The document discusses several alternative energy sources: 1) Hydrogen can power cars through fuel cells, producing only water as a byproduct. 2) Geothermal energy harnesses the Earth's natural underground heat through steam to power turbines. 3) Wind power uses turbines to convert kinetic energy from the wind into electricity. Large wind farms are often built. 4) Solar panels and photovoltaic cells capture the sun's energy and convert it to heat or electricity.