photovoltaic design and installation full presentation compressed

7/28/2019 Photovoltaic Design and Installation Full Presentation COMPRESSED

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Photovoltaic Design andInstallation

Bucknell UniversitySolar Scholars Program

Presenters:

Colin Davies 08

Eric Fournier 08


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Outline

Why Renewable Energy?

The Science of Photovoltaics

System Configurations

Principle Design Elements

The Solar Scholars program atBucknell (walking tour)


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40%

85% of our energy consumption

is from fossil fuels!


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Why Sustainable Energy Matters

The worlds current energy system is built aroundfossil fuels

Problems:

Fossil fuel reserves are ultimately finite

Two-thirds of the world' s proven oil reserves arelocating in the Middle-East and North Africa (which

can lead to political and economic instability)


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Why Sustainable Energy Matters

Detrimental environmental impacts

Extraction (mining operations)

Combustion

Global warming? (could lead to significantchanges in the world' s climate system, leadingto a rise in sea level and disruption of agriculture

and ecosystems)


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A Sustainable Energy Future

Develop and deploy renewable energy sourceson a much wider scale

Bring down cost of renewable energy

Make improvements in the efficiency of energyconversion, distribution, and use

Three Methods:- Incentives

- Economy of scale

- Regulation


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Making the Change to Renewable

Energy

Solar

Geothermal Wind

Hydroelectric


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Todays Solar Picture

Germany leads solar production (over 4.5 times morethen US production) Japan is 2nd (nearly 3 times

more then US production) this is mainly due toincentives

Financial Incentives Investment subsidies: cost of installation of a

system is subsidized Net metering: the electricity utility buys PV

electricity from the producer under a multiyearcontract at a guaranteed rate

Renewable Energy Certificates ("RECs")


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Solar in Pennsylvania

Pennsylvania is in fact a leader in renewable

energy Incentives

Local & state grant and loan programs

Tax deductions

RECs (in 2006: varied from $5 to $90 per MWh,median about $20)
http://www.depweb.state.pa.us/energindependent/site/default.asp


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Harnessing the Sun

Commonly known as solar cells, photovoltaic (PV)devices convert light energy into electrical energy

PV cells are constructed with semiconductormaterials, usually silicon-based

The photovoltaic effect is the basic physical processby which a PV cell converts sunlight into electricity

When light shines on a PV cell, it may bereflected, absorbed, or pass right through. Butonly the absorbed light generates electricity.


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Electricity


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Part 2: Learning Objectives

Compare AC and DC electrical current and

understand their important differences Explain the relationship between volts, amps,

amp-hours, watts, watt-hours, and kilowatt-hours

Learn about using electrical meters


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Electricity Terminology

Voltage (E or V)

Unit of electromotive force Can be thought of as electrical pressure

Amps (I or A)

Rate of electron flow

Electrical current

1 Amp = 1 coulomb/second = 6.3 x 1018electrons/second


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Watt (W) are a measure of Power

Unit rate of electrical energy Amps x Volts = Watts

1 Kilowatt (kW) = 1000 watts


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Watt-hour (Wh) is a measure of energy

Unit quantity of electrical energy (consumptionand production)

Watts x hours = Watt-hours

1 Kilowatt-hour (kWh) = 1000 Wh


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Power and Energy Calculation

Draw a PV array composed of four 75 watt

modules. What size is the system in watts ?


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Amp-hour (Ah)

Quantity of electron flow Used for battery sizing

Amps x hours = Amp-hours

Amp-hours x Volts = Watt-hours

A 200 Ah Battery delivering 1A will last _____ hours 200 Ah Battery delivering10 A will last _____ hours

100 Ah Battery x 12 V = _____ Wh


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Types of Electrical Current

DC = Direct Current

PV panels produce DC Batteries store DC

AC = Alternating Current

Utility power

Most consumer appliancesuse AC


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Meters and Testing

Clamp on meter Digital multimeter

Never test battery current using a multimeter!


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System Types


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Understand the functions of PV components

Identify different system types


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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


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Systems with DC Loads


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DC System Options

Battery backup vs. discontinuous use

LVD option in charge controller Load controllers


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Systems with AC loads


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AC System Options

Combined AC and DC loads

Hybrid system with back up generator Grid tied utility interactive system without

batteries

Grid tied interactive with battery backup

(why might you need this?)


