Energy Capture and Storage

1. 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.

2. 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!

3. 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.”

4. 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.

5. 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.

6. An Example of a Nanotechnology Experiment, Which Addresses the Standards: Constructing Nanocrystalline Solar Cells Using the Dye Extracted From Citrus • Four main parts: • Nanolayer • Dye • Electrolyte • 2 electrodes

7. Main component: Fluorine doped tin oxide conductive glass slides Nanocrystalline Solar Cells Test the slide with a multimeter to determine which side is conductive

8. 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.

9. 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.

10. 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.

11. 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)

12. 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

13. 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

14. How Does All This Work? • 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