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Time-of-use (TOU) energy cost management involves the use of energy storage systems (ESSs) by customers to reduce their electricity bills. The ESS is charged during off-peak time periods, when electricity energy prices are low, and discharged during times when on-peak energy prices are applied. This article addresses the question whether it is economically viable to install medium-scale distributed ESSs designed to lower the electricity cost for a customer-side application, assuming flexible electricity tariffs. The technical/economical evaluation is carried out referring to lithium-ion (Li-ion), sodium sulfur (NaS) and vanadium redox battery (VRB) technologies, performing a parametric analysis by changing the capital cost of the batteries and the difference between the maximum and minimum electricity price. A case study is performed to show the advantages/disadvantages of the proposed approach. The analysis reveals that, at the current costs of ESSs, the use of batteries for TOU applications is economically advantageous for a public institution facility in Italy only if there is a significant difference between the maximum and the minimum electricity price. The decrease in the cost of storage, stimulated by the implementation of support policies, will make ESS even more convenient for load shifting applications. [ABSTRACT FROM AUTHOR]

The paper focuses on the evaluation of the impact on residential buildings of innovative control logics defined for a rational utilization of the electric loads and air-conditioning systems. The control logics are implementable thanks to a Decision Support and Energy Management Systems developed by the same authors and easily installable in new and still-existing houses. The paper shows how a significant reduction of the primary energy consumption can be obtained by controlling the air-conditioning units together with the other electric loads of the house. After having explained how the control logics operate, a simulation tool is described, developed for a preliminary evaluation of their effects on the energy consumptions of residential buildings in the design stage. An application of the simulation tool on a typical house, considering different scenarios and varying the climatic conditions and the energy performance class of the envelope, is presented. Finally, a measurement campaign on two real existing houses, equipped with the Decision Support and Energy Management System, is described, and the effects of the control logics are assessed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Relation between BACS and energy performance of buildings. [•] Economic impact of BACS and TBM. [•] Effects of the application of EN 15232 to the Italian procedure for energy certification of buildings. [•] Calculation of the PBP of the investment for installing BACS in a residential building. [ABSTRACT FROM AUTHOR]

Abstract: The subject addressed in this paper is the definition of some strategies for the design and the optimaized management of EES (Electrical Energy Storage) systems, for an existing islanded distribution network supplying the Island of Pantelleria (Italy) in the Mediterranean Sea. In the paper the authors have drawn interesting conclusions through the application of an efficient MO (multi-objective) optimization algorithm, the NSGA-II, minimizing the energy losses in the grid, the total electricity generation cost and the greenhouse gas emissions. The results obtained for different installation scenarios of the EES are presented and discussed, putting into evidence the technical, environmental and economical benefits of using EES as well as the technical issues connected to their installation into an existing distribution network. The paper describes in details the second part of a feasibility study about the transition from a “fuel-based” traditional centralized electrical system to an active and smart “renewables-based” electrical distribution system. [Copyright &y& Elsevier]

Abstract: This paper proposes an improvement of an efficient multiobjective optimization algorithm, Non-dominated Sorting Genetic Algorithm II, NSGA-II, that has been here applied to solve the problem of optimal capacitors placement in distribution systems. The studied improvement involves the Crowded Comparison Operator and modifies it in order to handle several constraints. The problem of optimal location and sizing of capacitor banks for losses reduction and voltage profile flattening in medium voltage (MV) automated distribution systems is a difficult combinatorial constrained optimization problem which is deeply studied in literature. In this paper, the efficiency of the proposed Crowded Comparison Operator, CCO1, is compared to the efficiency of another Crowded Comparison Operator, CCO2, whose definition derives from the constraint-domination principle proposed by Deb et al. The two operators are tested on difficult test problems as well as on the optimal capacitors placement problem. [Copyright &y& Elsevier]

