energy auditing techniques for small commercial facilities energy auditing techniques for small...

Energy Auditing Techniques for Small Commercial Facilities

Sean Harleman, kW Engineering

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HVAC Systems

Learning Objectives• Recognize common system types and controls• Understand economizers and outside air• Gather useful nameplate data• Provide recommendations for replacements• Do some simple energy savings calculations

Energy Auditing Techniques

Energy Auditor Role and ActivitiesBasic• Inspect HVAC equipment• Record nameplate information• Review equipment operating schedules and controls• Develop a list of energy efficiency measures (EEMs)• Present EEMs, savings, incentives, and costs to the client

Advanced• Above items plus:• Log existing power use (status, amps, or kW)• Log economizer operation (OAT, MAT, etc.)



HVAC Fundamentals• Heating

– Offset heat that is lost to the environment– Temper ventilation air

• Ventilating– Provide fresh air to building occupants

• Air Conditioning (or Cooling)– Offset heat that gained from the environment– Offset heat generated internally– Control interior moisture (Relative Humidity)– Temper ventilation air


Why is HVAC Important?

California Commercial End Use Survey, Itron, CEC-400-2006-005.

CA Commercial Sector Electricity Use


Primary Purposes of HVAC1. Comfort for occupants (ASHRAE 55)

– Temperature– Humidity– Air movement

2. Fresh air (ASHRAE 62.1 & T24)– We need about 15 cfm per person (occupancy)– Remove dust, pollutants, contaminants

& “bio-effluents”


Heat Sources, Sinks & Paths• Envelope

– Solar– Conduction

• Ventilation Air– Required for IAQ

• Internal Loads– Lighting– Computers– Equipment– People


What is a HVAC Zone?• A discreet physical area

that is conditioned by an HVAC system

• Heat enters/leaves a zone through Conduction, Convection and Radiation

• Borders on zones are not always clear, obvious, or tangible

• Distinct zones in HVAC system marked by separate thermostats

ReturnAir

HOTCOLD

ExhaustAir

OutsideAir


Single Zone HVAC SystemReturn

Air

HOTCOLD

ExhaustAir

OutsideAir

T


Primary Cooling Technologies• Mechanical Cooling

– Unitary equipment uses a direct expansion (DX) cooling coil

• accounts for ≈ 67% of all commercial and ≈ 90% of all small commercial

• this will be our focus today

– Chilled water systems used in large buildings

en.wikipedia.org


Unitary HVAC Equipment• Unitary refers to equipment where components are

matched and rated together. These components include a compressor, condenser, evaporator and fan.

• Unitary equipment has two main classes: Packaged and Split-System– Packaged equipment houses all components in the same

enclosure– Split-Systems have the compressor & condenser in one

enclosure and the evaporator and fan in another, connected by refrigeration tubing

• Units can be cooling only or cooling with heating• All units circulate air, most provide ventilation


Unitary Equipment Identification• Packaged Unit

– All components contained in one location– Ventilation is introduced through the unit– Heating is supplied by a gas furnace, heat pump,

electric resistance or a hot water coil

http://www.carrier.com


Packaged Unit Components

Compressor

Heating Coils

Economizer

Filter

TControls

OA

Supply Fan

Cooling Coils

EA

SA

RACondenser

Fan and Coils

Thermostat

Packaged Unit Building


Packaged With Horizontal Discharge



Packaged With Vertical Discharge




Unitary Equipment Identification• Split-System

– Compressor Component Only– No Ventilation provided by unit– Only heating is heat pump

http://air-condition-units.com


Split-System

www.carrier.com


Split-System Examples

www.geo4va.vt.edu/A3/A3.htm


Split-System Examples

www.letricharddoit.com/products.htm

www.amvair.com/typesofac.html


Unclear on the concept


Primary Cooling Technologies• Mechanical cooling (e.g. DX) energy use can be

reduced through the use of economizers and evaporative cooling

• HVAC equipment is sized for design day loads, but operates the majority of the time under part load (~30-50% average is typical)


Economizers• The economizer cycle refers to using controls and

dampers to make use of outside air for “free” cooling when it makes sense

• Controls used to bring in outside air instead of return air

• An “economizer” is generally not a single piece of equipment, although people may refer to it as such

