Renewable generation technologies are experiencing rapid growth worldwide. As global priorities shift toward sustainability and reducing carbon emissions, renewable energy sources, such as solar, wind, hydro, and geothermal, are central to transforming the global energy landscape. This chapter provides an in-depth exploration of solar energy as a key component of renewable generation, emphasizing its role in the transition toward a sustainable and low-emission electricity supply. It begins by addressing the critical need for renewable energy sources in the context of climate change and energy security, highlighting the benefits of solar power in reducing greenhouse gas emissions and reliance on fossil fuels. The chapter then delves into the various methods of harnessing solar energy, with a particular focus on solar radiation, its potential, and the factors that influence its availability and efficiency, such as the angle of incidence and global irradiance. The first part of the chapter examines the fundamental principles of photovoltaic (PV) electricity generation, explaining the processes that enable the conversion of sunlight into electrical energy. It covers the physical principles behind solar cells, the different types of solar cells, and the electrical characteristics of solar modules. The chapter further explores the components of PV systems, including the operation of solar modules, inverters, and the practical applications of PV systems. Key topics such as energy payback time, harvest factor, and the costs of PV systems are discussed in detail, along with future advancements in grid-connected PV technologies and concentrating photovoltaics. The second part of the chapter focuses on solar thermal systems, providing an introduction to the thermodynamic principles that underlie the conversion of solar energy into heat. The chapter also investigates concentrating solar thermal systems. Overall, this chapter presents a comprehensive overview of solar energy generation, highlighting both photovoltaic and solar thermal technologies. It provides essential insights into the fundamentals, technologies, and future potential of solar power as a clean and reliable source of energy, emphasizing its importance in achieving a sustainable and decarbonized energy future and thus, provides a clear understanding of the behavior of these generation units in active distribution networks.