Post on 07-Apr-2018
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Solar Electric Fundamentals
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Photovoltaics (PV)or Solar Electric
• Direct conversion of sunlight into dc electricity.
• Solid-state electronics, no-moving parts.
• High reliability, warranties of 20 years or more.
• PV modules are series- and parallel-
interconnected to meet the voltage and currentrequirements.
• Energy storage (battery) is needed for nighttime
operation.
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Basic Electricity Terms• Ampere (Amp, A) – Basic unit of electric current, like
the flow of water in a pipe.• Volt (V) – Basic unit of electric voltage (potential),
like the pressure of water in a pipe.
• Watt (W) – Basic unit of electric power.
1 Volt X 1 Amp = 1 Watt
• Watt-Hour – Basic unit of electric energy.1 Watt for 1 hour = 1 Watt-hour (Wh)
100 Watts for 10 hours = 1 kiloWatt-hour (kWh)
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Outline
• Solar Industry Status
• Solar Electric – Systems View
• Solar PV Technology
• Stand-alone Off-grid Applications
• Grid-connected Applications
• Intro to Hybrid Systems• Solar System Analysis Tools
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Outline
• Solar Industry Status
• Solar Electric – Systems View• Solar PV Technology
• Stand-alone Off-grid Applications• Grid-connected Applications
• Intro to Hybrid Systems• Solar System Analysis Tools
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A typical solar cell (10cm x 10cm)
generates about 1W at about 0.5V.
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Individual cells are connected in
series (increases the voltage) and inparallel (increases the current)into a module.
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World PV Cell/Module Production (MW)World PV Cell/Module Production (MW)
1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 20010
200
400
600
800
Rest of world
Europe
Japan
U.S.
2002
1000
1200
744.1
2003
40.2 46.5 55.4 60.1 69.4 77.6 88.6125.8
154.9 201.3
287.7
390.5
561.8
2004
57.9
1194.7
Average annual growthAverage annual growthrate of 43% over last 5rate of 43% over last 5
years; 57% in 2004years; 57% in 2004
Source: Paul Maycock, PV News , February 2005026587210
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Grid Interactive
Remote
CommunicationsConsumerGoods
Transportation
Water Pumping
Cells/Modules
To OEM
Health
Other
Industrial
Residential
Commercial
Transportation
UtilityGovernment
Other
PV Markets
• Most Cost Effective:
– Small Loads
• Emergency Call
Boxes• Irrigation
Controls
• Sign lighting
– Avoided LineExtensions ($20k to$100k/mile)
• Water Pumping
• Residential – Remote Diesel
Generators ($0.19to $1.68/kWh)
2001 EIA data
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Outline• Solar Industry Status
• Solar Electric – Systems View• Solar PV Technology
• Stand-alone Off-grid Applications• Grid-connected Applications
• Intro to Hybrid Systems• Solar System Analysis Tools
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Simple Direct Drive PV System
What determines the system design?
The amount of sun?
The size of the solar array?
The characteristics of the pump?
The cow?Evaporation from the tank?
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Simple Direct Drive PV System
Where do you start in a system design?
With the LoadEvaporation from the tankAnd the cow.
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Simple Direct Drive PV System
Simplified Design Process
The Load determinesthe size of the pump
(power & flow)
The sun & weather determine theenergy available
The solar array is sized to
deliver the needed energyin the time available.
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Simple Direct Drive PV System
What is the PV array size?
1000 W/m2 for 6 hours
10% array efficiency= 100W/m2
1200 gal/day
200 gal/hr, from50ft, for 100W
1200 gal/day6 hours/day
= 200 gal/hour
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Design Basics• dc motors make simplest systems; PV
modules heart of the system.• Non-grid remote systems like lights,communications, etc. require energy storage
(batteries); batteries are the heart of thesystem.
• Complex loads like remote homes may
require other generators and inverter; inverter is the heart of the system.
• All designs start with the electrical (load)
requirements.
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Design Basics• Total daily (use cycle) energy must be known
or best estimate in kWh/cycle.• Largest power level must be known todetermine wire size, safety gear, inverter
specifications, etc.• Required system availability must be
established.
• Site specific resources must bedetermined.......resource maps and the likeare not usable for design.
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Design Procedure
• Determine loads—both kWh and ac or
dc kW• Determine energy storage requirements
• Set System availability
• Size PV and other generation to meetload directly or charge the energy
storage subsystem
• Chose voltage, wiring, inverter, controls
to match ampacity (Max current plus)
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Outline• Solar Industry Status
• Solar Electric – Systems View• Solar PV Technology
• Stand-alone Off-grid Applications• Grid-connected Applications
• Intro to Hybrid Systems• Solar System Analysis Tools
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The Photovoltaic Effect
P
Si
B
Phosphorous: 5 valenceelectrons
Silicon: 4 valence
electrons
Boron: 3 valenceelectrons
P-N Junction
No material is consumed and the process could continue indefinitNo material is consumed and the process could continue indefinitelyely
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““CzochralskiCzochralski”” TechnologyTechnology
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Cast Polycrystalline TechnologyCast Polycrystalline Technology
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““SheetSheet”” TechnologiesTechnologies
“Thin film” SiliconEdge-defined
Film-fedGrowth(EFG)
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PV Cells
and in parallel to increase
current
PV Cells are wired in
series to increase voltage...
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PV is Modular
Cells are assembled into modules, and modules into arrays.
