The inherent day-night and sunny-cloudy cycles of solar radiation necessitate an effective method to store the converted solar energy for later dispatch and distribution. The most attractive and economical method of storage is conversion to chemical fuels. The challenge in solar fuel technology is to produce chemical fuels directly from sunlight in a robust, cost-efficient fashion.
For millennia, cheap solar fuel production from biomass has been the primary energy source on the planet. For the last two centuries, however, energy demand has outpaced biomass supply. The use of existing types of plants requires large land areas to meet a significant portion of primary energy demand. Almost all of the arable land on Earth would need to be covered with the fastest-growing known energy crops, such as switchgrass, to produce the amount of energy currently consumed from fossil fuels annually.
Hence, the key research goals are
Â (1) application of the revolutionary advances in biology and biotechnology to the design of plants and organisms that are more efficient energy conversion â€œmachines,â€ and
(2) design of highly efficient, allartificial, molecular-level energy conversion machines exploiting the principles of natural photosynthesis.
A key element in both approaches is the continued elucidation â€” by means of structural biology, genome sequencing, and proteomics â€” of the structure and dynamics involved in the biological conversion of solar radiation to sugars and carbohydrates. The revelation of these long-held secrets of natural solar conversion by means of cutting-edge experiment and theory will enable a host of exciting new approaches to direct solar fuel production. Artificial nanoscale assemblies of new organic and inorganic materials and morphologies, replacing natural plants or algae, can now use sunlight to directly produce H2 by splitting water and hydrocarbons via reduction of atmospheric CO2. While these laboratory successes demonstrate the appealing promise of direct solar fuel production by artificial molecular machines, there is an enormous gap between the present state of the art and a deployable technology. The current laboratory systems are unstable over long time periods, too expensive, and too inefficient for practical implementation. Basic research is needed to develop approaches and systems to bridge the gap between the scientific frontier and practical technology.