Renewable energy comes from sources that naturally replenish. Sunlight, wind, water, geothermal heat, and biomass. Unlike coal, oil, and gas, they do not run out. They also produce little or no greenhouse gas emissions. The shift to renewables is the biggest energy transition in history.

Solar panels convert sunlight into electricity. Wind turbines convert kinetic energy into electricity. Hydropower uses falling water. Geothermal uses heat from the Earth. Biomass burns organic matter. Each has strengths and limits. Solar and wind are intermittent. Storage and grid upgrades are needed.

Types of renewable energy

• Solar: photovoltaic and thermal
• Wind: onshore and offshore
• Hydro: dams and run-of-river
• Geothermal: heat pumps and power plants
• Biomass: wood, crops, waste

Renewables are now the cheapest source of new electricity in many markets. Costs have fallen dramatically. Solar is down over 90% since 2010. Wind is down over 70%. The challenge is no longer cost. It is integration, storage, and politics.