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Thi Fil T h l iThi Fil T h l i
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Thin Film TechnologiesThin Film Technologies
On Flexible SubstratesOn Flexible Substrates
B ildi I t t d PV (BIPV)
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Building-Integrated PV (BIPV)
C t ti PV S tC t ti PV S t
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Concentrating PV SystemsConcentrating PV Systems
LineFocus30-50XPointFocus
100-1000X
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36 cells in Series
About 18 Volts
S
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Series connection increases voltage
Parallel connection increases current
M d l t d i i d
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Modules are connected in series and
parallel to achieve the voltage and currentneeded for the system
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Collector Technology Considerations
• Flat plate, single crystal and
polycrystalline Si most common andhigh acceptance
• Higher efficiencies usually mean lesscost for wiring and structure
• Tracking can provide more power andenergy in less space but fixed costsmust be compared
• Long term performance essential.
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Outline• Solar Industry Status
• Solar Electric – Systems View• Solar PV Technology
• Stand-alone Off-grid Applications• Grid-connected Applications
• Intro to Hybrid Systems
• Solar System Analysis Tools
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Simple Direct Drive PV System
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Water
PumpingDesigns
Rural Electrification: Classics
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Rural Electrification: Classics
Historically, the primary means of providing power have been through grid
extension and diesel generators. – Grid Extension: Very high initial cost, poor cost
recovery, time intensive (generation, transmission,distribution) and usually must be subsidized. Mostoften used.
– Diesel Generators: Inexpensive installation but
expensive to operate, environmentaldamage/pollution, and subject to volatile fuel costsand availability.
Solar Water Pumping
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Ute Mt. Ute Tribe , CO
Inadequate Wind & HighMaintenance Costs
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Simple DC PV System with
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Simple DC PV System with
Battery Storage
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Energy Storage• Deep cycle storage batteries are common
• Batteries require a temperature moderatedenclosure and maintenance
• Storage size tied to electrical usage
• Technical issues are temperature,temperature, and temperature-I’ll explain
• Most systems with batteries use a chargecontrol device
Just like solar cells, batteries are connected in seriesand parallel to achieve the storage requirements
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and parallel to achieve the storage requirements
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12 volt PV-Battery System
Typical PVTypical PV -- Battery SystemsBattery Systems
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DC PV System Example:
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PJKK Federal Building, HI
• 2 solar panels per lamp with peakoutput of 96 watts
• 39 Watt fluorescentlamps, 2500 lumens
• 90 amp-hour batterypowers 12 hours per night
• ~$2500 per light
Department ofInterior
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Interior
National Park Service
Military Field
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Military Field
Applications
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USDA Forest Service
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Wedding Day!!!
In Xinjiang, China, the groombought 2-40 watt PV panels for the bride as a wedding present.
AC PV System with InverterAC PV System with Inverter
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Inverter5kW
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5kW
Converts Direct Current (DC) to Alternating Current (AC)
50 kW Inverter
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AC System Controls• Inverters convert dc to ac
• Inverters require an enclosure and maybe placed with switchgear andcontrollers
• Inverters are matched to system voltageand maximum aggregate load
• System controls represent the leastreliable components in a PV system
System Efficiency
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Efficiency = power out / power in
Array 10%
Efficiency
Battery 80%Round-tripEfficiency
Inverter 90%Efficiency
100 Watts from sun > 10 Watts >8 Watts > 7.2 AC Watts to load
Overall system efficiency is product of component efficiencies.Example 0.10*0.80*0.90=0.072
...exacerbated by “mismatch” losses, typical system efficiency = 0.06
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Outline• Solar Industry Status
• Solar Electric – Systems View• Solar PV Technology
• Stand-alone Off-grid Applications
• Grid-connected Applications• Intro to Hybrid Systems
• Solar System Analysis Tools
UtilityUtility--Connected (LineConnected (Line--Tie)Tie)
PV SystemPV System
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PV SystemPV System
Grid-connected Metering RequirementsDepend on the Local Electric Utility
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Depend on the Local Electric Utility
Jicarilla, Apache, AZ2.4 kW Grid Connected
Dulce High School
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Dulce High School
Building-Integrated PV (BIPV)
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Utility-Connected PV Example:Presidio Thoreau Center
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Presidio Thoreau Center
• Building-IntegratedPhotovoltaics
• 1.25 kW PV Array
• Spacing between
cells admits daylightinto entry atriumbelow
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Outline• Solar Industry Status
• Solar Electric – Systems View• Solar PV Technology
• Stand-alone Off-grid Applications
• Grid-connected Applications
• Intro to Hybrid Systems• Solar System Analysis Tools
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Hybrid Power System Examples:“Communications”
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Carol Spring Mtn., AZ Mt. Home AFB, ID
Test Ban Treaty Monitoring,Antarctica McMurdo Station, Antarctica
Village Power HybridsSimulation Models for Options Analysis
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A C
B u s
D C
B u s
Rectifier
Inverter
DumpLoad
Diesel
BatteryBankLoad
losses
losses
WindPV
losses
losses
Bio-Power
µ-Turbines
Fuel Cell
Wind
µ-Hydro
Rate Structure
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Outline• Solar Industry Status
• Solar Electric – Systems View• Solar PV Technology
• Stand-alone Off-grid Applications
• Grid-connected Applications
• Intro to Hybrid Systems
• Solar System Analysis Tools
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PV Design Tools
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• PV Wattshttp://rredc.nrel.gov/solar/codes_algs/PVWATTS/
– Google: PVWATTS
• RETScreen – PV – Google: RETScreen
• HOMER Distributed System Hybrid Optimization
Model – www.nrel.gov/homer