Renewable energy sources and sustainable environmental physics.

Renewable energy is energy obtained from renewable sources that are replenished naturally over time. This includes sources such as sunlight, wind, water movement, and geothermal heat. While most renewable energy sources are sustainable, some are not. For example, some biomass energy sources are considered unsustainable in their current operation. Renewable energy often generates energy to generate electricity for power grids, heating and cooling of air and water, as well as autonomous energy systems.