Compressed Air Systems Scott Wetteland, CEM, DNV GL July 2018 1
Free technology Smart networked thermostats Free equipment and installation Centralized management of heating and cooling equipment Monitor & control from a centralized web portal Typical 10% heating and cooling energy savings Must participate in limited number of community energy events
Participation requirements Must participate in 15 community energy events or 75% of all events, whichever is less At least 75% of devices have to participate to get credit for event Events are two hours and held 1 p.m.-7 p.m. (typically 3 p.m.-5 p.m.) South: 1 June September 30; North: 1 July September 30 No events the day before or on holidays 2 event max per week Facility cannot have an energy management system Prefer five or more thermostats
SolarGenerations 4
SolarGenerations incentives Expected Performance- Based Buydown Performance-Based Incentive Up to 25 kw size 25 kw 500 kw size Public, Low Income, Non-profit $490 per kilowatt $0.0527 per kwh Residential, Commercial, Industrial $245 per kilowatt $0.0264 per kwh 5
SolarGenerations offering Continuously open Eligible for system size up to 500 kw Incentives are paid up front for small systems (EPBB) and over time for larger systems (PBI) 6
Instructor Scott Wetteland Senior Energy Consultant, CEM, DNV GL Compressed air and process systems auditor for 20 years Specialized in design, manufacturing and processing Performed compressed air energy audits for a diverse group of companies and manufacturers Performed design/build contracts including performance guarantee Perform direct installation audits for end users
Today s agenda Fundamentals of compressed air Types of compressors and controls Types of air treatment (dryers and filtration) Compressed air system management Identifying energy efficiency opportunities Solutions NV Energy offerings and incentives Q & A
Fundamentals of Compressed Air
Compressed air it s not rocket science 10
Total life cycle costs of an air compressor 11
Cut waste, generate results Consider system and component improvements With a 10-30% realistic energy savings Reduce downtime and maintenance costs Increase production with less rejects Improve compressed air quality Improve product quality 12
Variety of applications Used in 70% of manufacturing facilities Blowing Clamping Conveying Injection molding Mixing Packing Stamping Apparel Automotive Chemicals Food Metal Plastics Textiles 13
Compressed air definitions SCFM = Standard Cubic Feet per Minute defined mass air flow rate ACFM = Actual Cubic Feet per Minute the actual volumetric air flow Inlet Pressure = The actual pressure at the inlet flange of the compressor PSIA = Pounds per Square Inch Absolute PSIG= Pounds Per Square Inch Gauge Pressure Dew Point = For a given pressure, the temperature at which water will begin to condense out of air
Types of Compressors and Controls
Types of air compressors 16 http://www.nrcan.gc.ca/energy/products/reference/14968
Single acting, reciprocating compressor 17 http://nuclearpowertraining.tpub.com/h1018v2/css/h1018v2_85.htm
Double acting, reciprocating compressor 18 http://nuclearpowertraining.tpub.com/h1018v2/css/h1018v2_85.htm
Single stage, oil flooded rotary screw compressor 19 http://www.gellertco.com/oil-free-nirvana/ http://www.aircompressorworks.com/blog/index.php?mode=post&id=20
Single stage, oil flooded rotary screw compressor 20
Two stage, oil flooded rotary screw compressor 21
Two stage, oil flooded rotary screw compressor 22
Two stage, oil free rotary screw compressor 23 http://www.gellertco.com/oil-free-nirvana/ http://www.aircompressorworks.com/blog/index.php?mode=post&id=20
Two stage, oil free rotary screw compressor 24
Single stage, oil less rotary scroll compressor 25
Single stage, oil less rotary scroll compressor 26
Three stage centrifugal compressor 27
Three stage centrifugal compressor 28
Compressor controls types Start/Stop Turns the motor driving the compressor on or off in response to a pressure signal Load/Unload Allows the motor to run continuously, but unloads the compressor when a predetermined pressure is reached Modulation Restricts inlet air to the compressor, which reduces compressor output 29 http://www.nrcan.gc.ca/energy/products/reference/14970
