Energy Wheel Economic Analysis

INSTRUCTIONS

Input Instructions

Data InputGeneral Information

City and AltitudeThe next information is the City and Altitude. Altitude should be entered in feet above (or below) sea level.

Weather Bin Data

Return Air Conditions

Equipment Efficiency

Costs

Interest rate and inflation rate are both entered as percent. Use "10", to enter 10%.

©2001 McQuay International - www.mcquay.com

This workbook is set up for help analyze the life cycle difference between a heat pipe and an enthalpy wheel device, as well as the difference between an enthalpy wheel and no heat recovery device. If you have any questions about the operation of this sheet, please contact the Applications Group.

Enter the Date, Customer Name, Job Name, Rep Firm and Salesperson on the input page. This information will carry forward to all other pages.

Next the weather bin data is required. If you do not have your bin data, you may purchase it from ASHRAE, or contact Carol Marriott in the Applications Group ([email protected]).

If you do know your weather bin data, then in the weather data section, you will need to enter the average dry bulb and coincident wet bulb for each of the given temperature ranges. You will also need the number of occurrences (in number of hours) at these temperatures. These may change depending on the occupied hours that you wish to perform the analysis for. For a building operating 24 hours a day, 365 days a year, this column would total 8760 occurrences.

Next you must enter the Return Air Conditions. These are the space conditions during the summer and winter. If humidification is not required in the analysis enter "0" under relative humidity.

Next the average efficiency of each product must be entered. Enthalpy Wheel, Heat Pipe, and Boiler Efficiency are all entered as percent. Enter 50% efficiency as "50". Cooling Plant Efficiency is entered in kW/Ton and should make allowance for ancillary devices such as cooling tower fans, pumps, etc.. Pressure drop across the Enthalpy Wheel and Heat Pipe are both entered in inches of water. Purge Factor is also entered as a percent. To omit the purge, enter "0".

Electricity and Gas Rates are entered according to the units as they may be purchased. Electricity is shown as a blended rate; this means that the price of demand is already calculated into the electricity price.

Next the capital or first costs are entered for the Enthalpy Wheel, the Heat Pipe and the Heat Recovery Unit. Since one of the sheets compares an Enthalpy Wheel to a Heat Pipe, all costs associated with heat recovery (such as fan size, duct work etc.) are the same in each unit, this input cell requires the price of the wheel and the pipe only. However the Heat Recovery Cost is the additional capital cost of installing a heat recovery unit compared to not installing one. This number is used in the comparison sheet which compares no recovery to an enthalpy wheel, thus the entire cost of heat recovery with an enthalpy wheel is required for this input cell.

INSTRUCTIONS

Output Instructions

Savings/Costs

Payback Analysis

Simple Payback

Present Value

Internal Rate of Return or IRR


Costs are presented in negative values, where as savings are in positive numbers. The program will automatically calculate whether there are savings or costs in Heating, Cooling and Humidification, and will show you the values. A total annual savings is also calculated.

Savings are the amount of money saved by using an enthalpy wheel over a heat pipe during the heating or cooling season. Heating and cooling are defined by comparing the outdoor air enthalpy to the return air enthalpy. By comparing enthalpy, we are able to take into account any humidification load required.

Simple Payback is defined as the number of years required to pay off the increased capital cost. For instance if an enthalpy wheel is more expensive than a heat pipe, yet it saves a certain amount of money every year in operating costs, then simple pay back is the amount of time required (in years) to get back the initial higher cost of the investment.

Present Value takes the annual savings and gives it a value in today's dollars. For example, if you were to spend an extra $20,000 to buy an enthalpy wheel over a heat pipe and the savings were $2000, every year for the next 20 years, and the interest rate at the bank was set at 8%, then the present value of that savings is $19,636. Since we would be paying an extra $20,000 for the wheel and getting $19,636 worth of savings out of it, one would conclude that it would not be a good investment. However with a savings of $3,000 annually the present value is $29,454 and one would conclude that it would be a wise investment.

Internal Rate of Return or IRR is the interest rate that one would have to invest their money at in order to generate the same revenue as the total savings does. For instance if the additional capital cost is $20,000, and the savings are $2000 annually, one would have to invest that $20,000 at a rate of 9.6% in order to generate that same amount of revenue. By looking at the current interest rate, one could determine if it is better to put the money in the bank, or to buy an enthalpy wheel. However if the additional capital cost is $20,000 and the savings are $10,000 annually, then one would have to invest that $20,000 at an interest rate of 52% to generate the same amount of revenue. Most banks do not offer this sort of interest rate on a regular basis.

The information in this document represents information available to McQuay International at the time of publication. McQuay makes no representations or warranties that any particular result or performance will be obtained from the equipment other than as set out in the written limited warranty applicable to a specific unit, or that the equipment will be fit and sufficient for any particular purpose. Suitability of the application and installation of the equipment and system must be determined by the system engineer.

