New emerging technologies and regulations are among the forces which are driving the changes in energy systems. This favorable circumstance paves the way to the design of more advanced and effective energy architectures, the solution of old problems with new means, and the solution of issues unresolved because of the lack of tools and methodologies.

Renewable Energy Sources (RES), such as wind and solar power, are rapidly becoming the backbone of the future electric power system since they are environmental-friendly although they create great distress in power grids which should accommodate larger and larger amounts of intermittent power generation. With the increase in efficiency of energy conversion and power electronics, storage systems have become more reliable, less expensive and cleaner, making viable the option of storing significant amount of power, under any form of chemical, thermal, mechanical or electric energy. The potential impact of electric vehicles in energy systems is also huge. The diffusion of such vehicles might move, with regard to the overall energy consumption balance, a significant amount of power from conventional transport fuels to electricity, requiring a complete redesign of most distribution power grids. They will introduce new randomness in the electric system operations due to “moving around” loads.

At residential and urban levels, the increasing penetration of electric vehicles and distributed generation will rapidly transform consumers into “prosumers” that will be able to operate their own devices in order to generate, store and use energy. Managing these micro energy systems will require the achievement of a higher efficiency, which can be reached only through a radical integration of all energy services at urban/residential level (electric supply, natural gas supply, heating, cooling, water, transportation, etc.).

A major example of a key enabling technology (KET) which can drive the transformation of energy infrastructures is the smart grid concept. Smart grids combine a number of technologies with end-user solutions and address new paradigms in the dispersed generation, storage and utilization of the electrical energy, which can find an effective application by a new regulation environment.

In this multifaceted scenario, the energy hub constitutes another key paradigm. It can be conceived as a unit where multiple energy carriers can be converted and conditioned by using a wide spectrum of technologies, such as combined heat and power technology, power-electronic devices and heat exchangers. Consequently, energy hubs could be considered as the trait d’union between different energy infrastructures (i.e. electrical networks, natural gas distribution systems, heat distribution systems) and/or energy users (i.e. producers, consumers) allowing more market and energy efficiency, increasing reliability and facilitating the penetration of intermittent generation. This model can be applied on different scales including industrial plants, larger buildings, urban districts and isolated energy systems.

Starting from the experience in the power sector, in this book, it is shown how some concepts and methodologies developed in this field can be effectively utilized in other realms. Different energy infrastructures share the same needs for more automation, optimization in operations, tools for planning and integration between multiple energy carriers to achieve better performances and efficiency. These issues require new methods and application software whose main core, generally, resides in optimization tools.

The focus of this book is on distribution energy systems and urban energy infrastructures since they show the potential to improve their efficiency and flexibility through the implementation of smart monitoring, new control functions and the integration with other energy carriers. This assumption has been made with the firm belief that, in these areas, smart grids will provide more profound changes in response to challenging problems such as: a wide dispersed generation mostly due to intermittent RES, integrated production, utilization and storage of both thermal and electrical energy for enhancing energy efficiency, more advanced home distribution systems, demand response, etc.

The dramatic changes modern towns are facing during these years require smarter operation of grids according to overall framework of the “smart city” paradigm. A new urbanization is giving rise to the so-called “mega-towns” which require more advanced and secure energy infrastructures. The entrance of new technologies such as photo voltaics widely utilized for residential and tertiary buildings, electrical vehicles, combined heat cooling and power (CHCP), heat pumps for demand response and energy districts changes the usual way energy grids have been operated in cities so far. Other issues are related to a different attitude of customers, which are willing to participate more actively to the energy market and choose among new energy services, this aim being nurtured by a forward-thinking regulation of the sector.

The scope of the book is to provide an integrated vision of problems to researcher, engineers, practitioners, defining the contour of new subjects in energy system optimization. The authors involved in this book were encouraged by a common motivation: to bring together issues that, although in continuity with their previous experience, sketch a new scenario in the energy systems.

