Photosynthesis is the process by
which plants, some bacteria, and some protists use the energy from
sunlight to produce sugar, which cellular respiration converts into
ATP, the “fuel” used by all living things. The conversion of unusable
sunlight energy into usable chemical energy, is associated with the
actions of the green pigment chlorophyll.
They release molecular oxygen and remove CO2 (Carbon Dioxide) from the air.
ATP: Adenosine Tri-Phosphate
(ATP) Here the energy is stored in living systems; it consists of a
Nucleotide (with Ribose sugar) with Three Phosphate groups.
Why is photosynthesis important:
Nearly
all living things depend on the energy produced from photosynthesis
for their nourishment. Animals need the plants for food as well as
oxygen. Only green plants are able to change light energy into chemical
energy stored in food, thus they are vital to life on Earth.
Solar cells:
Conventional
solar cells are also called as Photo Voltaic Cells. These cells are
made out of semiconducting material, usually silicon. When light hits
the cells, they absorb energy though photons. This absorbed energy
knocks out electrons in the silicon, allowing them to flow. By adding
different impurities to the silicon such as phosphorus or boron, an
electric field can be established. This electric field acts as a diode,
because it only allows electrons to flow in one direction.
Consequently, the end result is a current of electrons, better known to
us as electricity.
Drawbacks of Solar cells:
They can only achieve
efficiencies around 10% and they are expensive to manufacture. The
first drawback, inefficiency, is almost unavoidable with silicon cells.
This is because the incoming photons, or light, must have the right
energy, called the band gap energy, to knock out an electron. If the
photon has less energy than the band gap energy then it will pass
through. If it has more energy than the band gap, then that extra
energy will be wasted as heat.
Artificial Leaf:
Mixing of Photosynthesis + Conventional Solar Cells + Hydrogen Fuel Cell
This
Leaf device combines a commercially available solar cell (Silicon)
with a pair of inexpensive catalysts made of Cobalt and Nickel that
split water into Oxygen and Hydrogen. The hydrogen can be stored and
used as an energy source. (For example to power a fuel cell).
The
collection and storage of the sun’s energy as hydrogen fuel is a key
step in overcoming one of the limitations of solar power — it generates
energy when the sun is shining, but it needs to be stored somewhere to
be useful at night and in cloudy weather. Batteries are one place to
store the energy, but it is limited. Storing solar energy as hydrogen
fuel could be an answer for producing the electricity continuously.
Using
this approach, a solar panel roughly one square meter bathed in water
could produce enough hydrogen to supply electricity for a house.
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