The densification of raw material into fuel briquettes is one of the routes to convert biomass into energy. This method provides uniformity to the solid fuel, better physical and energy properties, facilitating its storage and transport, in addition to more homogeneous combustion. Given the importance of these characteristics, this work presents a literature review, emphasizing the experimental levels of the variables of the briquetting process, as well as on the most relevant quality parameters for obtaining briquettes. We also carry out a survey of the main technologies used in the production of briquettes, as well as the experimental methodologies and statistical analysis used in the planning and validation of processes. It was observed among the studies that the raw material granulometry, followed by pressure, initial moisture, compaction time and binder are the most used process variables for the production of briquettes. Other factors, such as the proportion of biomass, process temperature and thermal pre-treatments are used to obtain greater energetic and physical responses. Among the works, divergences were observed regarding the relevance and interaction of some process variables on the quality variables of the briquettes, indicating the need for the experiments to be mathematically modeled.

The introduction of environmental impact targets around the world has highlighted the need to adopt alternative sources of energy, which can supply the demand and mitigate the damage caused to the environment. Solar energy is one of the main sources of alternative energy, and is considered an abundant source of clean energy. However, to facilitate and encourage investors interested in the installation of photovoltaic energy systems for electricity production, it is essential to evaluate the factors that impact the economic viability of the projects. Therefore, the objective of this research is to present a systematic analytical framework, in order to identify and analyze the main factors that impact the financial feasibility of projects for the installation of photovoltaic energy plants. For this purpose, a systematic literature review was carried out, analyzing the main studies related to the topic and identifying the main factors that may financially affect investments in photovoltaic energy systems. From this review, 29 influencing factors were identified and separated into five categories, namely, location, economic, political, climatic and environmental, and technical factors. The main factors highlighted are the investment cost, power generation, operation and maintenance costs, solar radiation, lifetime, energy tariff, efficiency, electricity consumption, and interest and taxes. The results may assist policy makers, investors, researchers, and other stakeholders to identify the key factors that are being examined in the literature, and to evaluate which ones should be considered in their study to ensure the sustainable development of power generation through the solar source.