3a- solar power.pdf

7/23/2019 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


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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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

=

=


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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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?


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.


Complete Electricity Basics Worksheet


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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.


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


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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Verify: Does 5.11 Amps times 36.21 Volts =

185.0 Watts?


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Solar Irradiance


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


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


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.

55

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.


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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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

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