This chapter focuses on modern renewable energy sources such as solar, wind, and marine energy. For each technology option, the chapter outlines the fundamental technological aspects and the key global production and consumption trends. By doing so, the chapter also assesses the cost dimension of the various sources, by presenting the evolution of global levelized costs of electricity in the last decade. The chapter also discusses the applicability of renewables to both centralised and distributed power systems, and outlines the importance of digital technologies in facilitating the integration of variable renewable energy sources into the grid. The chapter concludes with an outline of the barriers to renewable energy implementation and of the strategies to address them.