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Grid-Tied System(With Batteries)

Complexity High: Due to the

addition of batteries

Grid Interaction Grid still supplements

power

When grid goes downbatteries supply powerto loads (aka batterybackup)


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PV Modules


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Learn how a PV cell produces electricity fromsunlight

Discuss the 3 basic types of PV celltechnologies

Understand the effects of cell temperatureand solar insolation on PV performance

Gain understanding of module specification

Identify the various parts of a module


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Solar Cells and the PV Effect

Usually produced with Semi-conductor gradesilicon

Doping agents create positive and negativeregions

P/N junction results in 0.5 volts per cell

Sunlight knocks available electrons loose

Wire grid provides a path to direct current


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Inside a PV Cell


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Available Cell Technologies

Single-crystal or Mono-crystalline Silicon

Polycrystalline or Multi-crystalline Silicon

Thin film

Ex. Amorphous silicon or Cadmium Telluride


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Polycrystalline Silicon Modules

Less expensive to makethan single crystalline

modules Cells slightly less

efficient than a singlecrystalline (10% - 12%)

Square shape cells fitinto module efficientlyusing the entire space


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Amorphous Thin Film

Most inexpensivetechnology to produce

Metal grid replaced withtransparent oxides

Efficiency = 6 8 %

Can be deposited on

flexible substrates Less susceptible to

shading problems

Better performance in lowlight conditions that with

crystalline modules


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Selecting the Correct Module

Practical Criteria

Size

Voltage

Availability

Warranty

Mounting Characteristics Cost (per watt)


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Voltage Terminology

Nominal Voltage Ex. A PV panel that is sized to charge a 12 V battery, but

reads higher than 12 V)

Maximum Power Voltage (Vmax / Vmp) Ex. A PV panel with a 12 V nominal voltage will read 17V-

18V under MPPT conditions)

Open Circuit Voltage (Voc ) This is seen in the early morning, late evening, and while

testing the module)

Standard Test Conditions (STC) 25 C (77 ) cell temperature and 1000 W/m2 insolation


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Effects of Temperature

As the PV cell

temperatureincreases above 25C, the module Vmpdecreases by

approximately 0.5%per degree C


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Effects of Shading/Low Insolation

As insolationdecreasesamperagedecreases whilevoltage remains

roughly constant


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Other Issues

Surface temperature can be measured usinglaser thermometers

Insolation can be measured with a digitalpyranometer

Attaching a battery bank to a solar array will

decrease power production capacity


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PV Wiring


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List the characteristics of series circuits andparallel circuits

Understand wiring of modules and batteries

Describe 12V, 24V, and 48V designs


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Series Connections

Loads/sources wired in series

VOLTAGES ARE ADDITIVE

CURRENT IS EQUAL

One interconnection wire is usedbetween two components (negative

connects with positive) Combined modules make series string

Leave the series string from a terminalnot used in the series connection


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Quiz Time

If you have 4 12V / 3A panels in an arraywhat would the power output be if that arraywere wired in series?

What if it were wired in parallel?

Is it possible to have a configuration that

would produce 24 V / 6 A? Why?


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Dissimilar Modules in Series

Voltage remains additive

If module A is 30V / 6A and module B is 15V / 3Athe resulting voltage will be?

Current taken on the lowest value

For modules A and B wired in series what wouldbe the current level of the array?


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Dissimilar Modules in Parallel

Amperage remains additive

For the same modules A and B what would thevoltage be?

Voltage takes on the lower value.

What would the voltage level of A and B wired inparallel be?


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Shading on Modules

Depends on orientation of internal modulecircuitry relative to the orientation of theshading.

SHADING can half

or even completely

eliminate the output

of a solar array!


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Wiring Introduction

PV installations must be in compliance with theNational Electrical Code (NEC)

Refer to NEC Article 690 (Solar Photovoltaic Systems) fordetailed electrical requirements

Discussion points Wire types, wire sizes

Cables and conduit Voltage drops

Disconnects

Grounding


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Wire Types

Conductor material = copper (most common)

Insulation material = thermoplastic (most common) THHN: most commonly used is dry, indoor locations

THW, THWN, and TW can be used indoors or for wetoutdoor applications in conduit

UF and USE are good for moist or underground applications

Wire exposed to sunlight must be classed assunlight resistant


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Color Coding of Wires

Electrical wire insulation is color coded to designate itsfunction and use

Alternating Current (AC) Wiring Direct Current (DC) Wiring

Color App l icat ion Color App l icat ion

Black Ungrounded Hot Red (not NEC req.) Positive

White Grounded

Conductor

White Negative or

GroundedConductor

Green or Bare EquipmentGround

Green or Bare EquipmentGround

Red or anyother color

Ungrounded Hot


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Cables and Conduit

Cable:two or more insulated conductors having anoverall covering

As with typical wire insulation, protective covering on cable israted for specific uses (resistance to moisture, UV light, heat,chemicals, or abrasion)

