Research Spurs Hope of Mimicking Photosynthesis to Boost Solar Efficiency

Scientists at Lawrence Berkeley Lab begin to demystify quantum entanglement

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Biomimicry is all the rage in cleantech these days. There are solar cells modeled after butterfly wings, fans borrowing from humpback whales to become more aerodynamic and wind turbine blades mimicking whale flippers.

And now scientists at the U.S. Department of Energy’s Lawrence Berkeley Lab have inched closer to being able to replicate the mechanical processes underlying photosynthesis — a discovery that could one day lead to cleaner and more efficient solar power systems.

It all comes down to "quantum entanglement," a scientific phrase usually reserved for discussions of teleportation and creating one’s own reality. While the theory is popular among science fiction fans, it’s also a very real and potentially powerful quantum effect behind many natural processes, researchers say.

In the simplest of terms, the Berkeley team puts it thusly:

"When two quantum-sized particles, for example a pair of electrons, are ‘entangled,’ any change to one will be instantly reflected in the other, no matter how far apart they might be. Though physically separated, the two particles act as a single entity."

In their most recent experiment, the Berkeley scientists discovered for the first time that quantum entanglement is a naturally occurring feature of photosynthesis. Graham Fleming — a physical chemist holding joint appointments with Berkeley Lab and University of California Berkeley and a member of the "entanglement team" — laid the groundwork for the finding.

In 2007, Fleming first pointed to quantum mechanical effects as the key to unlocking the mysteries of photosynthesis, most notably the perplexing ability of plants to instantaneously convert sunlight to energy with almost 100 percent efficiency.

"Our results suggested that correlated protein environments surrounding pigment molecules (such as chlorophyll) preserve quantum coherence in photosynthetic complexes, allowing the excitation energy to move coherently in space, which in turn enables highly efficient energy harvesting and trapping in photosynthesis," Fleming said of his conclusions in a statement.

By better understanding exactly how photosynthesis works, this latest research suggests, engineers may be able to design and build more efficient and greener solar energy systems.  Structures could be engineered to mimic the exact anatomy of a plant’s leaf — and to mechanically replicate the process of photosynthesis inside a solar panel.

The results could be game changing.

"The results of this study hold implications…for the development of artificial photosynthesis systems as a renewable non-polluting source of electrical energy," the Berkeley Lab scientists said.

At the very least, fewer solar cells would be needed to squeeze the same amount of energy
from a solar installation. That would translate into fewer materials
and less energy used up in manufacturing and maintenance.

Berkeley Lab: No Breakthrough Expected Soon

Still, a major breakthrough could be a very long time coming.

Mohan Sarovar, a post-doctoral researcher on the Berkeley team, notes that for the time being, this research is more about understanding the process than applying findings to the real world.

"This is really a fundamental study rather than an applied one," Sarovar said. "In my opinion, the possible impacts of this study on photovoltaic technologies are in the long-term."

Nonetheless, Sarovar said the study does reinforce the evidence that quantum effects are prevalent in what he calls "natural light harvesting systems."

"Such detailed microscopic knowledge of natural light harvesting gives us new ideas on how to improve artificial photovoltaic technologies," he said.

"For example, it lays out design principles to follow when making synthetic structures for use in organic photovoltaics. By purposefully designing in quantum properties perhaps we can improve the light harvesting attributes of these synthetic antennas for light."

Sarovar said "the exact role" of quantum effects in natural light harvesting structures remains "poorly understood." But the expectation, at least, is that "they play some beneficial role."

In addition to discovering that quantum entanglement is a feature of photosynthesis, the team also discovered that entanglement is not nearly as fragile or exotic as once thought. That’s good news for scientists and engineers hoping to recreate the process with synthetic structures — though Sarovar was again careful not to jump the gun.

"Our research does show that entanglement is more robust than previously thought," he said. "But one should keep in mind that the demonstrated entanglement in light harvesting complexes is still fairly short-lived (picoseconds). The reason it’s interesting is that this duration is significant on the timescales that the energy transfer in light harvesting complexes occurs in," Sarovar added.

"So, although it provides an impetus to create and study entanglement in synthetic (and naturally occurring) molecular structures, we do not currently have enough control over the ‘quality’ and timescales of the entanglement in such molecular structures to perform the novel technological tasks usually associated with entanglement (e.g. teleportation)."


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