Solar fuel

A solar fuel is a synthetic chemical fuel produced directly/indirectly from solar energy sunlight/solar heat through photochemical/photobiological (i.e., artificial photosynthesis, experimental as of 2013), thermochemical, and electrochemical reaction. Light is used as an energy source, with solar energy being transduced to chemical energy, typically by reducing protons to hydrogen, or carbon dioxide to organic compounds. A solar fuel can be produced and stored for later usage, when sunlight is not available, making it an alternative to fossil fuels. Diverse are being developed to carry these reactions in a sustainable, environmentally friendly way.

The world's dependence on the declining reserves of fossil fuels poses not only environmental problems but also geopolitical ones. Solar fuels, in particular hydrogen, are viewed as an alternative source of energy for replacing fossil fuels especially where storage is essential. Electricity can be produced directly from sunlight through photovoltaics, but this form of energy is rather inefficient to store compared to hydrogen. A solar fuel can be produced when and where sunlight is available, and stored and transported for later usage.

...
Wikipedia