The increase in global energy demand, environmental problems and geopolitical tensions due to the control of finite conventional energy resources; these are reasons that have currently focused the attention of scientists on the applications of solar energy. The objective of this contribution is to reflect the trends in research regarding applications of solar energy. The materials and methods used in this investigation consisted of a search and bibliometric analysis carried out in the academic directory Scopus. A group of publications was detected under specific search criteria. The information detected was processed with text mining elements in the visualization software and bibliometric map exploration of VOSviewer science. The article dead sections, records of the first applications of solar energy, the social environment of solar energy applications, the first scientific meetings of global connotation in this subject, and bibliometrics of scientific activity focused on the applications of solar energy in the 21st century. As a result of the research, a sociological and anthropological vision of the man / energy interaction is exposed; This complements lines of research such as sustainable production and consumption, energy management and climate change. Conclusions: The trend in these investigations today, is to growth, and are focused on: heating and cooling of buildings, electric power generation, both in concentrated and distributed forms; and energy conversion for industrial processes.

In this paper, we present an experimental study and statistical modeling of High-Performance Concrete subjected to high temperatures. The main objective of this study is to examine the effect of concrete age subjected to high temperature cycles (ranging from 20 °C to 1000 °C) on the physical and the mechanical properties of (HPC). The compressive strength, flexural strength, dynamic modulus and the physical characteristics were evaluated based on the mass loss and ultrasonic pulse velocity. The experiments have been performed at different age 90 and 210days. The analysis of the results shows that increasing temperature decreases the mechanical properties of the concrete especially after 90 days. The factorial design and analysis of variance (ANOVA) were used to establish the influence of experimental parameters on the HPC. Based on several criteria, mathematical models can be used to predict HPC properties under high temperature.

Buildings contain the environment in which almost all human activities take place, and therefore, nowadays, they represent a great sink of energy. Establishing thermal comfort conditions within these buildings is responsible for a large portion of their energy demand. This paper aims at providing a theoretical framework of the performance and the trends in research and implementation of night air conditioning by outside air ventilation. The bibliographic search was conducted in the academic directory Scopus, and the information extracted was processed in the VOSviewer software, through which text mining, map of terms and networks of investigative action were carried out. The literature showed that direct ventilation has a more significant cooling potential in regions characterized by a high difference between day and night air temperatures. The effectiveness of night cooling and the reliable prediction of thermal behavior are strongly related to the model adopted for the convection algorithm. A reliable prediction of heat transfer by convection requires an approach based on computational simulations of fluid dynamics, which are much more demanding in terms of computational power, compared to simulations of the variation of energy flows as a function of time. Most studies showed that the position of the thermal mass is not significant, while the amount of ventilation air is of great importance. In particular, the energy demand for cooling a building decreases sharply if the air flow rates increase.

Context: The energy and environmental panorama that our societies confront nowadays, demand for renew-able, clean and abundant sources of energy, not reliant on fossil fuels and detached from the geopolitical pressures the latter represent. In this scenario solar thermal energy arises as a viable and functional option. The main disadvantage of this emerging source of energy lies in the intermittent availability of solar radiation. Because of this difficulty, efficient processes for the storage of thermal solar energy becomes a highly relevant area of research. The aim of this paper is to present a survey on this topic.Method: A bibliographic review was carried out using the Scopus catalog. The search criteria for this purpose was defined using the following terms: solar+thermal+energy+storage+materials. This search pattern was applied to the title, abstracts and keywords of the contributions. Using the bibliometric tools of the citation database, the most cited documents were selected and the survey was developed.Results: A growing interest in the scientific community regarding this energy practice is evident starting from 2010. Characteristics, advances and trends in systems that use thermal energy storage materials are presented for sensible and latent heat, materials compound changeover phase, and finally thermo-chemical thermal storage materials.Conclusions: Improving the thermal conductivity of thermal storage materials is an important trend in current re-search. On the other hand, profitable practices for micro-encapsulated phase change materials and composite materials are analyzed. The optimization of thermo-physical properties as the melting point of thermal storage materials is explored with techniques such as eutectic mixtures and hydro-carbon chain length. Although the thermochemical materials are still in laboratory stage, they have a great potential as thermal storage materials in the future, given their large energy storage capacity per unit volume.

The objective of this contribution is to provide a state-of-the-art on research in solar thermal electricity systems. This objective is achieved using Scopus, and the softwears “Publish or Perish” and “VOSviewer”. The results of the research show the behavior of scientific productivity in this area. As well as the most productive thematic areas. Nations that lead the research in the generation of electric power on a large scale, using solar thermal energy. Network of scientific collaboration among nations, referring to the research of electricity generation through solar thermal energy. Correlation network among the most productive authors, in this subject within the Scopus directory. Most cited articles by each of the main journals that disseminate this theme. Conceptual bases of the generation of electricity with solar thermal energy. Properties of thermal energy storage technologies (TES) in power plants with parabolic solar concentrators or solar concentration towers. Current technologies and trends. Technological trends. Trends in the global energy market.

Buildings contain the environment in which almost all human activities take place, and therefore, nowadays, they represent a great sink of energy. Establishing thermal comfort conditions within these buildings is responsible for a large portion of their energy demand. This paper aims at providing a theoretical framework of the performance and the trends in research and implementation of night air conditioning by outside air ventilation. The bibliographic search was conducted in the academic directory Scopus, and the information extracted was processed in the VOSviewer software, through which text mining, map of terms and networks of investigative action were carried out. The literature showed that direct ventilation has a more significant cooling potential in regions characterized by a high difference between day and night air temperatures. The effectiveness of night cooling and the reliable prediction of thermal behavior are strongly related to the model adopted for the convection algorithm. A reliable prediction of heat transfer by convection requires an approach based on computational simulations of fluid dynamics, which are much more demanding in terms of computational power, compared to simulations of the variation of energy flows as a function of time. Most studies showed that the position of the thermal mass is not significant, while the amount of ventilation air is of great importance. In particular, the energy demand for cooling a building decreases sharply if the air flow rates increase.