Definition and scope of renewable energy

Summary

Renewable energy (also called green energy) is energy generated from natural resources that are replenished on a human timescale. Common renewable sources include solar energy, wind power, and hydropower, with bioenergy and geothermal power also playing major roles in some countries. Renewable energy installations can be small or large and can serve both urban and rural areas, and they are often deployed alongside further electrification because electricity can be used efficiently for heating and transport while producing less pollution at the point of use. Renewable energy is often categorized by how controllable it is. Variable renewables—such as solar and wind—fluctuate with weather and time, which can create challenges for matching supply to demand. Controllable renewables include sources like dammed hydropower, bioenergy, and geothermal power, which can be dispatched more predictably. The scope of renewable energy also extends beyond electricity generation to include hot water/space heating, transportation, and off-grid rural energy services, though the term “renewable” does not automatically mean “low-carbon.” Some renewables can still be carbon-intensive depending on practices (e.g., certain biomass use), and nuclear power is sometimes discussed as “renewable” in some contexts but remains controversial because it relies on nonrenewable uranium. In climate policy, renewable energy is widely used as a substitute for fossil fuels to reduce greenhouse gas emissions and improve air quality and public health. However, the transition faces obstacles such as fossil fuel subsidies, opposition to land use, and environmental impacts from mining and manufacturing materials needed for renewable technologies. Despite these challenges, renewable energy has expanded rapidly: renewables have grown from about 20% to 28% of global electricity supply between 2011 and 2021, and they are projected to exceed 45% by 2030, with many countries already generating more than 20% (and in some cases over half or nearly all) of their electricity from renewables.

Key Points

• 1

  Renewable energy is energy derived from replenished natural resources on a human timescale, commonly including solar, wind, hydropower, bioenergy, and geothermal power.

• 2

  Renewables can be variable (solar, wind) or more controllable (dammed hydro, bioenergy, geothermal), affecting how they integrate with power grids and other energy sectors.

• 3

  Renewable energy is a major tool for climate mitigation and air-quality improvement, but it is not always synonymous with low-carbon energy and still faces deployment, policy, and environmental challenges.