nsol v4_6 manual

7/31/2019 NSol V4_6 Manual

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PV System Sizing Program

2

NSol!PV SYSTEM SIZING PROGRAM

Version 4.6

Contents1 Introduction ........................................................................................................................................... 5

2 Installation............................................................................................................................................. 7

2.1 Installation File ............................................................................................................................. 7

2.2 Registration and Activation .......................................................................................................... 7

2.2.1 Purchase ................................................................................................................................ 72.2.2 Registration ........................................................................................................................... 7

2.2.3 Activation .............................................................................................................................. 7

2.2.4 Updates ................................................................................................................................. 8

2.2.5 Demo Version ....................................................................................................................... 8

2.3 Borland BDE Database Configuration .......................................................................................... 8

2.3.1 Background ........................................................................................................................... 8

2.3.2 Manual Configuration ........................................................................................................... 8

2.3.3 Rebuild NSol4 Config ........................................................................................................... 9

3 Program Overview .............................................................................................................................. 10

3.1 Overview ..................................................................................................................................... 10

3.2 Starting the Program ................................................................................................................... 10

3.3 Opening a File ............................................................................................................ ................. 10

3.4 Navigating the Notebook ............................................................................................................ 10

3.5 Printing a Report ......................................................................................................................... 11

3.6 Saving the File ............................................................................................................................ 11

3.7 Closing the Program.................................................................................................................... 11

4 Data Entry ........................................................................................................................................... 12

4.1 Overview ..................................................................................................................................... 12

4.2 Data Entry Page .......................................................................................................................... 12

4.3 Site Data ...................................................................................................................................... 12

4.4 Insolation /Temperature Data ...................................................................................................... 12

4.5 Insolation Database ..................................................................................................................... 12

4.5.1 Navigating the Database ..................................................................................................... 13


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4.5.2 Search City .......................................................................................................................... 13

4.5.3 Search State/Region ............................................................................................................ 13

4.5.4 Search Country .................................................................................................................... 13

4.5.5 Search Latitude / Longitude ................................................................................................ 13

4.6 Editing the Database ................................................................................................................... 144.7 System Data ................................................................................................................................ 14

4.8 Component Data ......................................................................................................................... 14

4.8.1 Battery ................................................................................................................................. 14

4.8.2 PV Modules ........................................................................................................................ 15

4.8.3 Hybrid Components ............................................................................................................ 15

4.8.4 Inverter ................................................................................................................................ 16

4.9 Load Data .................................................................................................................................... 16

4.9.1 Load Summary Report ........................................................................................................ 17

5 Array Tilt Calculation ......................................................................................................................... 18

5.1 Overview ..................................................................................................................................... 18

5.2 Array Tilt .................................................................................................................................... 18

5.3 Tracking Options ........................................................................................................................ 19

5.4 Optimization ............................................................................................................................... 19

5.5 Array Insolation Report .............................................................................................................. 19

6 System Sizing Standalone PV .......................................................................................................... 20

6.1 Overview ..................................................................................................................................... 20

6.2 Selecting Components................................................................................................................. 20

6.3 Setting Array Tilt ........................................................................................................................ 20

6.4 ALR Method ............................................................................................................................... 20

6.4.1 MPPT vs. Non MPPT Controller ........................................................................................ 22

6.5 LOLP Method ............................................................................................................................. 23

6.5.1 LOLP Page .......................................................................................................................... 23

6.5.2 BSOC Page ......................................................................................................................... 24

6.5.3 Note on Calculations ........................................................................................................... 25

6.6 LOLP Methodology .................................................................................................................... 25

6.7 IV Curve Analysis ....................................................................................................................... 266.8 Reports ........................................................................................................................................ 26

6.8.1 System Sizing Report .......................................................................................................... 26

6.8.2 System Availability (LOLP) Report .................................................................................. 26

6.8.3 Battery SOC Report ............................................................................................................ 27

6.8.4 Standalone System Summary Report .................................................................................. 27


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7 System Sizing - Hybrid ....................................................................................................................... 28

7.1 Overview ..................................................................................................................................... 28



7.4 Hybrid System Analysis.............................................................................................................. 287.5 Hybrid System Analysis Screen .................................................................................................. 29

7.6 Hybrid Sizing Report .................................................................................................................. 30

8 System Sizing Grid Systems ............................................................................................................ 31

8.1 Overview ..................................................................................................................................... 31



8.4 Grid System Analysis ................................................................................................................. 31

8.5 Grid System Screens ................................................................................................................... 32

8.6 Grid System Report ..................................................................................................................... 32

9 Reports and Exporting Data ................................................................................................................ 33

9.1 Report Summary ......................................................................................................................... 33

9.2 Printing Reports .......................................................................................................................... 33

9.2.1 Printing ................................................................................................................................ 33

9.2.2 Page Setup ........................................................................................................................... 33

9.2.3 PDF Files ............................................................................................................................ 33

9.3 Printing Charts ............................................................................................................................ 33

9.4 Exporting Charts ......................................................................................................................... 33

9.5 Exporting ASCII Data for Spreadsheets ..................................................................................... 33

9.6 Exporting Grid Data for Spreadsheets ........................................................................................ 33

APPENDIX 1 - SAMPLE REPORTS ...................................................................................................................

APPENDIX 2 - GLOSSARY OF TERMS .............................................................................................................

APPENDIX 3 - LIST OF SIZING REFERENCES ................................................................................................

For more information or technical support, contact:

FearTheSkunk

Web: www.nsolpv.com

Email: [email protected]


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NREL solar insolation databases, and has

the ability to search for specific sites by city,

state,

country or latitude / longitude. This databaseis user-modifiable.

Advanced statistical system performanceanalysis. NSol!uses a proprietary LOLP

algorithm developed by Professor L. L.

Bucciarelli of the Massachusetts Institute of

Technology. Based on the concept of

"Markov Transition Matrices," this

algorithm calculates the statistical

performance of the solar insolation resource,

then applies this to the battery-based PV

system. The result is a "Loss-ofLoad

Probability" which gives a concise estimate

of system reliability.

Hybrid System Analysis Basicperformance calculations for PV-Battery-Generator hybrids

Grid System Analysis Basic performancecalculations for utility-tied PV systems

Laser Quality Printouts - summary anddetailed printouts are ready for inclusion

directly into your proposals.

A graphic "Tool-Bar" -- icon-basedshortcuts to common file functions

NSol!is easy enough to use that a new user can just

jump right in without reading the manual. For a

quick overview of the program, Section 3 contains asummary of program operation.