The book begins with applications of smart grids in the power sector and concludes with applications to urban distribution systems involving other energy carriers such natural gas, heat/cool district heating, hydrogen. This cultural contamination and novelty is found in the theory as well as in real-world applications. It stems from power systems, which is doubtless the most complex and technologically advanced energy infrastructure, the first one to make a pervasive use of automation and Information and Communication Technologies (ICT) and to experience a drastic market re-regulation and dramatic technological advancements worldwide.

Particular attention is devoted to the actual implementation of the methods proposed here. As a matter of fact, most of the chapters refer to applications developed in research activities which have now finalized to give way to the actual implementation of pilot projects. These projects are briefly described and funding resources are acknowledged in throughout the book. Some of the pilot projects addressed here pushed the equipment and material needs of the research activity and nurtured the support of some companies giving rise to a new laboratory called LabZERO located at the Politecnico di Bari and at the ENEA Research Center in Brindisi, Italy. It was set up carrying out the activities of the “Project ZERO”, concerning the development of research and experimentation activities in the field of green smart technologies and the use of simulation tools and equipment for fast prototyping to reduce the risks of applied research and support product innovation in the path “from concept to market”. Lab ZERO was conceived as a living lab, a user-centered, open-innovation ecosystem combining research, development and innovation processes within a public-private-people partnership. This experience is worth mentioning to underline the link of the book with real applications and to show how pilot projects area good instrument to draw the attention of public institutions and companies to engineering research issues.

The above-mentioned ideas inspired the book whose topics are summarized here.

In the Introduction, terminology, definitions, economical and technical drivers for smart grids are introduced. Smart grids are defined in a broad sense including all energy grids and the integration of advanced distribution grids. Potentials for operation and environmental issues enhancement, safe and secure operations and energy efficiency are addressed with a special insight to the urban environment and its evolution toward smart cities.

In Chapter 1, the features of Advanced Distribution Management Systems are summarized and the optimal power flow (OPF) is presented as basic function, which can be applied effectively for controlling power distribution grids at both medium voltage (MV) and low voltage (LV) level. Specialized formulations, based on nonlinear programming algorithms and a three-phase unbalanced representation of the power grid, are developed for controlling active and reactive resources in distribution systems. Particular attention is devoted to the LV distribution system due to the lack of automation and tools accompanied by the profound changes these grids are experiencing nowadays.

In Chapter 2, mixed integer linear programming (MILP)algorithms are presented for the solution of two optimization problems, which characterize distribution power network operations, namely: the minimum-loss configuration of the network the so-called voltage/var optimization (VVO) problem. The quality of the results and the effects of the proposed linearization are assessed on MV test systems by performing a comparison with nonlinear calculations for optimal configurations.

In Chapter 3, metaheuristic-based optimization algorithms have been addressed for solving complex problems in the smart grid domain. A review of the most advanced metaheuristic algorithms in the task of solving a complex smart grid optimization problems and a comprehensive analysis of the expected performances of the optimization algorithms in terms of convergence, robustness and accuracy are presented in this chapter. The benefits and the limitations of the different solution techniques are highlighted through simulation results obtained on realistic power networks and an actual urban power grid.

In Chapter 4, a review of approaches to urban energy systems study is presented. Urban energy systems are proposed as networks of multi-source hybrid energy hubs, where different energy flows are collected at the same bus and can be stored, delivered or transformed as needed. Since resources and infrastructures interact with each other, definition and boundaries of such energy systems at urban level and the possibility to generate new operational models based on existing critical urban infrastructures is a challenging problem. Thermal, electrical and mobility infrastructures operation are considered as qualifying features of the hub. An optimized design of the energy system serving two different districts is considered as a function of these urban features. The analysis, reported in the chapter, shows how there is a link between energy planning and urban features at district level paving the way to an energy-based territorial planning for urban contexts.

