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

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

Teacher Knowledge of Attention-Deficit/Hyperactivity Disorder and Classroom Management

There is limited research on teacher knowledge of Attention Deficit Hyperactivity Disorder (ADHD) and classroom management; however, research suggests that teacher knowledge of ADHD influences teaching behaviors. This study investigates general education teachers’ and special education teachers’ knowledge of ADHD and the interaction with classroom management. In this study, 17 teachers responded to surveys about knowledge of ADHD and classroom management. Teachers scored an average of 61% on the knowledge of ADHD questionnaire. Contrary to the hypothesis, teacher knowledge of ADHD was not significantly related to classroom management. The relationship between knowledge of ADHD and classroom management needs further examination to determine if the two constructs are significantly related

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

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

Senior Inquiry: Diversity of the Human Experience

This collaboratively created poster summarizes, in graphic form, the Senior Inquiry students\u27 year-long course of study

Contrastive focus and emphasis

The paper puts forward a discourse-semantic account of the notoriously evasive phenomena of contrastivity and emphasis. Based on new evidence from Chadic, it is argued that occurrences of focus that are treated in terms of ‘contrastive focus’, ‘kontrast’ (Vallduví-Vilkuna 1998) or ‘identificational focus’ (É. Kiss 1998) in the literature should not be analyzed in familiar semantic terms as involving the introduction and subsequent exclusion of alternatives. Rather, an adequate analysis must take into account discourse-semantic notions like ‘hearer expectation’ or ‘discourse expectability’ of the focused content in a given discourse situation. The less expected the focus content is judged to be for the hearer, relative to the Common Ground, the more likely a speaker is to mark the focus constituent by means of special grammatical devices, thus giving rise to emphasis

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