Authors

Energy transition technology roadmap. Distinguishing hype from reality – 2020 strategic technological plan and business targets

Daniele Rosati, Pietro Raboni, Carlalberto Guglielminotti

White paper // 23 may 2017

Climate change and global warming in particular may be a controversial scientific theory, particularly in the US, but its growing impact on business is undeniable. The energy generation landscape, to begin with, is being disrupted by the growth of renewables; transport is witnessing the affirmation of the electric car, in its pure form or as a hybrid, and, most pervasive of all, the search for energy efficiency is creating new businesses – think for example smart metering or behind-the-meter distributed generation – and is modifying existing ones in a variety of ways. Our vision of the macrotrends shaping the energy transition is consistent with the narrative of Bloomberg New Energy Finance's New Energy Outlook, to which we make extensive reference in this overview.

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Optimization Models for Islanded Micro-Grids: A Comparative Analysis between Linear Programming and Mixed Integer Programming

Alberto Dolara, Francesco Grimaccia, Giulia Magistrati, Gabriele Marchegiani

Energies 2017, 10(2), 241 // 16 February 2017

"This paper presents a comparison of optimization methods applied to islanded micro-grids including renewable energy sources, diesel generators and battery energy storage systems. In particular, a comparative analysis between an optimization model based on linear programming and a model based on mixed integer programming has been carried out. The general formulation of these models has been presented and applied to a real case study micro-grid installed in Somalia. The case study is an islanded micro-grid supplying the city of Garowe by means of a hybrid power plant, consisting of diesel generators, photovoltaic systems and batteries. In both models the optimization is based on load demand and renewable energy production forecast. The optimized control of the battery state of charge, of the spinning reserve and diesel generators allows harvesting as much renewable power as possible or to minimize the use of fossil fuels in energy production.”

Performance Analysis of a hybrid micro-grid in Somalia

Alberto Dolara, Elisa Donadoni, Sonia Leva, Giulia Magistrati, Gabriele Marchegiani

IEEE PES PowerTech 2017 // 2017

This paper presents a data analysis of an islanded diesel-PV-battery system, placed in Somalia. Operation of each generator is observed, concerning the most relevant performance indicators. Analysis is carried out during the first 11 months of operation, from November 2015 to September 2016. Investigations are divided into two periods, according to a significant load variation due to the connection of a new distribution line to the power plant. Thus, a comparison on load demand sharing among generators is realized between the two periods. In conclusion, benefits in terms of fuel consumption, CO2 emissions and money savings are presented.

Distributed storage for provision of ancillary services to the main grid: project PRESTO

S. Nassuato, G. Magistrati, G. Marchegiani, D. Falabretti, M. Delfanti, M. Merlo

Energy Procedia, vol. 99, pp. 182-193 // November 2016

This paper presents the three-year PRESTO research project (2013-2015). PRESTO is a self-funded project developed by the Department of Energy of Politecnico di Milano in cooperation with FIAMM Storage, Elvi Energy and MCM Energy Lab (an Italian spin-off). Within the project, experimental tests and numerical simulations were performed in order to evaluate the effectiveness of an Energy Storage System (ESS) in the provision of ancillary services to the main grid. This paper focuses specifically on the experimental and numerical analyses carried out in the project to develop an innovative control law for the primary frequency regulation, able to maximize the performances of the regulating service and effectively manage the ESS state of charge.

Optimal Management Algorithm for Battery Energy Storage System Included in an Islanded Micro-Grid

Alberto Dolara, Giulia Magistrati, Francesco Grimaccia and Gabriele Marchegiani

16th International Conference on Environment and Electrical Engineering (EEEIC) // 7-10 June 2016

This work proposes an optimization method for the management of a Battery Energy Storage System (BESS) integrated in an islanded Micro-Grid, including Renewable Energy Systems (RESs) and generators burning fossil fuels. The optimized control of the battery State of Charge (SOC) allows to get the BESS available as much as possible to support the RES power production, hence minimizing the use of fossil fuels. The optimization of the BESS is based on load demand and RES production forecast. The Optimization Algorithm that has been adopted is the Linear Programming, using the method of the Interior Point.

