When it comes to being as close to self-sustaining as possible, the denizens of the plant kingdom have it much easier than us poor animals. While we fauna generally have to hunt and gather (or line up at the drive through) for our sustenance, flora get to sit around lazily in the warm, glowing light of the sun, gathering it up and turning it into food. Some hungry predators have to stalk their prey for days on an empty stomach before securing a meal, while the geranium gets by with what amounts to a relaxing layabout on the beach in Acapulco.
It hardly seems fair, does it?
And while human beings can’t enjoy the benefits of photosynthesis directly for between meals snacking on a sunny day, we can certainly apply the process to learning how to efficiently harness solar power for our constantly expanding energy needs.
Graham Fleming, Vice Chancellor for Research at the University of California in Berkeley, says: “Solar energy is forecasted to provide a significant fraction of the world’s energy needs over the next century, as sunlight is the most abundant source of energy we have at our disposal. However, to utilize solar energy harvested from sunlight efficiently we must understand and improve both the effective capture of photons and the transfer of electronic excitation energy.”
What better way to “understand and improve” upon our current utilization of solar power than to study a system that works — and has worked — for millions of years? It’s certainly not a new idea, but new discoveries — such as one made by Fleming’s team that quantum coherence helps transport electronic excitation energy in the photosynthetic process — are just now uncovering some of the long-standing mysteries that have baffled scientists for years.
The optimization of solar power collection is an elusive goal. In nature, plants absorb solar power in chromophores, molecules that act like the antenna complexes in man-made solar power collection systems. Solar power captured under natural photosynthesis then goes to chemical reaction centers almost instantaneously, whereas energy transferred in man-made solar power collection systems to acceptor molecular complexes takes time (losing some of its “punch” in the process).
“In solar cells made from organic film, this brief timescale constrains the size of the chromophore arrays and how far excitation energy can travel,” Fleming says. “Therefore energy-transfer needs and antenna design can make a significant difference to the efficiency of an artificial photosynthetic system.”
Lessons from Nature About Solar Light Harvesting by Graham Fleming, Gregory Scholes, Alexandra Olaya-Castro, and Rienk van Grondelle is published in the recent edition of Nature Chemistry.