March 3, 2014

Uncovering nature's solar energy machines

Over several billion years of natural selection, nature has developed machinery that is far more technologically advanced than what humans are capable of building.

Such machines include the light-harvesting cells found in plants and bacteria, capable of converting solar energy to usable energy with near perfect efficiency. Peter Dahlberg, a third-year graduate student in the Biophysical Sciences working in chemistry professor Greg Engel’s laboratory, is eager to uncover the energy-transfer mechanism found in these light-harvesting cells.

“Nature has found out a way to robustly harvest more solar energy to use–six times more energy than humans use–with simple chemical constituents, and do it in a very noisy environment of a cell, compared to the defined systems, like photovoltaics,” he said.

Photovoltaics refers to the process of converting light energy into solar energy, usually using solar panels.

In light-harvesting complexes found in nature, solar energy is first harvested through light-harvesting proteins and converted to usable energy, which is transferred throughout the cell. The light-harvesting complexes have found ways to minimize any energy losses during the energy transfer process.

Previous studies have shown that the reason for the high efficiency of energy transfer is due to a phenomenon called quantum coherence. However, these studies were all done with light-harvesting complexes isolated from their natural environment—the inside of a cell.

Dahlberg has developed new spectroscopic techniques that made his lab the first group of researchers to observe quantum coherence and energy transfer in light harvesting complexes in live cells.

“I figured out a way to do 2-D spectroscopy in only three seconds, which used to take at least 10 hours. This has allowed us to look at light harvesting complexes in live cells rather than in isolated environment,” he said.

Dahlberg’s method demonstrated that the energy transfer mechanism studied in isolated systems accurately represents the energy transfer mechanism in live cells, reassuring the validity of this new field of research, which is only about a decade old.

In the future, Dahlberg hopes that his research will inspire others to engineer more efficient solar panels. “If we understand how plants move around the energy that they absorb from the sun, it can provide inspiration in how we should design energy transfer in photovoltaics.”