Introduction to the Concepts of:◦ Sustainability (The Big Picture)◦ How Solar Photovoltaic Cells work◦ How Solar Photovoltaic (PV) System works

Introduction to Solar Photovoltaic (PV) Systems – Part 2

Ice Breaker Game Lecture on:

◦ Sustainability (The Big Picture)◦ How Solar Photovoltaic Cells work◦ How Solar Photovoltaic (PV) System works

PV Cell Lab

Agenda

Group Activity◦ Your teacher will assign each of you a word and

you need to define it in your own words.◦ Write down your own definition on a piece of

paper.◦ Your group can help you if you are completely

lost on how to define the word.◦ Go around the classroom and read your word

and your own definition out loud.

Ice Breaker

Energy Photovoltaic Power Voltage Fission Physics Direct Current (DC) Alternate Current (AC) Power Inverter Energy Management

Current Efficiency Sustainability Electric Circuit Conservation of

Energy Charge (Electrons) Environment Fusion Series Circuit Parallel Circuit

Ice Breaker:

The Big Picture – Sustainability: Capacity to Endure

Sustainability

Environment

Economic Social

Human Consumptio

n

Natural & Physical

Resources

Biofuel, Biomass, Geothermal, Hydropower, Tidal, Wave, Wind, and Solar

Energy

Solar Technologies

Solar Energy

Solar Power

Water Heating

Building Heating

Biological Environments

Photovoltaics

Architecture & Urban Planning

Photosynthesis

Charge Controller

Batteries Inverter

Energy cannot be created or destroyed, it can be only transferred from one form to another.

Energy Conservation

Nuclear Energy (Fusion)

Solar Radiation

Photovoltaic Systems

Electrical Energy

Sun Earth

Charge can be positive (holes) or negative (electrons)

Silicon (Si) is an atom with 4 valence electrons.

In pure silicon it is difficult to control conductivity.◦ n-type semiconductor – Silicon with impurity

atoms having 5 valence electrons.◦ p-type semiconductor – Silicon with impurity

atoms having 3 valence electrons.

Semiconductor Devices – Basics

Physics of Photovoltaics

N-type silicon

P-type silicon

Pure silicon

How Photovoltaics Work?A negatively charged electron in the n-type silicon layer is repelled by the diode and can’t move through to the p-type silicon layer.

A negatively charged electron in the p-type silicon layer can move through the diode to the n-type silicon layer.

N-type Silicon Layer

Junction where electrical field or diode

is formed

P-type Silicon Layer

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PN - Junction

How Photovoltaics Work?

N-type Silicon Layer

Junction where electrical field or diode

is formed

P-type Silicon Layer

Solar energy (photons of light) hit the cell, passing through the n-type layer and releasing electrons from atoms in the p-type layer. These electrons pass upwards through the diode and to the n-type layer.

PN Junction

How Photovoltaics Work?

Metal Conductor

Junction where electrical field or diode

is formed

Metal Conductor

Metal conductors are added to the top and bottom of the cell and are connected to an electrical load. This creates an electrical circuit.

A LED is an electronic light source.

When a voltage is applied, electrons combine with holes and energy is released in the form of light.

Light Emitting Diode (LED)

In concept, a Photovoltaic is an LED working in reverse.

A Photovoltaic (in Concept)

Photovoltaics

Cell -> Panels -> Arrays

Cell Panel Array

Efficiency of Photovoltaics

)()(

PowerINSolarPowerPowerOUTPowerElectrical

Efficiency =

Photovoltaics - Efficiency

Higher Efficiency = Lower Ohmic Losses◦ Ohmic Loss – Occurs when charges move through a

conductor.

Higher Efficiency = Lower Dielectric Losses◦ Dielectric Loss – Occurs when plates and/or any other

adjacent contacts or surfaces are charged or discharged.

How to Improve Efficiency?

Components of a Photovoltaic System

Photovoltaic System (One)

Photovoltaic System (Two)

Inverter◦ Converts DC power from solar

array to AC for use in your home

Wiring◦ Connects the system

components

Batteries◦ Used to store solar-produced

electricity for nighttime or emergency use

Photovoltaic System Components

Charge Controller Prevents batteries from

being over charged

Disconnect Switches Allows power from a PV

system to be turned off

Electrical Meter Measures electrical

production and use

Deep Cycle Batteries are designed to be discharged down as much as 80% time after time, and have much thicker plates.◦ Can’t provide large current surges.

Deep Cycle Batteries and Inverters

Inverter is the device that transforms direct current (DC) to alternating current (AC).

Can provide 115VAC from a 12 VDC.

Consider Efficiency and Power Rating.

Inverters

)()(

DCPowerINACPowerOUTEfficiency

=

Photovoltaics in Series◦ Increases Voltage◦ Available current is limited by individual photovoltaics.

Wiring Photovoltaics - Series

Ammeter11.25 A

Voltmeter36 V

135 W12 V11.25 A

Photovoltaics in Parallel◦ Increases Available Current◦ Individual connected photovoltaics should be rated for

the same voltage.

Wiring Photovoltaics - Parallel

Ammeter33.75 A

Voltmeter12 V

EachPanel:135 W12 V11.25 A

= 405 W

Direct Current (DC)

Can be stored. Can only be sent

over short distances due to losses.

Easy to manipulate◦ Change level (Voltage)◦ Flow rate (Current)

Alternating Current (AC)

Can’t be stored. Can be sent long

distances with low losses. Difficult to manipulate

◦ It is possible but requires usually larger and more complex circuits and devices.

DC versus AC

Solar Modules and Arrays

Cells are the building block of PV systems◦ Typically generate 1.5 - 3 watts of power

Modules or panels are made up of multiple cells Arrays are made up of multiple modules

◦ A typical array costs about $5 – $6/watt Still need lots of other components to make this

work Typical systems cost about $8/watt

Solar PV Systems

Florida Solar Energy Center

Florida Solar Energy Center

PV Modules have efficiencies approaching 17%

Florida Solar Energy Center

Solar Panel

http://en.wikipedia.org/wiki/Solar_panel

Solar panel by BP Solar at a German autobahn bridge

Florida Solar Energy Center

The purpose of this lab is to give students experience constructing operating circuits while reviewing the following ideas/concepts:

PV Cell Laboratory - Tomorrow

• Voltage • Current • Power • Energy/work • Photoelectric effect • Series/Parallel circuit design • Efficiency