Tourist activity strongly influences the energy consumption and the overall load profile of communities with isolated energy systems. One example is hotel sectors on small islands that are not connected to mainland energy distribution grids. The use of solar energy systems could be a smart option for reducing energy consumption and tackling seasonal fluctuation. The operation of a weak and isolated electric grid requires attention to the management of power profiles in very short time frames. Energy storage (thermal or electric), as well as building automation control technologies, can be utilised for these aims. In this context, the present paper illustrates a study conducted at a hotel located on Lampedusa Island (Italy) that was considering some energy-retrofit scenarios dealing with the exploitation of renewable energy sources and building automation control technologies. The hotel is equipped with an air-to-water heat pump able to fulfil air conditioning and domestic hot water demands. Data concerning the hotel's energy consumption was measured during summer months while yearly data was provided by the local electric utility company. Detailed simulation models have been validated by this data and used to assess the efficacy of retrofit scenarios and their effects on the average daily electric profile. [ABSTRACT FROM AUTHOR]

Over the last decade, the architecture of the energy market has radically changed. In many countries end-users are now able to directly access the market, which has given rise to the question of how they can actively participate in that market. End-users can comprise a critical mass through aggregation that is carried out by a third party – to wit the “loads aggregator.” This paper proposes a new framework for generating feasible real-time price curves for those end-users in a demand-response management process. The underlying algorithm generates output curves as the solution to a constrained optimization problem whose objective function is the aggregator's economic benefit. A case simulation study of the Italian market, with various parameter options, illustrates the procedure. [ABSTRACT FROM AUTHOR]

Abstract: Reactive flows compensation optimal design for losses reduction in MV automated distribution systems is a problem deeply studied in literature. In this paper, the design problem is formulated considering the new deregulated energy market. These new operational conditions allow the MV grid operator to consider the generation of reactive energy also as a service that can be sold to the transmission system above. In this case, the transmission system would be helped in all the working conditions in which a strong modulation of the reactive flow through the HV/MV node is required. Then, for the MV grid operator, the compensation system optimal design problem is therefore that of the search for the configuration (number, location and rated power of the capacitor banks) attaining the following main objectives: (i) to minimise power losses; (ii) to maximise the return on investment for the compensation system. Since results are strongly influenced by the parameter ‘economic value given to the reactive power’, RPEV, flowing from the MV network through the HV node, the optimisation problem has been parameterised for different values of RPEV and the total installed reactive power has been observed. A threshold value of this parameter has been identified. For values greater than the threshold, the proposed investment is economically profitable for the distribution grid operator, DGO. [Copyright &y& Elsevier]

The paper addresses the issue of the transition from a traditional electrical system without automation to a newer active and smart system allowing the possibility of implementing Demand Side Management policies, for little islands not supplied by the main grid. In particular, the paper focuses on two main topics related to the definition of: • an effective control, monitoring and communication system as a tool for the full exploitation of the opportunities given by Demand Response policies; • some solutions for the automation of the end-users’ electrical installations, in order to offer to the utility flexibility to be used for the improvement of the generation and distribution efficiency. After a brief discussion on the international regulatory framework on automation and ICT applications for power systems, the paper presents a feasibility study, based on the characteristics of the island of Lampedusa, of a hierarchical architecture of a suitable control system and of some DSM enabling solutions for residential end-users. The proposed solutions are defined taking into account some main elements: • distribution grids in small islands are generally equipped with outdated and hardly automatable devices; • utilities in small islands have reduced budget for new investments; • not less important, the most of the inhabitants has low income and unfamiliarity with automation. Therefore, main features of the proposed DSM enabling technologies are low cost and ease of use. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes an efficient solution to the problem of reactive power flow tracing in electrical transmission networks. For such systems, the tracing techniques used for active power flows cannot be used straightforwardly, due to reactive power variations induced by the line reactances, these variations often being comparable to the powers delivered to the loads. In other words, as is well known, in transmission systems the reactive flows are strongly influenced by the inductive and capacitive effects of the network, making the tracing of power flow and allocation of losses more critical. In this paper, after discussing some methodological aspects, an approach based on the use of transmission line models differentiated on the basis of the reactive behaviour of the lines is proposed. These models allow the power contributions due to reactive losses to be evaluated separately and compared to the flows exchanged between generators and loads; moreover, their application does not require the introduction of nodes or additional links, as is the case with other methods proposed in the literature. The proposed tracing technique is then presented; the method is straightforward and does not require the creation or inversion of matrices of participation factors. The paper concludes with two applications, a 4 node system and the IEEE test system with 30 nodes. [Copyright &y& Elsevier]