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2.2.4 UpdatesPeriodically, we will issue updates to the program.

Users will receive an email with instructions on how

to download / install the updates.

2.2.5 DemoVersionA demo version is available from the website. This

has the full set of design features of the main

program with three exceptions:

1) Saving is disabled.2) Printed reports will have a Demo Version

watermark.

3) The Company name and address cannot bechanged.

2.3 BorlandBDEDatabaseConfiguration

2.3.1 Background databases are managed using the Borland

Database Engine. Installation of this software is

automatic in most cases; however, because of the

widely disparate requirements of Windows operating

systems, manual intervention may be required in

some cases.

Known cases involve 64 bit operating systems,

installation on a non-C drive, and some issues with

XP permissions.In 64 bit system, the operating software will install

the program in a folder called C:\Program

Files (x86)\nsol! instead of the

c:\program files\nsol! folder. The

BDE is looking in the latter folder so it needs to be

manually changed.

A similar situation applies when the program is

installed on a non-C drive.

You will know if this is the situation if you try to

open one of the database tabs you will get some

sort of message (depending on the system) aboutmissing BDE configurations.

If this occurs, you can manually set the BDE

configuration using the following steps.

2.3.2 ManualConfiguration1. Open the Control Panel and start the BDE

Administration program (bdeadmin.exe), using

administrator privileges in Visa or Windows 7.

Note -- The actual program is found in

c:\program files\common

files\borland shared\bde.)

2. Click on the [Databases Tab] and then select

NSol46. Click on the [Path] field on the righthand side and set the path to the proper value,

using the [] to open a file browser. The

program is typically installed in \program

files\nsol! on one of the drives, but this

will be \program files

(x86)\nsol!

3. Next, click on the [Configuration] tab. Expandthe Configuration property, then Drivers, then

Native, then click on Paradox, which will

bring up the following screen:


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4. Change the NET DIR path to beC:\Program Files\Common

Files\bdeshare

5. Note on some XP systems, this may not bepossible. If so, set the path to c:\.

6. Close the program, saving the data as prompted.

2.3.3 RebuildNSol4ConfigOn some XP systems, it may not be possible to savethe BDE configuration file because of strange

system permissions restriction. If this occurs, please

use the following steps to fix the problem:

1. Delete the NSol4 database by clicking on theX of right clicking and selecting Delete.

2. Type Ctrl-N to insert a new database, choosingStandard when prompted.

3. Rename it NSol46Properties should be Standard, PARADOX

and False (under enable BCD)

4. Set the path as described above (Step 2).

5. Click on the configuration tab and set up as per3. and 4. above.

6. Close and save.

If there are other problems, please contact us at

[email protected] . Please include your operatingsystem (XP, Vista, Windows 7, 32 bit or 64 bit) and

your installation location. Windows is a funny thing

we have most of the situations covered, but I

would not be surprised to see some new variation.


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3 ProgramOverview3.1 OverviewNSol!is a project-based approach to sizing PV

systems. Each system is stored in a separate file with

the PV5 extension. The PV5 file opens to showthe summary page of a notebook with separate

pages for each of the major sizing functions.

Clicking on a component on the summary page

opens a data or load data entry form.

Multiple documents can be open at the same time,

allowing comparisons between different system

options.

The program also produces a variety of reports, and

data export capabilities.

3.2 StartingtheProgramThe program is opened by double-clicking on the

program icon, or its shortcut. Shortcuts can be

installed on the desktop, Start menu, or toolbar.

3.3 OpeningaFileOnce the program has started, it offers three choices:

The first option starts a new project using the data

stored in default.PV5 and names it new.PV5.

(Note -- The default file can be edited to include the

users most common module, battery, location, or

system parameters so that these will appear

automatically when a new file is started.)

The second option allows the user to open an

existing file via a standard file dialog box.

The third option allows the user to start a new file,

using an existing file as the initial data. This isuseful for analyzing one system design at multiple

locations, or for looking at multiple options for a

single site (e.g. hybrid vs. standalone).

3.4 NavigatingtheNotebookThe notebook contains four or five pages, depending

on the system configuration.

The pages are selected by clicking on tabs at the topof the project notebook.

The first page is the summary page, which isused to enter site information, loads and

components.

The second page is the Array Tilt page, usedfor calculated the insolation on the tilted /

tracking array surface.


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Standalone PV systems include the Sizing(ALR) page, the LOLP Analysis page, and

the BSOC page.

Hybrid systems include the Sizing (ALR)and Hybrid Sizing pages.

Grid connect systems include the GridSystem and Grid Typ Day pages.

3.5 PrintingaReportReports can be can be printed in three ways:

Clicking on the Printer speed button willprint a report appropriate for the active page,

if it is available.

Choosing File _Print from the main menuaccomplishes the same thing.

Choosing File_PrintAll from the mainmenu allows the user to choose a set of

reports to print with a single command.

3.6 SavingtheFileOnce the project is designed, it can be saved either

via a speed button in the top toolbar, or via a menu

command.

The menu also includes File _SaveAs which

allows the file to be saved under a different name.

If the file is new, the program will suggest a name

based on the city name.

3.7 ClosingtheProgramAn individual project can be closed via a speed

button, a menu command, or the X in the upper

right corner of the project screen. The entire

program can be closed in the same ways.

If the open projects have not been saved, the

program will prompt the user for an appropriate

action.


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4 DataEntry4.1 OverviewIn order to properly size a PV or hybrid power

system, information about the site, loads, and

components must be specified. In NSol!, this is donevia the Summary page of the project notebook.

4.2 DataEntryPageClicking on the corresponding symbol on the

Summary page accesses the appropriate data entry

form. For example, clicking on the PV Array will

bring up the PV page of the components dialog.

The site and component data is either entered

directly into the form, or selected from a database

(PV modules, batteries and Site Insolation only).

Loads are entered by clicking on the Load symbolat the right of the page (PV and hybrid only). Up to

ten distinct loads can be entered.

4.3 SiteDataTo enter site data, click on the site summary table on

the Summary screen. This will bring up the data

entry dialog box. This form includes pages for the

site data and system factors, as well as each of the

major components.

The following data is used for the site: Site Name City Region / State Country Latitude (decimal degrees North is

positive, South is negative)

Longitude (decimal degrees East ispositive, West is negative)

Elevation (meters) Comments / References

Insolation data is also entered from this page.

4.4 Insolation/TemperatureDataTo enter insolation data, click on the Sun in the

upper left of the Summary Page. This will bring up

the site data page in the data entry dialog.

