Base-load cycling on a system with significant wind penetration

Certain developments in the electricity sector may result in suboptimal operation of base-load generating units in countries worldwide. Despite the fact they were not designed to operate in a flexible manner, increasing penetration of variable power sources coupled with the deregulation of the electricity sector could lead to these base-load units being shut down or operated at part-load levels more often. This cycling operation would have onerous effects on the components of these units and potentially lead to increased outages and significant costs. This paper shows the serious impact increasing levels of wind power will have on the operation of base-load units. Those base-load units which are not large contributors of primary reserve to the system and have relatively shorter start-up times were found to be the most impacted as wind penetration increases. A sensitivity analysis shows the presence of storage or interconnection on a power system actually exacerbates base-load cycling until very high levels of wind power are reached. Finally, it is shown that if the total cycling costs of the individual base-load units are taken into consideration in the scheduling model, subsequent cycling operation can be reduced.Thermal Power Generation; Wind Power Generation; Pumped Storage Power Generation; Interconnected Power Systems; Power System Modeling; Costs

Towards a Semantic Perceptual Image Metric

We present a full reference, perceptual image metric based on VGG-16, an artificial neural network trained on object classification. We fit the metric to a new database based on 140k unique images annotated with ground truth by human raters who received minimal instruction. The resulting metric shows competitive performance on TID 2013, a database widely used to assess image quality assessments methods. More interestingly, it shows strong responses to objects potentially carrying semantic relevance such as faces and text, which we demonstrate using a visualization technique and ablation experiments. In effect, the metric appears to model a higher influence of semantic context on judgments, which we observe particularly in untrained raters. As the vast majority of users of image processing systems are unfamiliar with Image Quality Assessment (IQA) tasks, these findings may have significant impact on real-world applications of perceptual metrics

Effects of Anacetrapib in Patients with Atherosclerotic Vascular Disease

BACKGROUND: Patients with atherosclerotic vascular disease remain at high risk for cardiovascular events despite effective statin-based treatment of low-density lipoprotein (LDL) cholesterol levels. The inhibition of cholesteryl ester transfer protein (CETP) by anacetrapib reduces LDL cholesterol levels and increases high-density lipoprotein (HDL) cholesterol levels. However, trials of other CETP inhibitors have shown neutral or adverse effects on cardiovascular outcomes. METHODS: We conducted a randomized, double-blind, placebo-controlled trial involving 30,449 adults with atherosclerotic vascular disease who were receiving intensive atorvastatin therapy and who had a mean LDL cholesterol level of 61 mg per deciliter (1.58 mmol per liter), a mean non-HDL cholesterol level of 92 mg per deciliter (2.38 mmol per liter), and a mean HDL cholesterol level of 40 mg per deciliter (1.03 mmol per liter). The patients were assigned to receive either 100 mg of anacetrapib once daily (15,225 patients) or matching placebo (15,224 patients). The primary outcome was the first major coronary event, a composite of coronary death, myocardial infarction, or coronary revascularization. RESULTS: During the median follow-up period of 4.1 years, the primary outcome occurred in significantly fewer patients in the anacetrapib group than in the placebo group (1640 of 15,225 patients [10.8%] vs. 1803 of 15,224 patients [11.8%]; rate ratio, 0.91; 95% confidence interval, 0.85 to 0.97; P=0.004). The relative difference in risk was similar across multiple prespecified subgroups. At the trial midpoint, the mean level of HDL cholesterol was higher by 43 mg per deciliter (1.12 mmol per liter) in the anacetrapib group than in the placebo group (a relative difference of 104%), and the mean level of non-HDL cholesterol was lower by 17 mg per deciliter (0.44 mmol per liter), a relative difference of -18%. There were no significant between-group differences in the risk of death, cancer, or other serious adverse events. CONCLUSIONS: Among patients with atherosclerotic vascular disease who were receiving intensive statin therapy, the use of anacetrapib resulted in a lower incidence of major coronary events than the use of placebo. (Funded by Merck and others; Current Controlled Trials number, ISRCTN48678192 ; ClinicalTrials.gov number, NCT01252953 ; and EudraCT number, 2010-023467-18 .)

Evaluating which forms of flexibility most effectively reduce base load cycling at large wind penetrations

Paper presented at the 8th International Workshop on Large-Scale Integration of Wind Power into Power Systems, 14-15 October 2009, Bremen, GermanyIncreasing penetration of wind power on power systems worldwide is resulting in the unconventional operation of base-load generating units. These units which were originally designed for operation at full output are more frequently required to balance the variability of the wind. This results in increased start-stop cycling and hours at low load which causes severe deterioration to the plants components. Interconnection, storage and demand side management increase the flexibility of a power system and can balance variations in the wind power output, thus reducing the onus on thermal plants. This study will attempt to quantify which of these forms of flexibility is most effective at reducing base-load cycling on a thermal test system with a large amount of wind.Science Foundation IrelandCharles Parsons Energy Research AwardsCharles Parson. ISBN of proceedings: http://www.windintegrationworkshop.org/old_proceedings.htm

