alternative energy light waves hydrogen. photovoltaic cells made from semiconductor materials...
Post on 22-Dec-2015
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Alternative Energy
Light Waves
Hydrogen
Photovoltaic Cells
• Made from semiconductor materials
• Produce useful current flow when illuminated with light
Solar Modules
• Produces Direct Current Electricity
• Commercially Available
• Rated by Volts and Watts per Module
Advantages
• Silent • Have no moving
parts • Cause no
environmental pollution in operation
• Never run out
Advantages Cont.
• Can generate power where it is needed, without the need for electricity pylons and wires.
• Work in cloudy weather and are more efficient in low temperatures
• Are not unsightly
Method of Operation
• Three main types– Monocrystalline – Polycrystalline
– Amorphous
Monocrystalline
1. single crystal cells o The first generation of solar cells o excellent conversion rate (12 - 16%)
(23% under laboratory conditions)BUT,
o making them is a painstaking, therefore expensive process
o another drawback - it takes a lot of energy to obtain pure crystal
Polycrystalline
Lower production costs, requiring less energy to make
11 - 13% conversion efficiency (18% in the lab
Amorphous o a more recent technology (mid-70's) o lower production costs, but unfortunately
also o lower efficiency (8 - 10%) (13% in the lab)
Light Energy
• Photons are Phrens
• Light as a wave
• Light as a particle– Photons– Work horse of electrical production
How Does It Work?
• Pure silicon four electrons in outer shell
• Very stable at ambient temperature
• Shares electrons with companions a pair at a time
• Engineers intervene with doping– Deliberate contamination– Deliberate motives
N-Type Semiconductor
• N= negative (electrons are negative charged• Extra electrons from arsenic or phosphorus• Counting atoms at the moment
P-Type Semiconductor
• P= Positive (electron holes are not negative)• Deficient electron shells from gallium or boron• Still counting atoms
N-P Junction
• Where the action occurs
Finally Physics
Power to the People
• One square meter of solar panels can produce up to 150 watts of maintenance-free power for up to thirty years
• The voltage produced by PV panels remains roughly the same regardless of the weather, but the current (amps) and the power (watts) will vary
More Power
• A panel's power is expressed in peak watts, the number of watts it will produce in optimal conditions, i.e. at noon in direct sunlight in cold weather
• Maximum sun intensity is 1.000 W/m2
• VOLTS x AMPERES = WATTS
Configurations
A 12-volt PV panel producing 4 amperes of current has 48 watts of power
News and Discoveries
• Thin Film Technologies • Virginia Tech • Ionic Self-Assembled Multilayers (ISAM)
– nanometer-thick layers of materials – using polymers and molecules called
fullerenes
• Organic dyes from berries• Innovation continues