The world has witnessed an exponential increase of energy; those demands are mainly covered by fossil fuels. However, giving the unsustainable conditions of such source such as scarcity and harmful environmental effects, researchers were required to investigate newer alternative power sources. Solar energy is a clean, abundant and easily available renewable energy. It is also one of the most economical alternatives with outstanding processes and applications diversity machineries. Usage of solar energy for thermal applications provides a scope for several studies on energy, benefits, and bio-compounds analysis. The main objectives of this thesis are to promote the use of solar energy for extraction and drying applications, to confront them with the conventional technique usually used, and to better understand the process, outcomes and benefits of such green and sustainable source. Two matrices were considered: rosemary leaves as aromatic and medicinal plants and, orange peels as by-product. For solar extraction a distillation unit coupled with a solar reflector was used to deodorize rosemary leaves via steam distillation and to valorise orange peels targeting a zero-waste bio-refinery via hydro-distillation. The advantages of thermal solar energy extraction are noteworthy, allowing approximately 37 % decrease of extraction time for both the studied matrices in comparison to conventional processes. Quality wise, several analyses were carried in order to compare thermal solar and conventional systems. The rosemary and orange peels essential oil yield and quality obtained by GC/MS was relatively similar for both processes. However, antioxidants assayed by HPLC-DAD present in rosemary leaves were better preserved after solar extraction. Overall, the results indicate that Solar-Steam-Distillation (SSD) is a green alternative, efficient and economical process for essential oil extraction and leaves deodorization. Orange peels pectin and flavonoids (mainly narirutin and hesperidin) were also better preserved after solar hydro-distillation process. For drying, the study was performed on rosemary leaves and orange peels by thin convective solar drying to valorize these matrices, to increase their shelf-life, and to investigate the impact of solar drying on their antioxidant properties. The experimental study focused on the influence of drying temperatures on water loss and quality of fresh matrices dried at different temperatures: rosemary leaves (40°C, 50°C, 60°C, 70°C) and orange peels (60°C, 65°C, 70°C, 75°C°, 80C). Obtained results showed that Midilli– Kucuk and two terms were the most fitted and appropriate models to describe the convective solar drying kinetics of rosemary leaves and orange peels respectively. For rosemary leaves, it was found that with solar drying (40, 50, 60°C, and sun-dried) an increase of carnosol was observed, coupled with a decrease of carnosic acid values; while at high temperature (70°C) both carnosic acid and carnosol contents decrease. This could imply that high temperature may lead to quality deterioration of rosemary leaves. Moreover, at 70°C Total polyphenols (TPC) values decrease and the IC50 value increased illustrating the negative effect of high drying temperatures on rosemary leaves. Contrary to rosemary leaves, the results showed that TPC and DPPH degradation was elevated in both 60°C, 65°C and the natural shade dried orange peels in comparison to high temperatures 75°C, and 80°C.This may state that the product gives better TPC and DPPH concentration if being dried at high temperature. As for the DPPH analysis, it was found that starting from 75°C, the antioxidant activity improves. This may be due to the new substances formation or precursor that occurs between several molecules via non-enzymatic inter-conversion at 70 °C for citrus fruits. Thus, stating that drying at high temperature may be a way to improve the phenolic extraction of orange peels.