Ontario R&D: Scientists Lay Out Plans for Efficient Harvesting of Solar Energy | Product Design and Development

Ontario Universities including of Toronto (and Waterloo) have invested their
talents heavily in solar research as a result of the FIT. See some of what's
resulting

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Scientists Lay Out Plans for Efficient Harvesting of Solar Energy
By University College LondonFriday, September 23, 2011
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Solar power could be harvested more efficiently and transported over long
distances using tiny molecular circuits, according to research inspired by
new insights into natural photosynthesis.

Incorporating the latest research into how plants, algae and some bacteria
use quantum mechanics to optimise energy production via photosynthesis,
scientists have set out how to design molecular "circuitry" that is 10 times
smaller than the thinnest electrical wire in computer processors. Published
in Nature Chemistry, the report discusses how tiny molecular energy grids
could capture, direct, regulate and amplify raw solar energy.

Professor Gregory Scholes, lead author from the University of Toronto said:
"Solar fuel production often starts with the energy from light being
absorbed by an assembly of molecules. The energy is stored fleetingly as
vibrating electrons and then transferred to a suitable reactor.

"It is the same in biological systems. In photosynthesis, for example,
antenna complexes comprised of chlorophyll capture sunlight and direct the
energy to special proteins that help make oxygen and sugars. It is like
plugging those proteins (called reaction centres) into a solar power
socket."

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In natural systems energy from sunlight is captured by 'coloured' molecules
called dyes or pigments, but is only stored for a billionth of a second.
This leaves little time to route the energy from pigments to the molecular
machinery that produces fuel or electricity.

The key to transferring and storing energy very quickly is to harness the
collective quantum properties of antennae, which are made up of just a few
tens of pigments.

Dr Alexadra Olaya-Castro, co-author of the paper from UCL's department of
Physics and Astronomy said: "On a bright sunny day, more than 100 million
billion red and blue "coloured" photons strike a leaf each second.

"Under these conditions plants need to be able to both use the energy that
is required for growth but also to get rid of excess energy that can be
harmful. Transferring energy quickly and in a regulated manner are the two
key features of natural light-harvesting systems.

"By assuring that all relevant energy scales involved in the process of
energy transfer are more or less similar, natural antennae manage to combine
quantum and classical phenomena to guarantee efficient and regulated
capture, distribution and storage of the sun's energy."

Summary of lessons from nature about concentrating and distributing solar
power with nanoscopic antennae:

1. The basic components of the antenna are efficient light absorbing
molecules. These photo-energy absorbers should be appropriately distributed
to guarantee that there is an even probability of converting sun energy into
vibrating electrons across the whole antennae.

2. Take advantage of the collective properties of light-absorbing molecules
by grouping them close together. This will make them exploit quantum
mechanical principles so that the antenna can: i) absorb different colours
ii) create energy gradients to favour unidirectional transfer and iii)
possibly exploit quantum coherence for energy distribution -several energy
transfer pathways can be exploited at once.

3. Make sure that the relevant energy scales involved in the energy transfer
process are more or less resonant. This will guarantee that both classical
and quantum transfer mechanisms are combined to create regulated and
efficient distribution of energy across short and long-range distances when
many antennae are connected.

4. An antenna should transfer energy not as fast as possible but as fast as
necessary. This means that regulatory mechanisms need to be integrated in
the antenna. For instance, if necessary, combine light-absorbing molecules
with a few local "sinks" that dissipate excess of damaging energy.

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