A lot of our energy comes from non-renewable sources such as coal, oil and gas. These resources are made up from the remains of ancient animals and plants that develop over millions and millions ...

As for the second category, which includes conventional sources, the team said it also includes geothermal and water electrolysis ... conventional 2-tier renewable and non-renewable energy sources ...

Fossil fuels - coal, oil and gas - on the other hand, are non-renewable resources that take ... Hydropower harnesses the energy of water moving from higher to lower elevations.