energies Review A Widespread Review of Smart Grids Towards Smart Cities Mina Farmanbar *, Kiyan Parham, Øystein Arild and Chunming Rong Faculty of Science and Technology, Engineering, University of Stavanger, 4036 Stavanger, Norway; [email protected] (K.P.); [email protected] (Ø.A.); [email protected] (C.R.) * Correspondence: [email protected] Received: 6 October 2019; Accepted: 22 November 2019; Published: 25 November 2019 Abstract: Nowadays, the importance of energy management and optimization by means of smart devices has arisen as an important issue. On the other hand, the intelligent application of smart devices stands as a key element in establishing smart cities, which have been suggested as the solution to complicated future urbanization difficulties in coming years. Considering the scarcity of traditional fossil fuels in the near future, besides their ecological problems the new smart grids have demonstrated the potential to merge the non-renewable and renewable energy resources into each other leading to the reduction of environmental problems and optimizing operating costs. The current paper clarifies the importance of smart grids in launching smart cities by reviewing the advancement of micro/nano grids, applications of renewable energies, energy-storage technologies, smart water grids in smart cities. Additionally a review of the major European smart city projects has been carried out. These will offer a wider vision for researchers in the operation, monitoring, control and audit of smart-grid systems. Keywords: smart city; smart grid; solar; wind; energy storage; smart water grid 1. Introduction Nowadays, considering the development of smart devices, there is a keen interest in linking interfacing items through available networks [1]. The aim of smart devices is to share/access information to/from other devices for taking smart decisions by having the capability of being integrated into current infrastructures as much as possible [2]. On the other hand, currently people move to cities to improve their life quality and the United Nations expects that by 2050, 70% of the world’s population will be settled in cities [3]. It is evident that urbanization has its own challenges including resource shortage, energy and waste management, aging of the existing infrastructures, human health problems etc. [4,5]. The smart city idea has been the spotlight during last decade and is suggested as an optimal solution of overcoming urbanization problems by researchers. Herein, smartness is defined as the desire of improving the quality of life within cities and residents living there from several points of views by utilizing information and communications technology (ICT). However, employing ICT in city setups does not construe a smart city [6]. For a smart city concept, there are many definitions and a widespread one describes a smart city as the connecting environment of physical, social, business, and ICT infrastructure for elevating the intelligence of the city [7] by balancing the demand and supply of different functionalities [8]; 75–80% of world energy consumption is attributed to cities [9,10], which leads to the generation of 80% of the total greenhouse gas emissions [11]. Bearing this in mind, besides the scarcity of fossil energy sources and increasing populations of cities, the renewable essence of renewable energy sources best fits the recent global energy demands of sustainable smart cities [12]. Smart grids (SGs) or the updated version of traditional “dumb” energy infrastructures stand as the key and vital items supporting the concept of a sustainable future city [10]. They merge the Energies 2019, 12, 4484; doi:10.3390/en12234484 www.mdpi.com/journal/energies Energies 2019, 12, x FOR PEER REVIEW 2 of 18 Energies 2019, 12, 4484 2 of 18 a sustainable future city [10]. They merge the non-renewable and renewable energy resources into eachnon-renewable other, reducing and the renewable environmental energy resources problems. into Meanwhile each other, they reducing carry the the benefits environmental of lower problems. power costMeanwhile and a reliable they carry energy the benefitsservice of[13–16]. lower powerThere costis a andlack a of reliable monitoring/real-time energy service [13 control–16]. 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