mean capacity factors of every facility operational in a given year is about 33% now in 2019 as it was in 2012. Additional to the flat trend in the average of the annual mean capacity factor, their variability is large at the individual facility level. With 5 min sampling frequency, the standard deviation of the capacity factor of an individual wind energy facility is about that same magnitude of the mean. This translates into a coefficient of variability—the ratio of the standard deviation to the mean—approaching unity. At the grid level, the variability of all the wind energy supply is still large and necessitates significant energy storage. Keywords Wind energy · Capacity factors · Trend analysis · Variability index
1 Introduction Wind energy is presently the most widespread and economic renewable energy. The wind energy facilities use the variable wind energy resource to generate electricity [1, 2]. Wind electricity supply is less variable than solar photovoltaics, but it still suffers from significant variability, because of the fluctuation of the wind energy resource [3, 4]. Junginger et al. [5] notes as the onshore wind has been characterized by reductions in the cost of installation per unit capacity for more than three decades. The reduction of the levelised cost of electricity (LCOE) is the parameter being used in this century to better assess the cost of electricity. [6] notes as turbine rotor sizes have grown from the early 1980s and with them the rated output
(capacity). While different designs were considered in the past, the industry is now settled on three-blade rotors that run upwind of the tower. The larger is the rotor, the more difficult it is the packaging in arrays on limited land. By increasing the rotor diameter, also the tower height increases, and this permits to harvest larger wind energy as the wind speed increases with height. Presently, the registered capacity of wind energy installations is simply the arithmetic sum of the rated power of every turbine, no matter how they are installed on a given terrain, whic
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