fansave 3.0 users manual

7/31/2019 FanSave 3.0 Users Manual

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FanSave 3.0 UsersManual

Energy Savings Calculator

for Fan Drives

Version 3.0

3BFE 64232681 R0225

Effective: 13.7.2001


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Copyright ABB Automation Group Ltd. 2001

1 General

FanSave is a calculation tool running on Microsoft Excel(version 97 or later) to estimate the energy savings availablewhen using a variable speed AC drive (frequency converter)compared to other fan control systems.

Comparisons can be made with damper control, pitch control,single speed vane control and 2-speed vane control.

Calculations are based on typical fan operatingcharacteristics. Consequently the accuracy of the results islimited to 10%. The accuracy of the results is also affectedby the accuracy of the input data.

Results should be used only for estimating purposes. Theresults of this program must not be used as the basis forguaranteed energy savings.Results of calculations can be printed out.

New in version 3.0

The user interface has been renewed to allow the user to seethe whole FanSave view without having to scroll the screen(applies to desktop area of 1024x768 pixels or more).

Reduction in greenhouse gas (GHG) emissions due to thereduced energy consumption can be evaluated.

The investment criteria include now also Net Present Value(NPV), and Profitability Index is provided for rankinginvestment projects.

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2 Starting and Running the Program

Software Required

Microsoft Excel 97 or later is required to run the energycalculation workbook. Before using the FanSave workbook,the user should have some familiarity with Microsoft Excel.

Files Provided

The FanSave files for fan drive calculations are incorporatedinto Excel workbook FanSave3.0.xls.

Installation

The calculation workbook can be opened and run from a CD-ROM or a floppy disk or the file can be copied to a hard disk.Hard disk installation is recommended if the program is to beused frequently.

Opening theWorkbook

Start Excel as usual. For fan calculations open FanSave3.0.xls.To open the workbook, select File from the menu bar at thetop of the screen and then select Open from the drop-downmenu. In the dialog box, select the drive in which the FanSavefile is located from the list of drives. Select the foldercontaining the FanSave file from the list of folders. SelectFanSave3.0.xls in the list of file names and click OK.

FanSave will open in Full Screen mode. Hence, the usual Exceltoolbars are not visible. Full Screen mode can be disabled andenabled by selecting Full Screen from the View menu.

As FanSave is opened, a welcome window is displayed. Figure1 shows the welcome window for FanSave. The welcomesheet presents four comparative calculation options. ClickContinue to close the window.

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Figure 1 Welcoming window for FanSave

Main Sheet

After having clicked Continue button, the main calculation

sheet will open. Figure 2 on page 5 shows a typical mainsheet. The main sheet is a calculation spreadsheet wheredata is entered and results are presented. Section 4 on page5 provides additional information about the calculationsheets.

Adjusting Screen Size

There are four buttons in the center of the sheet,Adjustscreen button, Printbutton, Graphics button and Exitbutton.

FanSave is optimized for desktop area of 1024 by 768 pixels.If the FanSave view is not fully visible, click the Adjust Screenbutton. This zooms the screen so that it should fit into thevisible area. It is also possible to zoom the sheet by selectingView Zoom from Excel menubar.

Printing the Main Sheet

To print the sheet, click the Printbutton. This will print thesheet to the default printer without prompting. The sheet canalso be printed by selecting File and Printfrom the Excelmenus.

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Viewing and Printing the Graphics

Click the Graphics button to display a graph of power usagevs. flow for adjustable speed flow control compared to thealternative method of flow control. Print the graph byselecting File from the menu bar and using the appropriate

commands from the drop down menu.

Exiting

To exit the program, click the Exitbutton in the center, or,click the Close Window cross button in the upper right cornerof the screen. It is also possible to select File Exit from theExcel menus.

After you click the Exit button, Excel will display the messageSave changes in FanSave3.0.xls? If you wish to save the

data, click Yes, otherwise click No. Note that if you arerunning FanSave from a CD-ROM, you will not be able to makechanges to it. Instead, you can save a copy to a hard disk byselecting File- Save as from Excel menu bar and save thecalculations and give it a different name if you wish.

4 Calculation Sheet

BasicsAll white cells on the calculation sheet are spaces for enteringinformation and data. Results are displayed on pale yellowbackground. Figure 2 on page 6 shows a typical calculationsheet.

Identification andComments

Space is provided in the upper right corner of the calculationsheet for filling in information to identify the application andthe name of the company.