Multi-mode operation of combined-cycle gas turbines with increasing wind penetration

As power systems evolve to incorporate greater penetrations of variable renewables, the demand for flexibility within the system is increased. Combined-cycle gas turbines are traditionally considered as relatively inflexible units, but those which incorporate a steam bypass stack are capable of opencycle operation. Facilitating these units to also operate in opencycle mode can benefit the power system via improved system reliability, while reducing the production needed from dedicated peaking units. The utilization of the multi-mode functionality is shown to be dependent on the flexibility inherent in the system and the manner in which the system is operated.Science Foundation IrelandOther funderCharles Parsons Energy Research AwardsWrong bibliographical details: see doi 10.1109/TPWRS.2011.2163649 and http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6006567 - AV 27/9/201

The relationship between base-load generation, start-up costs and generation cycling

Paper presented at the 28th USAEE/IAEE North American Conference "Unveiling the Future of Energy Frontiers", New Orleans, December 3-5 2008Developments in the electricity sector such as the integration of increasing levels of renewable power, mainly wind, and the deregulation of electricity markets have resulted in some unconventional operation of base-load units. These units, which were originally designed for continuous operation, are now being forced into more flexible or cycling operation. This cycling operation results in serious physical degeneration of the unit’s components and hence incurs substantial costs to the plant operator. Using a planning tool of the Irish electricity system, the impact of increasing wind penetration on the operation of the base-load units is modelled. The results show that as wind penetration on the system increased, the base-load units were required to start up and shut down more often. However the units found to be cycled the most were not those with the cheapest start-up cost, but in fact those units with the shortest synchronisation time1. On the basis that the resulting cycling costs would increase the start-up costs of the base-load unit to some degree, the effect of increasing start-up costs on the operation of the base-load units was also examined. The results show that by increasing the start-up costs of base-load units, those units will be scheduled to operate in a more conventional base-loaded manner, the extent of which depends on the amount of wind power present.Science Foundation IrelandOther funderConference detailshttp://www.usaee.org/usaee2008/index.htmlCharles Parsons Energy Research Award

Base-load cycling on a system with significant wind penetration

Certain developments in the electricity sector may result in suboptimal operation of base-load generating units in countries worldwide. Despite the fact they were not designed to operate in a flexible manner, increasing penetration of variable power sources coupled with the deregulation of the electricity sector could lead to these base-load units being shut down or operated at part-load levels more often. This cycling operation would have onerous effects on the components of these units and potentially lead to increased outages and significant costs. This paper shows the serious impact increasing levels of wind power will have on the operation of base-load units. Those base-load units which are not large contributors of primary reserve to the system and have relatively shorter start-up times were found to be the most impacted as wind penetration increases. A sensitivity analysis shows the presence of storage or interconnection on a power system actually exacerbates base-load cycling until very high levels of wind power are reached. Finally, it is shown that if the total cycling costs of the individual base-load units are taken into consideration in the scheduling model, subsequent cycling operation can be reduced.Science Foundation IrelandElectricity Research Centre (ERC) Industry MembersPublisher version at http://dx.doi.org/10.1109/TPWRS.2009.2037326. DG 07/07/10 ke - AL 23/07/201

Managing wind uncertainty and variability in the Irish power system

Paper presented at IEEE Power & Energy Society General Meeting, July 26-30, 2009, Calgary, CanadaThis paper summarizes work that has been done to examine the impact of the uncertainty and variability of significant installed wind power on the Irish system. As more and more wind power is installed on the system, the operation of conventional plant on the system will be dramatically different. In this paper, three different aspects of the hour-to-hour operation of the Irish power system are examined. An innovative method to schedule the system is described, together with key results giving the effect of the uncertainty of wind on unit commitment of the system. The increased cycling of traditionally base-load units due to large amounts of wind power is quantified, and the steps to reduce this unwanted behavior are outlined. Finally, the use of intelligent decision tools based on sophisticated wind power forecasts for scheduling and provision of reserve is described.Science Foundation IrelandOther funderCharles Parsons Energy Research Awardspe, la, ke, ab - kpw20/10/1

Short-Term Energy Balancing With Increasing Levels of Wind Energy

Increasing levels of wind energy are adding to the uncertainty and variability inherent in electricity grids and are consequently driving changes. Here, some of the possible evolutions in optimal short-term energy balancing to better deal with wind energy uncertainty are investigated. The focus is mainly on managing reserves through changes in scheduling, in particular market structure (more regular and higher resolution scheduling), reserve procurement (dynamic as opposed to static), and improved operational planning (stochastic as opposed to deterministic). Infrastructure changes including flexible plant, increased demand side participation, more interconnection, transmission, larger balancing areas, and critically improved forecasting can also be significant and are dealt with in the discussion. The evolutions are tightly coupled, their impact is system-dependent and so no “best” set is identifiable but experience of system operators will be critical to future developments.Science Foundation IrelandDeposited by bulk impor