Condui t :metal or plastic pipe that contains wires PVC is a common conduit used

Using too many wires or too large of wires in a given conduitsize can cause overheating and also causes problems whenpulling wire


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Wire Size

Wire size selection based on two criteria: Ampacity

Voltage drop Ampacity: current carrying ability of a wire

The larger the wire, the greater its capacity to carry current

Wire size given in terms of American Wire Gauge (AWG)

The higher the gauge number, the smaller the wire

Voltage drop: the loss of voltage due to a wiresresistance and length Function of wire gauge, length of wire, and current flow in the

wire


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Safety Considerations

Unsafe Wiring

Splices outside the box

Currents in grounding conductors

Indoor rated cable used outdoors

Single conductor cable exposed

Hot fuses Disconnects

Overcurrent Protection (Fuses & Breakers)


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Safety Equipment

Disconnects Allow electrical flow to be

physically severed(disconnected) to allowfor safe servicing ofequipment

Overcurrent Protection Protect an electrical

circuit from damagecaused by overload orshort circuit

Fuses

Circuit Breakers


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Grounding

Limit voltages due to: Lightning Power line surges Unintentional contact with higher voltage lines

Provides a current path for surplus electricity to travel too(earth)

Two types of grounding: Equipment grounding

(attach all exposed metal parts of PVsystem to the grounding electrode) System ground ing(at one point attach ground to one current

carrying conductor) DC side of system => Negative to ground AC side of system => Neutral to ground


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Batteries


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Battery basics

Battery functions Types of batteries

Charging/discharging

Depth of discharge

Battery safety


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Batteries in Series and Parallel

Series connections

Builds voltage

Parallel connections

Builds amp-hour capacity


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Battery Basics

Battery

A device that stores electrical energy (chemical energy toelectrical energy and vice-versa)

Capacity

Amount of electrical energy the battery will contain

State of Charge (SOC)

Available battery capacity

Depth of Discharge (DOD)

Energy taken out of the battery

Efficiency

Energy out/Energy in (typically 80-85%)

The Terms:


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Functions of a Battery

Storage for the night

Storage during cloudy weather

Portable power

Surge for starting motors

**Due to the expense and inherit inefficiencies of batteries it isrecommended that they only be used when absolutely necessary (i.e.in remote locations or as battery backup for grid-tied applications ifpower failures are common/lengthy)


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Batteries: The Details

Primary (single use)

Secondary (recharged) Shallow Cycle (20% DOD)

Deep Cycle (50-80% DOD)

Types:

Unless lead-acid batteries are charged up to 100%, they will loose

capacity over time

Batteries should be equalized on a regular basis

Charging/Discharging:


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Battery Capacity

Amps x Hours = Amp-hours (Ah)

Capacity:

100 amps for 1 hour

1 amp for 100 hours

20 amps for 5 hours

Capacity changes with Discharge Rate

The higher the discharge rate the lower the capacity and vice versa

The higher the temperature the higher the percent of rated capacity

100 Amp-hours =


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Rate of Charge or Discharge

Rate = C/T

C = Batterys rated capacity (Amp-hours)

T = The cycle time period (hours)

Maximum recommend charge/discharge rate =C/3 to C/5


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Cycle Life vs. Depth of Discharge

Depth Of Discharge (DOD) %

# of Cycles


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Battery Safety

Batteries are EXTREMELY DANGEROUS; handle withcare!

Keep batteries out of living space, and vent batterybox to the outside

Use a spill containment vessel

Dont mix batteries (different types or old with new)

Always disconnect batteries, and make sure toolshave insulated handles to prevent short circuiting


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Battery Wiring Considerations

Battery wiring leads should leave the batterybank from opposite corners

Ensures equal charging and discharging;prolongs battery life

Make sure configuration of battery bank

allows for proper connections to be easilymade


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Controllers & Inverters


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Controller basics

Controller features

Inverter basics

Specifying an inverter


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Controller Basics

To protect batteries from being overcharged

Function:

Maximum Power PointTracking

Tracks the peakpower point of thearray (can improvepower production by20%)!!

Features:


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Other Controller Considerations

When specifying a controller you must consider:

DC input and output voltage

Input and output current Any optional features you need

Controller redundancy: On a stand-alone system it mightbe desirable to have more then one controller per array in

the event of a failure


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Inverter Basics

An electronic device used to convert direct current (DC)electricity into alternating current (AC) electricity

Function:

Efficiency penalty

Complexity (read: a component which can fail)

Cost!!