ReturnAir

HOTCOLD

ExhaustAir

OutsideAir


Economizer Offsetting All Cooling

Return Air10,000 CFM, 75 deg FExhaust Air

8,000 CFM

2,000 CFM

Outside Air8,000 CFM,

50 deg F

Mixed Air10,000 CFM,

55 deg F

Discharge Air10,000 CFM,

55 deg F

CoolingCoil

HeatingCoil


Reduced Mechanical Cooling

Return Air10,000 CFM, 75 deg FExhaust Air

10,000 CFM

0 CFM

Outside Air10,000 CFM,

60 deg F

Mixed Air10,000 CFM,

60 deg F

Discharge Air10,000 CFM,

55 deg F

CoolingCoil

HeatingCoil


Air Side Economizer• Easy to show it’s not working, harder to show that it is

working• Spot checks not conclusive; must trend data over time

– Is the economizer bringing in 100% outside air when appropriate?

– Is the system always providing minimum ventilation air?


Economizer Expected Performance

Expected Economizer Operation

Time

Tem

pe

ratu

re

40

45

50

55

60

65

70

75

80

1 2 3 4 5 6 7 8 9

10 11 12

13

14

15

16

17

18

19

20

21

22

23

24

Outside Air Temperature

Return Air Temperature

Mixed Air Temperature

Supply Air Temperature

Mixed return and outside air

100% Outside air

Minimum outside air

Noon Midnight


Economizer Expected PerformanceAverage Compressor Loading

Coastal

Inland

Desert

Inland Valley

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Climate

Per

cen

t L

oad

ed

Economizer No Economizer

• Data taken from a study in Southern California

• Building type is Small Office

• Percent Loaded is calculated as Compressor Run Hours / by Total Cooling Hours


Economizers: Implementation• Assess economizer operation by observing damper

positions for various ambient conditions• Use temperature data loggers to better estimate

economizer performance• Consider add-on economizer kits for existing units

with failed economizers• Check for adequate relief for outside air


Evaporative Cooling• Cools air via evaporation of

water• Direct evaporative coolers draw

air through evaporative media lowering the temperature and increasing humidity

• Indirect evaporative coolers use a heat exchanger to reduce the air temperature without increasing humidity; less effective

www.muntersamerica.com/


Direct Evaporative Cooling

www.wikipedia.comThis image has been (or is hereby) released into the public domain by its creator, Buster2058. This applies worldwide.

http://www.wikipedia.com/


Evaporative Cooling: Implementation• Best when high percentage of outside

air is required• Supply air temperature limited by

ambient conditions• Direct evaporative cooling is best

suited for areas where high humidity won’t cause problems

• Indirect evaporative cooling can be used when humidity needs to be controlled or mechanical cooling will also be used

www.muntersamerica.com/

Direct Evaporative Cooler


Primary Heating Technologies• Gas Furnaces are the most common source for heat in small

commercial applications– Range of efficiencies available– Forced & Induced draft

• Electric Heat Pumps provide both heating and cooling– Air source– Water Source– Ground Coupled

• Electric Resistance Heat Strips can be convenient if natural gas is limited or combustion exhaust is an issue, but Heat pumps are more energy efficient

• Hot water or Steam coils can also be used, but are generally found in larger systems or systems with many zones

highperformancehvac.com


Air Source Heat PumpUtilizes same vapor compression refrigeration cycle, only now the condenser can be used to add heat to the space


Air Source Heat Pumpoee.nrcan.gc.ca/publications/infosource/pub/

h...


Air Source Heat Pump• Use air as heat sink• Therefore:

Efficiency depends on air temperatures (minimum outside operating temperature is ~ 17 °F)

• Typically smaller systems / single zone• Best applicability: mild climates • SEERs range from 8 to 16• Title 20 Sets minimum

standards by size• Also:

– Water Source– Ground Coupled

www.fmcs.coop/.../electrical_heat/air_source.htm


Field Identification of HVAC Zones• Ask facility staff/engineer• Review as-built mechanical

drawings• Inventory the number of

thermostats and HVAC units• Observe placement of units to

thermostats • Last resort: go after hours and

observe response to changed setpoints


Unitary HVAC Nameplate• Brand/Model #• Age• Voltage/Amperage/kW• Other information:

