Compressed Air. How to Justify Projects and Achieve Significant Savings in Multiple Compressor Environments

Transcription

1 Compressed Air How to Justify Projects and Achieve Significant Savings in Multiple Compressor Environments Tom Sherman, CEM, CDSM PCX Energy Services, LLC

2 Justifying Projects KEY: Reduce/Eliminate Perceived Risk Explain true cost of compressed air Identify all energy efficiency opportunities Requires system energy audit Measure thoroughly before calculating Show savings, investment, payback and ROI Include fast and slow paybacks for Explain financing options Performance contract vs. debt financing AEP Rebates Tax incentives Grants

3 True Cost Life Cycle Cost of an air compressor Installation Maintenance Investment Energy consumption Energy cost can account for up to 90% over a ten year working life Within 12 months, the capital cost is usually exceeded by the running costs Energy consumption by far is the most significant factor in operating cost of an air compressor

4 Energy Prices

5 Gas Storage

6 True Cost Market Capacity Price Market Capacity Price 660%

7 True Cost Example: 100 HP Rotary Screw Compression efficiency 100HP x.93 x.746 kw x $.08 x 24 hrs x 6 days x 50 weeks.91 HP kwh Motor efficiency = $43,914/ year

8 Energy Reduction Opportunities Starts with an Energy Audit ASHRAE, IPMVP Repair leaks (ultrasonic scan and tag) Reduce compressed air usage Reduce compressor discharge pressure Duct intake to outside, use exhaust - heat in winter, duct outside in summer or repurpose Piping: the hidden enemy Efficiently sequence air compressors Use efficient compressor controls Optimize PM for peak efficiency

9 Quantifying Leaks R = V (P i -P f ) ( T) 14.7 R = average leakage rate (scfm) V = system volume (ft 3 ) P i -P f = initial pressure final pressure T = time interval over leakage measurement

10 Benchmark Your System s Efficiency To make an accurate determination of energy savings solutions, it is important to measure your system flow, pressure and kw as well as evaluate any plans for future expansion Should be part of Energy Audit

11 Ultrasonic Leak Detection

12 Measure kw and kwh Over Time

13 Measure Pressure and Flow Over Time

14 Daily Profile of Flow 64% SCFM time Typical 24 hrs/day operation with low night shift and high day shift consumption. Steady weekend consumption (leakages). (64% of installations).

15 Daily Profile of Flow 28% SCFM Five days/week operation, erratic demand fluctuations (28% of installations). time

16 Daily Profile of Flow 8% SCFM Five days/week operation, constant air demand. (8% of installations). time

17 % Power Input kw vs. Capacity 100 Performance Comparison Total KW Input -vs- Capacity A B C D A) Modulation A) Control B) Active Rotor Length B) Active C) Full Rotor Load / Length No LoadAdj. D) VSD C) Full Load / No Load D) VFD % Capacity

18 Energy / Power Cost Power Cost Example #1 75 HP Lubricated screw compressor w/ Modulation Control..vs. 60 HP VSD 75 HP 125 psig 60HP 125 psig 82.5 Bhp full load power 66 Bhp full load power 320 CFM 290 CFM 91.5% Motor eff. 94% Average electrical cost = $0.08 / kwh A) 1st shift 250 CFM 2200 Hrs/YR B) 2nd shift 175 CFM 2200 Hrs/YR C) 3rd shift 100 CFM 2200 Hrs/YR

19 Energy / Power Cost % OF FULL LOAD CAPACITY 75 Hp modulating 60 Hp VFD 250 CFM: 250/320 = 78% (93% Bhp) 250/290 = 86% (86% Input kw) 175 CFM: 175/320 = 55% (86.5% Bhp) 175/290 = 60% (61% Input kw) 100 CFM: 100/320 = 31% (79% Bhp) 100/290 = 34% (38% Input kw)

20 Energy / Power Cost 75 HP lubricated screw with modulation control A) First shift 250 CFM: 82.5 Bhp x.93 (comp. eff.) x.746kw x $.08 x 2200Hrs = $11, (motor eff.) Hp kwh B) Second shift 175 CFM: 82.5 Bhp x (.865) x.746kw x $.08 x 2200Hrs = $10, Hp kwh C) Third shift 100 CFM: 82.5 Bhp x (.79) x.746kw x $.08 x 2200Hrs = $9, Hp kwh Total = $30,601

