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The Physics of Photovoltaics: An Analysis of Solar Panel Cost, E ffectiveness and Efficiency. Group 16: Angel Needham-Gilles, Nico Mongillo and Nick Pauley. Project Overview.
Group 16: Angel Needham-Gilles, NicoMongillo and Nick Pauley
As a group we decided to go the analytical route. The purpose of our project was to investigate the physics of solar panels including their production and how they convert light to energy. Also investigated are their efficiency and efficacy as long-term “green” solutions as well as some of the political implications of their use.
-Polycrystalline cells are slightly less efficient thanmonocrystallinesolar cells, but are cheaper to manufacture in wafer form.
-The diagram below from How Stuff Works illustrates the order of the raw ingredients needed to create a generic polycrystalline silicon cell.
A layer of glass for protection
Highly purified N-Type Silicon
The development of CIGS cells “might be slightly constrained by shortages of gallium and selenium,” while, mass production of CdTe cells may behamperedby tellurium availability (Lynn, 208, 2010).
Note that while they may all be made up of the same type of cell a module and an array will have different efficiencies due to the empty spaces between each cell
* A Positive P-type (Electron Poor)
* A Negative N-type (Electron Rich)
Pure Silicon – while it is the most commonly used element for solar cells, it is usually doped with other materials to create the specific type of semiconductor needed
*This is called the photovoltaic effect and explains why the true name for solar cells are PV cells
Energy of a photon
Solar cell efficiency ( ) depends on
- The total power light power density (JV) on the cell
- The actual potential difference of the system
- The actual current density of the system
- The “fill factor” constant which is the ratio between the actual values and the maximum values
Certain photon energy levels which are created by the sun get absorbed or reflected by the atmosphere, which prevents solar cells from accessing that particular level for its electrons. (Note: AM means Air Mass which is equivalent to the thickness of the atmosphere) (Picture Credit – Lynn 2010)
The Best Solar Cell Research Efficiencies as Recorded by the NREL (National Renewable Energy Lab) (Picture Credit - http://www.nrel.gov/pv/thin_film/docs/kaz_best_research_cells.ppt)
Multijunction ConcentratorsThree-junction (2-terminal, monolithic)Two-junction (2-terminal, monolithic)
Crystalline Si CellsSingle crystalMulticrystallineThin Si
Thin Film TechnologiesCu(In,Ga)Se2CdTeAmorphous Si:H (stabilized)
Emerging PVOrganic cells
* Energy Payback – how long does it take for the solar cell to make the energy it took to make the panel itself
* Cost Effectiveness – how long does it take for the solar cell to generate the energy equivalent to its cost
*It takes the average silicon solar cell in the United States between two (for the lower half) to four years (for the upper half)
* It currently costs about $7.00 per Watt but can go as low as $4.30 per Watt
(This is a significant decrease from the $300 per Watt cost during the 1970’s)
* Note that once installed unless it has a sun tracking system installed to it, its only needed fuel is sunlight
Data from Lynn 2010
* Total Cost: $1,921,330 – $3,537,151
* Total Area: 40,460 – 73,436 sq m
* Average Monthly Savings: $8000
* Cost Payback: 15.00 – 23.09 years
* Total Cost: $3,903,911 - $7,135,553
* Total Area: 80,921 – 146,873 sq m
* Average Monthly Savings: $ 16,000
* Cost Payback: 15.4 – 23.22 years
As of 2008, Vassar was paying $16,000 a month for dorm electricity alone. Based on some of the leading New York electric companies and New York’s average solar irradiance of 4.47 kWh/sq m per day…
Statistics Credit goes to Cooler Planet.com
Solar panels only generate electricity during daylight hours. In most cases this means that it will only provide energy for half of the day. Obviously, electricity used at night is gathered from energy stored during daylight collection hours.
Weather obviously also obstructs the absorption of photons. Temperature, however, has little effect on the efficiency of solar panels.
Pre-existing pollution can interfere as well which will prove difficult in industrial areas and in cities.
For these reasons, solar panels cannot, unfortunately, be the sole provider of energy for the United States
Additionally, Cadmium is a heavy metal known used in CdTe solar cells
It is known to cause harmful long term effects when ingested or inhaled such as kidney failure, lung damage and brittle bones
While dangerous, it is a by product of zinc mining and its application in solar cells would be a much more productive use
When recycled and carefully disposed of it there is hardly any risk using it
*solar panels on sattlelites which beam the energy back to earth in the form of microwaves
*desert spanning solar farms
*laser sunlight collectors to focus sun rays right at the solar cells
Moyer, Michael. "PopSci\'s Best of What\'s New 2007." Popular Science | New Technology, Science News, The Future Now. 2007. Web. 25 Apr. 2011. <http://www.popsci.com/popsci/flat/bown/2007/green/item_59.html>.
Coniff, Richard. "The Greenhouse Gas That Nobody Knew by Richard Conniff: Yale Environment 360." Yale Environment 360: Opinion, Analysis, Reporting & Debate. 13 Nov. 2008. Web. 25 Apr. 2011. <http://e360.yale.edu/content/feature.msp?id=2085>.
Lynn, Paul A. Electricity from Sunlight. (Chichester, West Sussex: John Wiley & Sons, 2010).