Thermal and tidal energy are renewable energy sources. Thermal energy comes from heat generated by particle motion, and is transferred through conduction, convection and radiation. Thermal power plants convert heat from fuels like coal into electricity. Tidal energy uses turbines or barrages to capture kinetic energy from tidal currents and potential energy from tidal height differences to generate electricity. Tidal energy has high efficiency but construction costs, while thermal plants are cheaper to build but produce pollution. Both sources have localized generation and environmental impacts to consider.