Drawbacks:


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Specifying an Inverter

What type of system are you designing? Stand-alone Stand-alone with back-up source (generator) Grid-Tied (without batteries) Grid-Tied (with battery back-up)

Specifics: AC Output (watts) Input voltage (based on modules and wiring)

Output voltage (120V/240V residential) Input current (based on modules and wiring) Surge Capacity Efficiency Weather protection

Metering/programming


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Solar Site


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Understand azimuth and altitude

Explain magnetic declination

Describe proper orientation and tilt angle forsolar collection

Describe the concept of solar window


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Site Selection Panel Direction

Face south

Correct formagnetic

declination


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Orientation and Tilt Angle


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Site Selection Tilt Angle

Year round tilt = latitudeWinter + 15 lat.Summer 15 lat.

Max performance isachieved when panels

are perpendicular to thesuns rays


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Solar Access

Optimum Solar Window 9 am 3 pm

Array should have NO SHADING in thiswindow (or longer if possible)


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Solar Pathfinder

An essential tool in finding a good site forsolar is the Solar Pathfinder

Provides daily, monthly, and yearly solarhours estimates


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Practical Determinants for Site

Analysis

Loads and time of use

Local climate characteristics

Distance from power conditioning equipment

Accessibility for maintenance

Aesthetics


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Energy Efficiency


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Identify cost effective electrical load reductionstrategies

List problematic loads for PV systems

Describe penalties of PV system components

Explain phantom loads

Evaluate types of lighting; efficiencycomparison


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Practical Efficiency Recommendations

For every $1 spent on energy efficiency, you save$3-$5 on system cost

Adopt a load dominated approach Do it efficiently

Do it another way

Do with less

Do without Do it using DC power

Do it while the sun shines


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Typical Wattage Requirements

Appliance Wattage

Blender 350

TV (25 inch) 130

Washer 1450

Sunfrost Refrigerator (7 hours aday)

refrigerator/freezer (13 hours aday)

112

475

Hair Dryer 1000

Microwave (.5 sq-ft)

Microwave (.8 1 sq-ft)

750

1400


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Improving Energy Efficiency in theHome

Space Heating: Super insulation

Passive solar design Wood stoves

Propane

Solar hot water

Radiant Floor/baseboard

Efficient windows

Domestic hot waterheating

Solar thermal Propane/natural gas

No electric heaters

On demand hot water


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Improving Energy Efficiency in theHome

Kitchen Stoves Solar cookers

Gas burners- no glowbar ignition

Microwaves

Washing machines High efficiency horizontal

axis

Cooling Ceiling fans

Window shades Evaporative cooling

Insulation

Trees

Reflective attic cover

Attic fan


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Phantom Loads

Cost the United States:

$3 Billion / year

10 power plants

18 million tons of CO2

More pollution than 6 million cars

TVs and VCRs alone cost the US $1Billion/year in lost electricity


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Lighting Efficiency

Factors effecting light efficiency

Type of light

Positioning of lights

Fixture design

Color of ceilings and walls

Placement of switches


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Incandescent Lamps

Advantages Most common

Least expensive Pleasing light

Disadvantages Low efficiency

Short life ~ 750 hours

Electricity is conducted through a filament which resiststhe flow of electricity, heats up, and glows

Efficiency increases as lamp wattage increases

FROM THE POWER PLANT TO YOUR HOMEINCANDESCENT BULBS ARE LESS THAN 2%

EFFICIENCT


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Fluorescent Bulbs

Les wattage, same amount of lumens

Longer life (~10,000 hours)

May have difficulty starting in coldenvironments

Not good for lights that are repeatedly turned

on and off Contain a small amount of mercury


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Mounting


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Evaluate structural considerations

List hardware requirements

Pros and cons of different mounting

techniques


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General Considerations

Weather characteristics Wind intensity

Estimated snowfall Site characteristics

Corrosive salt water

Animal interference

Human factors Vandalism

Theft protection

Aesthetics


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Basic Mounting Options

Fixed

Roof, ground, pole

Integrated

Tracking

Pole (active & passive)


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Roof Mount Considerations

Penetrate the roof as little as possible

Weatherproof all holes to prevent leaks May require the aid of a professional roofer

Re-roof before putting modules up

Ballasted roof mounts work on certain roofs

Leave 4-6 airspace between roof andmodules

On sloped roofs, fasten mounts to rafters notdecking


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Building Integrated PV


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Ready for a field tour?

Questions?

If you are interested in anything you have seen today

and would like to get involved, please contact anymember of the Solar Scholars team:

Colin Davies, Eric Fournier, or Jess Scott(cjdavies, efournie, jpscott)


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The END

Thank you for participating in this lectureseries

Now lets go out into the field and take a lookat the systems that we have already

installed.

photovoltaic design and installation full presentation compressed

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