– Rated efficiency– Heating/cooling capacity– Air flow rate– Liquid flow rate– Pressure rise– Refrigerant


It’s not always easy to get the size


Reinforcement Activity• HVAC system exercise…


Energy Efficiency Opportunities• Retrofits

– High Efficiency Units– Evaporative Cooling

• Controls– Scheduling / reduce operating

hours– Programmable thermostats– Economizer operation– Demand control ventilation

• Operations– Reduce cooling loads– Keep units maintained

www.carrier.com


High Efficiency Replacements• Package unit replacement isn’t generally cost

effective on energy savings alone• So where are the opportunities?

– Older units– Early retirement– New additions

• How do we promote it?– Comfort– Reliability– Reduced O&M Costs

www.trane.com


What to specify: Unitary AC and HP• For larger units, use

Consortium for Energy Efficiency (CEE) guidelines (www.cee1.org)

• Specify Tier 1 or 2 Efficiency level

www.trane.com

http://www.cee1.org/


What to specify: Unitary AC

© 2009 Consortium for Energy Efficiency, Inc. All rights reserved. www.cee1.org


What to specify: Heat pumps

© 2009 Consortium for Energy Efficiency, Inc. All rights reserved. www.cee1.org


Unitary HVAC: Calculations• Average Demand

– kW = (Cooling CapacitykBtu/h) / (SEER)

• Annual Energy Use– kWh/yr = (kW) * (hours per year)

Evaporative Pre-cooling

• Evaporative pre-cooling is available as add-on kit to fit many unitary systems

• Lower head pressure by pre-cooling condenser air by direct evaporation

• New units use microprocessor controls to minimize excess water

• Water off for outside air temps less than 70°F



Evaporative Pre-cooler Details


Evaporative Pre-Cooling

Dining Unit 1 Evaporative Condenser Performance

55

60

65

70

75

80

85

55 60 65 70 75 80 85 90 95 100

Temperature entering media (F)

Tem

pera

ture

exit

ing

med

ia (

F)


Evaporative Pre-cooler


Control Measures• On/off• Setbacks• Demand Control Ventilation


The Opportunity: ControlsGeneral Concepts• Controls are generally the most cost

effective of EEMs• Whatever doesn’t have controls

probably needs it• Controls reduce opportunity for

human “enhancements”• Limit hours of operation• Use to maximize system

efficiencies


Scheduling• Mechanical Time Clocks

http://www.moonlightinglls.com/


Commissioning is keyEven with simple equipment


Setbacks and Programmable Thermostats• Install Programmable

Thermostats on all units• Scroll through settings

during audit

www.white-rodgers.com


Where there’s a will…


Setback Thermostats / Scheduling• Pitfalls

– Need to be set correctly, not in “hold” mode

– Persistence: document with a system manual how things are intended to work

• Savings– Range widely depending on occupancy

and use. Typical is 5% to 50%.– Demand savings are minimal

• Non-Energy Benefits– Reduced wear on equipment

www.white-rodgers.com


Web-enabled Thermostats• Web-based now

available• About $170 to $300

each• Include ability to

monitor remotely

www.proliphixstore.com


For Classroom Control• Occupancy-based HVAC

controls e.g. Bard CS2000 Energy Monitor

• “Learns” occupancy patterns• No programming required• Can control lighting too• Outside air off when unoccupied

www.doersales.comwww.proliphixstore.com


Demand Control Ventilation (DCV)• Primary purpose of HVAC is to provide

adequate ventilation• Basic method has been to provide

sufficient ventilation for design conditions at all times

• DCV provides sufficient ventilation based on actual occupancy, rather than worst case

