3A- Solar Power.pdf
Transcript of 3A- Solar Power.pdf
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Renewable EnergyRenewable Energy
SolarSolar EnergyEnergy
Renewable EnergyRenewable Energy
SolarSolar EnergyEnergy
Slide 1
Solar TechnologiesActive Systems
Photovoltaic (PV) systems
Pump fluids through solar collector
Slide 2
Heating and cooling (desiccants orabsorption)
Passive Systems
Orientation to sunlight and shading
Natural convection
Solar Applications: Generate electricity using photovoltaic solar cells.
Generate electricity using concentrating solar power.
Generate electricity by heating trapped air which
Slide 3
.
Generate hydrogen using photoelectrochemical cells.
Heat water or air for domestic hot water and spaceheating needs using solar-thermal panels.
Heat buildings, directly, through passive solarbuilding design.
Heat foodstuffs, through solar ovens.
Desalination of brackish water.
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Agricultural Applications Pump water
Dry grain Heat greenhouse
Generateelectricit
Slide 4
Space heating & cooling
Courtesy of FAO
Courtesy of U Missouri
Advantages of a Solar EnergySystem
No fuel costs
Low maintenance
Modular
Extremely reliable
Silent (compared to generators) No emissions
This presentation will
Slide 6
ocus on p o ovo acsystems
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Solar Energy Systems
There are 4 types of photovoltaic
PV direct
Stand alone
Grid direct
Grid tied with battery backup
Solar Energy Systems
1. PV Direct
In a PV direct system, the electricity producedis put to immediate use. The electricity maypower a fan, for example.
The most logical applications for a PV directsystem are those that power something that isshort supply during peak sunlight hours. A fan,for ventilation, perhaps.
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Solar Energy Systems
The most common NRCS application in a PVdirect system is a solar powered pump.
But what if we want water at night?
Its usually better to store water in a tank thanstore electricity in a battery
Batteries are a headache. They work, but theyrequire TLC.
Solar Energy Systems2. Stand Alone
Electricity
on Demand
Solar Array Charge Controller Battery Bank
Types of Solar Energy System3. Grid Direct
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Types of Solar Energy System3. Grid Direct
(solar.mov)
Types of Solar Energy System
4. Grid Tied with Battery Backup
s s an op on or gr -connec e sys ems a neeback-up electricity when the grid goes down.
Its similar to a stand-alone PV system with a back-upgenerator, but instead the utility provides the back-up.
And, if the batteries are fully charged and the energy fromthe PV array exceeds the loads, electricity from theinverter can flow to the utility grid, as in a grid-directsystem.
Understanding PV Panels
Objectives
Wiring panels in series/parallel
Learn About Tilt Angles
Sun Charts
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Basics of Electricity
Electricity is the flow of electrons through acircuit.
The force or pressure of moving electronsin a circuit is measured as voltage.
The flow rate of electrons is measured asamperage.
The power of a system is measured aswatts.
Basics of Electricity
Watts = volts times amps
Example: How many amps does a typical 60watt light bulb draw?
US is 120 volts
ampsvolts
watts
ampsvoltswatts
5.0120
60
___12060
=
=
Understanding PV Panels
When we measure how fast and how far a
vehicle is traveling, we use a rate of miles per. When we measure water flowing, its in gallons
per minute and gallons. When we measure electrical energy use, the
rate is watts and the quantity is watt-hours.
Your home electricity bill is based on thenumber of kilowatt-hours you used.
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Understanding PV Panels
To calculate watt-hours, there are twothings youll need to know:
An appliances rated watts. The estimated duration of time the
appliance will be operated. Question: You leave a 100 watt light bulb
on for 24 hours. At 10 cents per kilowatt-hour, how much does it cost?
Understanding PV Panels
Direct Current (DC) vs.Alternating Current (AC)
Batteries store DC Most household appliances use AC In order to use PV to power your home, you will
need an inverter. An inverter is a device that willconvert DC to AC.
Quick class discussion: what are the voltagerequirements of common items? Are they AC or
DC? Look at your power brick for your computer.
Understanding PV Panels
Complete Electricity Basics Worksheet
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Understanding PV Panels
Solar Panels are typically given a PowerRatin (e. . 165 watts)
This rating is based on Standard TestConditions (STC)
The other common rating standard isPacific Test Conditions (PTC), a somewhatmore realistic standard.
Understanding PV Panels
Many solar panels are designed to be able tocharge a 12 volt battery.
actually charge the 12 V battery.Example: The nominal voltage of a solar panelis 34.6 volts. What size battery can this panelcharge?
