With the growth in population and frequent energy crisis, moving toward sustainable cities is a political and important plan for many countries [1
]. In this regard, the key role of energy is remarkable, because it plays a significant role in the economic and social development of countries [2
]. Green energy technologies are a rapidly growing reliable source of power, which can mitigate the energy crisis while conserving the environment [3
]. Essential renewable energy applications in smart city development are for green buildings (GBs) and electric vehicles (EVs). Limited resources of fossil fuels and an increase in demand for electricity have renewed interests in integrating GBs [4
] and moving towards EVs in urban areas [5
Several studies exploring different aspects of smart cities, including smart cities, utilization of EVs, and the importance of GBs for smart cities, have been investigated. For instance, Danuta Szpilko et al. (2019), argued the different advantages of smart cities: urban flexibility, appropriate consumption patterns, environmental issues, and clean energy utilization. They proved that smart city development has a lot of positive impacts on future cities and countries [6
]. Roberto Ruggieri et al., based on the 11th goal of the SGDs by 2030, investigated the management of existing cities and the planning of future ones, based on Sustainable Cities and communities regarding energy consumption and decarbonization of transport. In these regards, they investigated electric mobility performance in six Smart Cities (Oslo, London, Milan, Hamburg, Bologna and Florence). The analysis showed that electric vehicles’ use was positively affected by reducing PM2.5, PM10, and NO2
. In this respect, the cities demonstrated the most remarkable reduction in pollutant (above 20%) were Hamburg (−28% PM2.5 and −2%6 NO2
), Milan (−25% PM2.5 and −52% NO2
), and London (−26% NO2
]. To increase the power grid’s peak load by uncoordinated charging of EVs and an increasing extra expense of electricity, Zhang et al., proposed a new strategy based on three aspects: coordination, practicality, and autonomy.
In addition, this strategy includes a day-ahead pricing scheme, which can overcome the minimum optimization expense [8
]. Due to the increasing charging demand of EVs, Kamankesh et al. suggested optimal scheduling of GBs. The optimal energy management for GBs, including renewable energy sources (RESs), plug-in hybrid electric vehicles (PHEVs), and storage devices, was discussed. They introduced different charging methods through uncontrolled, controlled and smart charging strategies [9
]. Honarmand et al., proposed an energy resource management model for GBs to overcome issues related to integrating EVs, RES and, power networks. This method was able to investigate practical limitations, anticipating errors of renewable energy in the line of EVs owner satisfaction [10
]. Peter K. Joseph et al., using renewable energy, examined vehicle-to-grid, and wireless charging integration of electric vehicles using renewable energy for sustainable transportation.
This research, which was conducted in the pursuit of energy conservation, particularly in developing countries, demonstrated that combining electric vehicles with renewable energy sources can result in parking spaces being transformed into unlimited sources of clean energy and preventing energy loss [11
]. Anber Rana et al., investigated financial Incentives (FIs) for green buildings for Canada. They showed that FIs for buildings in Canada can be distributed into four categories: grants, tax, loans, and rebates, and among these, rebates are the most common in all provinces. They mentioned that these incentives belong to three end-users (aboriginal people, landlords and tenants, and low-income) and for three types of buildings (energy rated, heritage, and non-profit). With these incentives, four provinces (Ontario, Alberta, British Columbia, and Quebec) are leading green building efforts [12
Zhen Liu et al., examined the potential impact of the integration of building information management and blockchain on making buildings more sustainable in a smart city environment. They showed that a complete life cycle study could help constructors, designers, supervisors, and decision-makers make informed and accurate decisions for green buildings in smart city development [13
]. The importance of the Internet of Things (IOT) as an intelligent technology, examined by Waleed Ejazthe et al., enabled electric vehicles in smart cities. Actually, and due to this reality, the large-scale implementation of electric vehicles can make extra burdens on electric grids; thereby, they suggested smart scheduling using IOT technology to optimize smart cities’ charging process. Hongyu Chen et al. [14
], evaluated the environmental aspects of green buildings in smart cities based on the Internet of Things system. They showed that using IoT can reduce the negative environmental aspects in green buildings [15
1.1. Motivation and Objective of the Study
Energy consumption is likely to rise dramatically by 2050 as a result of predicted high population expansion, particularly in metropolitan areas. The expected exponential expansion emphasizes the significance of researching and deploying smart technologies in order to fulfill demand. Smart cities are critical for maintaining supply and demand equilibrium. However, it will not be possible until governments throughout the world adopt net-zero energy policy. Therefore, this study provides a comprehensive review of smart cities, including an introduction and literature review, investigating significant barriers and introduces feasible indicators for further analysis in this area. A fundamental component of a smart city is net-zero energy GB. In addition, electric vehicles provide essential benefits to smart cities, including CO2 emission reduction.
