Transcript JfJ Workshop Powerpoint

Juice from Juice
Teaching Workshop
NSF Center for Chemical Innovation: Solar Fuels
Overview of JfJ Project
• Goal: develop dye-sensitized solar cell (DSSC) kit that
1. Supports NGSS (3rd – 12th grade)
2. Gets students involved in solar-energy technology
3. Reinforces inquiry-based learning and invites further
discussion/investigation from students
• Integration of scientific concepts from multiple
disciplines into one hands-on, engineering-based
project
Physics
Light
absorption
Chemical
potential
DSSC
Biology
Electron
transfer
Chemistry
Engineering
Lesson Road Map
Pre-lab
Related Lessons
Experiment
Water
Splitting:
Photosynthesis
and Energy
Storage
Scientific
Notation: Using
a multimeter
DSSC
Background
Information
Inquiry
Opportunity:
Renewable
energy
Light as Energy:
Light reflection
and absorption
in gummy bears
Electrochemistry:
Galvanic Cells,
redox and the
activity series
DSSC
Fabrication
Circuits:
Connecting
cells in series
and parallel
Post-lab
Calculating
power and
efficiency of a
DSSC
Next Steps
Comparison to
silicon solar
cells and other
dyes
Inquiry
Opportunity:
Fuel Cells
What is a Solar Cell?
Sony Hana Akari (“flower light”) lamps:
lampshades are screenprinted DSSCs
Caltech Holliston parking structure
Solar window prototype by Solaronix - EPFL
Traditional Photovoltaics vs. DSSCs
DSSC Components
• Semiconductor
TiO2
• Dyes used as photosensitizers
–
–
–
–
Chlorophyll (spinach leaves)
Anthocyanin (berries, fruits)
Betalin (beets)
Synthetic Ru dyes
Blackberry Juice
• Conductive glass electrodes
FTO
• Redox electrolyte
I-/I3-
• Light source
Projector or Sun
Juice from Juice DSSCs
Dyed TiO2
Sandwiched layers
with electrolyte in
between
TiO2 layer
Graphite layer
Completed DSSC
How do the DSSCs work?
• It all has to to with energy levels and band
gaps
• Light provides energy to excite an electron
• As the electron moves down the energy levels,
it can do work and generate electricity
Energy Levels of DSSCs
Image from Tan et. al., 1994
Energy Levels of DSSCs
Light
excites
the from
dye,
moving
electron
higher
c) a)Electrons
b) An
collected
from
the
theTiO
dyeto
travel
isrelease
transferred
through
the
TiO
load
to reach
d)electron
Iodide
is oxidized
anto ato
2an
2 energy
the counter electrode,
wheretothey
are used
to reduce triiodide
electron back
the dye
molecule.
LUMO
CB
HOMO
LOAD
e-
VB
+
DYE*
DYE
+
TiO2
I-/I3-
Our load can be a light
bulb or other electronic
device.
Today it is a multimeter.
Energy Levels of DSSCs
Although we’ve spatially rearranged the energy
levels, they still sit at the same energies!
LUMO
CB
LOAD
HOMO
VB
I-/I3-
Energy Levels of DSSCs
The electron ‘rolls’ down the potential hill, passing through the load,
and returns to the ground state in the dye.
LUMO
CB
HOMO
eDYE
VB
TiO2
I-/I3-
LOAD
Energy Levels of DSSCs
The sun does all the work for us!
It throws the electrons to the
‘top of the hill,’ while we simply
make use of the energy of the
electron as it rolls down.
This is SOLAR ENERGY.
Chemical Reactions Resulting in Electron
Transfer for Current Flow
Reduction
I3- + 2e-  3I-
Oxidation
3I-  I3- +2e2
w
e- +
-
-
LEO the lion goes GER
OIL RIG
Image credit:
http://chemed.chem.purdue.edu/genchem/topicrevie
Why this System?
• Materials are cheap, abundant, non-toxic
• Right energy level alignment with all components
(dyes, FTO, TiO2, I-/I3-, etc.)
• Detectable current (I) and voltage (V)
• Other options?
– other fruits or synthetic dyes can be used as can other
metal oxides besides TiO2
– However, energy level alignment and electron transfer
rates must be satisfied
Side Lesson: Using Multimeters
DC = Direct Current
Variable
Units of Measurement
Context
Current
‘I’
Amps (A) = Coulomb/sec
Electron travel
rate
Voltage
‘V’
Volts (V) = Joules/Coulomb ‘Push’ [or
energy] per
electron packet
Resistance
Ohms (Ω)= Volts/Amps
Opposing force
[like friction in
mechanics]
Watts (W) = Joules/ sec =
Volts*Amps
Energy transfer
rate
‘R’
Power
‘P’
P = I*V
V = IR
Joule’s Law
Ohm’s Law
Side Lesson: Building Circuits
How do we maximize current or voltage from our
solar cells?
These symbols (resistors)
represent our DSSCs!
• In series
maximum voltage
• In parallel
maximum current
Side Lesson: Building Circuits
How do we maximize current or voltage from our
solar cells?
• In series
maximum voltage
• In parallel
maximum current
Related Expt: Water-splitting
DSSCs
Water Splitting
Uses sunlight to
generate clean,
renewable electricity
Makes clean,
renewable fuel from
water
Combine: H2 generation using DSSCs
Related Expt: Light & Energy
Nature of light
• White light can be made from individual colors
• Wavelengths of light can be absorbed or reflected, giving rise to the colors we see
• Different wavelengths have different colors and energies
Related Expt: Electrochemistry
• Electrochemistry key to the success of a DSSC
• Output voltage due to reduction/oxidation (redox) reactions
– Different metals have different reduction potentials
– Create activity series using Zn, Cu, Sn, and Mg
DSSC
Galvanic cell
-0.5
0.0
0.5
1.0
E (V)
DSSC Kit
• Juice from Juice kits
distributed by Arbor Scientific
• Includes all materials for the
experiment with a class of 30
– DSSC Fabrication…..$140
• Refill of chemicals or extra
glass for larger classes
available in refill kit
– Chemical Refill……...$39
– Glass Refill…............$15
• Most materials can be reused
for several years
Other experiment Kits
• Still in process of developing
kits/setting prices
• Also distributed by Arbor
Scientific with materials for a
class of 30
– Water-Splitting………..$79
– Electrochemistry….….$50
• Light & Energy Experiment
just requires
– red & green laser pointers
($10-20 online)
– Gummy bears
“I need help!”
• I don’t have enough $ for the kit!
– Kids in Need Foundation, DonorsChoose.org, local power company
grants
– Donations from parents, PTA, bake sales
– Even aluminum cans!
• I don’t remember how to do it!
– Lesson plans and instructional videos online
http://thesolararmy.org/jfromj
– We can do a demo at your school if you are in the LA area
– Email questions – [email protected]
• I don’t have time in my curriculum!
– Lesson fulfills NGSS standards, cross-cutting concepts in many areas
– Incorporate as much as you can – some renewable energy education is
better than none!
Conclusions and goals
• Integrate basic science with
push towards clean energy
• Get students and teachers
directed toward research in
solar energy conversion
• Feedback and continued
project development
Physics
Light
absorption
Chemical
potential
DSSC
Biology
Electron
transfer
Chemistry
Engineering
Thanks – and have fun!
Questions: [email protected]