24 volt battery
Understanding PV Panels
Solar Panels are rated at:
STC defines the output of a panel underspecific conditions specifically:
25 C (77 F) cell temperature
21
1000
meter
Wattsinsolationsolar =
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Understanding PV Panels
Understanding PV Panels
Understanding PV Panels
Verify: Does 5.11 Amps times 36.21 Volts =
185.0 Watts?
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Solar Irradiance
Understanding PV Panels
What happens when the sun isnt
Do we still get maximum output? No.
What varies? The current (amps) is lessthan the max.
Wiring the Panelsin Series
Connect the panelsnegat ve to pos t ve.
Add the voltages.
Amps stay the same.
Volts: 68V
Amps 5 A
Power: 340 Watts
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Wiring the Panelsin Series
Advantage: Wires are
s ze ase on amps,
so smaller, and more
inexpensive wires can
be used.
Wiring the Panelsin Parallel
Voltage: stays the
same
Amps are additive
Volts: 34V
Amps 10 A
Power: 340 Watts
Wiring the Panelsin Parallel
Reasons to do this:arge a spec c
battery bank (in this
case, a 24V battery
bank).
Load may be limited
to a max voltage.
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Wiring the Panels
What are the wiringoptions with these
four anels?
Wiring the Panels
4 in series
136 V
5 A
680 Watts
Wiring the Panels
4 in parallel
34 V
20 A340 Watts
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Wiring the Panels
2 in seriesThen in parallel
68 V
10 Amps
680 Watts
Wiring the Panelsin Parallel
Complete the series parallel worksheet
Shading
Percent of One Cell Shaded Percent o f Module PowerLost
0% 0%
50% 50%
75% 66%
100% 75%
3 cells shaded 93%
Table shows effect of shading on one cell (of the 36 in
this PV panel) that has no internal bypass diodes.
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Tilt Angle
For a fixed PV array, the tilt angleis the angle from horizontal (0=horizontal, 90=vertical).
ange equa o e oca onslatitude normally maximizesannual energy production.
Increasing the tilt angle favorsenergy production in the winter,and decreasing the tilt anglefavors energy production in thesummer.
Tilt Angle
One and two axis trackingsystems are also possible
allows the array to always beperpendicular to the suns rays:this maximizes the solar energyproduced
Tilt Angle
Both one and two axis trackingsystems follow the sun duringthe day.
adjustment is in the optimalposition only at solar noon on 2days of the year.
But the increase in productionobtained with a tracking systemmust be compared with the costof simply adding more modules.
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Tilt Angle
Solar Elevation Tilt Angle
Solar Elevation (at solar noon) plus
Tilt Angle = 90 degrees
Tilt Angle
To determine the optimal tiltangle for any given day, find
solar noon on that day.
Use a Sun Chart
The elevation of the sun plusthe tilt angle should equal 90
degrees
The green line shows the energy you would get from two-axis tracking, which alwayspoints the panel directly at the sun. These figures are calculated for 40 latitude.
The violet line is the amount of solar energy you would get each day if the panel is fixed atthe winter angle.
The turquoise line shows the energy per day if the panel is fixed at the full year angle. The red line shows how much you would get by adjusting the tilt four times a year.
2 axis tracking
Fixed arra ad usted 4 times
Fixed at winter angle
Fixed at full year angle
First day of winter
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Complete the tilt angle exercise
Changing the Tilt Angle
Winter October 7 to March 5
Spring March 5 to April 18
Summer April 18 to August 24
Autumn August 24 to October 7
If you are planning on changing the tilt angle,
these are the periods for four changes a year.
Complete the Sun Chart Exercise
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PV System - Solar Cells Crystalline
Silicon wafer $3.50 to $4.25 per watt Silicon intensive
Slide 49
14 16% efficiency
Thin film Si, CdTe, CuIn, etc $2.50 - $5.50 per watt 8 11% efficiency
Solar Thermal Efficiencies approx. 80%
Show video on modules
Slide 50
One Very Practical SolarPhotovoltaic (PV) Application
Livestock Water Pumping with Solar
Pumping water for irrigation is generallynot practical, except for very smallacreages (or very large solar arrays).
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Cost
New Mexico NRCS: $5,700 median
One exam le:
Solar pumping plant for $6,500:
320 watt sharp panels and
6SQF-2 Grundfos pump
Cost
Another Example:
Solar pump, well depth
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Remote Systems: Avoid Batteries
All solar water pumping systems use some type ofwater storage.
The idea is to store water rather than store electricityin batteries, thereby reducing the cost and complexityof the system.
