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Among different solutions to increase flexibility of electricity system, grid interactive water heaters (GIWHs) can make a large contribution, against a relatively low cost. They can advantageously be used within a single building, a local energy community or within an entire distribution grid, thanks to the very fast response time, low cost, highly distributed resource and widely demonstrated technology. In the near future, the flexibility potential of GIWHs will certainly increase, thanks to the advantageous flexibility programs that have been implementing in some area of the world, with the aim of coordinating several million of GIWHs with the electricity network. In this study, we assess the potential value that the flexibility of GIWHs can bring to the electrical power system, compared to the other sources of flexibility, focusing on the US market, specifically California, Oregon and Washington. The GIWH technology and the main GIWH control strategies are described, highlighting the flexibility behaviour of GIWHs. An overview of the GIWH pilot programs currently developed in the US market is provided, and current available technologies are shown, both for new and for retrofit GIWH installations. Most of the papers discussed in the literature focus on different aspects of demand response (DR), but very few of them focus specifically on GIWHs, and none of them offers a review of GIWHs in the US context. The present work thus constitutes a research gap, and could help stakeholders to assess the US GIWH market evolution, identifying the potential value of GIWH flexibility.

In this paper, the synthetic inertia need of the small island of Pantelleria in the Mediterranean Sea is assessed. Firstly, the optimal renewable energy mix able to minimize the Levelized Cost of Energy for the generation system of the island is evaluated, considering the yearly load demand and the characteristics of the local natural resources. The optimal energy mix introduces in the island a quota of power generation with static power converters interfaced to the grid that could jeopardize the security of the system if not suitably controlled. Therefore, the inherent inertial response of the diesel generators of the system is calculated hour by hour for each month of one year, considering the new schedule of the generators for various cases characterized by different percentages of production from the optimum renewable energy mix. Finally, the rated power and capacity of a battery energy storage system is calculated in order to compensate the reduction of the inertial response in the power system thanks to a suitable synthetic inertia control. The calculation is done by considering the maximum allowed frequency nadir in case of a disturbance. For each scenario, the maximum disturbance is also assessed with and without synthetic inertia. The results are compared with those obtained in a previous study on the same island where batteries were used for different purposes.

Demand side aggregation represents an important opportunity for ancillary services provision due to the potential that the coordinated management of distributed resources has on affecting power systems' operation. In this framework, the Aggregator has a main role and takes on different relationships with the other actors of the power system, usually becoming a mediator between the prosumers and the distribution system operator. The DEMAND project introduces a new point of view in demand side aggregation by proposing a new framework where the Aggregator is no more needed and prosumers can share and combine their flexibility in a new aggregation platform called Virtual Aggregation Environment (VAE). In this paper, an algorithm for the day- ahead estimation of each prosumer's flexibility is presented. The algorithm evaluates various couples of power variation and desired remuneration to send to the VAE for further elaborations. A case study shows how the algorithm works.

In last years, the energy efficiency in non-interconnected islands became an important topic, since the electricity production is often based on diesel generators, thus contributing to the global warming. Italian government recently emitted two decrees to promote the introduction of renewable energy technologies in 21 non-interconnected islands, both for electrical and thermal uses. In this paper, the economic and environmental feasibility of the introduction of renewable energies in the island of Pantelleria was assessed adopting an optimization approach. Furthermore, the flexibility provided from the local desalination plant and the domestic water heaters was evaluated. The final demands for electricity, air conditioning, domestic hot water and freshwater were analyzed, and the island was schematized as a multi-carrier energy hub and optimized through a mixed integer linear programming algorithm. Results prove that the renewable energies may provide a strong reduction of operating costs and greenhouse emissions of diesel generators in non-interconnected islands, although the optimal configurations differ according to the objective function of the optimization.

European renewable generation has been supported through several policy instruments in the last decades, and this has caused a significant growth of the renewable energy sector, spurred by the ambitious climate and energy policy targets. Despite this impetuous growth, the electricity infrastructure is not yet ready to accept increasing shares of variable renewable energy sources (RES) generation, and this is causing grid balance challenges, due to the inherently variable nature of the PV and wind energy. In order to overcome this issue, allowing higher shares of renewable generation in the energy sector, energy storage (ES) systems are becoming increasingly competitive in the global energy landscape, thanks to the positive momentum in research and innovation, making European energy supply more secure, sustainable and affordable. Despite the unarguable benefits, storage technologies still see significant needs for more education among stakeholders, since they are not familiar with technology's benefits and management solutions. In order to fill this gap, this study provides an overview of storage technologies for stationary applications in the EU (plus Bosnia-Erzegovina, Norway and Switzerland), addressing the main trends in European policy legislation, also identifying advantages and barriers for their implementation. Furthermore, based on the analysis of the US Department of Energy (DOE) storage database, the main trends in ES installations within the EU markets are identified, with reference to storage technologies. The analysis carried out in this work could help stakeholders to assess the European storage market evolution in the stationary sector, identifying the main drivers and barriers for each storage technology.