The following data specifies the solar resources and

temperature at the site:

GH Insol Average Global Horizontalinsolation for each month of the year.

Avg temp Average daily temperature atthe site for each month of the year (degrees

Celsius)

Temp Swing the average number ofdegrees between the average temperature

and the high or low temperature. Typically 5

to 8 deg C. Example average is 18C,

variation is 5C, so average high is 23C,

average low is 13C.)

Reflectance typically 0.2 (20%). Canrange from 0.02 (2%) for loose, dark soil or

asphalt, to 0.8 (80%) for smooth snow.

Each of these factors can be entered by month.

4.5 InsolationDatabaseNSol!includes an insolation / site database to

facilitate data entry. All data is public domain data,

primarily from NREL (for us sites) and the

University of Lowell (for international sites). Note

that version 4.6 includes an additional NASA

satellite database, which covers the entire globe at 1

degree latitude / longitude intervals. Since this data

does not include city, state or country information, it

can only be accessed via a Latitude / Longitude

search.


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To access the database, click on the InsolDatabase

button in the lower right of the site entry page.

This will bring up a form that allows access to the

entire NSol!Insolation database.

4.5.1 NavigatingtheDatabaseTo move through the database, use the four buttons

located below the search buttons. These buttons have

the following functions:

The left button (left arrow with bar) movesto the beginning of the database.

The left arrow moves back one record. The right arrow moves forward one record. The right arrow with bar moves to the last

record in the database.

4.5.2 SearchCityTo search the database by city, click on the search

city button, enter the city name in the Seach City

field, and click on Okay. This will sort the database

by city name, and find the nearest match. Note that it

is not necessary to enter the entire name, just the

first few letters.

4.5.3 SearchState/RegionThis button sorts the database by region, and finds

the nearest match. Most of the international sites do

not have a region entered, so this is primarily useful

for custom sites, or for US sites.

4.5.4 SearchCountryThis button sorts the database by country, and finds

the nearest match. This is useful when looking for a

site in a particular country.

4.5.5 SearchLatitude/LongitudeThis button filters the database so that it only

includes sites within the search criteria specified by

the search dialog box:

The user can then use the navigation buttons to

scroll through this data and find an appropriate site.


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4.6 EditingtheDatabaseThe insolation database has standard user-editing

capabilities. These are accessed by clicking on the

Edit DB button just below the navigation bar.

This changes the database from read only to

modifiable and adds six editing buttons to the

navigation tool bar. From left to right they are:

Plus -- Add new record Minus -- Delete record Up Arrow Edit Record Check Post record (save to database) X Cancel Edit Circle Arrow Refresh data

Please remember to keep a backup copy of the

database and all index files if you plan on editing the

database. In a default installation, the database files

are in a folder called DB under Program Files /OEC / NSol. If you chose a different folder during

installation, try searching for ns4ins.db.

4.7 SystemDataThe system tab opens a page which contains the

basic system sizing background data. These fields

include:

Battery Voltage Maximum Battery Depth-of-Discharge

Average Battery Volts/cell

AC Operating Voltage

Target ALR Target Battery Days System Losses (with seasonal loss option)

4.8 ComponentDataThe next four tabs contain the specific component

information:

Batteries PV Modules / Array

Grid InverterHybrid Info (generator, rectifier, battery charge

setpoints)

4.8.1 BatteryThis dialog page allows the user to specify the

battery used in the system design.

The user has the choice of entering the data directly

or choosing a module from a pre-designed database.

The user can edit the database using the same

techniques as with the insolation database.

Battery parameters are:

Battery Manufacturer Battery Model - Name of the battery. Cell Amp-hr -- Rate amp-hour capacity of

the battery at the C/100 rate.

Unit Volts -- voltage of the battery unit. Forindividual battery cells, this is two volts. For

monoblocs (pre-packaged groups of cells),

this may be 4, 6, 8 or 12 volts.

# Series -- The number of cells or blocks in

series # Parallel -- The number of parallel strings Auto Series -- If this block is selected, the

program will automatically calculate the

proper number of cells or blocks in series.

This should only be overridden with great

care.

Monobloc -- This box determines thebehavior of the battery sizing controls on the


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"Sizing (ALR)" page. If the box is not

selected, the program will simply increase or

decrease the number of amp-hour in

response to the up and down arrows. If

monobloc" is selected, the program will

leave the Ah capacity alone, and increase or

decrease the number of parallel strings.

4.8.2 PVModulesPV module information can be entered directly or

selected from a database.

The user can edit the database using the sametechniques as with the insolation database.

The data fields are as follows:

PV Module Mfgr - Name of the PV module

manufacturer. PV Module Model - Name of the PV

module.

Module W(p) - Rated power of the module.This is used in the system specifications and

BOM only.

Vmpp, or Vtyp - Module max power voltage Impp, or Ityp - Module max power current Voc - Module open circuit voltage Isc - module open circuit current V Temp Comp % - Voltage temperature

compensation for PV modules, expressed as

percent of open circuit voltage per degree Cabove/below 25 deg C. (Example value of

-0.4 means -0.004 * Voc per deg C)

I Temp Comp % - Current temperaturecompensation for PV modules, expressed as

percent of short circuit current per degree C

above/below 25 deg C. (Example value of

0.035 means 0.00035 * Isc per deg C)

# Series - This is the total number ofmodules in a single series string.

# Parallel - This is the total number ofstrings in parallel.

Auto Series - If this box is checked, theprogram will calculate the number of

modules in series automatically, with onemodule per 12V of nominal capacity. This

should typically be checked for systems up

to 48V. For 120 V systems, a careful

designer might be able to use only 9

modules in series, especially in colder

climates.

If the "# Parallel" field is initially left blank,the program will automatically calculate the

size of the array to meet the "Target ALR"

specified previously. This then forms a

starting point for sizing the system.

This dialog box can also be used later to change the

system size or configuration.

