Renewable Energy

About this topic

Renewable energy comes from sources naturally replenished: solar (photovoltaic cells and thermal), wind turbines, hydroelectric dams, geothermal heat, tidal and wave power, and biomass. They emit little or no greenhouse gas during operation and reduce dependence on imported fuels.

Challenges: intermittency (sun and wind vary), needing storage such as batteries or pumped hydro, land use, upfront costs and impacts on wildlife. Costs of solar and wind have fallen dramatically, and they are the fastest-growing power sources.

A modern wind turbine blade can be over 80 m long, and one turbine may power over 1,500 homes. Solar cells convert light directly into electricity through the photovoltaic effect, and panel prices have fallen by about 90 percent in a decade, making solar cheaper than new coal in many places. Hydroelectric power supplies about 15 percent of world electricity, and Norway gets nearly all of its electricity from it. Iceland uses geothermal heat for heating and electricity.

Because wind and sun vary, grids need batteries, pumped hydro storage, smart demand management, long-distance transmission and backup, and energy mix planning. Large dams displace communities and change rivers, while some biomass burning may have emissions and land impacts. Energy payback for solar panels is typically one to three years, after which they supply clean power for decades. A common misconception is that renewables never work at night or when it is cloudy; panels still produce some power, wind often blows at night and storage fills the gaps. Another is that renewable means no environmental effects; every source has some impact, but far lower emissions.