Control loops design in a grid supporting mode inverter connected to a microgrid

Giovanni M. Foglia, Luisa Frosio, Matteo F. Iacchetti, Roberto Perini

2015 17th European Conference on Power Electronics and Applications (EPE'15 ECCE-Europe) // 8-10 September 2015

This paper deals with some design aspects of the control loops in a droop-controlled VSI connected to other inverters of greater ratings or to a strong grid, which sets the frequency. The design of a damping resistor in series with the AC filter capacitor is discussed and the impact of strong feedback between the output current and the capacitor voltage is investigated. Moreover, an analysis of the derivative droop coefficients is carried out through a simplified equivalent circuit.

Hybrid micro-grid experimental application in Tanzania

M. S. Carmeli, M. Mauri, C. Brivio, P. Guidetti, S. Mandelli, M. Merlo, R. Perini, G. Marchegiani, D. Rosati

2015 International Conference on Clean Electrical Power (ICCEP) // 16-18 June 2015

This paper is intended to introduce the project Energy4Growing that aims at studying and setting up a hybrid micro-grid to supply power to a school in rural Tanzania. It describes the results of the early project actions which concerned in: (i) analysing the actual school power supply system through locally metered data; (ii) developing the first step of a new electro-mechanical model which addresses the simulation of operation and dynamics within an off-grid power system; (iii) validating the new model. In particular the paper focuses on describing the development and the first step implementation of the new modelling approach which address: (i) voltage and frequency analyses over medium term period by means of simplified electromechanical models of power sources and power electronics, (ii) the analysis of different dispatch strategies and their consequence on voltage and frequency trends, (iii) the effects of dispatch strategies on the energy performances of particular components such as battery bank or dump loads. The new approach has also been applied in modelling the current school power supply system.

Electricity tariff reform – Discourages energy efficiency

Giuseppe Artizzu

www.qualenergia.it // february 2015

The solution suggested by the authority to resolve problems is to penalise and shift part of the financial burden on to those who produce renewable energy power, which seems to be contrary to what the legislations state. Here follows Giuseppe Artizzu’s opinion on the proposal for reform of the electricity rates of residential customers. Having summarized the proposed reform of the electricity rates for residential customers deeply discussed by the energy authority, we will host a debate about it on the following pages. We have published the opinions of GB Zorzoli the Honorary President of FREE, and of Chicco Testa, the President of Assoelettrica.

Opec had no choice

Giuseppe Artizzu

www.huffingtonpost.it // january 2015

The long-awaited Opec Summit in Vienna on thursday ended with nothing concrete: cartel production in 2015 will remain the current one, despite the collapse of more than 30% of barrel price since this summer. Who has interpreted the decision as a deliberate choice by the Saudis to make a price war on American producers is wrong. Opec had no choice, the financial perspectives are grave for weaker members of the cartel, such as Venezuela and Nigeria, in a context of low oil prices. What determines the excess supply on the international oil market are not the big producers who challenge the hegemony of the Kingdom, but hundreds of small American oil companies, which drill as if there was no tomorrow. For these, the future consequences of petrol supply are not taken into consideration.

Technical Strategies for Voltage Power Regulation in LV Distribution Networks

M. Delfanti, L. Frosio, G. Monfredini, M. Merlo, C. Rosati, D. Rosati, G. Marchegiani

Distributed Generation and Alternative Energy Journal, vol. 30, no.4, pp. 7-14 // 1 January 2015

We report the integration of a novel voltage regulation strategy in the inverter control algorithm for Dispersed Generation (DG) applications. The adoption of a decentralized voltage control based on local curves allows the voltage profile to be controlled at the Point of Common Coupling (PCC) of the generators and, therefore, the capacity of existing distribution networks to host more generation from renewables. The work is focused on a low voltage distribution network and both the reactive power modulation and the real power curtailment are considered in the proposed local strategy. Both numerical and experimental analysis are necessary in order to test and validate the proposed voltage control strategy. Firstly, the performances of the proposed control are tested by a numeral analysis and the impact on both the electrical system and the inverter apparatus is evaluated. Secondly, the benefit of the control strategy is analysed by experimental analysis in a test facility to verify the feasibility of voltage regulation in a real feeder.