4.8.3 HybridComponents

The user must enter the following generator and

battery charger information:

Generator Manufacturer Generator Model Genset Power Rating Power in kilowatts

Genset Power Factor Rating Rating ofAlternator typically either 0.8 or 1.0 Full Load Fuel Consumption (FLFC) Fuel

use at full load either liters per hour

(diesel) or kg per hour (LPG)

Quarter Load Fuel Consumption (QLFC) Fuel use at 25% load (quarter load) in L/hr

or kg/hr


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Generator Maintenance Oil ChangeInterval in hours, typically between 100 and

500 hours

Generator Maintenance Decoke Interval inhours, typically 500-1500 hours for

decarbonization (also called top end

overhaul) Generator Maintenance Overhaul Interval

in hours, full overhaul of engine, typically at

6,000-10,000 hours

Generator Maintenance Generator Life,ranged between 1,000 hours for a small

gas/petrol engine to 20,000-40,000 for a

well maintained diesel engine

Battery Charger Current primary rating forbattery charger determines load on

engine/generator

Battery Charger Power Factor used to sizealternator

Battery Charger Efficiency used todetermine AC power requirement of battery

charger as seen by the generator

In addition, the data input screen allows thefollowing control setpoint inputs:

Generator Start Battery State of Charge typically 20-50% SOC

Generator Stop BSOC (normal charge) typically 80-90% SOC

Normal Charge Coloumbic (Amp-hr)Efficiency typically 90-95% for non-

equalization charging

Equalization Frequency typically one tofour times per month

4.8.4 Inverter

The user must enter the following inverter

information:

Inverter Manufacturer Inverter Model number Inverter rating in kW

Average efficiencyIn addition, the Type and Configuration need to beset using the radio buttons.

NOTE At this time, the inverter efficiency

number is used only for reporting. The actual

efficiency should be set under loads as described

in the next section.

4.9 LoadDataLoad information can be entered via the Load Input

dialog box. This is accessed by clicking on the

"Radio Tower" on the System Summary page, or via

the System Load menu. Up to ten different loads canbe entered.

The load dialog box consists of four data fields,

along with three "radio-button" selection fields and a

"Check Box". The load is specified by the load size,

load hours, load type (amps / amp-hrs / watts), AC /

DC, conversion efficiency and load profile. The load

size, load hours, and conversion efficiency are

entered via data fields. The other choices -- amps vs.

Ah vs. watt, AC vs. DC, and load profile are enteredvia "Radio buttons."


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If "Seasonal Loads" are selected, the loads can be set

by month via a separate dialog input.

The data is entered as follows:

Load Description - a brief description of the

equipment which is being powered, e.g."Streetlights," "Microwave Transmitter,"

"Refrigerator."

Load Size - The magnitude of the load,either in watts, amps or amp-hours. This is

entered as a real number.

Choose Amps, Amp-Hrs or Watts to matchthe design load by selecting one of the

"radio" buttons.

AC vs. DC - This choice is also made via"radio" buttons.

Conversion Efficiency - this is entered as an

integer percent, e.g. 80% is entered as "80".Typical inverters have efficiencies ranging

from 70% through 95%. DC to DC

converters used in many telecom systems

have efficiencies of 80 to 90%.

Load Hours - hours per day that the loadoperates, entered as a real number, with aminimum of 0.1 and a maximum of 24.0.

Load Profile - Selected from six choices via"radio" buttons on the right side of the

dialog box. The choices range from"Daytime only" though "Day/Night" (50%

each), on to "Night Only." The Dusk toDawn operation will automatically

calculate the number of hours between

sunset and sunrise and enter deratings under

seasonal load. (See Below.) This

information is used by the statistical LOLP

calculations. A system which has night loads

will have a higher LOLP (worse reliability)

than a system which is more closely

matched to the solar resource.

Seasonal Loads -- Clicking on this boxallows the user to specify the loads by

month. This can be useful for specifying

lighting loads which vary over the year, or

loads such as air-conditioners, which onlyoperate in one season. Note that the

maximum load is 100%. This means you

must specify the maximum design load, then

vary it as a percentage of the maximum.

When you are done entering the data, clickon the "OK" button or press [Enter] on the

keyboard. If you want to exit without saving

changes, click on the Cancel" button or

press [Esc] on the keyboard. To enter

another load, click on the Next arrow.

This will bring you to another load entry

page. You can enter up to ten separate loads.If there are more than ten loads, you must

group them into similar categories

("Lighting", "Telecom Equipment", etc.) and

enter the conglomerate data.

4.9.1 LoadSummaryReportThe Load Summary Report lists all of the details for

the loads which were entered, including: Load

Description, Load Size, Power Type, Conversion

Efficiency, Load Hours, Load Profile, and seasonal

loads. This information can be used to verify proper

load input.

A sample Load Summary Report is included in the

Appendix.


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5 ArrayTiltCalculation5.1 OverviewThe first step in the sizing process is to calculate the

average insolation on the tilted array. This step is

done using the "Tilt Analysis" page which isselected by clicking on the "Array Tilt" tab at the top

of the notebook, or by choosing Sizing, then Array

Tilt from the main menu.

5.2 ArrayTiltThe basic window is shown below.

The display consists of three sections - the control

buttons, the insolation graph or chart, and the

summary information.

The controls along the right side of the page control

the actions available. There are three types of

controls: Array Tilt and Azimuth using "spin

buttons", a box for selecting tracking items, and

program / display control (Text / Graph, Print, and

To Clipboard).

To change the array tilt and orientation, simply click

on the up and down arrows next to the tilt and

azimuth options, or enter a value directly.

In the northern hemisphere, an array with a positive

tilt points towards the equator, and in the southernhemisphere, an array with a negative tilt points

towards the equator.

Since the calculations do not do "time of day"

effects, the azimuth is simply the direction in

degrees either east or west of due north/south.

The "Text / Graph" button toggles the display

between the graphic display and a text chart of the

same data.

In the "text" mode, the display switches to tabular

data, as shown below.

The column labeled "Horiz" represents the global

horizontal insolation as entered previously. The

values are kilowatt hours per square meter per day,

or kWh/m2/d. The "Clearness" values are the ratio

between the measured insolation and the

extraterrestrial insolation. The "TiltFactor" is the

calculated ratio between the horizontal and tilted

insolation. The column labeled "Array" is themonthly average insolation on the array, also in

kWh/m2/d.

Two speed buttons control output of this

information:

Print - This button will print the Array Tilt Analysis

report to the active printer.

To Clipboard - This button will copy a bitmap of

either the graph or the chart to the clipboard. It can

then be pasted into a word processing document.

Note that since this is a bitmap, the resolution is not

especially good.Once you have finalized the tilt, you can choose

Print to print a single page report (see Section 9.1),

or click on the "Sizing (ALR)" tab at the top of the

notebook to move on to the next step.


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5.3 TrackingOptionsThe tracking buttons provide four choices for

tracking arrays:

The baseline choice is a fixed flat plate array.

Vertical is for single axis vertical axis tracking. Theazimuth input has no effect on this calculation, since

it assumes that the array is rotated from east to west

using a vertical axis.

