and also what are fuel cells?
In a flame of pure hydrogen gas, burning in air, the hydrogen (H2) reacts with oxygen (O2) to form water (H2O) and heat. It does not produce other chemical by-products, except for a small amount of nitrogen oxides. Hence a key feature of hydrogen as a fuel is that it is relatively non-polluting (since water is not a pollutant). Pure hydrogen does not occur naturally; it takes energy to manufacture it. Once manufactured it is an energy carrier (i.e. a store for energy first generated by other means). The energy is eventually delivered as heat when the hydrogen is burned. The heat in a hydrogen flame is a radiant emission from the newly formed water molecules. The water molecules are in an excited state on initial formation and then transition to a ground state, the transition unleashing thermal radiation. When burning in air, the temperature is roughly 2000°C. Hydrogen fuel can provide motive power for cars, boats and aeroplanes, portable fuel cell applications or stationary fuel cell applications, which can power an electric motor. A fuel cell is an electrochemical cell that converts energy from a fuel into electrical energy. Electricity is generated from the reaction between a fuel supply and an oxidizing agent. The reactants flow into the cell, and the reaction products flow out of it, while the electrolyte remains within it. Fuel cells can operate continuously as long as the necessary reactant and oxidant flows are maintained.
