Energy Capture and
Storage
Ever consider how much
sunlight actually strikes the
earth?
On average every square yard of land exposed to the sun
will receive 5 kW-hours of solar energy per day. So if you
had an area covering 100 square yards you would generate
500 kW-hours per day.
Upon careful inspection of our energy bill we discover that
the average U.S. household generates 500-1000 kW-hours of
electrical energy in ONE MONTH. So if we could efficiently
harness the sun’s energy there could be limitless energy for
us to use.
Ubiquitous?
Alan Heeger, 2000 Nobel
Prize winner in chemistry for
the materials used in PDA
screens. These materials
conduct electricity and emit
light.
It was discovered that these
SAME materials could
absorb light and emit
electricity
Goal: inexpensive solar cells EVERYWHERE!
It Is All About the
Benjamins!
•Silicon is a costly semi-conductor
•Silicon is bulky
•Silicon is inflexible
•THREE time more expensive than fuel currently
used on the power grid.
•Costs, due to scale, are going down by 7% per
year, which is TOO slow.
“More people have lost money in bets against silicon
than I know,”-Arno Penzias ( Nobel Prize winner in
Physics) – “But then you’re talking a HUGE possible
payback: The power market is about $1 trillion.”
We Think It IS Achievable!
Goal: To capture 10% of the incoming solar energy.
Plan: To develop, using
nanoparticles such as titanium
dioxide, solar cells which are
made from cheap plastics.
These plastics are very
flexible. The solar cell can
even be printed out using an
ink jet printer onto the plastic
and rolled up during
manufacturing.
Applications of Thin Film Solar Cells
Manufacturing will come first, but
then:???
The idea is that these solar cells can be taken
EVERYWHERE to supply a steady amount of
electricity, reducing the need to PLUG IN for power.
Eventually, we believe these materials might be able
to be sprayed onto business tiles, vehicles, and
billboards, and then wired up to electrodes. It might
even be possible to eventually feed into the electric
power grid.
An Example of a Nanotechnology
Experiment, Which Addresses
the Standards: Constructing
Nanocrystalline Solar Cells Using
the Dye Extracted From Citrus
Four main parts:
1. Nanolayer
2. Dye
3. Electrolyte
4. 2 electrodes
Nanocrystalline Solar Cells
Main component:
Fluorine doped tin
oxide conductive
glass slides
Test the slide with a
multimeter to
determine which side
is conductive
Synthesis of the
Nanotitanium Suspension
Procedure:
• Add 9 ml (in 1 ml increments) of
nitric or acetic acid (ph3-4) to
six grams of titanium dioxide in
a mortar and pestle.
• Grinding for 30 minutes will
produce a lump free paste.
• 1 drop of a surfactant is then
added ( triton X 100 or dish
washing detergent).
• Suspension is then stored and
allow to equilibrate for 15
minutes.
Coating the Cell
• After testing to determine
which side is conductive,
one of the glass slides is
then masked off 1-2 mm on
THREE sides with masking
tape. This is to form a mold.
• A couple of drops of the
titanium dioxide suspension
is then added and distributed
across the area of the mold
with a glass rod.
• The slide is then set aside to
dry for one minute.
Calcination of the Solar
Cells
• After the first slide has dried the
tape can be removed.
• The titanium dioxide layer needs
to be heat sintered and this can
be done by using a hot air gun
that can reach a temperature of at
least 450 degrees Celsius.
• This heating process should last
30 minutes.
Dye Preparation
• Crush 5-6 fresh berries in a mortar and pestle
with 2-ml of de-ionized water.
• The dye is then filtered through tissue or a
coffee filter and collected.
• As an optional method, the dye can be
purified by crushing only 2-3 berries and
adding 10-ml of methanol/acetic acid/water
(25:4:21 by volume)
Dye Absorption and Coating
the Counter Electrode
• Allow the heat sintered slide to
cool to room temperature.
• Once the slide has cooled,
place the slide face down in the
filtered dye and allow the dye to
be absorbed for 5 or more
minutes.
•While the first slide is soaking,
determine which side of the second
slide is conducting.
•Place the second slide over an open
flame and move back and forth.
•This will coat the second slide with a
carbon catalyst layer
Assembling the Solar Cell
• After the first slide had
absorbed the dye, it is
quickly rinsed with ethanol to
remove any water. It is then
blotted dry with tissue paper.
• Quickly, the two slides are
placed in an offset manner
together so that the layers
are touching.
• Binder clips can be used to
keep the two slides together.
•One drop of a liquid
iodide/iodine solution is
then added between the
slides. Capillary action will
stain the entire inside of
the slides
How Does All This Work?
1.
2.
3.
The dye absorbs
light and transfers
excited electrons
to the TiO2.
The electron is
quickly replaced
by the electrolyte
added.
The electrolyte in
turns obtains an
electron from the
catalyst coated
counter electrode.
TiO2=electron acceptor; Iodide = electron donor;
Dye = photochemical pump