Input Conditions

Date: April 30, 2001Customer: Enter Customer NameJob Name: Enter Job NameRep Firm: Your Rep Firm HereSalesperson: Your Initials Here

Weather Information

City ChicagoAltitude (ft) 673

00001 97.5 72.7

47 92.5 74.8114 87.5 71.4297 82.5 68.5412 77.5 65.6379 72.5 63.0244 67.5 59.0310 62.5 54.4225 57.5 50.5241 52.5 45.8235 47.5 41.4207 42.5 37.7383 37.5 33.7363 32.5 29.3236 27.5 24.7120 22.5 20.188 17.5 15.551 12.5 10.329 7.5 5.517 2.5 0.89 -2.5 -3.87 -7.5 -8.4000000

Temp Range DB (oF)

Number of Occurances

(hr)

OA Average DB (oF)

OA Average WB (oF)

115-120 oF110-115 oF105-110 oF100-105 oF95-100 oF90-95 oF85-90 oF80-85 oF75-80 oF70-75 oF65-70 oF60-65 oF55-60 oF50-55 oF45-50 oF40-45 oF35-40 oF30-35 oF25-30 oF20-25 oF15-20 oF10-15 oF5-10 oF0-5 oF-5-0 oF

-10-(-5) oF-15-(-10) oF-20-(-15) oF-25-(-20) oF-30-(-25) oF-35-(-30) oF-40-(-35) oF

Input Conditions

Return Air Conditions

75Summer Return Air Relative Humidity (%) 50

72Winter Return Air Relative Humidity (%) 30

Supply Air CFM 14,000 Return Air CFM 11,750

Efficiency

Enthalpy Wheel Efficiency (%) 70Heat Pipe Efficiency (%) 70Boiler Efficiency (%) 80Cooling Plant Efficiency (kW/Ton) 1.10

APD Across Enthalpy Wheel (inches H2O) 0.80APD Across Heat Pipe (inches H2O) 0.60

Purge Factor (%) 5.00

Electricity & Natural Gas Rates

Blended Electricity Rate ($/kWh) 0.10Natural Gas Rate ($/therm) 0.50

Costs

Enthalpy Wheel Capital Cost ($) 14,000 Heat Pipe Capital Cost ($) 12,000 Heat Recovery Unit Cost ($) 30,000

Interest Rate (%) 5 Inflation Rate (%) 2


Summer Return Air Dry Bulb (oF)

Winter Return Air Dry Bulb (oF)

TOTAL VS SENSIBLE ENERGY RECOVERY ANALYSIS


Weather InformationCity ChicagoAltitude (ft) 673Total Operating Hours 4,015

Operating Air Conditions75

Summer Return Air Relative Humidity (%) 50

72Winter Return Air Relative Humidity (%) 30Outdoor Air CFM 14,000 Return Air CFM 11,750

EfficiencyEnthalpy Wheel Efficiency (%) 70Heat Pipe Efficiency (%) 70Boiler Efficiency (%) 80Cooling Plant Efficiency (kW/Ton) 1.1APD Across Enthalpy Wheel (inches H2O) 0.80APD Across Heat Pipe (inches H2O) 0.60Purge Factor (%) 5.00

Electricity & Natural Gas RatesBlended Electricity Rate ($/kWh) 0.10Natural Gas Rate ($/therm) 0.50

Savings Of Enthalpy Wheel Over Heat PipeWheel Capital Cost ($) (14,000)Heat Pipe Capital Cost ($) (12,000)Heating Savings ($) 131 Cooling Savings ($) 801 Humidification Savings ($) 5,053 Miscellaneous Cost ($) (445)

Total Annual Savings ($) 5,541

Payback AnalysisSimple Payback (Years) 0.36 Present Value $69,050 Internal Rate of Return (IRR) 279.0%




ENERGY RECOVERY ANALYSIS


Weather InformationCity ChicagoAltitude (ft) 673Total Operating Hours 4,015

Operating Air Conditions75

Summer Return Air Relative Humidity (%) 50

72Winter Return Air Relative Humidity (%) 30Outdoor Air CFM 14,000 Return Air CFM 11,750

EfficiencyEnthalpy Wheel Efficiency (%) 70Boiler Efficiency (%) 80Cooling Plant Efficiency (kW/Ton) 1.1APD Across Enthalpy Wheel (inches H2O) 0.80Purge Factor (%) 5.00

Electricity & Natural Gas RatesBlended Electricity Rate ($/kWh) 0.10Natural Gas Rate ($/therm) 0.50

Savings Of Enthalpy Wheel Over No Heat RecoveryHeat Recovery Capital Cost ($) (30,000)Heating Savings ($) 4,458 Cooling Savings ($) 1,254 Humidification Savings ($) 5,053 Miscellaneous Cost ($) (1,485)

Total Annual Savings ($) 9,279

Payback AnalysisSimple Payback (Years) 3.23 Present Value $62,975 Internal Rate of Return (IRR) 32.8%




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