The only energy source that can cope with the increasing demand of mankind in the long run is the sun. Apart from geothermal and tidal energy, which cannot satisfy our demand, it is the only source being fully regenerative. It is nearly inexhaustible, the energy impinging on the earths surface during one hour being enough to satisfy the current annual world energy consumption 2 . Since the major drawback of solar energy is its intermittent availability, means to store it have to be found. Wherever high energy and power densities are sought, chemical storage is needed.
Every additional transformation decreases the overall efficiency and increases expenses.
Therefore the direct conversion of solar to chemical energy should be aimed at.