21 Energy / Power Cost 60 Hp Variable Speed compressor A) First shift 250 CFM: 66 Bhp x.746 kw x.86 x $.08 x 2200Hrs = $7, Hp kwh B) Second shift 175 CFM: 66 Bhp x.746 kw x.61 x $.08 x 2200Hrs = $5, Hp kwh C) Third shift 100 CFM: 66 Bhp x.746 kw x.38 x $.08 x 2200Hrs = $3, Hp kwh Total = $17,054

22 Energy / Power Cost Total Power Savings: $30,601 - $17,054 = $13,547 annual savings

23 Reduce Compressed Air Usage Fix Leaks Leaks can account for 10-50% of the total compressed air usage! 1/8 inch dia. hole = 25 SCFM = $3,000/yr 1/4 inch dia. hole = 100 SCFM = $12,000/yr 3/8 inch dia. hole = 230 SCFM = $26,000/yr * Based on 8,760 operating $0.07 per kwh energy cost

24 Lower System Pressure to Lower Air Consumption 85 psig 825 CFM air usage 95 psig 950 CFM air usage 70 psig 700 CFM air usage

25 Reduce Compressed Air Usage Reduce system air pressure Use intermediate controllers with storage to regulate system air pressure Effective when part of the plant operates at a lower pressure Lowers air consumption Does not lower compressor pressure

26 Receiver Tank Sizing Useful Free Air Stored = V x P 14.7 Compressor output pressure = 100 psig V = storage volume (ft 3 ) P = pressure differential (Pressure Drop in Tank) Example: Pneumatic conveyor requires 200 cfm of 40 psig air for 2 minutes every 10 minutes. 200 X 2=400 CF required useful free air to be stored P= =60 400=V x 60/14.7 V=400 x 14.7/60= 98 CF =735 gallons 400 CF/8 minutes = 50 CFM to refill System sees 50 CFM instead of 200 CFM!

27 Sequence Air Compressors

28 Typical System Without a Sequencer Cascading Systems C1 C2 C3 C4 120 unload load 125 PSIG PSIG Individual settings Large pressure band Multiple units at part load Very inefficient

29 Poor efficiency of a cascaded system due to multiple units at part load kwh/100cf kwh/100cf

30 Sequencing Narrow Pressure Band SCFM VFD VFD Fixed Speed VFD VFD Fixed Speed Fixed Speed Fixed Speed VFD 24 hours

31 kwh/100cf stays consistent even under varying loads.32 kwh/100cf versus.85 kwh/100cf (63% Savings!)

32 Sequencers Can Improve Efficiency to Minimize Energy Costs Total system energy savings of 20-50% are expected

33 System Pressure remains consistent as flow rate varies

34 Sequencers Significantly Improve Efficiency to Minimize Energy Costs Can regulate system pressure within 5 psi Lower system pressure significantly reduces air demand (leaks and unregulated demand) Operates the minimum # of compressors to meet the demand Only one compressor trims at all times Automatic scheduled system pressure changes and/or start/stop of system Most efficient compressor sequence order determined from flow data Can automatically select optimum sequence

35 Sequencers pay for themselves in energy savings by reducing pressure band differentials and lowering air usage EXAMPLE: 4x100 Hp Compressors Required = 1700 SCFM at 100 Psig Pressure Switch Settings Between 95 to 125Psig Pressure Band of 30 Psig 400 Hp x kw/hp x 8760/year x 0.08 kwh = $222, (motor efficiency) Reduce Pressure Band by 25 Psig to save 12%=$26,696.00

36 Sequencing Significantly Improves Efficiency to Minimize Energy Costs Total Anual Savings! $140,000 $120,000 $100,000 Total System Horsepower % Savings Tighter Pressure Band 10% $5,621 $11,243 $22,486 $44,972 Reduced Unregulated Demand/Leaks 6% $3,373 $6,746 $13,492 $26,983 More Efficient Sequencing 20% $11,243 $22,486 $44,972 $89,944 Total Estimated Savings! 36% $20,337 $40,675 $81,349 $162,698 $162,698 $80,000 $60,000 $81,349 $40,000 $20,000 $20,337 $40,675 $ Total System Horsepower Basis 3 shift operation, $.06/kWhr, 20 PSI pressure band reduction

