This paper reviews the use of Artificial Intelligence (AI) and the Internet of Things (IoT) in better managing renewable energy in smart cities. With a growing focus on sustainable living globally, many cities are updating their infrastructure to be more eco-friendly. This includes improving waste management, increasing renewable energy production, and using modern technology for better energy systems. A key idea discussed is the Smart Green Energy (IoT-SGE) system for smart cities, which uses IoT to help finely control energy use through constant monitoring and secure communication. By using AI, this system can learn and improve over time, making energy management more efficient. The paper also looks at examples from successful smart cities around the world, like London and Singapore, highlighting how good policies can help overcome challenges in energy, transport, and building sectors. It emphasises the importance of working together with local government and other stakeholders to bring about better use of clean energy, making cities smarter and more sustainable. Through reviewing a wide range of studies, this paper aims to provide a clear path forward for developing smarter cities with better renewable energy management.