A general rule of thumb is to size the tank to hold atleast three days worth of water.
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Making the Decision
Analyzing the monthly water demand requirement;
Conducting a resource assessment;
Decidin whether a wind orsolar water um insystem would be best.
Analyzing the monthly waterdemand requirement
Need to know the height the water
Need to know the water demand
Slide 57
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Slide 58
Slide 59
Resource Assessment
Slide 60
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Solar vs Wind
Solar and Wind resource assessment for locale
The choice for stand-alone water pumping systems less than2 kW being predominantly between using mechanicalwindmills or solar-PV.
Components
Solar PV module;
Understanding how controller can affect the
Selecting pump type (diaphragm, piston,helical, or centrifugal).
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Math Wont Be a Big Part of ThisPresentation, But.
1000 Watts =1 KiloWatt
You can add up the nominal wattage of solarpanels to get the system size.
Panels have a output voltage rating and thevoltage output of a system depends on the wiring
.
Determining the type of PV module
Currently there are two types of PV modules that are used forsolar-PV water pumping:
mu -crys a ne an
thin film
High voltage PV modules are only an advantage if the pumpmotor requires high voltage.
Diaphragm pump motors are rated at 24V, so they dont requirehigh voltage modules.
Whether a passive or motorized tracking system is used, it is
usually better to just add more PV modules in a fixed array
Determining the type of PV module
higher than 500W.
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Pump and Charge Controllers
Pump and Charge Controllers
A charge controller is installed when batteries are used in thesysem. s purpose s o eep e a eres romovercharging or becoming completely discharged.
Pump Controllers
Controllers for PV water pumping systems can range
Pump Controllers
rom no us ng any con ro er o sop s cae smarcontrollers.
The pump controller is an electronic linear currentbooster that acts as an interface between the PVarray and the water pump.
It operates very much like an automatic transmission,providing optimum power to the pump despite widevariations in energy production from the sun.
It is particularly helpful in starting the pump in lowlight conditions.
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Slide 70
Pump Controllers
The voltage output of a PV is relatively fixed as the level of
Pump Controllers
suns ne vares.
Motors on the other hand are basically constant currentdevices with the voltage varying with power and speed.
The controller acts as an automatically adjusting dc/dcconverter to convert high voltage/low current pv arrayoutputs (low sun conditions) to lower voltage/higher currentto better operate a dc motor
Pump Controllers
One helical pump manufacturer (Grundfos) has
Pump Controllers
embedded most of the controller function inside thesubmersible motor casing.
This embedded controller also has the capability ofdetermining if input power is DC or single phase ACand if single phase AC, it is rectified to DC electricitybefore connecting to DC motor.
This means that water can be pumped on cloudydays by switching from PV array to a gasolinegenerator.
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Selecting pump typediaphragm, piston, helical, or centrifugal
Conventional pumps require steady AC current thatutility lines or generators supply.
Solar pumps use DC current from batteries and/or PVpanels.
Solar pumps are designed to work effectively duringlow-light conditions, at reduced voltage, withoutstalling or overheating.
Selecting pump typediaphragm, piston, helical, or centrifugal
For the past fifteen years, solar-PV (photo-voltaic) waterpumping systems have been installed with either diaphragm,
, .
The diaphragm pumps have been used successfully for smalldaily water volumes and shallow pumping depths (125 to 400gallons/day and 15 to 200 feet pumping depths).
The centrifugal pumps have been used for larger daily watervolumes and moderate pumping depths (500 to 2,500gallons/day and 15 to 250 feet pumping depths).
Slide 75
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Selecting pump typediaphragm, piston, helical, or centrifugal
Lastly, the piston pumps (with a pump jack) have been usedto pump water for small to moderate daily water volumes and
,1000 feet pumping depths).
Helical Pumps: rapid adoption since 2002. Pumping depthsfrom 150 to 500 feet.
Helical Pump
Summary
Solar-PV water pumping systems less than 1.5 kW are morelikely to be used in U.S. than wind powered water pumpingsystems due to:
a better match to water demand,
less maintenance requirements (e.g. fewer moving parts), and
a larger area of land with a good solar resource than with a good windresource.
As power requirements increase however, a wind only or ahybrid wind/solar water pumping system is desirable until theprice per Watt for solar-PV modules can be decreasedsignificantly and/or efficiency of Solar-P V modules can beimproved significantly.
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Summary
Analyzing the monthly water demand requirement; Conducting a resource assessment;
Decidin whether a wind orsolar water um insystem would be best.
Summary
Three Components of a livestock watering system
Solar Panels
Pump Controller
Pump