Polar is for single axis polar tracking. The azimuth

input has no effect on this calculation, since it

assumes that the array is aligned north-south at the

specified tilt

Two Axis tracking assumes an array than can fully

track the sun while it is above the horizon.

5.4 OptimizationWhen optimizing the array tilt, the orientation of thearray is entered first, using the Azmith control box.

The array is then tilted used the array tilt control

button. When in Graph mode, the array insolation is

plotted along with the horizontal insolation. The

minimum and average insolation values are also

displayed on the bottom center of the page.

For standalone PV systems, the array is typically

tilted to maximize the worst month insolation. For

hybrid systems, the array tilt is often optimized for

annual average insolation.

5.5 ArrayInsolationReportThe Array Insolation Report shows both horizontal

and tilted / array data in both tabular and graphic

forms. The report also shows the average

temperature and Clearness Index.

A sample Array Insolation Report is included in the

Appendix.


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The system summary section at the bottom of the

screen gives values for the PV array (# of modules,

array kW and array amps), and the battery (# of

days, battery kW, battery Ah, and battery volts).

6.4.1 MPPTvs.NonMPPTControllerOne of the new features ofNSol!V4.6 is the optionto specify a Max Power Point Tracking (MPPT)

controller.

With a standard (non-MPPT) controller, the system

treats the array as a current source, that is a

constant current device. The current is set to the

maximum power current of the module, derated

properly for temperature. This tends to be slightly

on the conservative side, as long as the module as

sufficient voltage to so that it does not drop over

the knee of the IV curve. This can be checked by

clicking on the [IV Check] button.

The user can specify an MPTT controller on the

[Summary] tab of the Inputs dialog. There is a

checkbox just below the System Voltage selection

box.

When an MPPT controller is selected, there is a

flag on the summary page just below the controller

symbol, as shown in the following screenshot:

When this feature is selected, the system determines

the array output by calculating the maximum power

of the array at each point over a typical day for

each month (15 minute intervals). This value is

derated for temperature, and the battery chargecurrent is calculated by dividing the power by the

battery charge voltage (average system voltage plus

0.2 volts per cell).

This value is then multiplied by 97% to account for

losses in the controller. To approximate a change in

this value, adjust the system losses value up or

down.

Note that this method does not check whether the

array voltage is properly configured to operate

with the controller. It is up to the system designer

to ensure that the array is properly configured

according to the controller manufacturerspecifications.

Typically, MPPT controllers use a step down

controller, so the array voltage is higher than would

normally be used. To do this, uncheck the Auto

Series box on the PV Module page of the inputs

dialog, and set the number of series modules

manually.


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6.5 LOLPMethodOccasionally, the system designer needs to consider

factors other than a simple energy balance in a

system. For example, in high reliability

telecommunications systems, the customer will often

specify that the system must have an availability of99.9%, or a minimum battery state of charge of 50%

under worst case conditions. If the sun always shone

with the average value, then these would be easy

calculations. However, the solar insolation varies

day by day as well as month by month, meaning that

you must have additional information to perform

these calculations. The program provides the system

designer with a powerful statistical tool called

"Loss-Of-Load-Probability" (LOLP) calculations to

estimate these advanced parameters using the same

input data as in the ALR calculations described in

Section 6.4.

This section describes the screens used to display the

results of these advanced calculations; the next

section gives an overview of the LOLP calculation

methodology.

This analysis is done within the "LOLP Analysis"

and "BSOC Reports" pages of the project notebook.

The LOLP Analysis page can be accessed by

clicking on the appropriate tab at the top of the

notebook, or by choosing Sizing, then LOLP from

the main menu.

6.5.1LOLP

Page

The basic LOLP Analysis notebook page is shown

below.

This page has three sections -- the Graph / Chart,

summary sizing information, and one control button:

Text / Graph -- This button switches thedisplay between the LOLP graph and the

data tables with detailed statistical

information. (Shown below, with an

explanation of the terms in the tableimmediately following)

Terms in the LOLP Analysis table:

The column labeled "Variability (%)" givesthe tilted insolation variability, which is

defined as the standard deviation of the

monthly insolation values divided by the

average monthly insolation. The variabilityis an indication of how "steadily" the sun

shines. A site with a low "variability" with

have very consistent weather, while a site

with a higher variability with have a greater

mix of sunny and cloudy days.

The column labeled "Correlation (%)" givesthe day-to-day correlation of the solar

insolation. The correlation is the probability

that one day will be like the next (e.g. that a

sunny day will follow a sunny day). In

general a higher correlation means more

steady weather. The column labeled "Array/Load Ratio" is

simply the ALR from the previous section,

repeated here for information's sake.

The "BSOC Avg (%)" column gives themonthly average battery state-of-charge of

the battery. Note that this is never 100%,

since the load is never perfectly matched

with the array, and the battery is usually


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discharging at night. However, this gives a

good indication of the ability of the system

to maintain the health of the battery.

The "LOLP %" column gives the "Loss-OfLoad-Probability" (LOLP) for that

month. The LOLP is the statistical

probability that the system will not havesufficient energy to supply the load on one

of the days during that month. The value is

given as a percentage of days that will

encounter an LOLP event. (For example, an

LOLP value of 1.0 percent in October means

that the system will "go down" one day out

of every 100 "October days," or about once

every three years since October has 31 days.

An LOLP of 3.0 percent means

approximately one outage per month, while

an LOLP of 0.3 percent means

approximately one outage every 10 years.) The SEP % page shows the Surplus

Energy Probability, which is analogous to

the LOLP, except at the top end of the

battery. This is the probability that the

battery will be fully charged and will require

regulation on any given day.

6.5.2 BSOCPageThe "BSOC" page shows the LOLP data in a

somewhat different format, as shown below. It

concentrates on the part of the analysis that shows

the probability of the battery being at differentstates-of-charge during different months of the year.

This page displays a choice of two graphs or a

tabular report.

The default choice displays a graph showing the

average Battery SOC for each month.

The second graph and the table show the percentage

of time that the battery will spend in each state-of-

charge during each month. The battery is divided up

into ten segments. This means that if the maximum

battery DOD is 80%, the segments will be 8% SOC.

Likewise with 100% max DOD, the segments will

be 10% and with 50% max DOD, the segments will

be 5%.

The third graph is in the form of a three-dimensional

bar chart, with the higher states of charge towards

the rear of the graph. If the chart looks like a steep

green cliff with a flat sea in front (as shownabove), the system is fine.

