Performance-Based Pricing of Frequency Regulation in Electricity Markets

The emergence of high penetration of renewable energy sources in the energy mix of power systems has substantially increased the need for faster-ramping resources participating in the frequency regulation service procured via market mechanisms by the system operators. However, current market mechanisms do not properly align the incentives for participation since resources are not compensated for the actual frequency regulation they provide nor for the accuracy with which they follow the automatic generation control (AGC) dispatch signal. In this paper, we evaluate the current mechanisms for procuring, dispatching and compensating resources for the frequency regulation service. We also propose a comprehensive approach for calculating the performance payment that includes the actual service they provide and the accuracy with which they follow the AGC signal. Finally, we perform a study by deploying actual operational AGC data for analyzing the proposed methodology

Market design for the simultaneous optimization of the Day-Ahead market and the reliability unit commitment applications

The design of restructured electricity markets requires a mechanism to ensure that differences between the bid-in demand that clears in the Day-Ahead Market (DAM) and the ISO's demand forecast do not compromise reliability requirements. This mechanism is usually called Reliability (or Residual) Unit Commitment (RUC), and is deployed to procure additional resources, beyond the DAM energy schedules, to meet the demand forecast. In this paper, we present the theoretical foundation of the RUC process and key important considerations in implementing the RUC application. We also provide a description of the general sequential approach in which the DAM application is executed first and then the RUC process is completed. We then offer the design framework for the implementation of an integrated approach which combines the functionality of the DAM and the RUC into one market application. The integrated approach offers substantial efficiencies by procuring all DAM products simultaneously. © 2013 IEEE

Day ahead energy market and Reliability Unit Commitment: An integrated approach

The restructured electricity markets typically involve a Day-Ahead Market (DAM), which clears bid-in demand that may be generally different (lower) than the demand forecast. This difference gives rise to reliability concerns to the Independent System Operators (ISOs), which are addressed with the deployment of a mechanism that is usually called Reliability (or Residual) Unit Commitment (RUC). Currently, the ISOs execute the RUC process after the DAM application, to procure additional resources, beyond the DAM energy schedules, to meet the demand forecast. In this paper, we compare the currently employed sequential approach, with a proposed integrated approach which combines the functionality of the DAM and the RUC into one market application. We present the market model including all market commodities, namely energy, ancillary services and RUC capacity, for both methodologies, and apply them on a realistic test case, using actual market/system data. We derive quantitative and qualitative results for a practical system, which illustrate the value of the integration of the market and the reliability functions in the forward spot market. The key conclusion from our simulation runs, is that the integrated approach offers substantial efficiencies by procuring all DAM products simultaneously. © 2014 Power Systems Computation Conference

A Thorough Analysis of the Endocrown Restoration: A Literature Review

Aim: The aim of this literature review is to determine whether endocrowns are a reliable alternative for endodontically treated teeth with extensive loss of tooth structure, the indications and contraindications of this restorative choice, the principles that should be followed for tooth preparation and which material is most appropriate for endocrown fabrication. Background: Rehabilitation of endodontically treated teeth with severe coronal destruction has always been a challenge for the dental clinician. Until recently, the fabrication of a metal-ceramic or all-ceramic full-coverage crown along with a metal or glass fiber post has been the “gold standard” proving its efficacy via numerous clinical studies. With the development of CAD/CAM technology and the evolution of dental materials, new minimally invasive techniques have been introduced with less need for adjustments and less incorporation of structural defects. One of them, the “monoblock technique,” proposed by Pissis in 1995, was the forerunner of endocrown restoration, a term used by Bindl and Mörmann to describe an all-ceramic crown anchored to the internal portion of the pulp chamber and on the cavity margins, thus obtaining macromechanical retention provided by the axial opposing pulpal walls and microretention attained with the use of adhesive cementation. Review results: Endocrowns require a decay-oriented preparation taking advantage of both the adhesion and the retention from the pulpchamber walls, they are strongly indicated in endodontically treated molars in cases where minimal interocclusal space and curved or narrow root canals are present and they should be manufactured from materials that can be bonded to the tooth structure. Conclusion: Endocrowns are a reliable alternative to traditional restorative choices, given that the clinicians respect the requirements and indications describing this technique. Clinical significance: Traditional restorative techniques demanding tooth substance removal and minimizing the opportunity for reinterventions should be reconsidered. © Jaypee Brothers Medical Publishers. 2021 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted use, distribution, and non-commercial reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated

