Which one of the following is a non-conventional source of energy?

Non-conventional (renewable) sources of energy include solar, wind, tidal, geothermal, biomass, and hydroelectric energy. These sources are sustainable and have minimal environmental impact. Tidal energy, harnessed from the rise and fall of ocean tides, is a non-conventional renewable source. Petroleum, natural gas, and coal are all fossil fuels and are classified as conventional sources of energy, which are non-renewable and contribute significantly to environmental pollution and greenhouse gas emissions.