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