A comprehensive study of renewable energy sources: Classifications, challenges and suggestions

A comprehensive study of renewable energy sources: Classifications, challenges and suggestions Renewable energy (RE) is the key element of sustainable, environmentally friendly, and cost-effective electricity generation. An official report by International Energy Agency (IEA) states that the demand on fossil fuel usage to generate electricity has started to decrease since year 2019, along with the rise of RE usage to supply global energy demands. Researches on RE technologies are continuously g...