The evolution of modern power distribution systems into smart grids requires the development of dedicated state estimation (SE) algorithms for real-time identification of the overall system state variables. This paper proposes a strategy to evaluate the minimum number and best position of power injection meters in radial distribution systems for SE purposes. Measurement points are identified with the aim of reducing uncertainty in branch power flow estimations. An incremental heuristic meter placement (IHMP) approach is proposed to select the locations and total number of power measurements. The meter placement procedure was implemented for a backward/forward load flow algorithm proposed by the authors, which allows the evaluation of medium-voltage power flows starting from low-voltage load measurements. This allows the reduction of the overall costs of measurement equipment and setup. The IHMP method was tested in the real 25-bus medium-voltage (MV) radial distribution network of the Island of Ustica (Mediterranean Sea). The proposed method is useful both for finding the best measurement configuration in a new distribution network and also for implementing an incremental enhancement of an existing measurement configuration, reaching a good tradeoff between instrumentation costs and measurement uncertainty.

Battery energy storage systems (BESSs) are becoming increasingly competitive in the global energy landscape, thanks to the strong cost reduction that has taken place in recent years and it is expected to continue in the next future. Among the many benefits BESSs can provide, time shifting can be exploited by electricity consumers to save on the electricity bill, charging the storage during the off-peak hours and discharging when the cost of electricity is high. This paper describes a simple procedure to optimize the BESS capacity under a peak load shaving strategy, in presence of a time-of-use (TOU) electricity rate, able to guarantee, at the same time, the flattest daily power diagram and the maximum benefit for the electricity consumers, reducing both the energy and the power component of the electricity bill. A case study is also presented and the modifications of the load diagram due to the BESS operation are shown.

Battery energy storage systems (BESS) are becoming increasingly widespread in modern power systems, thanks to the important benefits they can provide to the electricity grid. Indeed, BESS can be used in time shifting applications, storing energy during off-peak periods and discharging during peak times (when the cost of electricity is high). When BESS are used for peak shaving purposes, they also contribute to relieve peak demand charges, thus ensuring a saving for the consumers. This paper describes a peak load shaving strategy defined within the DEMAND project. The strategy is able to guarantee the flattest daily power diagram and the maximum benefit for the electricity consumers, reducing both the energy and the power component of the electricity bill. As a further alternative, the consumer can choose to participate in a flexibility program, under the DEMAND project, by making available energy capacities, exploiting the charging/discharging capability of the BESS.

The purpose of this paper is to study the positions of some European Union (EU) countries on the development of PV systems. After a review of the main support policies for PV systems in Europe, the specific situations of five representative countries (France, Germany, Greece, Italy and the U.K.) are examined, with the purpose of describing the main differences in their implementation of support policies adopted for PV systems. In particular, comparisons based on economic indexes such as the net present value (NPV) and the internal rate of return (IRR) are carried out for different sized PV systems, showing that in some situations support policies can be inconvenient for the PV system owner. The paper also shows that the best profitability for a PV system owner is obtained in those countries in which there is an active electricity compensation scheme. The comparative analysis carried out in this work could help: – to assess the impact of PV energy policies in European member states; – to predict how the PV market could evolve in the selected EU member states; – to gain an insight into the future of possible energy policies.

In the last years, stationary battery systems started to attract the attention of stakeholders thanks to their unique ability to decouple power generation and load over time, providing the ancillary services necessary for the stability and the reliability of the electrical system. This is especially true in the presence of high levels of penetration of renewable energy technologies, like wind and solar photovoltaic (PV), because of increased fluctuations in the electricity produced by these renewable sources. Despite the growing interest in energy storage technologies, the academic literature has not completely assessed the development trends of this sector. In order to fill this gap, this study strives to address the trends in the spread of stationary battery systems within the U.S. territory. First, the U.S. policy legislation within the different U.S. states is reviewed, with particular emphasis on support policies put in place in the different states. Second, based on the analysis of the Department of Energy (DOE) Energy Storage Database, the main trends in battery systems installations within the U.S. are identified and presented in this paper, with reference both to the viable use cases and to the main electrochemical technologies currently spread in the storage market. The analysis carried out in this work could help stakeholders to assess the impact of energy storage policies in the different U.S. states, identifying the future trends and the most promising markets within the U.S. territory.

