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Due to the growing concerns of emissions from the shipping industry, the International Maritime Organization (IMO) has set strategies to reduce the CO 2 intensity by 40% in 2030 and cut total GHGs emissions by at least 50% by 2050, with 2008 as a baseline. Clean alternative marine fuels are widely recognized and used as a viable solution for reducing ship-related air pollution. Several studies including traditional reviews have been conducted to examine the literature on cleaner alternative marine fuels and their role in decarbonizing the shipping sector. However, these studies fail to unpack the main research actors, evolutionary nuances, and emerging research hotspots in this field. To quantitatively and qualitatively explore this research field, the current study adopts a bibliometric analysis. 583 eligible documents published from 2000 to 2020 were retrieved and merged from the Web of Science Core Collection and Scopus databases, and analyzed with the R-studio bibliometrix package (Biblioshiny). Results revealed that the field is growing significantly at a growth rate of 15.8%, with key contributions to the field originating from the USA. Liquified Natural Gas has been identified as the most researched alternative shipping fuel. However, recent trends show researchers turning their attention towards methanol, ammonia, and hydrogen fuels. By analyzing the frequently used keywords and relevant articles, it became clear that the research community has focused mainly on the potential of different alternative fuels as a replacement to conventional marine fuels to limit the emissions from the shipping sector from an environmental, technical, and economic perspective. The current study offers a basis for future research into the decarbonization of the shipping industry. [Display omitted] • Bibliometric study on clean marine fuels based on Web of Science and Scopus databases. • A growing research field with an annual growth rate of 15.8%. • Key authors, institutions and countries in the field have been identified. • LNG emerged as the most researched alternative shipping fuel. • Research hotspots and trends on clean marine fuels discussed. [ABSTRACT FROM AUTHOR]

With rapid industrialization, rising fossil fuel consumption, and environmental concerns, developing clean and green energy is an inescapable option. Hydrogen has emerged as a significant potential energy carrier and a viable future replacement fuel for fossil fuels due to its renewable and pollution-free properties. Previous review papers have significantly contributed to the body of literature on the various technologies for producing hydrogen by revealing key insights into their working principles and conditions, as well as the economic and environmental aspects. In addition, they also highlighted the potential pathways to enable the application of these technologies in the context of carbon neutrality. However, these studies have not broken down the evolutionary patterns and developmental progress of either fossil fuel-based or renewable energy-based technologies used to produce hydrogen. In addition, the currently available literature does not contain the most recent research that focuses on the evolution and life cycle of each technology category from a chronological point of view. The key drivers, countries/regions, and their contributions to the field's development have received little attention. As a result, it is critical to monitor technological advances in hydrogen energy production and investigate the key enablers of these advancements. Against this backdrop, the current study employs patent analysis tools to achieve four primary goals: (1) to track the development trends in the field of hydrogen production from 2000 to 2019; (2) to identify and compare the recent development trends in the last five years according to the feedstock, i.e., fossil fuel, water, and biomass-based technologies; (3) to predict the technology life cycle of the two main groups of hydrogen production technologies (fossil and renewable); (4) to identify and compare the key drivers of hydrogen production technologies from a statistical standpoint. The findings of the study may aid in identifying technical prospects in the field of fossil and renewable-based hydrogen production, and decision-makers may use them as a reference in developing a strategic plan for future technological growth. • Patent review on hydrogen production technologies from 2000 to 2019. • Japan, US, China are the leading countries in the field. • Recent developments are focused on renewable energy-based technologies especially water. • Technology maturity rate of renewable-based technologies is about 57%. • R&D expenditure strongly promotes hydrogen production innovations. [ABSTRACT FROM AUTHOR]

One of the main setbacks to electric vehicles (EVs) adoption relates to the unavailability of the required charging stations across a jurisdiction. In addition, drawing the required energy of the EVs from a fossil fuel-dominated grid does not only minimize the cleaner benefits of EVs but also puts enormous pressure on an already stressed grid network in electricity-deficient regions like Sub-Saharan Africa (SSA). Hence, in the current study, six different 100% hybrid renewable energy systems based on powerplants of solar, wind, and biomass have been proposed for meeting the energy needs of 70 and 30 battery and fuel cell electric vehicles, respectively using Ghana as a case study. With the aid of HOMER Pro software and multicriteria decision-making tools, the hybrid system, biogas generator-photovoltaic emerged as the most feasible of the six proposed solutions from a technical, economic, and environmental standpoint. This winning system produces 3.9 GWh/yr and 55.6 tonnes/yr of electricity and hydrogen, respectively. The NPC, LCOE, LCOH, and payback period was recorded as $6.53 million, $0.52/kWh, $9.09/kg and ∼8 years, respectively. Approximately, 4 tonnes of GHG emissions are produced by the HRECS each year, and the amount of CO 2 emissions avoided from replacing 100 gasoline vehicles with the proposed EVs has been obtained as 460 tons/yr. With the aid of sensitivity analysis, it became apparent that the feasibility of the proposed systems could improve with improvement in components' efficiencies and lifetime, and reduction in unit costs. The current work has several contributions to the sustainable development goals (7, 8, 11, 13), and could aid in accelerating EV penetration in SSA. [Display omitted] • A hybrid RE standalone HRECS for EVs in Ghana. • Investigation by HOMER and CRITIC-PROMETHEE II methods. • PV + Biogas generator presents most feasible results for HRECS. • Break-even Grid Extension Distance investigated. • Standalone vrs grid-connectivity analysis. [ABSTRACT FROM AUTHOR]