Intro to Photovoltaics Technological Design. What is Power? Rate at which energy is delivered Power...
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Transcript of Intro to Photovoltaics Technological Design. What is Power? Rate at which energy is delivered Power...
![Page 1: Intro to Photovoltaics Technological Design. What is Power? Rate at which energy is delivered Power = Energy Time Measured in Watts (W), kilowatts (kW),](https://reader036.fdocuments.us/reader036/viewer/2022062804/5697bf8a1a28abf838c8a49d/html5/thumbnails/1.jpg)
Intro to PhotovoltaicsTechnological Design
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What is Power?Rate at which energy is delivered
Power = Energy Time
• Measured in Watts (W), kilowatts (kW), or horsepower (HP)• Power is an instantaneous quantity• Power does not accumulate• Think gallons per minute
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What is Energy?• Ability to do work• Often measured in kilowatt Hours (kWh)
• Since Power = Energy/Time, • Then Power Time = Energy
• Energy does accumulates over time• Think gallons• Gallons = (gallons/min) minutes
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Power • Power is the rate at which energy is being delivered or consumed
Power = (Current)(Voltage)P = IV
• Units: Watt (W)
• So if 2 A of current is flowing through a load at 120 V, the Power used by the load is
P = IV = (2A)(120V) = 240 W
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How much electricity do you use per month?
• The average household uses 1,200 kWh per month (NREL.gov)
• WWHS main building uses 17,500 kWh per month ~ $3500 power bill
• What is the daily usage?• 583.33 kWh per day ~ $117.00 per day
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•Enormous nuclear reactor. Source of energy is “hydrogen burning”
•Approx 1 / 2,000,000,000 of Sun’s emitted energy reaches Earth
•Power that reaches Earth is approx. 15,000 times our total consumption
•Energy delivered in the form of electromagnetic radiation
•Electromagnetic radiation: Oscillating electric and magnetic fields: WAVES
The Sun
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Solar Radiation is:49% infrared (animals and NVG’s see this)46% visible (what you see)5% ultraviolet (sun burns)
http://imagers.gsfc.nasa.gov/ems/waves3.html
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Radiation Types
• Direct-beam Radiation: Radiation that has NOT been scattered. Is traveling directly from Sun.
• Diffuse Radiation: Radiation that has been scattered, and isn’t traveling directly from Sun.
• Why important?
• Flat-Plate collectors harvest only direct-beam, not diffuse radiation!
• Concentrating collectors – ones that use focusing mirrors – only harvest direct-beam radiation
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Solar Constant (S): Amount of solar energy that reaches the upper atmosphere of the Earth per area per time
S = 1,370 W/m2
Solar Constant is independent of Earth’s tilt, cloud cover, etc…
Solar Irradiance: How much solar energy reaches the Earth’s surface
Varies with season, time, cloud cover, …
Irradiance at which PV panels are rated is 1,000 W/m2, called “1 sun”
Definitions
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Quantify
We’re usually interested in how much ENERGY reaches (and is collected by) our module each day!
Energy = Power Time
Unit: kWhr/m2/day
This quantity is called solar insolation
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Sizing?
• Series and parallel are the same as batteries• For off-grid systems, you must calculate total energy
used during highest month in order to size appropriately• For grid-tied system, you must use tie to the grid and
trade energy when needed.• How much energy from a PV panel do we need for the
daily average energy usage? (Use the numbers we used previously for daily average and average solar insulation in Wilkes county)
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How about solar-powered vehicles?• Limited by space• Limits available power• Result?
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How about solar charged EV?• Average vehicle is only used for 30 miles a day.• Why not charge while parked in the sun?
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Experimentation Procedure• Working in teams of two, use a multimeter to measure the
voltage and amperage of two solar panels individually, in series, and in parallel.
• Part One: Measure and write down the voltage and amperage of each solar panel by themselves in your EDJ
• Part Two: Wire the solar panels in series and write down the voltage and amperage in your EDJ
• Part Three: Wire the solar panels in parallel and write down the voltage and amperage in your EDJ
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Questions for your Journal• Write out these questions in your journal:• Current (Amperage): Compare the current in Parts 2 and 3
with the current measured in Part 1.• How much did the current change in each case? (Compare all
thee parts)• How do you connect cells to obtain a higher current output?
• Voltage (Volts): Compare the voltage from Parts 2 and 3 with the voltage measured in part 1.• How much did the voltage change in each case?• How do you connect cells to obtain a higher voltage output?
• Extra* - Take your solar panel outside and keep it hooked to the multimeter, place your finger over one corner of the solar panel.• What happened to the voltage?• Why?