Compressor controls types Dual/Auto Dual Allows selection of either start/stop or load/unload On rotary screw compressors will stop compressor after running unloaded for a set time Variable Displacement Allows progressive reduction of the compressor s displacement without reducing inlet pressure (recip multi step or pockets) (rotary turn valve, slide valve, lift valve) Variable Speed Adjusts the compressor capacity by varying the speed of the electric motor 30 http://www.nrcan.gc.ca/energy/products/reference/14970
Compressor controls types VFD Variable Capacity 31
Replacing load/unload compressor with a VSD compressor Example 32
Replacing load/unload compressor with a VSD compressor Example A 100 HP L/UL compressor rated at 75 kw and unloaded power 20 kw On an average the compressed air demand is 60% of its full load capacity Annual operating hours 5,000/yr (4,000 hrs loaded and 1000 hrs unloaded) EC L/UL = (75 x 4,000)+(20 x 1,000) = 375,000 kwh/yr EC VSD = 75 x 0.50 x 5000 = 187,500 kwh/yr Annual ES = 375,000-187,500 = 187,500 kwh/yr Project cost ~ $40,000 Incentive = 187,500 x 0.10 = $18,750.00 Simple payback = 2.13 yrs (w/o incentive) 33
Typical compressed air system http://www.nrcan.gc.ca/energy/products/reference/14968 34
Better compressed air system Air Intake Air Compressor 1 Aftercooler Zero Air Drain Zero Air Drain End Use Equipment Zero Air Drain Wet Receiver Air Dryer Filter Dry Receiver Pressure Control Air distribution pipes to plant Air Intake Air Compressor 2 Aftercooler Zero Air Drain End Use Equipment 35 http://www.nrcan.gc.ca/energy/products/reference/14968
Best compressed air system 36
Types of Air Treatment
Desiccant regenerative dryers http://www.goscorcompressedair.co.za/product/desiccant-dryers/
Non-cyclic refrigerated dryer
Cyclic refrigerated dryer http://www.airbestpractices.com/technology/air-treatment/n2/types-compressed-air-dryers-refrigerant-and-regenerative-desiccant
Difference between dryers Refrigerated dryers reduce the temperature of compressed air through contact with a cold medium Since cold air cannot hold as much moisture as hot air, saturated air condenses out moisture as the air temperature decreases, drying the air The resultant moisture is removed using a moisture separator within the dryer and eliminated from the dryer through the drain system Once a non-cycling dryer is powered on, the refrigeration system runs continuously regardless of demand. Most non-cycling dryers include a hot gas bypass valve to keep the dryer from freezing.
Difference between dryers A cycling dryer can store cold energy within the unit until it is needed, which offers the ability to use energy in proportion to the demand. Most non-cycling dryers include a hot gas bypass valve to keep the dryer from freezing. Desiccant dryers use porous desiccant beads to adsorb moisture from untreated air. They don t rely on a refrigeration system to cool the air. Desiccant dryers can use up to 30% of the compressed air to remove moisture Non-cycling dryers just keep running Cycling dryers cost the most but save the most energy and remove the most moisture
Quiz #1 What type of compressor dominates the compressed air industry in the 40 HP to 500 HP range? Screw compressor Why are screw compressors so common? Low purchase and operating cost What is the maintenance over time? Oil changes, filters, oil separators, compressor rebuild, etc. What is the most efficient dryer? Cyclic refrigerant dryer
Compressed Air System Management
Spotting inefficiencies Inappropriate use of compressed air Incorrect compressor type based on the application Compressed air leaks Operating compressors at higher pressure Inappropriate part-load control Inefficient air dryer system 45
Inappropriate use of compressed air To provide cooling, aspirating, agitating, mixing Blasts to move parts To clean parts or remove debris To cool electric cabinets For personal cooling Used on abandoned equipment
Compressed air leaks Can be significant waste of energy, sometimes wasting 20-30% of compressor s output Cause a drop in system pressure, which can make air tools function less efficiently, adversely affecting production Forces equipment to cycle more frequently