FanSave CalculationOptions

There are four calculation options possible in FanSave. Damper control compares the energy required to controlthe volume flow using adjustable frequency drive control withthe energy required to control the volume flow by throttling itwith a damper. Single Speed Vane Control compares the energy requiredto control the volume flow using adjustable frequency drivecontrol with the energy required to control the volume flow byinlet vane installed at the fan inlet.

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2-Speed Vane Control compares the energy required tocontrol the volume flow using adjustable frequency drivecontrol with the energy required to control the volume flow bystepwise control achieved either by a two-speed motor or anintermediate gearbox.

Pitch control compares the energy required to control thevolume flow using adjustable frequency drive control with theenergy required to control the volume flow by adjusting thepitch angle of axial-flow fan.

The control method that is compared to variable speed ACdrive control is selected from a drop-down list on the top ofthe main sheet of FanSave.

Input Data

The input data that must be filled in by the user includes

various physical constants and other data that apply to theparticular fan application. Since the accuracy of the resultsdepends on the accuracy of the initial data, this informationshould be determined or estimated as accurately as possible.

The required data includes the gas density, the nominalvolume flow, the operating pressures and the efficiencies ofthe fan, motor and drive. Operating time at different volumeflow rates must be estimated for flow rates between 100%and 20% of nominal volume flow at 10-percent intervals. Theoperating time at each volume flow rate is expressed as apercentage of the total operating time per year.

Financial data such as energy price and investment cost isrequired in order to get figures for investment appraisal.

The input data is discussed in more detail in the description ofthe calculation sheet.

Results ofCalculations

The results of the calculations include the estimated annualenergy consumption for the selected conventional method offlow control and for variable speed AC drive control, the

difference of these two which equals the annual energysaving achieved by using a variable speed AC drive. FanSavealso estimates the reduction in greenhouse gas (GHG)emissions due to the reduced electricity demand.

Payback period is calculated for the investment in the drive ascompared to the alternative method of flow control. Netpresent value is also calculated provided that the user entersan interest rate and service life.

The program also calculates the required motor power to

check if the motor power given by the user is high enough forthe situation specified.

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The results of calculations are discussed in more detail in thedetailed descriptions of the calculation sheet.

5 Fan Drive Calculations

Input Data

The initial data is entered on the left side of the calculationsheet as shown in Figure 2.

Figure 2 FanSave main view

Existing Control Method

First, pick the conventional control method that you want tocompare with VSD control. The control method is selectedfrom the drop-down list on the upper left part of the sheet.

The options are: Damper, 1-speed vane, 2-speed vane andPitch control. If nothing is selected, no savings can becalculated, only the energy consumed in VSD control case is

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shown. The conventional control method selected can bechanged anytime.

Fan data

Nominal Volume Flow, Qvn (m3/s)

Enter the nominal, maximum, or design-point volume flow forthe fan in cubic meters per second. The value entered shouldbe the maximum flow that the fan is normally expected todeliver. All energy saving calculations will be based on flowrates that are equal to or less than Qvn.

Rated Total Pressure Increase, ptF (Pa)

Required pressure increase of the fan for the given nominalvolume flow. Value is determined from the fan data.

Efficiency, (%)

Enter the nominal efficiency of the fan at nominal volume

flow.

Additional data

Gas Density, D (kg/m3)

Enter the density of the air or gas at the fan inlet at the drivetemperature in kilograms per cubic meter. The default value

is the density of air 1.2 kg/m3 at 20C dry temperature. Forother temperatures and humidities use available monographsto find out the correct density or calculate it using the

following formula.

Table 1 gives air densities for temperatures from 0 to 450 C.

21

1

1

sa

saxx

pT

pTDD

= , where D1 = required density

Dx = known density

T1 = temperature at required density

Tx = known temperature

Psa1 = pressure at required density

Psa2 = known pressure

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Table 1Density of dry air as function of temperature at normal air pressure1013 mbar

TemperatureC

Density

kg/m3

0 1.293010 1.2471

20 1.2045

30 1.1647

40 1.1267

50 1.0924

60 1.0595

70 1.0287

80 0.9998

90 0.9719

100 0.9458

120 0.8980140 0.8535

160 0.8150180 0.7785

200 0.7457250 0.6745

300 0.6157350 0.5662

400 0.5242

450 0.4875

Inlet Static Pressure pta (kPa)

This is the absolute static pressure at suction inlet. Pressuredepends on application. It can be estimated as 0.88 to 0.9times total pressure of fan. If not known, use value of 101.3kPa, which corresponds to the standard air pressure (1013mbar).