If the blue segments of the chart are level or taller


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than the green in any month, this is an indication of

a problem. An example is shown below:

6.5.3 NoteonCalculationsThe LOLP calculations are very "math intensive"

and take quite a while, even on powerful computers,

so a status window appears to indicate which month

is being analyzed. In general, systems with larger

batteries take longer to analyze. This used to be a big

problem (when NSol!first came out, the

recalculation could take up to three minutes) but

now, most computers are fast enough so that a

manual recalculation feature has been removed from

the program.

Note - occasionally, the statistical model will notwork for a specific set of data. This does not imply

that the system is not reliable during that month, it

merely means that the model cannot find a

mathematically valid solution. When this occurs, the

program will print out a set of three asterisks (***)

in the place of the Variability, correlation, average

BSOC, and LOLP.

The user must then use engineering judgment as to

whether the system is reliable for that month. For

example, if the array to load ratio is greater than 2.0

and there is sufficient battery storage and the months

on either side of the asterisks are valid, you canassume that the system is reliable. Alternatively, you

can try changing the solar insolation data slightly to

see if the model will work.

Once you have finished examining the LOLP

screens, you can click on the Print speed button to

print a single page "Availability Analysis" report.

6.6 LOLPMethodologyOne of the functions of the NSol!program is to

reduce the complexity of the statistical

calculations to a useful format. The purpose of this

section is to elaborate a little on the actual

calculations used.Two cautions apply:

First, this discussion is not for the fainthearted

when it comes to math. Even the simplified

discussion cannot avoid some complexity.

Second, this is not a rigorous presentation of the

exact methodology. The algorithm was adapted from

existing published papers, using techniques

proprietary to Orion Energy Corporation. Professor

L. L. Bucciarelli of the MIT School of Engineering

developed the actual algorithm under contract to

Orion Energy Corporation. There is a list oftechnical papers in the appendix, which themathematically inquisitive reader can reference for

more details.

There are two basic parts of the LOLP algorithm -

determination of the insolation variability incident

upon the photovoltaic array, and determination ofthe probability distribution for the Battery SOC (its

stationary states) and subsequent LOLP.

The first part is an adaptation of the concept of the

use of Markov Transition Matrices in determining

solar insolation variability, as presented by Aguiar,

Collares-Pereira and Conde in their paper SimpleProcedure for Generating Sequences of Daily

Radiation Values Using a Library of Markov

Transition Matrices (Solar Energy, Vol 40. No. 3

pp. 269-279, 1988). Their paper presents the

methodology for using Markov Transition Matrices

(MTMs) to generate radiation sequences for

simulation models.

An MTM is a matrix which gives estimates for the

probability that the insolation value for the next day

will be at level "j" given that it was at level "i"

today. Aguiar et. al, and we, take the

month as the fundamental period during which the

statistical analysis applies. They, as do we, break the

range of possible insolation values into ten discrete

steps and use the clearness index as its measure. For

example, if one day during the month has a clearness

of 45%, the matrix then gives the probabilities of the

next day being at 40%, 35%, 50, 55%, 60%, etc.

These day to day transition matrices can be used to


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calculate the probability distribution for the daily,

global horizontal insolation for any month. Each

transition matrix has associated with it a mean

clearness index and a variance. Knowing the

monthly values for the mean clearness index at a

particular site, we can judiciously choose an

appropriate MTM from the set constructed byAguiar et. al. A day-to-day correlation coefficient is

also computed for each transition matrix.

The major limitation of this method is that the

MTMs in the paper apply only to global horizontal

(GH) insolation data. Previous work by various

authors has shown that the variability of the tilted

insolation is significantly different from that of the

horizontal insolation, primarily because of the

effects of direct and reflected radiation. The

technique used by NSol!converts the MTMs for the

GH insolation into equivalent matrices for the tilted

insolation, using GH to

array insolation conversions for each insolation level

of the original MTM. The result is an MTM that

describes the behavior of the insolation resource on

the tilted array, as well as its probability distribution

and a measure of day-to-day correlation. Unlike

other statistical methods which use table-lookups to

approximate these values based on standard tilts and

latitudes, this method calculates the values for the

exact tilt and latitude of the system.

The next step is to apply this data to the system

specifications (array/load ratio and battery size) inorder to determine the statistical performance - the

stationary states for the battery state of charge - of

the proposed PV system. This section of the

algorithm is based on previous work by Bucciarelli

(ref L. L. Bucciarelli Jr., Estimating Loss-Of-Power

Probabilities of Stand-Alone Photovoltaic Solar

Energy Systems, Solar Energy Vol 32, pp. 205-209,

1984) but adapted and generalized to use the

transition matrices derived in the first steps. These

are combined with the system loads, array/load ratio,

and battery size to calculate a battery transition

matrix showing the probability of the battery beingat any given SOC on any day during that month.

There are two refinements over the previous method.

First, the battery is divided into 10 discrete SOC

levels (thus the 8% "battery segment" for a lead acid

battery). Second, the load can have both "day" and

"night" components defined by the given load

profile. A load which is "night only" will exhibit

poorer system performance than a load which is

daytime only and matched more closely to the solar

resource.

In addition to probability distribution for the battery

SOC levels, the algorithm also gives the probability

of a deficit (LOLP), an estimate of that deficit, the

probability of a surplus, the estimate of that surplus,

and a measure of the robustness of these

calculations. In fact there is so much information

that we found it impossible to get it all into the

output reports of this version of NSol !.

In summary, NSol!presents a great deal of data to

help the systems engineer evaluate the projected

performance of the system, and to compare it to

other options available. However, the user must

remember that these results are subject to the

accuracy of the input data, and to a number of

assumptions discussed above. Annual variations in

insolation may cause significant variations in systemperformance, even when the best input data is used.

In final judgment, it is up to the systems engineer to

design a system to best meet customer requirements.

6.7 IVCurveAnalysisThis features enables a closer look at a simulated

array IV curve for different periods of the standard

day for each month. The user can look at either IV or

PV curves for either a module or over the entire

year.

The simulated data is calculated using the modules /

array

6.8 Reports6.8.1 SystemSizingReportThe System Sizing Report shows basic sizing

information using the ALR sizing method. Data is

presented in both tabular and graphic formats, and

includes array insolation, temperature, array output,

system losses, daily load, night load %, monthly

battery size and array/load ratio.

A sample System Sizing Report is included in the

Appendix.

6.8.2 SystemAvailability(LOLP)ReportThe System Availability Report presents details of

standalone system performance using the LOLP

sizing method. Data is presented in both tabular and

graphic formats, and includes array insolation,

insolation variability, day-to-day correlation, and


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array/load ratio, monthly battery size, average

BSOC, monthly LOLP and month SEP.