Hybrid distributed generation system for a rural village in Africa

M. S. Carmeli, P. Guidetti, M. Mancini, S. Mandelli, M. Mauri, M. Merlo, R. Perini, G. Tomasini, G. Marchegiani, D. Rosati

3rd Renewable Power Generation Conference (RPG 2014), pp. 1-6 // 24-25 September 2014

Nowadays the use of distributed generating systems, which use a renewable energy source, has experienced a fast development. Moreover, their intrinsic intermittent nature can be overcome using hybrid systems which combine more energy sources. This paper proposes the study and design of a hybrid generation system able to cover the energy needs of a school in a rural village in Africa (Tanzania), combining renewable and/or alternative sources and storage systems. The final results consist in the definition of an electric grid architecture suitable to interface renewable and energy needs in the most reliable way, exploiting advanced regulation and control techniques.

Why solar energy has systemic relevance

Giuseppe Artizzu

www.qualenergia.it // june 2014

Photovoltaics has assumed a role, sometimes that is a dominant one in the coverage of daily requirements. Its cost, especially in southern Italy, is competitive with that of fossil fuels. The near future is auto-consumption and accumulation. How can we change the logic of the electricity market? Giuseppe Artizzu’s article published in the latest issue of the magazine QualEnergia. In 2013 photovoltaics covered 7% of Italian electric requirements, a share that has no equal in the world. But due to the seasonal profile and time, this figure is not representative of the actual role that technology has taken. However in winter, there is a tangible impact on the wholesale price of electricity, the weight on the need is still limited, in summer and even more in the late spring technology has transformed the market, arriving to cover in a structural way 15-20% of the working day (significantly more for the holidays).

Harmonic Analysis of Output Filters for Grid Connected Converters in Battery Energy Storage Systems

Alberto Dolara, Giulia Magistrati, Riccardo Zich, Luisa Frosio and Gabriele Marchegiani

16th International Conference on Harmonics and Quality of Power (ICHQP) // 25-28 May 2014

Battery Energy Storage Systems, as well as many distributed generation systems, use voltage source inverter as interface with the grid. These converters require a filtering section to reduce current harmonics injected to the grid. Usually, harmonic filter is a series inductance connected between grid and inverter. Higher order filters can provide better harmonic attenuation at lower switching frequency and reduce filter size, with potential benefits for high power applications. This paper deals with the sizing and the frequency response of three different harmonic filters suitable to reduce the ripple in the grid current waveform. Dynamic simulations of a 100 kW Battery Energy Storage System highlight the better performance of high order filters.

Ho to put an end to dependence on russian gas

Giuseppe Artizzu

www.huffingtonpost.it // may 2014

A couple of weeks ago it was suggested, provocatively but not too much so that the Russian gas taps should be closed to buyers. Provocation or not, the developments of recent days demonstrate that the energy dependence has a political cost which is too high. Now let’s spare ourselves yet another sterile call for a diversification of sources: we need a plan and its concrete and immediate implementation. Who says it takes decades does not know the market or has a conflict of interests. Exiting from this dependance doesn’t mean stopping the import gas from Russia; it simply means reducing imports to a level that could enable, if necessary, alternatives at a tolerable cost.

Electricity market. Is the design really obsolete?

Giuseppe Artizzu

www.qualenergia.it // february 2014

In the Italian electricity system outlined there is the hypothesis that the closure of part of the thermoelectric capacity would compromise system security. It would be better to leave the reserve margin to drop and see if commodity prices return to levels compatible with ensuring the system. An article by Giuseppe Artizzu. Until three years ago, the time profile of the equilibrium price in the market followed the electric load curve faithfully. By 2012 the photovoltaics had brought a gradual but systematic reduction of price in the central hours of the day, preceded and followed by two short spikes in the early morning and late afternoon, also helped by migrating to those times of the programmable power production. In substance the hourly price curve doesn’t follow the load but the residual load, i.e. the portion not covered by intermittent sources at zero marginal cost.

The big bluff of oil companies

Giuseppe Artizzu

www.huffingtonpost.it // february 2014

The Eni media campaign focuses on the emergency of a competitive European industry, penalized by gas and electricity which is much more expensive than in the United States. The problem is real, but there are also real doubts about the sustainability of a model founded on cheap hydrocarbons. Besides this, what is striking is the unscrupulousness with which Eni, alone among the big oil companies, has chosen to play a controversial match. The leaders of the company have taken a position contrary to community strategies of decarbonisation, claiming them to be ineffective, a high cost to the economy and a potential injury to the security of supply. The economical alternative, according to Eni, would be the American choice in favor of shale gas, which means drilling in Europe and renewing the pacts with historical suppliers like Algeria and Russia.