A recent report from the German Energy Agency analyzes the possible introduction of the blockchain technology in energy transactions in power distribution. The issue deserves attention since the extensive digitalization of business models puts new challenges to utilities in the power sector. The German decision makers in the energy field claim that blockchain appears as a close perspective and, at the same time, the Gartner hypecycle puts this technology at the peak of inflated expectations in 2016. Diffuse perception however provides hints for further investigation on the topic. This paper provides insight into the problem of peer-to-peer energy exchange from a technical perspective, providing evidence about an impossible guarantee for the so-called ‘transparency’ in energy transactions. A generic customer that buys energy from his neighbor that produces clean energy cannot have any guarantee about the origin of the energy he consumes, since it depends from the voltage distribution across the network. This assumption is even more realistic when different generation sources are distributed in the power distribution network, providing also voltage regulation services. It will be proved through some easy examples that, differently from other digital business models, such as Airbnb and Uber, the physical asset here plays a crucial role that cannot so easily be neglected.

Battery Energy Storage Systems (BESSs) are gaining more and more attention in the current global energy landscape, thanks to some peculiar characteristics such as the versatility, modularity, scalability, fast response time, etc. BESSs can advantageously be used in the ancillary services market, in order to provide all the services necessary to ensure the stability and the reliability of the power system. Among other applications, BESS can also be used to shift electricity demand from on-peak to off-peak periods, also contributing to relieve peak demand charges, thus ensuring a saving for the customers. The BESS is charged when the electricity prices are the lowest (during the night) and discharged when the prices are the highest (during the daily hours), contemporary achieving a leveling of the daily usage pattern. This paper is the first of a two-part series, aiming to evaluate the economic feasibility of electrochemical storage systems in peak load shaving applications. The sizing and the operating strategy of the BESS are defined, so as to obtain, at the same time, the flattest daily usage pattern and the maximum benefit for the customer. A case study is analyzed, showing the modification of the power diagram when the BESS is added. The simulation results show a customer daily power profile perfectly leveled in shoulder seasons and a peak shaving effect in all other days.

This paper is the second of a two-part series, aiming to evaluate the economic feasibility of electrochemical storage systems in peak load shaving applications. The battery energy storage system (BESS) is considered to be added to a private facility, with the aim of reducing the customer electricity bill. The BESS is charged during the night, when the electricity prices are the lowest and discharged during the daily hours, when the prices are the highest, contemporary achieving a leveling of the daily usage pattern. The economical evaluations are carried out considering four different electrochemical technologies: lithium-ion (li-ion), advanced lead-acid, sodium-sulphur (NaS) and flow batteries. First, the total costs and savings are estimated, calculating the net present value (NPV) and the internal rate of return (IRR) for each BESS technology. The economic indexes are calculated referring both to 2015 and to the estimated 2020 BESS prices. Second, a parametric analysis is carried out to investigate the effect of several parameters on the economic feasibility of installing a BESS. The considered parameters are: i) the gap between high and low electricity prices; ii) the peak demand charges; iii) the BESS investment costs. The economic analysis reveals that none of the BESS technologies are cost effective at the current BESS prices, without incentives, but the situation could already change in 2020 thanks to the sharp cost decline expected in the coming years.

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. © 2015 Elsevier Ltd. All rights reserved.

This paper proposes a novel measurement procedure for load flow analysis in medium voltage (MV) smart grids. The new approach is based on power measurements at low voltage (LV) side of MV/LV distribution substations. Such measurements are carried out by means of power quality analyzers. If compared with the load flow methods based on measurements at the MV side, the proposed approach has a lower cost and it offers an equally reliable measurement system. The proposed algorithm takes the basic concept of the current summation backward/forward method; some modifications are introduced to use LV load powers measurements. To this aim, the MV/LV power transformer is properly modeled and taken into account in the algorithm. The proposed approach is validated by means of both simulations and experimental measurements; the test system is the MV distribution grid of Ustica Island, Italy. First, the proposed algorithm is compared with the MATLAB/Simulink load flow tool, which is based on the traditional Newton-Raphson method. Second, a comparison is carried out between the proposed method and the measurement data collected in the actual MV network of Ustica. Such comparison takes into account the uncertainties of both proposed method, and experimental active and reactive MV power measurements.

