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Electricity
• Compare AC and DC electrical current and understand their important differences• Explain the relationship between volts, amps, amp-hour, watts, watt-hours, and kilowatt-hours• Learn about using electrical meters
Electricity Terminology
• Electricity = flowing electrons• Differences in electrical potential creates
electron flow• Loads harness the kinetic energy of these
flowing electrons to do work• Water flow is a good analogy for electron flow
• Electricity = flowing electrons• Differences in electrical potential creates
electron flow• Loads harness the kinetic energy of these
flowing electrons to do work• Water flow is a good analogy for electron flow
Electricity Terminology
• Resistance ()
- The opposition of the material to the flow of an electrical current
- Depends on material, cross sectional area, length, and temperature
• Resistance ()
- The opposition of the material to the flow of an electrical current
- Depends on material, cross sectional area, length, and temperature
Electricity Terminology
• Watt (W) is a measure of power
- Unit rate of electrical energy (joules/sec)
- 1 horsepower (hp) = 746 watts
• Volts × Amps = Watts
• 1000 watts = 1 kW
Electricity Terminology
• Watt-hour (Wh) is a measure of energy
- Unit quantity of electrical energy
- Watts × hours = Watt-hours
• 1kilowatt-hour (1 kWh) = 1000 Wh
Electricity Terminology
• Amp-hour (Ah)
- Quantity of electron flow
- Used for battery sizing
- Amps × hours = Amp-hours
- Amp-hours × Volts = Watt-hours
A 200 Ah battery delivering 1 A will last ________ hours
A 200 Ah battery delivering 10 A will last _________ hours
100 Ah battery × 12 V = __________ Wh
Electricity Terminology
• DC = direct current
- PV panels produce DC
- Batteries store DC• AC = alternating current
- Utility
- Most consumer appliances
uses AC
Meters and Testing
Never test battery current using a multimeter!
Clamp-on meter Digital multimeter (DMM)
System Types
• Understand the functions of PV components
• Identify different system types
Photovoltaic (PV) Terminology
• Cell < Module < Panel < Array• Battery – stores DC energy• Controller – senses battery voltage and
regulates charging• Inverter – converts direct current (DC) energy to
alternating current (AC) energy• Loads – anything that consumes energy
Grid-Tied System (without batteries)
• Complexity- Low: Easy to install (less components)
• Grid Interaction- Grid can supplement power- No power when grid goes down
Grid-Tied System (with batteries)
• Complexity- High: Due to addition of batteries
• Grid Interaction- Grid still supplements power- Batteries supply power to loads when the grid goes down
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