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Energy Auditing Techniques for Small Commercial Facilities Energy Auditing Techniques for Small Commercial Facilities Sean Harleman, kW Engineering.

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Presentation on theme: "Energy Auditing Techniques for Small Commercial Facilities Energy Auditing Techniques for Small Commercial Facilities Sean Harleman, kW Engineering."— Presentation transcript:

1 Energy Auditing Techniques for Small Commercial Facilities Energy Auditing Techniques for Small Commercial Facilities Sean Harleman, kW Engineering

2 HVAC Systems

3 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

4 Energy Auditor Role and Activities Basic 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.) Energy Auditing Techniques

5 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 Energy Auditing Techniques

6 Why is HVAC Important? California Commercial End Use Survey, Itron, CEC CA Commercial Sector Electricity Use Energy Auditing Techniques

7 Primary Purposes of HVAC 1.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” Energy Auditing Techniques

8 Heat Sources, Sinks & Paths Envelope –Solar –Conduction Ventilation Air –Required for IAQ Internal Loads –Lighting –Computers –Equipment –People Energy Auditing Techniques

9 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 Energy Auditing Techniques

10 Single Zone HVAC System T Energy Auditing Techniques

11 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 Energy Auditing Techniques

12 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 Energy Auditing Techniques

13 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 Energy Auditing Techniques

14 Packaged Unit Components Compressor Heating Coils Economizer Filter T Controls OA Supply Fan Cooling Coils EA SA RA Condenser Fan and Coils Thermostat Packaged UnitBuilding Energy Auditing Techniques

15 Packaged With Horizontal Discharge Energy Auditing Techniques

16 Packaged With Vertical Discharge Energy Auditing Techniques

17 Unitary Equipment Identification Split-System –Compressor Component Only –No Ventilation provided by unit –Only heating is heat pump Energy Auditing Techniques

18 Split-System Energy Auditing Techniques

19 Split-System Examples Energy Auditing Techniques

20 Split-System Examples Energy Auditing Techniques

21 Unclear on the concept Energy Auditing Techniques

22 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) Energy Auditing Techniques

23 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 Energy Auditing Techniques

24 Economizer Offsetting All Cooling Energy Auditing Techniques

25 Reduced Mechanical Cooling Energy Auditing Techniques

26 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? Energy Auditing Techniques

27 Economizer Expected Performance Expected Economizer Operation Time Temperature 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 Energy Auditing Techniques

28 Economizer Expected Performance 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 Energy Auditing Techniques

29 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 Energy Auditing Techniques

30 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 Energy Auditing Techniques

31 Direct Evaporative Cooling This image has been (or is hereby) released into the public domain by its creator, Buster2058. This applies worldwide. Energy Auditing Techniques

32 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 Direct Evaporative Cooler Energy Auditing Techniques

33 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 Energy Auditing Techniques

34 Air Source Heat Pump Utilizes same vapor compression refrigeration cycle, only now the condenser can be used to add heat to the space Energy Auditing Techniques

35 Air Source Heat Pump Energy Auditing Techniques

36 Air Source Heat Pump Energy Auditing Techniques

37 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 Energy Auditing Techniques

38 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 Energy Auditing Techniques

39 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 Energy Auditing Techniques

40 It’s not always easy to get the size Energy Auditing Techniques

41 It’s not always easy to get the size Energy Auditing Techniques

42 Reinforcement Activity HVAC system exercise… Energy Auditing Techniques

43 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 Energy Auditing Techniques

44 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 Energy Auditing Techniques

45 What to specify: Unitary AC and HP For larger units, use Consortium for Energy Efficiency (CEE) guidelines ( Specify Tier 1 or 2 Efficiency level Energy Auditing Techniques

46 What to specify: Unitary AC © 2009 Consortium for Energy Efficiency, Inc. All rights reserved. Energy Auditing Techniques

47 What to specify: Heat pumps © 2009 Consortium for Energy Efficiency, Inc. All rights reserved. Energy Auditing Techniques

48 Unitary HVAC: Calculations Average Demand –kW = (Cooling Capacity kBtu/h ) / (SEER) Annual Energy Use –kWh/yr = (kW) * (hours per year) Energy Auditing Techniques

49 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 Energy Auditing Techniques

50 Evaporative Pre-cooler Details Energy Auditing Techniques

51 Evaporative Pre-cooler Details Energy Auditing Techniques

52 Evaporative Pre-Cooling Energy Auditing Techniques

53 Evaporative Pre-cooler Energy Auditing Techniques

54 Control Measures On/off Setbacks Demand Control Ventilation Energy Auditing Techniques

55 The Opportunity: Controls General 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 Energy Auditing Techniques

56 Scheduling Mechanical Time Clocks Energy Auditing Techniques

57 Commissioning is key Even with simple equipment Energy Auditing Techniques

58 Setbacks and Programmable Thermostats Install Programmable Thermostats on all units Scroll through settings during audit Energy Auditing Techniques

59 Where there’s a will… Energy Auditing Techniques

60 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 Energy Auditing Techniques

61 Web-enabled Thermostats Web-based now available About $170 to $300 each Include ability to monitor remotely Energy Auditing Techniques