Today, photovoltaic (PV) attracts considerable interest in relation to renewable energy technologies, because of its potential to contribute significantly to the future of renewable energy. However, PV market development is related strongly to the support policies introduced by national governments, defined in national laws. The modification or fading out of such incentive schemes can strongly influence the development of the PV market in any given country. In this paper, after a brief review of national support policies in PV technology in eastern European Union (EU) countries, the authors perform an economic analysis of the main support mechanisms that are implemented in these countries. The comparative analysis is based on the calculation of the cash flow, the Net Present Value (NPV) and the Internal Rate of Return (IRR) indices. The analysis shows that in some situations, support policies can be inconvenient for the owner of the PV system and that, in many cases, the differences between the implementation of the same support policy in different countries, can give rise to significantly different results.

In the 9th of March 2007, the European Council decided a fixing goal of 20% contribution of the renewable energy sources (RES) on the total European electric energy production in 2020. In order to reach such an ambitious goal, all the European countries are adopting different support policies for encouraging the installations of RES-based generation systems. In this paper, after a brief review on the main support policies for RES in Europe, the specific situations of four representative countries (France, Germany, Italy and Spain) are examined, with the purpose of putting into evidence the main differences in the support policies adopted for Photovoltaic (PV) and Wind systems. In particular, a comparison based on the calculation of the pay-back-period (PBP), the net present value (NPV) and the internal rate of return (IRR), for different sized PV and Wind systems, shows that in some situations a support policy can be not convenient for the owner of the RES-based generation system and that, in many cases, the differences between the way of implementation of the same support policy in different countries, can give place to significantly different results.

The proliferation of Distributed Generation (DG) in power systems calls for a redesign of electricity network management, which should be able to accommodate large amounts of intermittent generation. This issue requires a discussion about the current dispatching regulation, giving distributed storage systems and qualified electricity consumption the opportunity to provide ancillary services to the distribution grid. In this work, a new dispatching strategy for the integration of active-demand and distributed storage in the Italian electricity market is presented. The strategy is focused on a distribution Smart Grid (SG), where customers can indirectly participate to the Day-Ahead (DA) and the Ancillary Services Market (ASM) through a load aggregator, able to manage the consumers' flexible consumption through Direct Load Control (DLC). The dispatching strategy is described both in the architectural framework and in the functional aspects. The proposed dispatching strategy has been designed in order to fit the current Italian electricity market, giving the opportunity to increase the electricity market flexibility, ensuring a reduction of electricity zonal prices and contributing to the benefit of all the players involved.

Electricity prices show significant short-term variations during the day due to the need of balancing supply and demand in real time. Normally, customers are not exposed to these variations but pay a constant electricity price. In an attempt to reduce the volatility of the wholesale prices, several utilities are moving from conventional fixed-rate pricing schemes to new market-based models, where the electricity price can fluctuate during the day depending on the market conditions. Examples of time-dependent pricing schemes are Time-Of-Use (TOU) tariffs, where the electricity price can take two or three price levels during the day, or Real-Time Pricing (RTP) tariffs, where the energy price can vary hourly depending on the wholesale market. Electricity customers can thus take profit from the installation of storage technologies, storing electricity when the price is low and reselling it back to the grid during peak hours, at a significantly higher price. In this paper, a sodium-sulfur (NaS) battery is considered to be added to a medium-scale public facility, in order to reduce the electricity bill. The storage is operated exploiting a simple strategy (charging during off-peak, discharging during on-peak prices) with the aim of maximizing the saving for the end-user. The economic viability of using the storage is evaluated and discussed, referring both to the hourly national prices and to the zonal electricity prices of the Italian energy market. The results show that the payback period (PBP) is greater than the battery life when the customer prices are assumed proportional to the single national prices. The situation could change in the near future, thanks to the cost reduction of storage technologies expected in coming years.

The paper presents a comparison of two prototypes of innovative Customer Power Devices designed for applications in Smart Micro-Grids. The devices are both equipped with Energy Storage Systems, consisting in Lithium batteries and have been assembled, independently, by the DIAEE of the University of Rome 'La Sapienza' and the DEIM of the University of Palermo in collaboration with the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA). In the paper, the characteristics and the operating modes of the devices are examined and some consideration on their application in Low Voltage Smart Micro-Grids are provided. © 2015 IEEE.