• Requires continuous monitoring of CO2 as proxy for occupancy


DCV: CO2 and Ventilation Rates


DCV: Implementation• All major controls companies support• Best practice is to measure outside air and indoor air CO2

concentrations• If only indoor concentrations monitored, typical outside CO2

concentration is 400 ppm• Controls typically set to introduce OA when indoor concentration

is about 500 ppm higher than outside (T-24 requires 600 or better)• DCV should be overridden when system in economizer mode• Commission to ensure ventilation rates are not compromised• Select equipment that automates building purge for overnight

buildup of contaminants ReturnAir

HOTCOLD

ExhaustAir

OutsideAir


Load Shifting for Small Commercial• “Ice Bear” makes ice at

night for use the next day• Thermal Energy Storage• Capacity = 5 tons• Storage = 30 tonhrs• Primary savings are in

cost of energy due to load shifting

• Peak kW cost savings• May have small energy

savings too, depending… www.ice-energy.com


Ice Bear Installations

www.ice-energy.com


Ice Bear Performance

www.ice-energy.com


Operations and Maintenance• Commissioning: check set points, schedules and resets• Check for controls overrides (e.g. bypassed time-clocks)• Filter changes for IAQ• Check fixed damper and minimum damper positions

• Adjust/tighten/replace belts• Lubricate rotary equipment


Operations and Maintenance (cont.)

• Clean condenser coils• Clean evaporator coils• Insulate suction lines• Check refrigerant charge• Check thermostat/sensor

calibration• Insulate/seal ductwork


O&M horrors from HVACfun.com


Small HVAC: Frequent Issues

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http://www.energy.ca.gov/pier


Reinforcement Activity• HVAC calculation system exercise…


Key Points to Remember• Economizers fail frequently and make a big difference in

CA climates• HVAC units are sized for design-day conditions, but

typically operate at 40-50% load• Calculating unitary HVAC annual energy use:

Energy (kWh/yr ) = [Capacity (kBtu/h) *hours (hr)] / SEER

• Evaporative pre-cooling can yield big savings in dry climates

• Record the entire model number from HVAC units• DCV provides savings for building with variable

occupancies

References and Resources


• PG&E http://www.pge.com/mybusiness/• Database for Energy Efficiency Resources

http://www.deeresources.com• CEC Guide to Preparing Feasibility Studies for Energy Efficiency

Projects www.energy.ca.gov/efficiency• Consortium for Energy Efficiency(guidelines for specifying EERs

& rough costs/savings) www.cee1.org• Energy Design Resources www.energydesignresources.com• Washington State University (calculators & other resources)

www.energyexperts.org

http://www.pge.com/mybusiness/

http://www.deeresources.com/

http://www.energy.ca.gov/efficiency

http://www.cee1.org/

http://www.energydesignresources.com/

http://www.energyexperts.org/

Please take a moment to fill out your Course Tracker excel sheet.


Course Tracker


What is that?1. Split - condenser

2. Packaged unit

3. Exhaust fan

4. Split - evaporator

A.

C.

B.

D.

Exhaust fan Packaged Unit

Split - evaporator Split - condenser


Model number: DPS-007-AHCY3

1. Cooling capacity:2. EER: 4. Heating type:

3. Line voltage:7.5 tonsHigh? Need more info

230 None


Appendix


VFD’s for Fans• Many systems use variable flow

air distribution• Fan power laws dictate that

power is roughly proportional to the flow rate cubed

• VFD quality/reliability have improved greatly over time

• VFD costs have dropped significantly with wider adoption

• Now required by code for many applications in new construction

www.abb.com


Why Fans with VFD’s Save Energy

This relationships between fan energy and fan flow are taken from the California Energy Commission Guide to Preparing Feasibility Studies and the 1998 Nonresidential ACM Approval Manual. Note that a typical system curve, DOE2 default, is assumed and these relationships are not applicable to all systems.

VFD

0%

20%

40%

60%

80%

100%

0% 20% 40% 60% 80% 100%

Flow

Po

we

r

A Note on IPLV• IPLV is being replaced by IEER

– Integrated Energy Efficiency Ratio (IEER)– IEER Used for unitary equipment ≥ 65 kBtu/h– AHRI is dropping use of IPLV because it did not

accurately represent efficiencies for units with multi-stage compressors

– AHRI Standard 340/360 2007 defines IEER as "a single number figure of merit expressing cooling part-load EER…”

– Incorporated by addendum into ASHRAE 90.1 2007– Not yet adopted by CEE, but soon


A Note on IPLV• Source: http://www.cee1.org/com/hecac/Prog_Guidance_IEER.pdf


DCV Savings

www.energy.ca.gov/pier PIER Buildings Program Design Guide: Commercial Buildings Breathe Right with Demand-Controlled Ventilation