Operating Profile

Annual Running Time

In other words, this is the total operating time per year, Tk (h).Enter the estimated number of hours that the fan is expectedto run during a years time. For 24 hour, 365-day operation,enter 8760 hours.

Operating Time at Different Flow Rates (%)

Enter the estimated time as a percentage of the totaloperating time for operation at each of the listed flow ratesfrom 100% to 20% of nominal volume flow. Leave blank orenter zero for flow rates that are not used. The sum of theentered percentages must be 100%. A figure under the whitecells shows if the sum equals 100. If it does not, a commentTHIS SUM MUST EQUAL 100! shows.

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Transmission

Efficiency, (%)

Efficiency of the transmission method e.g. belt transmission. Ifthe fan has been connected directly to the motor, use 100%.

Motor Data

Nominal Power, P (kW)

Enter the nameplate power rating of the motor. This entry isused only to verify that the motor is large enough for the load.

The program uses calculated power demand to determineenergy savings. The entered value should be at least as big asthe recommended value on the right of it, which is 10%greater than the calculated load power demand (shaft powerof the fan). 10% margin is considered as safety factor indimensioning the motor.

Supply Voltage, U (V)Enter the supply and motor voltage used in application. Thevalue should be between 200 and 690 V.

Nominal Efficiency, m (%)

Enter the motor efficiency from the motor nameplate or fromother data supplied by the motor manufacturer. Use theefficiency for full load operation on fixed frequency utilitypower. The program will adjust the efficiency for operation atreduced speeds and loads. If the motor is oversized for theapplication, enter the efficiency for operation at the maximumapplied load.

Drive Data

Nominal Efficiency, m (%)

Enter the drive efficiency from the data supplied by the drivemanufacturer. Use the efficiency for full speed, full loadoperation. The program will adjust the efficiency for operationat reduced speeds and loads.

Based on motor power and voltage, FanSave suggestsappropriate drive type to be used. It is shown on the right sideof the Drive Data box.

Economic Data

Currency Unit

Specify here the currency to be used in calculations.

Energy Price (per kWh)

Enter the price of energy per kilowatt-hour (kWh). TheFanSave program does not have provisions for calculatingdemand charges. To estimate energy cost including demandcharges, enter the average cost of energy per kWh includingaverage demand charges.

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Investment Cost

Enter the estimated additional cost of purchasing andinstalling a variable speed AC drive as compared to thealternative method of flow control used in the comparison.Use the same currency units as entered for energy cost. This

entry will be used to calculate the direct payback time.Interest Rate (%)

This is the rate of return that a company demands for itsinvestments. This figure is needed in order to be able todetermine the net present value.

Service Life (years)

The expected service life of the drive. Also this is required forthe net present value calculation.

CalculationResults

The results of the calculations are presented on the right sideof the FanSave calculation sheet.

Energy Results

Energy Consumed (kWh)

The calculated energy used annually with the conventionalcontrol method and using a frequency converter for flowcontrol are both illustrated in two-column chart.

Annual Energy Saving (kWh)

This is the energy difference in favor of frequency convertercontrol. The total energy saving is the calculated energy usedannually using an adjustable frequency drive for flow controlsubtracted from the calculated energy used annually with thealternative flow control method

Annual GHG Reduction (kg)

The reduction in greenhouse gases (GHG), which results fromthe reduced energy consumption due to variable speedcontrol. Carbon dioxide CO2 is the primary greenhouse gascausing global warming.

The GHG reduction depends on the per unit emission ofGHGs, which should reflect the way and emissions theelectricity used has been generated with. The per unitemission is given in kg/kWh consumed, and it can be alteredby the user.

Economic Results

Annual Money Saving

This is how much money you save thanks to the variablespeed control by AC drive. Money saving comes in the form ofsmaller electricity bill.

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Payback period

This direct payback time shows that in how many years theinvestment in AC drive has paid its back.

Net Present Value

Net Present Value (NPV) is a more advanced method foranalyzing investments than the payback period rule. If theNPV is positive, then the investment should be accepted.Profitability Index is NPV per investment. It can be used torank different projects. For example, if you have manydifferent fan applications running without variable speed ACdrive control and you are considering, which ones to equipwith drive. The project(s) with highest Profitability Indexshould be implemented first.

Estimated Cut in Energy Cost (%)

The reduction in electricity costs in percents. This is also, of

course, the energy saving in percents.

