Opportunities for and challenges to further reductions in the “specific power” rating of wind turbines installed in the United States

A wind turbine’s “specific power” rating relates its capacity to the swept area of its rotor in terms of Watt per square meter. For a given generator capacity, specific power declines as rotor size increases. In land-rich but capacity-constrained wind power markets, such as the United States, developers have an economic incentive to maximize megawatt-hours per constrained megawatt, and so have favored turbines with ever-lower specific power. To date, this trend toward lower specific power has pushed capacity factors higher while reducing the levelized cost of energy. We employ geospatial levelized cost of energy analysis across the United States to explore whether this trend is likely to continue. We find that under reasonable cost scenarios (i.e. presuming that logistical challenges from very large blades are surmountable), low-specific-power turbines could continue to be in demand going forward. Beyond levelized cost of energy, the boost in market value that low-specific-power turbines provide could become increasingly important as wind penetration grows

How Does Wind Project Performance Change with Age in the United States?

Wind-plant performance declines with age, and the rate of decline varies between regions. The rate of performance decline is important when determining wind-plant financial viability and expected lifetime generation. We determine the rate of age-related performance decline in the United States wind fleet by evaluating generation records from 917 plants. We find the rate of performance decline to be 0.53%/year for older vintages of plants and 0.17%/year for newer vintages of plants on an energy basis for the first 10 years of operation, which is on the lower end of prior estimates in Europe. Unique to the United States, we find a significant drop in performance by 3.6% after 10 years, as plants lose eligibility for the production tax credit. Certain plant characteristics, such as the ratio of blade length to nameplate capacity, influence the rate of performance decline. These results indicate that the performance decline rate can be partially managed and influenced by policy

Annual report on U.S. wind power installation, cost, and performance trends: 2006

This report--the first in what is envisioned to be an ongoing annual series--attempts to fill this need by providing a detailed overview of developments and trends in the U.S. wind power market, with a particular focus on 2006

Annual Report on U.S. Wind Power Installation, Cost, and Performance Trends: 2007 (Revised)

This report focuses on key trends in the U.S. wind power market, with an emphasis on the latest year, and presents a wealth of data, some of which has not historically been mined by wind power analysts

Effects of temperature and pH on equine skeletal muscle mitochondrial membrane potential

Despite its significant contribution to metabolism, the relationship between membrane potential ([Delta][Psi]mt) and the physiological extremes of hyperthermia and acidosis has not been investigated. This study uses high-resolution respirometry (HRR) to test the hypothesis that conditions of hyperthermia and acidosis will result in decreased mitochondrial membrane potential.Mitochondria were isolated from fresh semitendinosus muscle biopsies acquired from five Thoroughbred horses. Isolated mitochondria from these biopsies were analyzed using HRR to monitor oxygen consumption and relative changes in [Delta][Psi]mt (using TMRM). Assays will be conducted at simulated baseline physiological conditions (38 degrees C, pH = 7.0) as well as all other combinations of two temperatures (38 degrees C or 43 degrees C) and two pH levels (6.5 or 7.0). ANOVA two factor with replication, with the horse as repeating variable, was used to analyze the resulting data. P<0.05 was considered significantHyperthermia and acidosis resulted in decreased [Delta][Psi]mt both individually and in combination with each other during non-phosphorylating and phosphorylating respiration, although by different magnitudes. Acidosis decreased oxygen consumption during non-phosphorylating and phosphorylating respiration, but hyperthermia had no effect. Oxygen consumption per unit of [Delta][Psi]mt (JO2/[Delta]TMRM) was significantly increased by hyperthermia in both states, but acidosis only affected maximal phosphorylating respirationThe variations in how hyperthermia and acidosis each affected [Delta][Psi]mt and oxygen consumption suggests that they affect the Electron Transfer System (ETS) in different ways. The oxygen results of this study are in direct contrast to previous studies but can be explained by JO2/[Delta]TMRM results which likely show that acidosis inhibited respiration through complex I while hyperthermia increased membrane permeability. This study also demonstrates that ROS production is likely the result of inefficiencies in the ETS rather than proportionate to respiration. This study allows for the observation of comparative differences in membrane potential, but further calibration assays will be required to assign specific voltage across the inner membrane.Although it is likely that they affect mitochondrial function in different ways and to varying degrees, it almost certainly results in decreased ATP synthesis, contributing to the development of fatigue in exercising horses. Understanding how hyperthermia and acidosis affect [Delta][Psi]mt illustrates how they may contribute to the development of fatigue in exercising horses

The Error in Trial and Error: Exercises on Phrasal Verbs

An analysis of 44 commercially available EFL textbooks found that it is common for textbooks to present learners with exercises on phrasal verbs without first providing relevant input to help them. In these cases, the learners are likely to resort to trial-and-error and are then expected to learn from feedback. We report an experiment conducted with Japanese EFL students (N=140) in which we compare the effectiveness of such a trial-and-error method with a retrieval procedure in which students first study a set of phrasal verbs and then complete an exercise. Scores on both an immediate and a one-week delayed post-test suggest superiority of retrieval over the trial-and-error procedure, where, despite the provision of feedback, 25% of the wrong exercise responses were reproduced in the delayed post-test

Morally Respectful Listening and its Epistemic Consequences

What does it mean to listen to someone respectfully, that is, insofar as they are due recognition respect? This paper addresses that question and gives the following answer: it is to listen in such a way that you are open to being surprised. A specific interpretation of this openness to surprise is then defended

Notions and subnotions in information structure

Three dimensions can be distinguished in a cross-linguistic account of information structure. First, there is the definition of the focus constituent, the part of the linguistic expression which is subject to some focus meaning. Second and third, there are the focus meanings and the array of structural devices that encode them. In a given language, the expression of focus is facilitated as well as constrained by the grammar within which the focus devices operate. The prevalence of focus ambiguity, the structural inability to make focus distinctions, will thus vary across languages, and within a language, across focus meanings

Power System Modeling of 20% Wind-Generated Electricity by 2030

This presentation describes the methods used to analyze the potential for provided 20% of our nation's electricity demand with wind energy by 203

Power System Modeling of 20% Wind-Generated Electricity by 2030: Preprint

This paper shows the results of the Wind Energy Deployment System model used to estimate the costs and benefits associated with producing 20% of the nation's electricity from wind technology by 2030