## 1 Introduction
Therefore, new techniques are needed to improve manufacturing quality and inspect products [24], as well as to optimize large-scale hydrogen transport and storage configurations [25]. As for economic barriers, the low market share does not allow taking advantage of the economy of scale benefits [26]. It is important to identify applications and locations with characteristics that will increase the Return on Investment (ROI) to guide deployment strategies [27]. From an environmental perspective, hydrogen requires approximately 9 L of water per unit mass of hydrogen, so large plants can have a significant impact in water-scarce regions [28]. At the regulatory level, there is a need for tailored hydrogen regulations that reflect local conditions. Finally, social acceptance is also a key aspect. Technologies to improve safety [29], as well as the training of qualified professionals in the energy sector and in other fields [30], can help to overcome these social barriers. In the early stages of renewable hydrogen deployment, it is important that decision-making processes consider as much information as possible at the local level. This ensures that solutions are tailored to the specific location, and that installations are cost-effective. In this regard, geospatial techniques are considered to add value to the deployment of renewable hydrogen, since they enable the collection, analysis, interpretation, management, and visualization of location-related information [31]. However, they are also tools and techniques that enable the spatial characteristics of objects or phenomena to be analyzed in an agile, fast, and automated manner [32]. Geospatial techniques are central to the CET due to their cross-cutting nature and ability to integrate multiple perspectives. They enable evaluation of the CET beyond purely economic criteria. Geospatial techniques have proven to be very useful in locating and estimating all types of renewable resources. [PERSON], [PERSON] et al. [33] have carried out a literature review that compiles studies related to Geographic Information Systems (GIS) on the potential of agricultural residues to meet the European renewable energy targets. Geospatial techniques are used for harmonizing data from the different EU-27 countries. They also enable statistical analyses to estimate the energy potential of agricultural residues, reaching approximately 1500 PJ/yr. [PERSON], [PERSON] et al. [34] perform a compilation of studies related to solar and wind energy. Specifically, they focus on the application of geospatial techniques to predict suitable locations for wind and solar power plants. GIS is used to process multiple layers of information and to integrate Multi-Criteria Decision-Making (MCDM) methods, which help identify and rank the best resource areas. However, geospatial techniques also have applications in other areas of the CET, such as the integration of renewable energies and the decarbonization of urban environments. [PERSON], [PERSON] and [PERSON] [35] analyzed 204 studies applied to net-zero energy buildings. The objective was to identify the applicability of geospatial techniques, the challenges, and future lines of development. The identified challenges are related to data resolution, interoperability, and lack of standardization. Recent systematic reviews such as the one conducted by [PERSON], [PERSON] et al. [36] demonstrate the applicability and usefulness of GIS applications in many critical sectors in the CET, such as maritime ports. The results obtained from the bibliometric analysis reveal a growth of 8.59% in scientific publications related to environmental monitoring, Machine Learning (ML), and digitization. Specifically, in the case of the maritime sector, they detected a need for reinforcement in interoperability and integration of data. The objective would be to facilitate the integration of ML with GIS. [PERSON] et al.