Hydrogen fuel cell, illustration. This is a clean and efficient power source. Hydrogen is liberated from a natural source such as methanol or natural gases. It is then pumped into the cell, where the hydrogen nuclei are separated from their electrons. The electrons flow around a conducting loop as an electric current, which can be harnessed. The hydrogen nuclei pass through a membrane and then combine with the electrons and oxygen from the air to form steam as the only waste product.