Pigments in green plants and certain bacteria are able to capture energy from sunlight, and pigment-protein complexes are then able to transfer the energy into reaction centers at lightning speeds with nearly 100% efficiency. The LBNL researchers found that solar photons caused electronic oscillations in the closely packed pigment-protein complex, inducing similar electronic oscillations in the reaction centers.
The wavelike oscillations occur on the scale of femtoseconds-millionths of a billionth of a second-and take advantage of the unique physics of quantum mechanics, which govern the behavior of atoms, photons, and other subatomic particles. Essentially, the wavelike quality of oscillations allows them to simultaneously sample all the potential energy transfer pathways in the photosynthetic system and choose the most efficient one. This is the key to fast, efficient energy transfer within photosynthetic systems.
What remained unclear to LBNL researchers was how wavelike oscillations are sustained in the pigment-protein complex. The answer to that puzzle turns out to be quantum entanglement, a phenomenon that typically occurs between two subatomic particles, such as electrons.
Electrons are often created in pairs, with one electron having a spin "up" and the other having a spin "down." According to quantum mechanics, the spin of each electron is not fixed until it is measured, existing instead as a probability of either choice. This remains true even when electrons are separated at a great distance, but once the spin of one electron is measured, the other electron instantaneously assumes the opposite spin, because the two are entangled at a quantum level. Einstein referred to this effect as "spooky action at a distance."
According to the LBNL researchers, such quantum entanglement is present across the entire light harvesting complex and sustains wavelike oscillation, marking the first time the effect has been examined and quantified in a real biological system. The scientists were surprised to find entanglement persisting for relatively long times at room temperature and between molecules that were not strongly coupled to one another. The findings have implications not only for mimicking photosynthesis, but also for quantum-based computing. See the LBNL press release.
EPA Helps Partners Find Commercial Energy Efficiency Savings
The U.S. EPA, in partnership with several states and utilities, announced on a new Energy Star pilot program designed to further improve commercial building energy efficiency.
The Building Performance with Energy Star program will link eight Energy Star partner utilities and state energy efficiency programs throughout the country in a pilot designed to strategically pursue whole-building energy improvements with commercial customers.
The effort includes a number of Energy Star elements to improve energy efficiency, including: measuring energy use with EPA's online energy measurement and tracking tool on building performance; finding energy efficiency opportunities based on whole building assessments; and creating a delivery network for whole-building efficiency services.
A benefit of this pilot program will be to help business customers identify buildings that could most use an efficiency tune-up and then to give technical assistance and incentives for the projects that yield the largest energy savings. Energy use in commercial buildings accounts for 17% of U.S. GHG emissions, at an energy cost of more than $100 billion per year. See the EPA press release and a fact sheet on the program (PDF 36 KB).
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EREE Network News is a weekly publication of the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE).
