**1. Introduction**

Unconventional energy sources have gained and will continue to gain an increasing share in energy systems around the world [1], due to both the research and political efforts [2–8] involved in their development, as well as due to the price increases of energy obtained by traditional methods [9]. The primary energy sources, generally called renewable, are those sources found in the natural environment, available in virtually unlimited quantities or regenerated through natural processes, at a faster rate than they are consumed. Officially recognized renewable energies originate from the Sun's rays, the internal temperature of the Earth or the gravitational interactions of the Sun and the Moon with the oceans. The processes and methods of producing or capturing these types of alternative energy are in the process of being improved, the lower costs of infrastructure investments and the improved efficiency of conversion processes have made renewable energy sources provide a small part of the

energy needs on a planetary scale [10]. The more optimistic forecasts estimate that renewable energy production will enjoy a 30–50% share of the total energy market by around 2050, but this depends on reducing production costs and finding massive energy storage possibilities [11]. In addition, none of these forms of energy can also provide fuels in satisfactory quantities for use in various stationary, mobile or industrial applications [5].

In this context, we are currently looking for alternatives for obtaining energy by using technologies that offer maximum efficiency, high reliability and minimum pollution. Such a technology, considered at the moment the cleanest, through which sustainable energy can be obtained, is based on fuel cells [12]. As fuel cells develop, hydrogen-based energy production has become a reality [13]. The future hydrogen-based economy presents hydrogen as an energy carrier within a secure and sustainable energy system [14]. Humanity is on the verge of a new era characterized by advanced technologies and new fuels. We will witness new and completely different ways of producing and using energy. The energy could be generated by sources with virtually zero pollution. Hydrogen can be considered as a synthetic fuel, carrying secondary energy in a future era after the fossil fuel economy [15–18].

In order to outline an overview of the sustainability elements, the potential of using hydrogen as an alternative energy source for stationary applications and for identifying the possibilities of increasing the share of hydrogen energy in stationary applications, in this paper, a SWOT analysis was performed.

The work was structured as follows: the first part introduces the topic, presents and briefly describes the issues addressed. In Section 2 the Materials and Methods used in the present study are described. The data of the theme regarding the technical aspects and the sustainability elements are presented in Section 3—Hydrogen energy and Fuel cells—Hydrogen conversion technology. For the identification of the own potential of harnessing the hydrogen energy in stationary applications, but also of the opportunities and possible threats from the external environment, a SWOT analysis was developed in Section 4 and all aspects involved are discussed and critically analyzed, with the aim to evaluate the options and establish strategies to address the issues that best align the resources and capacities of hydrogen energy to the requirements of the stationary applications domain. The conclusions are presented is Section 5 as short bullet points that convey the essential conclusions of this paper.
