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Photovoltaic Systems 1

JEE4980 – Sr Design Project

• Photovoltaic System (PV)

– Module through Main Service Panel

• Project Implementation Discussion

– Wilcox Chapter 2

• Lab Time – continued project design work

• Refer to your electronic handout /3 PV Systems folder for Sandia and SEI design tools

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Residential Concept

• PV Modules

• PV Array

• Battery

• Protection

• Inverter

• Disconnects

• Main Service Panel

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Photovoltaic Systems 4

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Cells to Array

• Connect cells to make a

module

• Connect modules to make

an Array

• STP Module Ratings

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Bypass Diode

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Residential Use vs Solar

Generation

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Battery Sizing Flowchart

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Lead Acid Battery

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Battery discharge – supply loadExternal circuit Electrons enter the Anode and

leave the Cathode

Anode Cathode

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Discharge• Both electrodes converted to lead sulfate

– Lead sulfate build up reduces surfaces area and performance

– Avoid full discharge

• Size system considering depth of discharge– Lead Antimony can cycle down to 20% of charge

• Simple battery model circuit is an ideal dependent DC source in series with a resistor– 2.12v / cell (no load) when fully charged

– Voltage diminishes as it discharges

– Temperature and rate of discharge affect performance

– Typically 95% efficient

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Charge Battery from PV SourceExternal circuit Electrons enter the Cathode and

leave the Anode

AnodeCathode

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Charge• Some H atoms converted to H2 gas

• Cathode is converted back to Pb

– Overcharging increases H2 gas

• Need higher voltage to charge

– Typically 95% efficient

• Cell voltage drops to 1.95 V at full discharge (depends on chemical formulation)

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Charge & Discharge V for Lead Acid Battery

• Capacity ‘C’ in Ah gives

coulombs of charge

stored

• Energy = (Vterminal)(Ah)

• / 5 (10, 20) hour charge

or discharge

• Internal losses I2R so

less efficient at 5 h

• Higher temperature

stores more energy

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Battery Considerations• Must respect Depth of Discharge (DoD)

• Vented (flooded) vs Non-vented (sealed)

• Maintenance– Short term: Water, connections

– Long term: End of life, replacement cost

• Lifetime - # of cycles affected by DoD

• Temperature

• Enclosures, space

• Other battery types: NiCad, NiZn, NiMH

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Protection

• DC

• AC

• Inverter

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Small PV Interconnection

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Wiring Example & Method

From “Photovoltaics Design & Installation Manual” by Solar Energy

International

• See 6 handout sheets from “PhotovoltaicsDesign & Installation Manual” in folder

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Wiring Example

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Wiring Solution

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AC & DC Schematic

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Grounding and Bonding

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From ‘Battery Management Systems’

by Pop, Bergveld et al

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Lithium Ion Battery

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Lithium Ion Battery –

Discharge Capacity vs Cycle #

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Lithium Ion Battery

•State of Charge is a function of Voltage, Impedance,

and Relaxation Time

•Most of these depend on Temperature too.

•Relaxation Time is how long it takes the battery to relax

to its internal EMF when current is interrupted.

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Lithium Ion Battery

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Lithium Ion Battery

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Appendix

• Slides after this for reference only

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Power Flow Controller

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Power Compensators