Planning integrated energy systems in towns implies a complex design, which should take into account also a different operation of underlying grids. Interdependencies among different systems should be carefully represented and special solvers are required for optimization. In Chapter 5, an optimization approach was formulated and tested to be applied in operations in presence of multiple energy sources and storage systems according to two strategies aimed to fully take advantage of storage facilities: a greedy algorithm and optimal control. In addition, a design methodology was proposed to maximize the return of the investment in planning new multi-source hybrid energy systems considering optimized operations during the lifespan of the infrastructure. The approach is tested on a real case of an urban regeneration project, aimed to the development of energy facilities to provide discounted energy services in degraded suburban areas to attract new investments. The project includes the installation of a trigeneration plant, district heating and cooling and an on-site steam methane reformer to supply hydrogen to a fleet of public transport vehicles.

In Chapter 6, it is shown how urban gas distribution grids are experiencing changes similar to electric distribution grids due to the deployment of gas smart meters and the more and more pervasive use of ICT tools and automation which allows more effective, safe and secure operations. In this chapter, selected results of a pilot project for the implementation of a gas smart grid in the middle-sized town of Bari in Italy are presented. A SCADA (supervisory control and data acquisition) prototype and a gas flow optimization algorithm (gas optimal flow algorithm) for pressure control across the natural gas grid are described in their actual implementation. This kind of real-time control shows the potential of increasing the power generated by turbo expanders at gas city gates, reducing metering and billing errors due to excessive pressure deviations, ensuring a safe distribution of odorants and providing load relief and peak shaving during emergency conditions. What reported in this chapter is an interesting example of a ‘transposition’ and shifting of experiences coming from two different realms: the power smart grid area and the urban natural gas distribution.

Once presented issues relevant to the integration of different energy substrates in future cities and essential changes in the planning and optimization process, in Chapter 7, the focus is on the concurrent optimization of the distribution grids of two main energy carriers: power and natural gas. The complexity of both networks in terms of their structure, a possible future energy-hub-like architecture, energy flow equations, and different related equality and inequality constraints make the optimization problem highly nonlinear, non-convex and high dimensional. An optimization heuristic method, namely the time varying acceleration coefficient gravitational search algorithm (TVAC-GSA), is proposed to solve OPF problems in multi-carrier energy systems focusing on the interactions between power grid and gas network. The proposed algorithm is based on the Newtonian laws of gravitation and motion. The effectiveness of the approach is tested on a multi-carrier energy architecture characterized by the assumed presence of multiple energy hubs. The concurrent solution of the two grids provide better results than the ones associated to the solution of the two separated systems. Consequently, the concurrent optimization of multiple grids seems to be a good candidate for smart distribution systems, gaining efficiency in the overall system.

After this effort, the authors share the feeling that many results are still on the shelf and many others are still coming out from pilot projects and, in general, what reported here is not exhaustive of the topic. Somehow, this book can appear linked to the Italian experience and regulation. This is due mainly to the territorial basis of the pilot projects and the affiliation of most the authors. It is believed that this not by itself detrimental since the Italian experience in the development of smart grids and smart cities presents some peculiarities such as the early large deployment of smart metering technologies and the setting up of an advanced regulatory framework.

The book covers a wide ground of topics and applications and could not be written without benefitting from the published efforts of other researchers and Institutions reported in the references at the end of each chapter. The authors gratefully acknowledge the financial support from the Italian Ministry of Economic Development and Regione Puglia Government as well as the technical support from the Municipality of Bari for providing technical assistance and support in the implementation of some pilot projects. The authors also acknowledge the contribution of the many people who, in various ways, contributed to the realization of the projects mentioned in the book.

This work would not have been possible without the patience of our families and the encouraging assistance of the publishing editors, to which I express, even on behalf of all contributors, our gratitude.

Finally, I wish to express my sincere thanks to all the authors who contributed to the publication of this book. After all, the book reports the story of the cooperative efforts of a group of enthusiastic researchers working on the same challenging issue of transposing theoretical results on actual demonstrators useful for the everyday life.

Massimo La Scala
Bari, Italy
October 2016