Romano Giglioli

Use of electrochemical storage in substations to enhance energy and cost efficiency of tramways

This paper evaluates, in a case study with real data, the advantages of using regenerative braking in a tram line, both in case of non-reversible substations and substations equipped with battery energy storage. It shows that the addition of storage enhances energy efficiency a lot, and therefore this is a very cost-effective solution.

Control strategies and real time operation of storage systems integrated with MV photovoltaic plants

Nowadays the increasing share of renewable sources requires a direct participation of all form of generation to the secure operation of the electric power system, at least in terms of power balancing and voltage regulation. Resiliency, controllability and flexibility are the key factors that characterize a smart grid, compared to traditional energy systems. In this regard, storage systems can be used to provide the grid with a large range of services, such as frequency and voltage regulation, short-term power reserve and power quality. Nevertheless, persistent power modulation can originate a progressive drift of the battery State of Charge, thus reducing the real exploitability of the storage system for other scheduled energy services, like load levelling. This paper describes in a systematic approach a novel control architecture, in which an external loop aimed to compensate the SOC drift, in addition to the conventional frequency droop regulation, has been implemented and tested on an existing MV photovoltaic plant integrated with energy storage.

Aggregation and management of the demand in a deregulated electricity market

The deregulation of electricity markets, now coming into force in several countries, has a strong impact on the behavior of electricity customers and stimulates the use of tools for increasing the flexibility of consumption, since markets encourage price responsive demand. Load management and customer aggregation can improve the role of demand within markets, if consumers are able to respond to price signals by handling load. This paper discusses the benefits of demand aggregation and load flexibility in a deregulated context, from the point of view of customers; in addition, an example of load management procedure based on neural networks is presented.

Cost effective storage for energy saving in feeding systems of tramways

This paper evaluates the cost effectiveness of using regenerative braking in a tram line in case of non-reversible substations equipped with battery energy storage. It shows, by the combination of results by numerical simulation model and experimental tests, how it is possible to effectively transform an existing tramway to improve its energy efficiency. Results have shown that also from the economical point of view the proposed solution can be of great interest for the transport company wishful to update its system technology.

Short-term operation of a hybrid minigrid under load and renewable production uncertainty

Properly sized and operated hybrid minigrids can assure good-quality electricity to rural households at an affordable price. A system composed by renewable sources, a diesel generator and batteries can be a cheaper option, but it requires daily operation in order to reduce fuel consumption, to assure fuel availability, and to avoid quick degradation of the batteries. Variability in load and renewable generation introduces uncertainties that must be considered in order to assure a proper operation, thus reducing the curtailment of both load and renewable production. This paper proposes a procedure for short-term operation of a hybrid minigrid in order to cope with errors in forecasting of both load and renewable generation. A probabilistic tool based on Monte Carlo simulations and mixed-integer programming is developed to estimate the optimal working point of the diesel generator and batteries. The Monte Carlo scenarios are singularly optimized, thus defining several optimal schedules that are combined to define the proposed stochastic commitment and dispatchment. The methodology is supported by numerical case studies that even confirm the applicability of Monte Carlo simulations to the short-term operation.

Impact of a large fleet of EVs on the efficiency and reliability of an electric power system

The influence of electric vehicles on the power system has been traditionally analyzed in terms of recharge infrastructures and adequacy of the electric distribution network. Nevertheless, the additional power demand due to the recharge of a large number of batteries could significantly modify the national load profile, hence the dispatching of production plants. The recent literature approaches this issue using deterministic methods or simplified probabilistic considerations. In this framework, the present paper proposes the use of a Monte Carlo probabilistic approach to assess the impact of large fleet of EVs on the efficiency and reliability of the generating park of an electric power system. A Sequential Monte Carlo simulator has been developed and applied to the hourly operation of the Italian power system. Several 2020 scenarios, diversified in terms of number of vehicles and recharge timing, have been assumed for the future fleet of EVs. The study was mainly realized within the PRIME project, funded by the Italian Ministry for the Environment.

Optimal storage operation in EV charging stations delivering grid services

This paper presents criteria for the optimal operation of an EV charging station, capable of providing the grid with regulation services such as frequency and voltage control, peak shaving, and load leveling. The presence of an additional storage device connected to the charging station is investigated; both configurations are analyzed in which the storage device of each vehicle contributes to such services and in which the charging profile is independently imposed by the vehicle charging control system.

Optimal sizing of a mini-grid in developing countries, taking into account the operation of an electrochemical storage and a fuel tank

Nowadays, mini-grids can provide reliable and cheap electricity also to far communities of developing countries. Diesel generators can ensure backup power, in addition to renewable sources and energy storage devices. However, poor infrastructures, severe weather conditions and a difficult procurement chain can strongly influence the fuel delivery, thus reducing the continuity of supply. The present paper proposes a stochastic method to optimize the design of a rural mini-grid composed by a photovoltaic plant, a lithium battery, a diesel generator and a fuel tank. The fuel procurement strategy and its mathematical model are also discussed and simulated. A Particle Swarm Optimization (PSO) procedure is applied to the optimal sizing of components, in combination with a Monte Carlo technique aimed to handle the uncertainties of fuel delivery, irradiance and load. A case study for a possible mini-grid in Uganda is discussed, also performing a sensitivity analysis of the results with respect to the fuel delivery time, the fuel price and the cost of load curtailment.

Optimal sizing of a hybrid mini-grid considering the fuel procurement and a rolling horizon system operation

Hybrid mini-grids are promising solutions to foster the universal electricity access in developing countries. While renewable sources, possibly combined with energy storage devices, help in reducing the environmental impact and the operational costs of electricity supply, a backup diesel generator can increase the continuity of service when RES are not available or very discontinuous. The fuel procurement can be a serious issue in rural areas, due to lack of good infrastructures, combined to long distances existing between the mini-grid and the fuel station; however, this aspect is usually disregarded in designing the mini-grid. Moreover, the traditional sizing of rural mini-grids is based on simulating simple operational strategies. Rolling horizon strategies can be more efficient since the system is redispatched also infradaily, thus leading to possible reductions of operational costs and load curtailment. The present paper proposes a novel probabilistic technique for the optimal sizing of a mini-grid, considering both the fuel procurement issues and a short-term rolling-horizon scheduling of resources. This method is applied to a system composed by a photovoltaic plant, a lithium battery, a diesel generator, and a fuel tank, minimizing the net present cost of the system over the project lifetime. A numerical case study is discussed.

Hybrid energy systems for static applications

Through a couple of examples this paper describes how hybrid systems can play an important role in todays energy systems. They are valuable and efficient solutions in both isolated systems and for large interconnected networks. Different technologies for storage and generation as well as different operation techniques are needed for each application, but the benefits that can be achieved with respect to traditional solution are important in easing the transition towards a sustainable energy system.