Therefore, evaluating the GBs, EVs, and their correlations in smart cities is the main motivation of this study. Currently, EVs are presented as eco-friendly for the environment and reliable power backup systems in the transport sector. They can mitigate high percentages of CO2 emissions, which is better for the environment for they run on electrical energy instead of combustible fuels. Therefore, this type of technology creates an appropriate opportunity to utilize them as storage systems. By increasing the use of renewable energy sources, the capacity of the energy storage system is increased to control power generation and fluctuation. On the other hand, creating, and developing GBs, is a positive step for reduction of CO2 emissions, and providing energy for the citizens of smart cities.
1.2. Hierarchical Structure of Smart Cities
shows the hierarchical structure of application areas related to smart cities.
Additionally, Table 1
shows the previous investigations related to EVs and GBs by different researchers. As can see the key role of renewable energy for smart city development is significant in these studies.
In this study, smart cities examined comprehensively with emphasis on policy, GBs, and EVs impacts. To obtain the information required for this work, in the first stage, we used “smart city”, policy and strategy for smart cities, renewable energy, barriers, and solutions for smart cities development,” as titles, abstracts, and keywords in the query entry and started the search process by using established scientific databases, such as Scopus, Google Scholar, Web of Science and journal sites (Elsevier, Springer, Tylor & Francis, MDPI, Willey, etc.). In this stage, every author collected related research for the corresponding author and sent it. Then, and based on the eligibility criteria and their accessibility, we have, over three years, identified and conducted an exhaustive review of more than 300 relevant publications and scientific reports related to smart cities such as EU Smart Cities Marketplace, governmental reports and European energy reports. After the collection information stage, we evaluated the journals based on titles, abstracts, and introductions and selected the appropriate articles to collect 98 articles. Next, we did two stages in parallel:
Reviewing reports and review articles to have a global understanding of smart cities development issues and find the proper solutions to overcome these problems. These studies helped us improve our background and knowledge for writing the manuscript.
Reviewing technical articles. These articles were fruitful in identifying appropriate policies to address barriers in the development of smart cities and defining the correct pathway for the study.
4. Results and Discussion
Confronting the essential issues such as climate change and energy crisis for the people in the future using creating smart cities can be achieved. In this regard, the key role of GBs and EVs and correlations between them in the line of smart cities development is crucial. Thereby, this research investigates smart cities development based on two of these crucial sections. Indeed, this paper has several novelties, including investigating different aspects of smart cities development, presenting the main barriers with relevant solutions to overcome them for smart cities development, and introduces new feasible indicators related to GBs and EVs in designing SCs. This section discusses achievable policies, recognizing barriers with the solutions in the line of smart cities development, and efficient indicators for GBs and EVs.
4.1. Crucial Role of Policy for Creation and Development Smart Cities
Undoubtedly, one of the most critical sectors for progressing and developing smart cities is policy [38
]. Additionally, the policy has a decisive role in advancing the goals of governments [39
]. The use of the appropriate policies and strategies by policymakers leads to effective and good results for the development of smart cities [40
]. However, implementing appropriate policies in societies is not easy and requires public support. To do this, the diversity of stakeholders’ rationales to implementing participatory processes should be investigated using proper methods and correct instruments for participation [41
As active involvement is a key aspect in achieving success, policymakers should include stakeholder expectations into decision-making in order to successfully implement policies and avoid public resistance [42
In this sense, elected leaders must work to ensure that inhabitants have the finest possible living conditions in future cities. Policies such as the use of smart technology (IoT) to maximize efficiency and reduce costs, developing GBs, developing smart meters systems in buildings, the integration of connected local energy storage systems to improve quality of life and foster economic development, the development of electric vehicles (EV) systems in cities and encouraging people to use these vehicles more, strict monitoring of electric energy companies, and zero energy buildings are just a few examples.
