Capturing the sun
Solar power is one of the fastest growing renewable energy sources in the world. The challenge is to make it more efficient and robust. Dr Alexandra Olaya-Castro at UCL’s Department of Physics and Astronomy, is part of an international team using their understanding of the quantum mechanics of energy transfer in photosynthesis, to investigate how nature does it so efficiently.

Their work has highlighted the machinery of natural photosynthesis, where more than 100 million billion photons of light hit a leaf each second. The concept of light energy being transferred and regulated quickly, for the plant to grow, is helping scientists to design molecular ‘circuitry’. It is 10 times smaller than the thinnest electrical wire in computer processors for tiny molecular energy grids to capture, direct, regulate and amplify raw solar energy.

Quantum mechanical machinery
Olaya-Castro has been fascinated by the quantum mechanics of photosynthesis since 2008 and began her collaboration with Gregory Scholes, Graham Fleming and Rienk van Grondelle after meeting them at different conferences presenting their work on light harvesting.

Olaya-Castro explains, ‘we decided to gather all the research of several groups, including ours, trying to understand the photosynthesis machinery and present it as a set of methods to implement in artificial combining systems that can exploit sunlight.’ They are using the principles of quantum mechanics to describe how small particles like electrons and atoms behave in the process of photosynthesis. Working in a nanoscale, where a nanometre is one billionth of a metre, they are studying the pigments, such as chlorophyll whose molecular machinery capture light.

Sharing the energy
In photosynthesis each pigment in the plant acts collectively to capture more frequencies of light and that energy is transported to a particular molecule where it is converted into the chemical energy ATP (Adenosine triphosphate). Using the image of passing a ball around, Olaya-Castro explains that the theoretical breakthrough is that the energy transfer process is conceived as many hands on the ball at once, hence a sharing process rather than passing from one to the other.

From the technological viewpoint, she says, ‘one can explore this phenomenon to make the transfer of energy a process that is more efficient but also more controlled. This could be the basis of a new innovative energy technology.’ Now they aim to turn this into a blueprint for an artificial light harvesting system.