For decades, and even today the vast majority of energy is produced using non-renewable sources. Generally, to generate electricity fossil fuels are burned. These sources such as coal, oil, and gas are considered non-renewable because there is a finite amount of these commodities. Once they are burned or consumed, the fuels cannot be reclaimed. One feature of many non-renewable sources of energy is that they are also highly polluting. The burning of the fuels releases gasses into the atmosphere. Nuclear, too, is a non-renewable source, though it does not emit any gasses into the atmosphere and is, in essence, carbon-neutral. Though nuclear has its own set of risks and concerns.
So what sources are renewable and what is actually the definition of renewable energy? Renewable energy is energy that is generated from a source that is not depleted, or naturally replenished on a human timescale.
Wind is perhaps one of the most commonly known renewable energy sources. Wind turbines are installed in locations where they can harness power generated by the wind as it flows over the specially engineered blades. Best located in areas with near constant winds, many wind farms are close to coastlines and even located offshore, though inland locations are also highly suitable for development for wind.
Along with wind, solar is perhaps also the best-known renewable energy source. A common misconception is that it always needs to be sunny for solar panels to generate energy. And while bright, direct sunlight certainly increases the output, and has panels operating at their most efficient, even on cloudy days solar installations are productive.
One of the most reliable sources of renewable energy and one of the most prevalent, hydroelectricity uses the flow of water stemmed by dams through turbines to generate electricity. Hydroelectric plants cannot be built just anywhere and require specific geographical features. Though once built, there are few external factors that influence the production of electricity, which is why this renewable source has been a staple of renewable energy production for many years and in many countries.