The american energy model is not a model

Giuseppe Artizzu

www.huffingtonpost.it // january 2014

Americans are paying a third of the cost of gas in Europe, and half of that of electricity. The America of Bush and Obama is an enlightened energy model, to be imported to this side of the Atlantic. The numbers are not far from reality, but this conclusion is somewhat hasty. That Scaroni and his colleagues pester the European press with slogans is understandable, however the Ministers of Industry being their sounding board is not. This is a brief recent American history, : in the past decade the soaring prices of oil and gas has made it for the first time economically exploitable, with innovative technologies and known reserves of non-conventional hydrocarbons. Money, skills and infrastructure, combined with private ownership of the subsoil, triggered a typical American rush to deposit: within a few years, the seemingly irreversible decline of gas production has turned into a boom, shortly followed by an oil production boom too.

A novel mechanical hardware in the loop platform for distributed generation systems

M. S. Carmeli, F. Castelli-Dezza, M. Mauri, G. Marchegiani

Distributed Generation and Alternative Energy Journal, vol. 28, no. 3, pp. 7-27 // 24 September 2013

The growing number of distributed generation (DG) plants has emphasized the need to perform tests before the plants begin to operate. DG systems are complex enough that setting up of an experimental phase requires high costs and efforts. Moreover, renewable energy sources are intrinsically intermittent as they vary randomly with the time of day, the season and the weather. Consequently, the possibility of emulating the behavior of the whole renewable generation system in a real time environment, where a part of the real system, the natural energy source, is replaced by a real time computer simulation allows one to test the actual system in all the operating conditions, optimizing the control strategy before its service entrance, overcoming the randomness of renewable energy sources. This article proposes a mechanical hardware in the loop approach applied to a renewable energy generating system, where the whole drive (control, power electronics and electric machine) is tested and the mechanical part is simulated in real time environment. The problem of emulating the inertial torque, which can have a significant high value, is solved through an approach that relaxes the high dynamic requirements of the electrical drive that emulates the mechanical part. The hardware in the loop test bench emulates two energy sources (hydro and wind). In addition, a control strategy that emulates the inertial torque is implemented. An experimental phase in which different energy sources are modeled and emulated in a real time environment is presented as well. The underlying hardware-in-the-loop energy source emulation and experimentation scheme is shown to accurately represent real systems performance, under various control strategies and varying operating conditions.

Dispersed generation to provide ancillary services: AlpStore project

M. Delfanti, L. Frosio, M. Merlo, G. Monfredini, L. Pandolfi, C. Rosati, D. Rosati,

International Conference on Clean Electrical Power (ICCEP), pp. 133-138 // 29 August 2013

In the future, electrical systems should be able to integrate all users at the same time and guarantee power quality, stability and safety over time. The integration of renewable energy sources leads to new issues involving the intermittence of this generation typology. A high penetration of intermittent power plants will reduce the capability of the system to overcome critical events (e.g. frequency oscillations and voltage profile perturbation). This work presents new regulation schemes/functions developed in the AlpStore project framework, devoted to managing dispersed generation in order to provide ancillary services to the main grid. The work developed can be split into two main items: reactive injection regulation and frequency control regulation. The first regulation is devoted to increasing the Hosting Capacity of the distribution grid (i.e. it results to be a local control), whereas the latter aims to guarantee the energy balance of the national electric grid (i.e. it could be classified as a grid control).

Commercial bills are cut with the carbon tax

Giuseppe Artizzu

www.huffingtonpost.it // august 2013

In 2012 the electric bills have been loaded wth 10 and a half billion euros of incentives for renewable energy sources. Who benefits is who works in the green industry, at least indirectly. I do not intend to defend the reasons for incentives, nor stigmatize mistakes. I will look at the facts: the average charge in a bill is over 4 cents per kilowatt hour. Aside from second homes and families with high consumption, users most affected are small and medium-sized enterprises. On the other hand there are a number of exempted consumers like those of railways and a number of big businesses. Cutting bills is a cornerstone of the relaunch of the industrial sector. But the proposals, from a further opening of the gas market, the modification of charges between categories of users, the extension of charges of auto consumption (a blatant stupidity), have limited the short-term impact. If you want to make a big difference then you need to act with a direct cut of the administration part of the bill: the rational way to do this is to transfer the renewable energy incentivation costs , with the introduction of a carbon tax.