The main source of energy at present is fossil fuel.
Some alternative sources of energy are wave energy, solar energy, biofuels, natural gas, geothermal power, wind energy, biomass energy, tidal energy, hydrogen gas, etc.
Their advantages are that they are renewable and is most likely to never run out. Also, they are easier to find than fossil fuels. They produce little or no waste that is harmful to the environment like carbon dioxide or methane so they are more environmentally friendly. Their disadvantages are that they don't produce as much energy/electricity as fossil fuels. Another disadvantage is that they rely on their surrounding. For example, wind energy needs to be generated at a windy location and needs wind turbines that take up a lot of space or solar energy needs to be generated at a sunny area and needs lots of solar panels.
