• Energy Research

The goal of this paper is to demonstrate the powerful contribution of the electric active power flow tracing methods on studying the electric transmission systems operating conditions. The tracing methods allow to impute to every generation unit and/or load the responsibility of the power flows of all the elements connected to the network. This study propose the numerical implementation of two different tracing methods on two transmission networks through Matlab® scripts developed on purpose; then the analysis is focused on identifying the loads which mostly affect the power line flows of the system. The results of this analysis point out the loads on which the application of the Demand Response (DR) programs are more effective in view of solving system congestions.

This paper presents an assessment of the levelized cost of clean hydrogen produced in Sicily, a region in Southern Italy particularly rich in renewable energy and where nearly 50% of Italy’s refineries are located, making a comparison between on-site production, that is, near the end users who will use the hydrogen, and centralized production, comparing the costs obtained by employing the two types of electrolyzers already commercially available. In the study for centralized production, the scale factor method was applied on the costs of electrolyzers, and the optimal transport modes were considered based on the distance and amount of hydrogen to be transported. The results obtained indicate higher prices for hydrogen produced locally (from about 7 €/kg to 10 €/kg) and lower prices (from 2.66 €/kg to 5.80 €/kg) for hydrogen produced in centralized plants due to economies of scale and higher conversion efficiencies. How-ever, meeting the demand for clean hydrogen at minimal cost requires hydrogen distribution pipelines to transport it from centralized production sites to users, which currently do not exist in Sicily, as well as a significant amount of renewable energy ranging from 1.4 to 1.7 TWh per year to cover only 16% of refineries’ hydrogen needs.

Institutions, companies, research centers and universities are paying special attention to green hydrogen, a key energy carrier for the decarbonization of various sectors because it is produced from renewable sources without producing emissions. Currently, however, the cost of producing it is high and does not make it competitive with that produced from fossil fuels. One way to cut costs could be to exploit the oxygen obtained as a by-product of water electrolysis, selling it instead of releasing it into the atmosphere as is usually done. In some studies, this idea has already been analyzed, but very often without considering the costs due to the additional components for treating the oxygen, which must be properly compressed and stored, or without directly showing how the LCOH (levelized cost of hydrogen) varies according to this choice, especially in an Italian context, limiting the study to an evaluation of the NPV. The paper analyzes plant configurations for the production of green hydrogen installed in southern Italy, in Sicily, in which a photovoltaic system powers an alkaline electrolyzer and two compressors: one for hydrogen and one for oxygen. The system is completed by the storage systems for the two gases. Levelized cost values for green hydrogen are calculated by considering the sale of oxygen either at prices found in the literature in similar studies, or at prices in the European Union for oxygen produced by air distillation, taking into account the operating and investment costs for the compressor and oxygen storage, and comparing the values obtained with the costs of green hydrogen without oxygen valorization.

This work examines the operation of the autonomous power system of a geographical island assuming the integration of significant generation shares from renewable energy sources and the installation of the required storage systems. The frequency stability of the system is investigated considering different operating conditions, in terms of load demand and renewable power generation. The main focus of the work is an original control strategy specifically designed for power converters interfacing storage units to the grid. The proposed strategy is based on an extended frequency droop control, which selects specific droop settings depending on the operating mode—charge or discharge—of the storage unit. A simulation model of the whole electrical system is developed for dynamic analysis. The model also implements the possibility of including specific auxiliary frequency controls for synthetic inertia and primary reserve. The results of the simulation and analysis indicate that the proposed control strategy has a significant positive effect, making the storage units able to provide a fundamental and more effective support to the frequency stability of the system. The application of the proposed control strategy to storage units also reduces the need for a contribution to the frequency control from intermittent and variable sources, making the whole system more robust, stable and reliable.

The exploitation of power lines currently in operation has now become a common practice among electric system operators. The construction of new power lines requires taking economic, political and social problems into consideration. This paper considers two methodologies adopted by the Italian Transmission System Operator (TSO), Terna S.p.A.: Dynamic Thermal Rating (DTR) and Laser Imaging Detection and Ranging-Geographic Information System (L-GIS). DTR systems dynamically calculate the real transport capacity of a power line. The L-GIS system allows, after the geo-referencing of the power line, the management of any interference between the line and the nearby obstacles, permitting the optimization of the high voltage line operation. In this paper, after a brief illustration of the two methods, the authors report the results of some applications in the Sicilian electrical power High Voltage (HV) system.

The advent of electricity market deregulation, the increased operating and overload temperatures of transmission line conductors have caused concern among TSOs (Transmission System Operators) and DSOs (Distribution System Operators) about the effect of elevated temperatures on conventional bare conductors of existing line. Nowadays building new lines is very difficult cause of increased costs to obtain rights of way, public intervention, etc.... Cost and lead times required to place new lines into service are now increased and the business in electric market is reduced for the limited possibility of transmission. Therefore, utilities are attempting to gain as much capacity as possible modifying operation on existing lines. In the past, utilities have been conservative in rating their lines; today the uncertainties in parameters which influence conductor temperature, with a better understanding of environmental conditions and improvements in monitoring instruments and sophisticated analysis tools, utilities are rating lines at higher temperatures with higher level of confidence than in the past. In this paper will be discussed the effects of high temperature plastic creep elongation on the sags and tensions for a conventional conductor. Using equations developed by IEEE Std. the predicted creep for a conductor under high temperature operation can be calculated. The aim of this paper is to provide general recommendations to maintain adequate ground clearance for the safe operation of a line; itpsilas possible to operate at a higher temperature if the associated negative effects are adequately understood, considered and managed.

In the face of escalating global energy demands and the imperative to transition towards sustainable energy sources, the widespread diffusion of Renewable Energy Communities aims at sharing the energy, environmental and social benefits deriving from renewable energies. In this context, understanding and quantifying the uncertainties associated with renewable energy generation as well as the final demands becomes paramount. This paper delves into the main aspects of probabilistic modeling and uncertainty assessment in the context of multi-source Renewable Energy Communities, employing the Monte Carlo simulation method as a robust tool for comprehensive analysis. The results of the demonstrative case study show that the optimal size of the equipment among the several uncertain scenarios can be effectively identified using the mode of the results.

The paper presents an analysis of the Feed'in Tariffs (FIT) mechanism development in Italy from 2005 to 2013 and named “Conto Energia”. In particular the work examines the five editions of the “Conto Energia”, highlighting both advantages and critical issues for the PV market development in Italy; this analysis is particular interesting due to the fact that the cap on FITs in Italy has been reached in June 2013.