1,720,988 research outputs found
Transmission grid flexibility assessment in electricity market: Bulk system indices for the operational planning
No full textThe paper includes a review of the concept of “flexibility”,
usually integrated as attribute in analysis of industry
processes, for making it applicable in the transmission grid
operational planning in electricity market context. Definitions
reported in the modern scientific literature, concerning
flexibility, are summarized and critically explained. Then a
specific definition of transmission system flexibility in
respect of the generation changes and some bulk system
flexibility indices are proposed. The mathematical models and
calculation methodology are presented, and a dedicated tool
for indices computation is briefly described. The tool is in test
at the Italian Transmission System Operator (TERNA) for the
flexibility evaluation of parts of the National Transmission
Grid
Novel Modulation with Flexible Power Distribution for Single-Phase Dual-Port DC-AC Converters
No full textDual-port dc-ac converters utilizing the Neutral-Point-Clamped (NPC) multilevel topology are increasingly considered for the compact integration of multiple sources and loads in various applications. NPC-based dual-port converters (NPCDPC) allow the interconnection of dc and ac systems in a single conversion stage, eliminating the need for magnetics typically required in conventional dc-dc converters. Despite increasing research interest in this area, the majority of studies have focused on three-phase applications, with no documented studies on NPCDPC in single-phase systems to date. This paper introduces a new modulation technique for NPC-DPC connecting two dc sources to a single-phase ac system. The innovative algorithm achieves the twofold objective of ac current control and flexible power distribution between dc sources. The mathematical formulation of the proposed modulation is described and the limits of linear modulation are discussed. To validate the proposed modulation, numerical simulations are conducted and their results are discussed
Impact of regulatory rules on economic performance of PV power plants
No full textThe rapid growth of Renewable Energy Sources (RES) power plants connected to the grid has introduced new problems related to the safe and reliable operation of the electricity network from transmission to distribution sectors. New regulatory rules can promote RES producers to make a commitment on the energy amount that is likely to be supplied to the network. The present paper concerns the analysis of the energy production of a PV power plant from the economic point of view, with reference to the presence of regulatory rules. Costs of penalty and value of energy are compared, in order to evaluate the economic efficiency of the plant. Use of auxiliary energy storage devices is investigated, with the aim to determine the relevant dimensions that increase the economic efficiency of the PV plant. A software instrument that implements these algorithms is described and applied to a case study
Optimization of the battery size for PV systems under regulatory rules using a Markov-Chains approach
No full textIn the last decade a high amount of photovoltaic and wind power generators have been connected to the electric grid, introducing operational problems for transmission and distribution system operators due to the variability and the non-programmability of solar radiation and wind. The paper concerns an analysis on the benefits in adopting storage systems to reduce the imbalance costs associated to renewable energy sources. An analysis on a photovoltaic system has been performed considering different battery technologies. Discrete-time Markov chains have been used to generate a 20 years' time series of irradiance, that has been used to calculate the PV power production. Markov simulation parameters have been deeply studied in order to optimize them and obtain reliable synthetic data of ground irradiance. This data was then used as input of a hybrid PV and storage model allowing to obtain realistic economic and technical results, improving thus the results respect to the methods based on probabilistic weather simulations. An imbalance tariff has been assumed and its cost has been analysed in relation to the storage system costs. An optimal size for the different battery technology has been investigated considering the reduction of variability of the photovoltaic production and the economic convenience of
the hybrid system. The use of Markov chains for the optimization of the battery size can be considered as the major novelty of the proposed approach
DESIGN OF SOLAR CHIMNEY POWER PLANT FOR MEDITERRANEAN COUNTRIES
No full textThe solar chimney, also known as solar updraft tower, is a proposed type of renewable-energy power plant that combines a solar air collector and a central high tube to generate a solar induced convective flow which drives turbines, generating thus electricity. In this paper, it is first described the functional principle of the solar chimney. Some results of the thermodynamic analysis performed are given, including a model for solar collector. The study also considers the performance of a particular reference plant equipped with a floating chimney, with specified climate conditions in Sicily, Italy. A basic economic analysis is finally performed. © 2011 IEEE.The solar chimney, also known as solar updraft
tower, is a proposed type of renewable-energy power plant
that combines a solar air collector and a central high tube to
generate a solar induced convective flow which drives
turbines, generating thus electricity. In this paper, it is first
described the functional principle of the solar chimney.
Some results of the thermodynamic analysis performed are
given, including a model for solar collector. The study also
considers the performance of a particular reference plant
equipped with a floating chimney, with specified climate
conditions in Sicily, Italy. A basic economic analysis is
finally performed
A fast and accurate battery model suitable for production profiling in smart grids
No full textIn each segment of the electricity chain, from the generation power plants to the final users, use of batteries is continuously increasing due to the necessity to have an energy storage system., particularly in the optimal management of Smart Grids. Batteries application are present both in transmission and in distribution grid, as a support for the dispatching of the renewable sources power plants, for a flexible operation of the networks and also as backup in order to ensure a reliable and safe energy service. In this context, it is very useful a mathematical model that can simulate the operation of electrochemical accumulators, using as input only the data provided by the manufacturers, without the necessity to perform experimental tests. In the present paper a battery model, based on the formulation of an equivalent electric circuit, is presented: it allows studying the battery as a black box, avoiding analyzing the chemical reactions and all processes which develop inside the unit. The study, applicable to all kinds of batteries, has as its specific object the stationary lead acid batteries, normally used for energy storage in renewable energy plants. The proposed model has been implemented in a MatLab software. The results of the application of the model to two different case studies are reported
Impact assessment of an energy management system on environmental pollution and economic performance
No full textThis paper proposes a fast and simple algorithm to assess the impact of an energy management system on the environmental and economic performance of a production process. The proposed technique is based on correlations among a set of energy drivers, uses quadratic regression methods and variance analysis. Modeling and parameter extrapolation, factors variability, multi-variable statistics and mean square error are used in order to derive a simple functional relationship between a set of state variables, allowing thus to obtain advanced solutions. Finally, the described mathematical models are implemented in software that is applied to the case study of a food products company. Results indicate the future research directions as well. It is worth notice that the proposed method is not restricted to energy management problems but can also be applied to many other engineering management systems
Technical and economic analysis of a micro-tri/cogeneration system with reference to the primary power source in a shopping center
No full textThe aim of this paper is to provide a method of
analysis for a technical and economic study on the
installation of a cogeneration or trigeneration system in a
commercial site. A case study is developed with particular
reference to the economics a type of micro CHP is be
considered for this application.
Keywords - cogeneration, trigeneration, biomass,
renewable energy, technical and economic analysis,
energy saving
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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