A sample System Availability Report is included in

the Appendix.

6.8.3 BatterySOCReportThe Battery SOC Report presents details of battery

performance based on the LOLP sizing method.

Data is presented in both tabular and graphic

formats, and includes system summary information,

as well as battery SOC bin data information similar

to that presented in the program. The graph shows

average battery SOC by month.

A sample Battery SOC Report is included in the

Appendix.

6.8.4Standalone

System

Summary

Report

The System Availability Report presents details of

standalone system performance using the LOLP

sizing method. Data is presented in both tabular and

graphic formats, and includes array insolation,

insolation variability, day-to-day correlation, and

array/load ratio, monthly battery size, average

BSOC, monthly LOLP and month SEP.

A sample System Availability Report is included in

the Appendix.


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7 SystemSizing Hybrid7.1 OverviewNSol!uses a simplified sizing calculation for

estimating performance of hybrid power systems.

The basic process is to calculate the energy requiredby the load during a typical month, subtract the

energy available from the PV array, and calculate

generator performance based on supplying the

remaining energy. The result is a description ofgenerator operating hours, fuel consumption, and

number of charge cycles for each month.

7.2 SelectingComponentsPrior to starting the sizing process, the user must

select a PV module, a battery, and at least one valid

load. The user should also select a site, and enter a

valid system voltage.

The user must also enter the following generator and

battery charger information:

Generator Manufacturer Generator Model Genset Power Rating

Genset Power Factor Rating Full Load Fuel Consumption (FLFC) Quarter Load Fuel Consumption (QLFC)

Maintenance Information: Oil Change Interval Decoke Interval Overhaul Interval Generator Life

Battery Charger Current Battery Charger Power Factor Battery Charger Efficiency In addition, the data input screen allows the

following control setpoint inputs: Generator Start Battery State of Charge Generator Stop BSOC (normal charge) Normal Charge Coloumbic (Amp-hr)

Efficiency

Equalization Frequency The followingfigure shows the Hybrid system input

screen:

7.3 SettingArrayTiltThe array tilt, azimuth and tracking options should

be set as described in Section 5.

In general, hybrid system should have the arraytilted for maximum energy production, rather than

worst case month. This is typically at or near

latitude.

7.4 HybridSystemAnalysisThe following process is used to make the generator

calculations:

1. The amp-hour deficit that must besupplied by the generator is calculated by

subtracting the derated array amp-hours

from the DC load amp hours. This isexpressed as generator amp-hours per

month.

2. The typical cycle is determined by findingthe difference between in battery State-of-

Charge (SOC) for a typical charge cycle.

These values are entered in the Hybrid Page

of the Systems Inputs dialog box. Typical

start of charge is 40% SOC and end of


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charge is 85-95% SOC, so each cycle

typically replaces 45-55% of the battery

capacity.

3. The time it takes to recharge the battery iscalculated by dividing the net battery

charger output (rectifier rating minus the

average DC load) into the amp-hourrecharge requirement, and dividing by the

battery amp-hour recharge efficiency.

(Note this number is typically very high

for charge cycles up to 85% SOC, and

decreases rapidly beyond that.)

4. For example, with a 1000 Ah battery, a 100amp rectifier, a 10 amp load and a 95%

battery efficiency, it would take a generator

5.25 hours for a typical cycle from 40% to

85% SOC.

5. Generator fuel consumption is calculated

based on the electrical load presented to thegenerator (as a percentage of its full load)

multiplied by the number of hours that the

generator operates.

6. The number of cycles per month iscalculated by dividing the Gen Ah

requirement by the net number of amp-hours

during each charge cycle. This includes both

the amp-hours that recharge the battery and

the amp-hours that are supplied to the load

while the generator is operating. This is

often described as a fractional number of

cycles e.g., 8.4 cycles for a given month.This means that the long term average

would be 8.4, but any given year would

probably have 8 or 9 cycles.

7. Finally, a factor is added for periodicequalization of the batteries. This involves

running the generator for an extended period

of time to bring the batteries to full charge

(and slightly beyond). The user enters the

number of equalizations per month, which

depends on the battery technology and

control system being used.

8. Operating hours and fuel consumption permonth are calculated by multiplying the

parameters per typical cycle by the

number of cycles in a given month, and

adding the appropriate values for

equalization.

9. Monthly values are then totaled to giveannual values for the basic parameters.

This a simplified approach, and ignores such factors

as daily load profile, as well as daily, timed

operation of the generators, as opposed to battery

based demand operation, and the differences

between DC Bus and AC Bus hybrids. It also

simplifies factors such as multistage charging and

battery aging. However, it will give a reasonableestimate of generator performance for most typical

system designs.

General design goals typically call for a limited use

of generator-supplied energy, limited fuel use, or

limited operating hours. The NSol!algorithm allows

the designer to evaluate each of these variables in

real time using different sizing options.

7.5 HybridSystemAnalysisScreenThe basic hybrid system design tasks can be doneinteractively from the Hybrid page of the

notebook.

The Text button allows the user to switch between

the graphic Display and the Text Display.


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8.5 GridSystemScreensThere are two primary screens used for analysis of

Grid-Connect Systems. The first is a summary page

showing the monthly energy production of the PV

array in graphic and tabular format when printed out.

This information is also available in numerical form.

The second is a set of graphs that show typical daily

performance for each month of the year.

8.6 GridSystemReportThe Grid Sizing Report presents data on grid system

sizing and system performance. Data is presented in

both tabular and graphic formats, and includes

system summary information, as well as summary

and detailed monthly information on insolation, DC

performance and AC performance of the system.

A sample Grid Sizing Report is included in the

Appendix.


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9 ReportsandExportingData9.1 ReportSummarySeven formal reports are available from NSol!:

Tilt Analysis Report

ALR Sizing Report LOLP Report BSOC Report System Summary Report Hybrid Analysis Report Grid Analysis Report

Each of the individual graphs may be printed or

exported to the clipboard for inclusion in a proposal.

System data for the standalone and hybrid systems

may be exported for spreadsheet analysis or further

formatting and inclusion in a proposal.

Detailed grid analysis data can be exported forfurther spreadsheet analysis.

9.2 PrintingReports9.2.1 PrintingFormal reports can be printed in three ways:

Clicking on the Printer speed button will print a

report appropriate for the active page, if it is

available.

Choosing File _Print from the main menu

accomplishes the same thing.

Choosing File_PrintAll from the main menu

allows the user to choose a set of reports to print

with a single command.