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6 Explanation of Calculations

Fan PerformanceCurves

Fan performance can be defined from its performance curves

i.e.pressure curve (Qv/ptF-curve) andpower curve (Qv/PR-curve). Different fan types have different shaped performancecurves. Additionally, the position of the curves depends ongas density, rotation speed and fan size. For these reasons,the performance curves are often presented as sets of curveswith different parameters. The manufacturer of the fanprovides these performance diagrams.

Thepressure curve of the fan can also be referred as fancurve. The suitability of a fan to a certain duct systemdepends partly on the form of the fan curve. All thecalculations of FanSave are based on parabolic fan curve.

The useful mechanical power transferred into the mass flow is

called air power PF. It is proportional to the gas density,

volume flow and total fan pressure.

The impeller power PR (also called shaft power), i.e. the mechanical

power necessary for rotating the fan is then obtained bytaking the fan efficiency into account. For all centrifugal fansthe impeller power increases as the volume increases. Thisconnection is presented in thepower curve of the fan.

Further on, the electric fan power is calculated by taking themotor and drive efficiencies into account.

System Curve

All the duct systems have their special performance curve,system curve,

dependent on the resistances in the duct. In a turbulent flow,all the resistances caused either by friction or various ductelements are proportional to the square of the volume flow.From this follows that the total resistance of the duct system,i.e. system curve, often complies with the same rule.

Especially in industrial processes it is likely to encounter alsosystem curves with an additional constant pressure andpreviously mentioned changing pressure. The calculations ofFanSave are based on the basic system curve without anyconstant pressure.

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When adjusting

the fan speed tocontrol thevolume flow, theprocess movesvia system curve(a). Respectively,when throttlingthe duct the fan operates continuously at the same speed,and the movement of the process is via fan curve (b). SeeGraph.1.

Control Methods

For FanSave calculations the most important control methodsto control thefans during operation have been selected. Fig.3 below showsthe relationship of the electric fan power compared to thevolume flow in connection with these control methods. Thecontrol method presentations are average examples used incalculations.

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Qv

/ m3/s

ptF

/ kPa

FAN CURVE

SYSTEM CURVEpmax

pN

QVN

p2

QV2

b)

a)

Graph.1. An example of typical fan and system curves.


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Figure 3 The power curves of flow control methods.

Efficiencies

In calculation sheet the given values are actually filled in tothe givenformulas. Further, as shown in the formulas, the totalefficiency of the system depends on the given efficiencies offan, energy transmission, drive and motor, and on theadjustment method specific correcting factor. Thesecorrecting factors are defined based on experience.

Fan Drive Calculations

The following formulas are used for power calculations:

The impeller power i.e. nominal shaft power of a fan iscalculatedfrom the formula

( )20,1

10

=

ntnk

ptFQvnDkpPf

The input power for different control methods, and fordifferent flow ratesis calculated as follows.

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Frequency converter control

( )20,1

100000100

=

ndnmntnk

ptFQvnDkpPvs , where

( )[ ]ptankptFkp = 0035,01

10078,090 PvsPvs =

10061,080 PvsPvs =

10047,070 PvsPvs =

10037,060 PvsPvs =

10030,050 PvsPvs =

10023,040 PvsPvs =

10018,030 PvsPvs =

10015,020 PvsPvs =

Damper control

( )20,1

1000100

=

nmntnk

ptFQvnDkpPd

10099,090 PdPd =

10095,080 PdPd =

10089,070 PdPd =

10082,060 PdPd =

10073,050 PdPd =

10063,040 PdPd =

10052,030 PdPd =

10040,020 PdPd =

Single speed vane control

( )20,1

10001100

=

nmntnk

ptFQvnDkpPv

110086,0190 PvPv =

110076,0180 PvPv =

110069,0170 PvPv =

110064,0160 PvPv =

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110060,0150 PvPv =

110057,0140 PvPv =

110054,0130 PvPv =

110051,0120 PvPv =

2-speed vane control

( )20,1

10002100

=

nmntnk

ptFQvnDkpPv

210086,0290 PvPv =

210076,0280 PvPv =

210069,0270 PvPv =

--- speed change ---

210048,0270 PvPv =

210040,0260 PvPv =

210036,0250 PvPv =

210032,0240 PvPv =

210029,0230 PvPv =

210028,0220 PvPv =

Pitch control

( )20,1

1000100

=

nmntnk

ptFQvnDkpPp

10079,090 PpPp =

10062,080 PpPp =

10050,070 PpPp =

10040,060 PpPp =

10032,050 PpPp =

10026,040 PpPp =

10021,030 PpPp =

10020,020 PpPp =

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