DCV Savings

www.energy.ca.gov/pier PIER Buildings Program Design Guide: Commercial Buildings Breathe Right with Demand-Controlled Ventilation

Case studies show real energy savings with payback periods of 2 years or less


Water-source Heat Pumps• AKA “California Heat Pump” system• Uses water loop as heat sink• Requires supplemental heat rejection/supply• Cooling mode: rejects heat water loop• Heating mode: absorbs heat from water loop• Efficiency depends water loop temperatures• Typically mid-sized commercial systems / multiple zone• Best applicability: mild climates • Title 20 Sets minimum

standards by size

McQuay Water Source Heat Pump Design Manual, C:330-1


Water-source Heat Pump Configuration

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y W

ate

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ou

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Equipment Efficiencies• Efficiency: Ratios developed to represent equipment

ability to transfer or generate heat relative to the input energy required by that equipment

• COP - Coefficient of Performance (unit less)What you get divided by what you pay for (in same units)

• EER - Energy Efficiency Ratio (BTU/Watt-hrs)Fully loaded unit output / electrical input

• SEER - Seasonal Energy Efficiency Ratio (BTU/Watt-hrs)Average output over a range of conditions / Electrical input

• IPLV - Integrated Part Load Value (units vary)Weighted average at four part load conditions

• HSPF - Heating Seasonal Performance Factor (BTU/Watt-hrs) Similar to SEER (same units) but for Heat Pump heating

• AFUE - Annual Fuel Utilization Efficiency (%)Efficiency of gas furnaces and small boilers measured as the useful energy output divided by the input


Equipment EfficienciesEquipment Type Single Point Efficiency

Multi-Point or "Seasonal" Efficiency

Chiller kW/Ton IPLVPackaged AC COP / EER SEER / IPLV

Furnace Thermal Efficiency AFUEBoiler Combustion Efficiency AFUE (<300kBTUh)

Heat Pump COP / EER HSPF


Units• Energy

– Btu = Raises the temperature of 1 pound of water 1 degree Fahrenheit under standard conditions

– Watt-Hour = 3.413 Btu– kilowatt-hr = 1000 Watt-hours = 1 kWh– 100,000 Btu = 100 kBTU = 1 therm

• Rates (units of energy per time)– Watt = 3.413 Btu/h (Btu’s per hour)– kilowatt = 1000 Watts = 1 kW


Handy Equations• Motor Draw

– kWh = (hp)(0.746 kW/hp)(%Loaded)(hours)/Efficiency– kWh = (FLA)(Volts)(PF)(%Loaded)(hours)(Phase^½)

• Conduction– Btu/h = (U-Value)(Area in sq ft)(Toutside-Tinside)– Surface heat gain/loss due to Convection & Radiation

• Ventilation / Infiltration– Btu/h = (1.085)(CFM)(Toutside-Tinside)

• Radiation– Btu/h = Assess qualitatively


More Handy Equations• Efficiency Conversions

– kW/ton = 12 / EER– COP = EER / 3.412 – COP = 3.516 / (kW/ton)

• Heat Transfer in Water– Capacity (kBTUh) = GPM * ΔT / 2

• Power from hp– Power (kW) = 0.746 * Power (hp)

• Pump power– Water Power (hp) = (ft of head) * (GPM) / 3960– Pump Power = Water Power / [Pump eff * Motor eff]– Fan power– Fan Power (hp) = (cfm)*(SP) / [6354*ήfan* ήmotor]


Estimating Savings – Billing Data• Estimate amount of bill dedicated to air

conditioning• Estimate the average efficiency of the existing

equipment - SEER• Select new efficiency based on available

equipment• Estimate savings as:

proposed

Exist

SEER

SEEROldBillNewBill or

proposed

Exist

SEER

SEEROldBillSavings 1


Estimating Savings• Simplified Full

Load Hour Calculation

• Bin Simulation• SPC Software

– PGE.COM/SPC– Order CD

Single Zone Simulation (Constant Volume)

Fan kW

Supply Air Flow rate

(CFM)Minimum

OSAMinimum

OSA

Minimum Supply Air

Flow Design SATEst Min SAT (F)