9.2.2 PageSetupNote you can use File_Print Setup to set the

default print conditions. The reports work best when

printed in portrait mode.

9.2.3 PDFFilesReports can be printed out to a PDF file if the user

has an appropriate printer driver (such as an AdobeAcrobat driver or CutePDF) installed.

9.3 PrintingChartsCharts can be printed by clicking on the Print

Chart Button which shows a small picture of a

chart. (It is third from right on the Toolbar.) This

will print the current visible chart.

9.4 ExportingChartsCharts can be exported to the clipboard by clicking

on the Export Chart Button which shows a small

picture of a file with a red arrow. (It is second from

right on the Toolbar.) This will copy the current

visible chart to the as a Windows Metafile. This can

then be pasted into any standard document, such as a

word processing file.

9.5 ExportingASCIIDataforSpreadsheets

Summary Sizing Data can be exported by clickingchoosing File_Export from the main menu.

The data can be exported as either comma separated

values or tab separated values. This data can then be

imported into a spreadsheet or word processingdocument for further formatting or analysis.

9.6 ExportingGridDataforSpreadsheets

The detailed grid-calculation data can be saved to a

tab-separated file for further analysis by spreadsheet.

Click on the [Export Data] button, then select a filename.

The data fields are:

Month Time of day Irradiance (Plane of Array) Ambient Temp Cell temp Temp Derating Module Output (DC) Array Output (DC)

System Output (AC)


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Appendix 1Sample Reports


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Appendix 2Glossary of

Terms


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Extraterrestrial Insolation The amount of solar radiation that strikes a surface outside the earth's atmosphere.

Used to calculate the clearness ratio.

Global Horizontal Insolation Insolation as measured by a horizontally mounted pyranometer. Typically

expressed in Langleys, MJ/m2 or kWh/m2. NSol! uses the latter for its calculations.

Insolation Solar radiation.

Isc Short Circuit Current -- a measure of PV modules, typically found on the data sheet

Ityp Typical operating current of a PV module, also call peak power current. Typically

found on the datasheet.

Kilowatt-hours A measure of electrical consumption or production. One kilowatt hour is one kilowatt

for one hour.

KT_Bar Clearness factor

kWh Kilowatt-hour abbreviation

LOLP Loss of Load Probability

Loss-of-Load-Probability A measure of the reliability of a PV system. The LOLP in NSol ! is expressed as the

percentage of "month-days" which will experience an outage. Example - a value of

1.0% in October means that the load will be disconnected once every 100 "October"

days. Since October has 31 days this is approximately once every three years.

Markov Transition Matrix A matrix which gives estimates for the probability that the insolation value for the

next day will be at level "j" given that it was at level "i" today. Used in the NSol !

statistical LOLP calculations.

Module A single PV module, typically 12 V and 40 to 60 watts.

Monobloc A package with numerous battery cells in series. An automotive battery is an example

of a monobloc. (See "cell".)

MTM Markov Transition Matrix

Photovoltaics The process of converting solar energy directly into electricity.

PV Photovoltaics

PVs What right-handed people call Photovoltaics

Reflectance The percentage of insolation that strikes the ground which is reflected. A sandy desert

or snowy field would have a higher reflectance than a grassy field or a puddle of mud.

SOC State-of-Charge. The amount of energy remaining in a battery as a percentage of its

overall capacity.


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Sigma Ratio see variability

Temperature - Ambient The temperature in an open outdoor space. NSol ! uses monthly average ambient

temperatures to derate battery capacities.

Tilt Factor The correction applied to the Global Horizontal Insolation used to determine the

insolation on the tilted array.

Variability (Insolation) A measure of the "steadiness" of the solar insolation. The ratio between the standard

deviation (sigma) and the average value (mean) for the month.

Voc Open Circuit Voltage. The voltage of a PV module with no load connected to it.

Typically found on PV module data sheets.

Vtyp Operating voltage of a PV module at its peak power.

W(p ) Peak wattage output of a PV panel or PV array.


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Appendix 3Sizing

References


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Sizing References

L. L. Bucciarelli, "Estimating Loss-of-Power Probabilities of Standalone Photovoltaic Solar Energy

Systems," Solar Energy Vol 32, No. 2, pp. 205-209, 1984

L. L. Bucciarelli, "The Effect of Day-today Correlation in Solar Radiation on the Probability of Loss-ofPower

In a Standalone Photovoltaic Energy System," Solar Energy Vol

36, No. 1, pp. 11-14, 1986

R. J. Aguiar, et al, "Simple Procedures for Generating Sequences of Daily Radiation Values Using a Library

of Markov Transistion Matrices," Solar Energy Vol 40, No. 3, pp.

269-279, 1988

"The Frequency Distribution of Daily Insolation Values," Solar Energy Vol 27, pp. 1-5, 1981 DT

Reindl, et al, "Diffuse Fraction Correlations," Solar Energy Vol 45, No. 1, pp. 1-7, 1990

Insolation References

"Solar Radiation Data Manual for Flat-Plate and Concentrating Solar Collectors"

Document # NREL/TP-463-5607

National Renewable Energy Laboratory

1617 Cole Blvd

Golden, CO 80401-3393

USA

Phone: (303) 275-4099

"International Solar Irradiation Database"

University of Massachusetts-Lowell

Photovoltaic Program

1 University Ave

Lowell, MA 01854

USA

"National Solar Radiation Database"

National Climactic Data Center

Asheville, NC

Phone (704) 259-0682


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TECH MEMO

Subject: Insolation Conversions

There are three basic units used in solar insolation inputs - kWh/m2, MJ/m2 and Langleys. This memo

defines the conversion factors used between these factors.

1. kWh/m2 Since we are working with electrical systems, this is the most convent set of units. For this

reason, it is

the default and requires no conversion.

2. MJ/m2 1 Joule = 1 Watt-sec so

1 kWh-hr = 3.6 x 106 J = 3.6 MJ

(1 watt * 60 sec/min x 60 min/hr = 3600 watt-sec/hr

so 1 kilowatt = 1,000 watts = 3,600,000 watt-sec/hr = 3.6 MJ / hr so 1 kWh = 1kW x 1 hr = 3.6 MJ)

The conversion is thus: MJ/m2 / 3.6 = kWh/m2

3. Langleys

Langleys have the units cal per cm2 per hr.

1 Langley = 4.184 x 104 J/m2

so

1 Langley = (4.184 x 104 J/m2) / (3.6 MJ / kWh-hr) = 1 / 86.04 kWh/m2

The conversion is thus: Langleys / 86.04 = kWh/m2.

nsol v4_6 manual

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