The perfect clean, renewable energy will utilize the sun's light energy for efficient conversion into fuels and electric power and so attention is focusing on one of the most ancient groups of organism, the cyanobacteria.
3.7 billion years ago photosynthesis evolved in cyanobacteria that used water molecules as a source of electrons to transport energy derived from sunlight, while converting carbon dioxide into oxygen. The light harvesting systems gave the bacteria their blue ("cyano") color, and paved the way for plants to evolve by "kidnapping" bacteria to provide their photosynthetic engines, and for animals by liberating oxygen for them to breathe, by splitting water molecules.
Humans are only now coming close to tweaking the photosynthetic reactions of cyanobacteria to produce fuels we want such as hydrogen, alcohols or even hydrocarbons, rather than carbohydrates.