Immediate Dentin Sealing: A Literature Review

Theodora-Kalliopi Samartzi,1 Dimokritos Papalexopoulos,2 Aspasia Sarafianou,2 Stefanos Kourtis2 1Private Dentistry Practice, Athens, Greece; 2Department of Prosthodontics, National and Kapodistrian University of Athens, Athens, GreeceCorrespondence: Dimokritos PapalexopoulosDepartment of Prosthodontics, National and Kapodistrian University of Athens, Athens, GreeceEmail [email protected]: The immediate application of a dentin-bonding agent after tooth preparation and before impression-taking (immediate dentin sealing [IDS]) has been suggested to provide several advantages concerning bacterial microleakage, hypersensitivity, and bonding quality. We reviewed the literature and clarified certain aspects related to each step of IDS application.Materials and Methods: The search strategy comprised an electronic research in MEDLINE, Cochrane, Ovid and Scopus for studies published from January 1990 to December 2020 regarding the IDS technique and including both in vitro and clinical studies.Results: After exclusion of irrelevant or duplicate articles, 88 articles focusing on aspects of the IDS technique were assessed. IDS seems to be advantageous with regard to bond strength, gap formation, bacterial microleakage, and dentin hypersensitivity. However, issues arising from interaction with impression materials, the provisional phase, and conditioning methods before cementation require further investigation.Conclusion: There are no documented reasons preventing clinicians applying IDS in their everyday practice. On the contrary, the presented technique seems to be beneficial in certain aspects regarding indirect restorations.Keywords: IDS, indirect restorations, restorative dentistry, revie

Greek wholesale electricity market: Forthcoming market changes and bid/cost recovery

The Greek wholesale electricity market is based on a day-ahead unit commitment market clearing and generation dispatch formulation with co-optimization of energy and reserves without the participation of transmission. An important feature of the market design is the cost recovery mechanism, which explicitly compensates generation units for their commitment costs and guarantees a minimum profit equal to 10% of their variable costs. In this paper, we evaluate the current mechanism in comparison to an alternative bid/cost recovery mechanism by simulating the wholesale electricity market for a period of one year. As part of the study we take into account the forthcoming changes for the liberalization of the Greek market that include the physical and virtual sale of a portion of PPC lignite plants, and we examine a likely "business as usual" scenario concerning the resulting bidding strategies. Lastly, we perform a sensitivity analysis with respect to the hydro production and the carbon price

Immediate dentin sealing: A literature review

Purpose: The immediate application of a dentin-bonding agent after tooth preparation and before impression-taking (immediate dentin sealing [IDS]) has been suggested to provide several advantages concerning bacterial microleakage, hypersensitivity, and bonding quality. We reviewed the literature and clarified certain aspects related to each step of IDS application. Materials and Methods: The search strategy comprised an electronic research in MEDLINE, Cochrane, Ovid and Scopus for studies published from January 1990 to December 2020 regarding the IDS technique and including both in vitro and clinical studies. Results: After exclusion of irrelevant or duplicate articles, 88 articles focusing on aspects of the IDS technique were assessed. IDS seems to be advantageous with regard to bond strength, gap formation, bacterial microleakage, and dentin hypersensitivity. However, issues arising from interaction with impression materials, the provisional phase, and conditioning methods before cementation require further investigation. Conclusion: There are no documented reasons preventing clinicians applying IDS in their everyday practice. On the contrary, the presented technique seems to be beneficial in certain aspects regarding indirect restorations. © 2021 Samartzi et al

Recovery mechanisms in a joint energy/reserve day-ahead electricity market with non-convexities

The goal of this paper is to evaluate the incentive compatibility of several cost- and bid-based recovery mechanisms that may be implemented in a wholesale electricity market to make the generation units whole in the presence of non-convexities, which are due to unit commitment costs and capacity constraints. To this end, we simulate the bidding behavior of the participants in a simplified model of the Greek joint energy/reserve day-ahead electricity market, where we assume that the players (units) participate as potential price-makers in a non-cooperative game with complete information that is repeated for many rounds. The results suggest that a mechanism based on bid recovery with a regulated cap is quite promising. © 2010 IEEE

Recovery Mechanisms in Day-Ahead Electricity Markets With Non-Convexities-Part II: Implementation and Numerical Evaluation

In centralized day-ahead electricity markets with marginal pricing, unit commitment costs and capacity constraints give rise to non-convexities which may result in losses to some of the participating generating units. To compensate them for these losses, a recovery mechanism is required. In Part I of this two-part paper, we present certain recovery mechanisms that result in recovery payments after the market is cleared. We also propose a methodology for evaluating the bidding strategy behavior of the participating units for each mechanism. In this paper (Part II), we apply this methodology to evaluate the performance and incentive compatibility properties of each recovery mechanism on a test case model representing the Greek joint energy/reserve day-ahead electricity market. Lastly, we perform sensitivity analysis with respect to key parameters and assumptions and we provide directions for further research