Abstract: A methodology for the analysis of radial or weakly meshed distribution systems supplying voltage dependent loads is here developed. The solution process is iterative and, at each step, loads are simulated by means of impedances. Therefore, at each iteration, it is necessary to solve a network made up only of impedances; for this kind of network, all the voltages and currents can be expressed as linear functions of a single unknown current (in radial systems) or of two unknown currents for each independent mesh (for meshed systems). The methodology has been called “backward” since the unique equation, in case of radial network, and the linear system of equations, in case of meshed network, in which such unknown currents appear can be determined by starting from the ending nodes of the radial system, or of the radialized network (obtained by means of cuts in meshed networks). After a brief presentation of the b/f method, which is currently the most commonly used technique for solving distribution networks, the solution methodology is detailed both for radial and for meshed systems. Then, the way in which PV nodes can be considered is also described. Finally, the results obtained in the solution of some networks already studied in the literature are presented with other methods, in order to compare their performances. The applications show the efficiency of the proposed methodology in solving distribution networks with many meshes and PV nodes. [Copyright &y& Elsevier]

Abstract: In this paper an iterative backward methodology to solve radial distribution networks with fixed voltage (PV) nodes and with constant power loads or mixed loads (with at least one component with constant power) is proposed. The method developed, although deriving conceptually from the backward/forward (b/f) methodology, presents only the backward phase in which all the network variables are evaluated. In the methods developed up until now for the solution of such systems, PV nodes are taken into account at the end of each iteration by evaluating, based on the known quantities of the network, the unknowns associated with PV nodes. In the methodology developed here the unknowns relevant to PV nodes are considered within the search process together with the unknown state variables. The proposed method at each iteration requires the solution of a network made up only of impedances; for such a system, supplied only at one node, the susceptances of the PV nodes are unknown as well as the currents in shunt impedances of the terminal buses. In order to solve such a system, a simple and efficient technique has been established. It allows the determination during the backward sweep of all the unknowns. The main and most important feature of the simulation of PV nodes with shunt reactance is the high precision of results related to reactive power injection at PV nodes. The applications indeed show that precision does not differ from that related to the use of the classical Newton–Raphson method; furthermore, also the number of iteration is similar with reduced CPU times. After having reported the models of PV nodes already existing in the literature in the field of b/f analysis methods, the general methodology for solving a radial network made up of impedances is briefly presented. The new analysis method and its implementation are then presented in detail. The results of the applications carried out show the good performance of the model in terms of both speed of convergence and, mainly, of precision. [Copyright &y& Elsevier]

Abstract: In this paper, a new backward/forward (b/f) methodology for the analysis of distribution systems with constant power loads is presented. In the proposed method, at each iteration, the loads are considered as constant impedances; in the backward sweep all the network variables (bus voltages and branch currents) are evaluated considering a scaling factor which is determined at the end of the backward phase. Indeed the forward sweep is eliminated and the node voltages calculation does not demand the sequentiality needed in the b/f methodology. The developed method, although deriving conceptually from the b/f methodology, presents only the backward phase in which all the network variables are evaluated considering a scaling factor. Moreover the load simulation as impedances is particularly important when the network shows PV nodes for which the voltage displacement and the reactive power are the unknowns. The condition of 90° displacement between the PV node voltage and the current injected by the apparatus for voltage regulation is not usually satisfied in networks solved by methods using constant current load models. The possibility to solve, at each iteration, a network made up of impedances allows to evaluate the reactance that must be inserted into the PV node in order to set the voltage at the prescribed value. In this way the value of this reactance is updated at each iteration and, at the end of the iterative process, whatever it is the displacement of the PV node voltage, the current circulating into the voltage regulating apparatus will be at 90° from it. In the paper, after a description of the PV nodes models reported in the b/f analysis literature, the new method is presented. The way in which the constant power loads are represented by means of a constant impedance model is also illustrated as well as the method for the evaluation of the unknown reactance to be installed at the PV nodes. The results of the executed applications show the efficiency of the model in terms of precision in the calculation of the reactive power required to sustain the voltage at the PV nodes. [Copyright &y& Elsevier]