Solar is gaining great importance in the renewable
energy sector and is being preferred over other sources to generate electricity.
Major reason for this is the abandon availability at “0” input cost. Many
technical advances have made solar cells quite efficient and affordable in
recent years. A big disadvantage remains in the fact that solar cells produce
no power when it’s raining.
The International Energy Agency says, “under its “high
renewables” scenario, by 2050, solar photovoltaic and concentrated solar power
would contribute about 16 and 11 percent, respectively, (27% totally) of the
worldwide electricity consumption.” Moreover, in the journal Angewandte Chemie, Chinese researchers
have now introduced a new approach for making an all-weather solar cell that is
triggered by both sunlight and raindrops.
For the conversion of solar energy to electricity, the
team from the Ocean University of China (Qingdao) and Yunnan Normal University
(Kunming, China) developed a highly efficient dye-sensitized solar cell. In
order to allow rain to produce electricity as well, they coated this cell with
a whisper-thin film of graphene. Rain (after the shower) actually helps solar
cells to perform more efficiently by cleaning / washing away the dust and dirt
accumulated on the cells, which obstruct the sunrays to reach the solar cells.
However, the limitation of a photovoltaic cell is
their dependency on the sunlight to produce electricity and is negligible when
it’s cloudy overhead. Scientists have been working on this problem and today
the efficiency of solar panels is far better than earlier. Today there are
solar panels available which store quite a bit of energy when the sun is not
available, but still with lots of restrictions.
Chinese scientists’ team lead by Qunwei Tang,
(materials scientist) at the Ocean University of China in Qingdao and Yunnan
Normal University (Kunming) was working on all-weather solar cells. “We would
like to develop a solar cell that can be triggered by sun and rain,” says
Qunwei Tang. This team has discovered a technique to generate electricity with
assistance from raindrops. Solar cells that can generate electricity even
during rain showers with the help of graphene is what the study is about.
Graphene is a two-dimensional form of carbon in which
the atoms are bonded into a honeycomb arrangement. It can readily be prepared
by the oxidation, exfoliation, and subsequent reduction of graphite. Graphene
is characterized by its unusual electronic properties: It conducts electricity
and is rich in electrons that can move freely across the entire layer
(delocalized).
Contrary to common belief raindrops are not pure
water. They contain salts that split up into positive and negative ions. The
Ocean University researchers used graphene (one-atom-thick sheets of carbon)
property to attract the positively charged ions, such as sodium, calcium and
ammonium and bind them. They used graphene electrodes to obtain power from the
impact of raindrops. When the raindrop and the graphene come in contact, the
water becomes rich in positive ions and the graphene becomes enriched in
delocalized electrons. The result they achieved with this process was separated
layers of positive and negative ions that act much like a capacitor or pseudo
capacitors to store energy.
They added graphene to a dye-sensitized solar cell, (a
thin-film solar cell), then put it on a flexible, transparent backing of indium
tin oxide and plastic. The flexible solar cell with this combination had a
solar-to-electric conversion efficiency of up to 6.53% and generated hundreds
of microvolts from slightly salty water which was used to simulate rainwater.
Related Articles:
https://qz.com/658757/graphene-coated-solar-panels-can-create-electricity-from-raindrops/
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