# Understanding Microgrid Sustainability: A Systemic and Comprehensive Review
## 1 Introduction  
According to the United Nations, 789 million people are living with no access to electricity [1], and without a more engaged action, 650 million people will remain without energy access in 2030 [2]. The investment required for universal energy access by 2030 is estimated to cost more than $48 billion each year. In contrast, the renewable-energy-based technologies that can provide safe and clean electricity are now cheaper and more accessible than ever to the population [3]. Despite these encouraging developments, sustainable and affordable rural electrification remains a complex and risky endeavor [4]. There are essentially two solutions to provide electricity to a new location: extending the main grid or creating a local installation. Depending on the context, one solution will be preferable to the other [5]. However, a large part of the population that does not yet have access to energy does not have a reliable central electricity grid to connect to [6]. The decentralized approach seems to be more reliable and efficient for rural electrification because of its high versatility and lower cost [7]. Experts seem to be in consensus that decentralized electricity networks will have the capacity to power entire cities or medium-sized regions by 2040 [8]. However, despite all the qualities of microgrids, the uptake of this type of system in rural communities remains extremely low. The lack of economic and business consideration [9], the gap in strategic planning approach [10], the neglect of social issues [11], and the deficiency of an apparent global consideration on overall microgrid sustainability [4] make the implementation of microgrids even more difficult. The social development of a population is strongly linked to its access to energy which increases, at the same time, the quality of life of the community [12]. As the population grows, itsneeds will change, and so will the way it consumes energy, often creating the need for more energy [13]. The microgrid must therefore be able to evolve with its community. In this article, we conduct a review seeking to lay the foundations of bringing more understanding on microgrid sustainability and how to reach it. We use a systemic approach to understand the literature linking microgrids and their evolution over time to adapt to the development of the population to which it provides power. Because microgrids are such a vast and complex topic, this systemic review will cover various topics, from technical to social. Microgrids and their sustainability have been studied extensively in the literature, with a growing interest in the past ten years, as shown in Figure 1. This figure shows the annual publications related to sustainability or resilience for microgrids since 2007. The data were extracted from the search engine webofscience for the publishers IEEE, Elsevier, and MDPI. As a result, 837 publications were identified as relevant because they include the notions of sustainability and resilience in their study. We can see that the interest in these notions in microgrids has dramatically increased, showing the interest in finding solutions for the weaknesses of microgrids systems. The concept of sustainable energy development has evolved to become central in energy and microgrid creation and operation and is now a key factor for its study [14]. The literature tends to focus on identifying limiting actions or promising practices to be followed to optimize the microgrid [15], often using case studies to flesh out the recommendations [16]. However, the literature tends to overlook non-technical actions, which are also crucial to guaranteeing the long-term sustainability of the microgrid. A disproportionate focus on the technical or economic aspect of the microgrid overlooking other characteristics tends to increase the probability of failure [17]. The notion of the virtuous circle [18] illustrates the impact of non-technical elements on microgrid sustainability.