4.2. Existing Barriers against Smart Cities Development
Undoubtedly, recognizing main issues as mentioned above can help national governments and local governments in developing SC. Thereby, in this section, the main barriers against the progress of smart cities are presented and then discussed. We believe the main issues related to smart cities development are in this table and can be a good guide for researchers in the future. Therefore, with consideration of these barriers, policymakers will be able to find the appropriate solutions for them that lead to accelerating smart cities development. These barriers as a set cover small and big issues that policymakers are looking to overcome in SC development. These barriers are divided into technical, environmental, economic, social, and governmental categories in Table 2
and are including the barriers of governance, social, technology, environment, and economy. Each of these, as following, categories also includes other vital barriers, the impact of which can be removed or decreased as necessary to ease the creation and development of smart cities.
However, the main question is why these barriers are essential, and how can overcome them. The policymakers and energy experts should have appropriate policies based on recognizing the main barriers against smart cities development and reducing and removing these barriers. The policies that lead to improving transportation networks, more use of EVs, reduction of CO2
emission, developing GBs, energy-saving, more use of renewable energy, energy managing by the smart meter especially for buildings, affordable energy, improvement of IT networks, and increasing of green spaces. Therefore, the barriers presented cover the main issues in this way and are analytical. Table 3
shows the relevant references for these indicators.
4.3. Required Indicators
The indicators for smart cities focus on monitoring the evolution of a city towards an even more innovative city. Therefore, the appropriate indicators for smart cities regarding the importance of the GBs and EVs have been considered. Policymakers and energy experts will be able to use energy sustainability indicators to measure its viability, solve existing problems and improve the weak points connected with the smart cities development. Therefore, the indicator as a time component for the development of smart cities over the years is a significant feature. Furthermore, it means that recognizing proper and efficient indicators can show us to what extent overall policy goals have been reached or are within reach.
The most important indicators regarding GB and EVs that affect energy sustainability in smart cities are presented in Table 4
, which shows the indicators and sub-indicators for GBs and EVs [82
]. The implementation of these indicators presented leads to the improvement of the residential life quality of the smart cities in the future. These indicators cover all essential requirements for GBs and EVs development in smart cities. For example, in this Table, energy consumption, energy efficiency, energy saving, environmental adaptability, mentioned as indicators for both GBs, and EVs are essential, and implementation of these indicators on the GBs, and EVs leads to facilities and satisfaction of the citizens in the smart cities.
4.4. Finding Gaps and Solutions to Overcome and Confront with Barriers of Smart Cities Development and Present the Solutions
Different aspects of smart cities are investigated in this study concerning the GBs, EVs, which also cover environmental challenges, smart city concepts, and smart city development hurdles. Undoubtedly, smart cities can be a conducive solution to overcome the most existing problems involving present humans. However, creating and developing smart cities will have problems for governments and countries. Now the question is what we should do. To answer this question, it would be great to mention correct policies and strategies especially in the line of GBs, and EVs development. As if these sections investigate properly and relevant issues of these become remove, many problems of citizens will be eliminated, thereby, all governments and countries need to think for finding proper solutions and ways.
Appropriate policy and strategy can be investigated before facing these problems by policymakers who influence governments’ bodies. It means they can investigate and predict existing problems, and then present the best and logical solutions to overcome these problems.
shows the barriers to smart cities based on six crucial sections of the smart city. The results of this Table that obtained from the references of Table 3
, can be a good plan for policymakers that recognize them and implement them to overcome the problems related to smart cities development in the future. Indeed, this table shows how a city can convert to a smart city by using appropriate policies and strategies and showed the main barriers and solutions for each of them.
Therefore, this Table, with a deeper view of the existing barriers concerning smart cities development, present efficient solutions in this regard. Although we believe implementing these solutions is not easy but given them for policymakers activating in smart cities development is a benefit. For instance, skilled and talented people in proper places can prevent future issues, leading to a progressive acceleration in different smart cities. In addition, more use of new technology like IT systems in smart cities development is an essential factor. Therefore, special attention to these barriers and solutions is significant for policymakers.