37 Advanced sequencers provide system flow and pressure data System flow and pressure are logged automatically Determine the most efficient compressor sequence Useful for peak load shedding Measure leaks Spot system/ production problems Measure equipment/process air consumption

38 ManagAIR by Air Technologies System Report for Ferro 9/7/01 1:59:05 PM Alarm: No Faults Detected Current System Readings- Pressure=108 Flowrate=1347 Sequence=2,1,3 Previous 8hrs Data: Hour1 Hour2 Hour3 Hour4 Hour5 Hour6 Hour7 Hour8 Min Pressure Avg Pressure Max Pressure Min FlowRate Avg FlowRate Max FlowRate Min DewPoint Avg DewPoint Max DewPoint Compressor Data #1 ZT25 #2 ZT25 #3 ZT25 NONE NONE NONE NONE Delivery Air Press DP Air Filter Intercooler Pressure Oil Injection Press Delivery Air Temp Oil Injection Temp LP Outlet Temp HP Outlet Temp HP Inlet Temp Cooling Medium Inlet Temp MD Regen Air Out Temp MD Wet Air In Temp LP Element Temp Rise HP Element Temp Rise Cooling Water Temp Rise Oil Cooler Approach Temp Aftercooler Approach Temp Intercooler Approach Temp MD Regen Temperature Drop MD Inlet Temperature Diff Loaded Hours Running Hours Compressor Status UNLOADED LOADED STOPPED Motor Starts Link Type MKIII MKIII MKIII Isolated/Integrated CENTRAL CENTRAL CENTRAL Full Feature Dew Point Oil Filter Remaining Lifetime Oil Filter Total Lifetime Oil Remaining Lifetime Oil Total Lifetime Hours Until Regrease Bearings Hours Between Bearing Regreasing Daily System Report and graph faxed or ed to you automatically

39 Justifying a Project Your Objective Reduce Mgmt Risk! Audit system using measurements and engineering analysis (ASHRAE, IPMVP) Benchmark system efficiency Identify all savings opportunities EEM s Determine expense/investment for each EEM and total project Calculate individual EEM paybacks and total project payback

40 Justifying a Project EEM Annual Savings Cost to Implement Payback (years) Repair leaks (detect, tag, repair, verify) $54,000 $2, Add/move receiver tanks to high demand areas $4,000 $12,000 3 Change pipes to aluminum and resize $11,000 $15, Add shut off solenoids at machines $4,000 $3, Eliminate unnecessary CA uses $7,000 $1, Add second CA stage to reduce psig $10,000 $15, Reduce system pressure by 12 psig $14,000 $0 Immed. Add pressure and flow meters at key points $0 $2,500 none Add master sequencing controls $28,000 $20, Upgrade 300 HP unit to VFD $40,000 $120,000 3 Total $172,000 $191,

41 Justifying a Project Now is a good time to review PM program and make improvements

42 Financing Projects Performance contract vs debt financing PC; does not require out of pocket funds PC; paid through energy savings Debt; low interest rates/favorable terms available Debt; savings can offset debt service

43 Year Energy Savings Performance Contract Operational Savings Total Savings Contract Costs Savings - Costs Cumm Cash Flow 1 8,600 1,100 9,700 6,231 3,469 3, ,045 1,170 10,215 6,231 3,984 7, ,512 1,230 10,742 6,231 4,511 11, ,103 1,345 11,448 6,231 5,217 17, ,546 1,399 11,945 6,231 5,714 22, ,121 1,486 12,607 6,231 6,376 29, ,678 1,567 13,245 6,231 7,014 36, ,345 1,654 13,999 6,231 7,768 44, ,987 1,724 14,711 6,231 8,480 52, ,876 1,833 15,709 6,231 9,478 62, ,345 1,975 16,320 6,231 10,089 72, ,332 2,122 17,454 6,231 11,223 83, ,876 2,324 19,200 6,231 12,969 96, ,998 2,546 20,544 6,231 14, , ,765 2,621 21,386 6,231 15, ,760

44 Financing Projects Utility Rebates AEP has program for compressed air Tax Incentives EPAct 2005 approved through 2013 Grants and other incentives Come and go ODOD

45 Questions? Tom Sherman