The promising development of hydrogen and fuel cell technologies has garnered increased attention in recent years, assuming a significant role in industrial applications and the decarbonisation of the shipping industry. Given that the shipping industry generates considerable greenhouse gas emissions, it is crucial and imperative to implement integrated solutions based on clean energy sources, thereby meeting the proposed climate objectives. This study presents the standard hydrogen production, storage, and transport methods and analysis technologies that use hydrogen fuel cells in marine and industrial applications. Technologies based on hydrogen fuel cells and hybrid systems will have an increased perspective of application in industry and maritime transport under the conditions of optimising technological models, developing the hydrogen industrial chain, and updating standards and regulations in the field. However, there are still many shortcomings. The paper’s main contribution is analysing the hydrogen industrial chain, presenting the progress and obstacles associated with the technologies used in industrial and marine applications based on hydrogen energy.

In the current energy context, solar energy is the cheapest source of renewable energy. Photovoltaic solar cells (PV) and air thermal collectors (ATC) are used to convert solar irradiation into electricity and heat. In this research a model for a hybrid solar system consisting in a photovoltaic panel behind which is a hot air collector was designed and tested. This system produces both electricity and heat, from the sun, based on principle two in one. In the Romanian climatic conditions, such solar systems can be easily integrated into residential or office buildings. By cooling with air, the photovoltaic panel and recovering the thermal energy, the electric power increase with about 7.905% for a solar irradiance of 750 W/m². The warm air collected from behind the panel had a temperature of 5.5° C (Celsius degrees) higher, depending on the air velocity provided by the tangential fan. The experimental research demonstrates the efficiency of a PV-ATC hybrid system: 11.16% for the electrical efficiency, 45.27% for the thermal efficiency and 56.44% for the total efficiency.

In the current energy context, wind energy remains the main renewable energy source. Greater attention should be paid to small-sized wind turbines, mounted on the roofs of buildings, for their many advantages: easy to construct, do not require additional space, easy maintenance, eliminate losses from the system and transport costs, can provide alone or in addition to energy solar, the entire energy need of buildings, etc. The present paper analyzes three models of wind turbines that can be placed on the roofs of buildings: crossflow wind turbine Banki, ridge blade turbine and aeroMINE model. The analysis refers to their constructive solutions, the working principle, the optimal design for a good power coefficient and the energy that can be obtained with these small turbines for urban applications and not only.

The paper presents an analysis of the solar irradiation and the stability of the solar radiative regime, available for Bucharest and the southern area of Romania. The study is based on meteorological data measured at 3.6 seconds, on several consecutive days of each season, in the years 2017 and 2018. Data acquisition was performed at Technical University of Civil Engineering Bucharest. The daily mean values for sunshine number and sunshine stability number are computed and analysed. The analyses carried out in this research are useful for applications of solar energy and conversion to thermal energy in hot air solar collectors to estimate the temperature variation at the collector air outlet as well as for photovoltaic panels to estimate the resulting electrical energy.

Sustainable urban energy is based on innovative solar and wind solutions. The paper presents such a hybrid solar–wind system, which is easy to place on building terraces, highlighting the advantages of this technical solution: energy production as close as possible to consumers, the elimination of system losses, and small installation spaces being required. The system operates well in the low-speed range for the horizontal axis crossflow wind turbine placed under a flexible solar panel, at speeds between 2 and 8 m/s, and exhibits good efficiency in cooling the photovoltaic panels. The prototype proposed by the paper is a small-scale model that can produce on average 400 Wh/day and about 150 kWh/year. The paper analyses numerically the aerodynamic behaviour of the prototype at several wind speeds, as well as experimental results regarding the power and power coefficient for the wind turbine, as well as the power and efficiency of the flexible solar panel in the hybrid system. The research is complemented with comparative technical analysis and economic analysis.