As Table 5
mentioned, the barriers and solutions of smart cities, therefore can be added for a better understanding of presenting this table that a city to become a smart city needs to essential changes. The changes such as in technology, type of communication, use of skilled and talented people in proper places, encourage public in participation, utilization of electrical vehicles, development of internet infrastructure, development of green spaces to improve the environment in cities, improve energy affordability especially through the use of clean energy, development GBs, providing sufficient water and sanitation, and improvement of the security information networks. Therefore, the aim of Table 5
is to recognize the main barriers and solutions for them in the line of smart cities development.
4.5. Correlations between GB and EV in the Line of Smart Cities Development
Regarding rapid urbanization and the development of the cities the issues such as energy crisis, climate change, and resource depletion are concerning for the people. Therefore, special attention to these issues and having appropriate planning to overcome these for all governments are necessary, otherwise, shortly the people become involved more with these crucial issues [95
]. The two essential elements in creating sustainable cities are sustainable buildings [96
] and electrical transportation systems [97
The two main issues against creating, and developing sustainable cities, are the inefficiency of old buildings [98
], and old transportation that uses fossil fuels as the main energy source [99
]. In this case, the challenges are related to our total energy consumption and CO2
]. Thereby, more investment in the GBs and EVs for all policymakers and energy experts is significant and has an impressive impact on reducing the mentioned issues. In addition, if we will not have sustainable cities in the future, we need to develop GBs and EVs. As creating GBs, and EVs will reduce main social challenges such as loss of energy, CO2
emissions, and in the end, livable and sustainable city for our self, and the next generation. Thus, there are close correlations between GBs and EVs in the line of smart cities development [101
To complete this section, it can be added that the development of each of these sections has good results in smart cities. For example, in recent years the councils of the municipal cities have tried for the development of the green building in the line of smart cities as creating an energy-efficient world. It means that green buildings lead to environmentally friendly cities especially with consideration ecological materials that are used in building them. For this, the sustainable building councils, using the skilled teams of scientists, architects, and contractors a develop conceptual targets in the strict sense of sustainable building that new buildings become built based on the ecological, energy-saving, social-cultural, and economic concepts with high functional quality. In addition, these houses can have a low amount of energy consumption while providing satisfaction to residents, advanced life cycle assessment via the use of natural materials and concepts, capacity to deploy renewable energy sources (solar panels, wind turbines) in their roofs, and higher profitability via reduced energy consumption. On the other hand, these policymakers, and energy experts for implementing charge places for electric vehicles, and development of them have many tried that have succeeded to a great extent [102
Thereby, for explanation more accurate of the correlations between GBs and EVs in the line of smart cities, and development, can be said that since the aim of the smart cities’ development is make more welfare of citizens while conserving the environment, energy affordable, clean, and abundant for them.
5. Conclusions and Recommendations
The primary purpose of this research was to study existing barriers of smart cities development with identify appropriate solutions for each of them and present new feasible indicators related to GBs and EVs. After a comprehensive review of existing barriers and solutions for smart city development, new indicators have been presented that show the positive impact on designing and developing smart cities. First and foremost, this study addresses SC facility development in the context of the increasing prevalence of EV and GB in smart cities. In this regard, governments must have a coherent strategy for growth in EV and GB to develop smart cities, have adoption environmental methods to reduce CO2 emission, and use key demographic indicators that cause the implementation process.
The findings revealed that, in the 2020s, improvements in energy and resource efficiency will play a particularly important role in decreasing industrial emissions, paving the path for broad emissions reductions while infrastructure for profound decarbonization alternatives that can be built up for which new ideas and advancement in GBs and EVs and introduction to economic and financial benefits to consumers would be a key motivation in accelerating in achieving SCs. Additionally, the findings revealed that implementing strategies and embracing change in government policies would help to accelerate the net-zero energy vision, pay attention to design parameters, improve transportation policies while embracing change, implement efficient indicators for GBs and EVs, and implement strategies to reduce the cost of EV production while maintaining high quality. As a result, governments should have appropriate policies in place, such as boosting investment in EVs and developing GBs in terms of environmental approaches.
Without a doubt, this work has limitations like many similar works published that other researchers can consider in the future. The limitations are related to the causes of the lack of enough governments’ investments in GBs, and EVs development in cities, causes of the lack of proper cooperation between national governments with local governments in implementing the targets, etc. Therefore, recognizing the relevant political issues, and finding the efficient solutions for them, can be investigated by those interested in working in this regard.