Estimated Max Zone

Load

Supply Air 3 3,000 450 15% 100% 55 55 100%

Average Space

Temp (F)Avg RAT

(F)Balance Temp (F) Econ

Design Htg Temp (F)

Design Clg Temp (F)

72 74 60 N 32 102

EER OSA LO (F) Efficiency OSA LO (F)

Cooling 10.00 0 Heating 80% 120

Bin Mid-point Hours/yr % OSA MAT (F) SAT (F)

Heating (kBtu/yr)

Cooling (kBtu/yr)

107.5 4 15% 79 55 0 278102.5 10 15% 78 55 0 75997.5 38 15% 78 57 0 2,57692.5 74 15% 77 59 0 4,33887.5 114 15% 76 61 0 5,54682.5 163 15% 75 63 0 6,35377.5 219 15% 75 65 0 7,09372.5 263 15% 74 67 0 5,97667.5 318 15% 73 69 0 4,12562.5 436 15% 72 71 0 1,41257.5 558 15% 72 73 1,807 052.5 483 15% 71 75 6,264 047.5 330 15% 70 77 7,478 042.5 226 15% 69 79 7,310 037.5 105 15% 69 81 4,082 032.5 38 15% 68 83 1,836 027.5 8 15% 67 85 469 022.5 1 15% 66 87 49 0

TOTAL 3,388 29,295 38,456

COOLING 3,846 kWhHEATING 366 ThermsVENTILATION 10,163 kWh


Example Calculation: The Problem• Existing 5 ton air conditioner is on 24/7• Site is Sunnyvale, CA• EER is 10.0• Furnace is 80% efficient• Office environment with fan in “on” position

(i.e. not “auto”)• Propose to schedule M-F, 7 AM to 6 PM


Here’s the nameplate


Example Calculation: Scheduling RTUs

• Energy Savings from scheduling RTUs off consist primarily of two parts:

1. Reduced fan energy savings

2. Reduced ventilation loads• No simple way to take credit for transient effects


Example Calculation: Part 1 Fan Savings• Fan draw:

– 208V * (1 phase)^½ * 5.7A * (0.9 PF) = 1.07 kW

• Hours reduced:– Was 24*365 = 8760 hrs/yr– Now 11 hrs per day * 365 days * 5/7 ≈ 2868 hrs/yr– Savings: 5892 hrs/yr

• Savings = 1.07 kW * 5892 hrs = 6304 kWh• Assuming $0.15/kWh → $945.60


Example Calc: Part 2 Ventilation Savings• Use Sunnyvale bin weather data• Ventilation load

Btu/h = (1.085)(CFM)(Toutside-Tinside)

• If positive, then cooling load• If negative, then heating load• Multiply by hours in bin• Divide by equipment efficiency


Example bin method calc:Calculating decrease in ventilation loads

5 tons400 cfm/ton

2,000 cfmMin OA 15%

Outside Air Temp hrs Room T

Ventilation Cooling

Load (kBtu/h)

Ventilation Cooling

Load (kBtu)

Ventilation Heating

Load (kBtu/h)

Ventilation Heating

Load (kBtu)

97 1 72 8.0 8 0.0 092 6 72 7.0 42 0.0 0 Cooling87 18 72 5.0 90 0.0 0 709 kBtu82 75 72 3.0 225 0.0 0 EER 10.0 kBtu/kW77 172 72 2.0 344 0.0 0 71 kWh72 278 72 0.0 0 0.0 0 0.15$ /kWh67 437 72 0.0 0 2.0 874 10.64$ 62 671 72 0.0 0 3.0 2,01357 1,076 72 0.0 0 5.0 5,380 Heating52 1,229 72 0.0 0 7.0 8,603 34,883 kBtu47 976 72 0.0 0 8.0 7,808 Efficiency 80%42 562 72 0.0 0 10.0 5,620 43,604 kBtu37 262 72 0.0 0 11.0 2,882 436 therms32 116 72 0.0 0 13.0 1,508 1.00$ /therm27 13 72 0.0 0 15.0 195 436$

Total 5,892 709 34,883


Savings Summary


energy auditing techniques for small commercial facilities energy auditing techniques for small...

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energy auditor role

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