62 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 Energy Auditing Techniques

63 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 CO 2 as proxy for occupancy Energy Auditing Techniques

64 DCV: CO 2 and Ventilation Rates Energy Auditing Techniques

65 DCV: Implementation All major controls companies support Best practice is to measure outside air and indoor air CO 2 concentrations If only indoor concentrations monitored, typical outside CO 2 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 Energy Auditing Techniques

66 Load Shifting for Small Commercial “Ice Bear” makes ice at night for use the next day Thermal Energy Storage Capacity = 5 tons Storage = 30 ton  hrs Primary savings are in cost of energy due to load shifting Peak kW cost savings May have small energy savings too, depending… Energy Auditing Techniques

67 Ice Bear Installations Energy Auditing Techniques

68 Ice Bear Performance Energy Auditing Techniques

69 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 Energy Auditing Techniques

70 Operations and Maintenance (cont.) Clean condenser coils Clean evaporator coils Insulate suction lines Check refrigerant charge Check thermostat/sensor calibration Insulate/seal ductwork Energy Auditing Techniques

71 O&M horrors from Energy Auditing Techniques

72 Small HVAC: Frequent Issues PIER Buildings Program Design Guide: Big Savings on Small HVAC Systems Energy Auditing Techniques

73 Reinforcement Activity HVAC calculation system exercise… Energy Auditing Techniques

74 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 Energy Auditing Techniques

75 References and Resources Energy Auditing Techniques PG&E Database for Energy Efficiency Resources for Energy Efficiency Resources CEC Guide to Preparing Feasibility Studies for Energy Efficiency Projects Guide to Preparing Feasibility Studies for Energy Efficiency Projects Consortium for Energy Efficiency(guidelines for specifying EERs & rough costs/savings) for Energy Efficiency(guidelines for specifying EERs & rough costs/savings) Energy Design Resources Design Resources Washington State University (calculators & other resources) State University (calculators & other resources)

76 Please take a moment to fill out your Course Tracker excel sheet. Energy Auditing Techniques Course Tracker

77 Energy Auditing Techniques What is that? 1. Split - condenser 2. Packaged unit 3. Exhaust fan 4. Split - evaporator A. C. B. D. Exhaust fanPackaged Unit Split - evaporator Split - condenser

78 Energy Auditing Techniques Model number: DPS-007-AHCY3 1. Cooling capacity: 2. EER: 4. Heating type: 3. Line voltage:7.5 tons High? Need more info 230 None

79 Appendix Energy Auditing Techniques

80 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 Energy Auditing Techniques

81 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. Energy Auditing Techniques

82 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/ defines IEER as "a single number figure of merit expressing cooling part- load EER…” –Incorporated by addendum into ASHRAE –Not yet adopted by CEE, but soon Energy Auditing Techniques

83 A Note on IPLV Source: Energy Auditing Techniques

84 DCV Savings PIER Buildings Program Design Guide: Commercial Buildings Breathe Right with Demand-Controlled Ventilation Energy Auditing Techniques

85 DCV Savings 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 Energy Auditing Techniques

86 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 Energy Auditing Techniques

87 Water-source Heat Pump Configuration McQuay Water Source Heat Pump Design Manual, C:330-1 Energy Auditing Techniques

88 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 Energy Auditing Techniques

89 Equipment Efficiencies Energy Auditing Techniques

90 Units Energy –Btu = Raises the temperature of 1 pound of water 1 degree Fahrenheit under standard conditions –Watt-Hour = Btu –kilowatt-hr = 1000 Watt-hours = 1 kWh –100,000 Btu = 100 kBTU = 1 therm Rates (units of energy per time) –Watt = Btu/h (Btu’s per hour) –kilowatt = 1000 Watts = 1 kW Energy Auditing Techniques

91 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)(T outside -T inside ) –Surface heat gain/loss due to Convection & Radiation Ventilation / Infiltration –Btu/h = (1.085)(CFM)(T outside -T inside ) Radiation –Btu/h = Assess qualitatively Energy Auditing Techniques

92 More Handy Equations Efficiency Conversions –kW/ton = 12 / EER –COP = EER / –COP = / (kW/ton) Heat Transfer in Water –Capacity (kBTUh) = GPM * ΔT / 2 Power from hp –Power (kW) = * 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*ή fan * ή motor ] Energy Auditing Techniques

93 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: or Energy Auditing Techniques

94 Estimating Savings Simplified Full Load Hour Calculation Bin Simulation SPC Software –PGE.COM/SPC –Order CD Energy Auditing Techniques

95 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 Energy Auditing Techniques

96 Here’s the nameplate Energy Auditing Techniques

97 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 Energy Auditing Techniques

98 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 → $ Energy Auditing Techniques

99 Example Calc: Part 2 Ventilation Savings Use Sunnyvale bin weather data Ventilation load Btu/h = (1.085)(CFM)(T outside -T inside ) If positive, then cooling load If negative, then heating load Multiply by hours in bin Divide by equipment efficiency Energy Auditing Techniques

100 Example bin method calc: Energy Auditing Techniques

101 Savings Summary Energy Auditing Techniques

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