We present a simple method to calculate the marginal capacity credit of energy limited resources with increased penetration. Energy limited resources are defined as any resource with limited hours of ...dispatch across a day, month, or year. This includes emission limited resources, time-limited demand response, and diurnal energy storage such as batteries and pumped storage. This paper focuses on 4 h energy limited resources with daily dispatch. The method modifies well-established effective load carrying capability methodology by optimally allocating limited capacity to the highest loss of load hours. Subsequent energy limited resources are iteratively stacked upon the prior solution, creating a marginal capacity credit curve with increased penetration of energy limited resources. Two systems are tested using this method. The initial capacity credit depends on system characteristics such as load and renewable penetration. Regardless, the capacity credit for energy limited resources declines steeply with penetration.
Wind power forecasting can enhance the value of wind energy by improving the reliability of integrating this variable resource and improving the economic feasibility. The National Center for ...Atmospheric Research (NCAR) has collaborated with Xcel Energy to develop a multifaceted wind power prediction system. Both the day-ahead forecast that is used in trading and the short-term forecast are critical to economic decision making. This wind power forecasting system includes high resolution and ensemble modeling capabilities, data assimilation, now-casting, and statistical postprocessing technologies. The system utilizes publicly available model data and observations as well as wind forecasts produced from an NCAR-developed deterministic mesoscale wind forecast model with real-time four-dimensional data assimilation and a 30-member model ensemble system, which is calibrated using an Analogue Ensemble Kalman Filter and Quantile Regression. The model forecast data are combined using NCAR's Dynamic Integrated Forecast System (DICast). This system has substantially improved Xcel's overall ability to incorporate wind energy into their power mix.
This paper describes an advanced multi-scale weather modeling system, WRF–RTFDDA–LES, designed to simulate synoptic scale (∼2000
km) to small- and micro-scale (∼100
m) circulations of real weather in ...wind farms on simultaneous nested grids. This modeling system is built upon the National Center for Atmospheric Research (NCAR) community Weather Research and Forecasting (WRF) model. WRF has been enhanced with the NCAR Real-Time Four-Dimensional Data Assimilation (RTFDDA) capability. FDDA is an effective data assimilation algorithm, which is capable of assimilating diverse weather measurements on model grids and seamlessly providing realistic mesoscale weather forcing to drive a large eddy simulation (LES) model within the WRF framework. The WRF based RTFDDA LES modeling capability is referred to as WRF–RTFDDA–LES. In this study, WRF–RTFDDA–LES is employed to simulate real weather in a major wind farm located in northern Colorado with six nested domains. The grid sizes of the nested domains are 30, 10, 3.3, 1.1, 0.370 and 0.123
km, respectively. The model results are compared with wind–farm anemometer measurements and are found to capture many intra-farm wind features and microscale flows. Additional experiments are conducted to investigate the impacts of subgrid scale (SGS) mixing parameters and nesting approaches. This study demonstrates that the WRF–RTFDDA–LES system is a valuable tool for simulating real world microscale weather flows and for development of future real-time forecasting system, although further LES modeling refinements, such as adaptive SGS mixing parameterization and wall-effect modeling, are highly desired.
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High penetration of wind power has posed great challenges to power system operators. Extensive research has been done aiming to improve the power system operations. Various mechanisms such as ...stochastic unit commitment and reserve calculation methods have been proposed. However, the power system operators may have different views on the research results due to practical constraints. This paper looks at the needs of two Balancing Authorities, Public Service of Colorado (PSCo) and the California ISO (The ISO) that can be addressed by academia. The industry has a need to address various operating tools and stability concerns as they integrate large amount of wind generation into their areas.
The World Conservation Union (IUCN) Red List criteria endorsed in 1994 consist of a set of decision rules based on quantitative thresholds of population size, distributional range, rates of decline, ...and extinction risk. I evaluated these criteria using data on 68 vascular plant taxa from southeastern Australia and found that deficiencies could be overcome with modifications that did not substantially alter the structure of the IUCN rule set. These modifications included smaller distributional thresholds appropriate to sessile organisms, inclusion of life-history and land-based attributes, an amendment to account for skewed metapopulation structure, and inclusion of a rule addressing number of populations and qualitatively defined classes of threatening processes. I reviewed the strengths and weaknesses of decision rules for risk classification such as those endorsed by the World Conservation Union compared with intuitively based qualitative schemes in traditional use. I concluded that explicit schemes foster greater accuracy and precision in risk classification, are more defensible in the face of challenges, and define an agenda for data collection that is essential for the ongoing assessment and management of threatened species.
We describe a model of heath vegetation, in which species were classified into five functional groups based on characteristics of their propagule pools, post-fire growth, timing and mode of ...reproduction and competitive status. The model assumes no recruitment without fire and a simple competitive hierarchy based on vertical stature. A critical feature of the model is an initial post-fire window of 5-6 yr in which competition from overstorey species on understorey species is reduced. Understorey functional groups differ in their ability to exploit this window. In the field, we tested five predictions derived from the model: (a) overall species richness of understorey varies inversely with overstorey density as a result of a trend in richness of woody species, but not in herbaceous species; (b) where an overstorey was present in the previous fire interval, post-fire population density is reduced in a functional group of understorey serotinous resprouting shrubs, but not in a group of understorey obligate-seeding shrubs with soil seed banks; (c) in understorey serotinous resprouting shrubs, post-fire regrowth in resprouting individuals is adversely affected by the presence of an overstorey in the preceding fire interval; (d) in understorey serotinous resprouting shrubs, levels of pre-fire propagules are lower in the presence of an overstorey, reducing the density of post-fire recruits; and (e) in understorey serotinous resprouting shrubs, recruitment relative to the pre-fire population is unaffected by overstorey species within the window of reduced competition. Of these, three tests (a,b,d) supported the model, one (e) may support the model, but the results were inconclusive and one (c) did not support the model. Limitations and further applications of the model are discussed. Our results suggest that maintenance of high densities of overstorey populations is in conflict with conservation of some understorey species. Models of the type we propose will help identify and resolve such conflicts and promote the judicious use of fire to maintain full species diversity of plant communities.
FLOW is a composition for percussion quartet. The instrumentation consists of concrete blocks, bricks, two sizes of textured ceramic tile, 5 lb. and 10 lb. metal weights, metal theater fly-house ...counter weights, three sizes of gravel, and three sizes of metal bolts. The materials are suspended on specially-built wooden resonating tables. Sound events are manipulated and developed by means which model electroacoustic techniques I have been exploring for the past several years, e.g., granular time compression and expansion, granular coalescence and dispersal, and spectral filtering. FLOW is approximately 22 minutes in duration.
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