Find, fix air leaks* Leaks reduce output Continuous drain on power Leakage rate increases exponentially with diameter *Compressed Air System Leaks Compressed Air System Fact Sheets 48
Identifying Energy Efficiency Opportunities
Replace air tools with electric Air power motors use 25 cfm/hp, 7 times more electricity than electric motor Higher maintenance cost increases with air motor Impact on air driven tools due to moisture Choose high-efficiency electric motor 50
Replace air tools with electric Air motors use 7 x more electricity than electrical motors* Example Replace 100 x 1 HP air pumps with electric pumps Cost savings = 100 HP/0.9x6/7x0.75 kw/hp x 6,000 hr/yr x $0.10/kWh = $43,000/yr A 15-HP electric pump can do the job replacing a 100-HP air compressor * Improving Compressed Air Energy Efficiency in Automotive Plants Nasr Alkadi, Kelly Kissock
Small changes, big savings Small reduction in pressure has a big impact on efficiency 1% reduction in power per 2 psi pressure reduction Example: Reducing pressure setting from 110 psig to 100 psig on fully loaded compressor operating 6,000 hr/yr saves $2,600 a year 52
Switch desiccant to refrigerated dryer Air Intake Air Compressor 1 Aftercooler Zero Air Drain Zero Air Drain End Use Equipment Zero Air Drain Wet Receiver Air Dryer Filter Dry Receiver Pressure Control Air distribution pipes to plant Air Intake Air Compressor 2 Aftercooler Zero Air Drain End Use Equipment 53 http://www.elliott-scott.com/h000212.htm
Use refrigerated rather than desiccant dryer
Other measures? Smart air compressor controls Savings varies from 20-60% Re-use waste heat generated by the compressor in a suitable application Space heating Pre-heating boiler feed water Pre-heating process water Water heating in laundries Use storage tank of 4-5 gal/cfm when coupled with a load/no-load compressor 55
Benefits Great energy, cost savings potential Reduce downtime Eliminate maintenance crises Increase competitive advantage 56
Quiz #2 What parameters change when air is compressed? Pressure and temperature Which of the compressors is used to supply large quantities of air for a medium to high pressure range? Centrifugal
Solutions
Identifying opportunities for improvement Review your compressor control strategies Check the dryer capacity Check compressor system s operating schedule Check pressure at unit vs. on the floor Air leakage Moisture issues CFM versus kwh
Check pressure Check the system pressure against plant required pressure http://universalmasterproducts.com/products/the-endocube/installation/
Air audits Performing air audits Reviewing compressed air end use in the plant
Simultaneous flow and power measurement http://www.onsetcomp.com/files/aircompressormonitoring-wp.pdf
Short and long metering intervals http://www.onsetcomp.com/files/aircompressormonitoring-wp.pdf
NV Energy success story 1 Injection molding facility upgraded their existing compressed air system consisting of a 75 HP air compressor to a 75 HP VFD Piping was modified as needed Existing system averaged 47 kw New system averaged 30 kw Results: More than 100,000 kwh savings/year $10,000/year in electrical cost savings $6,000 NV Energy incentive Project cost = $45,000 Simple payback = 4 years
NV Energy success story 2 ACH Foam upgraded their existing compressed air system consisting of a 20 HP, 50 HP and 75 HP air compressor to a single 125 HP VFD The existing piping and flow control valve were also replaced and modified
NV Energy success story 2 The existing system averaged 93 kw and the new system averaged 32 kw The retrofit resulted in more than 500,000 kwh savings per year, $40,000 per year in electrical cost savings and an NV Energy incentive of $30,000 With a project cost of $80,000, the simple payback was 1.2 years
NV Energy Offerings and Incentives
NV Energy air compressor incentives <50 HP air compressors are eligible for $45/HP when upgrading to a VFD air compressor All incentives capped at 50% of project cost and there are additional cost capping and requirements that must be met >50 HP air compressors central control automation, flow controllers, process upgrades, distribution upgrades and dryer upgrades are eligible for custom incentive $0.05 for non-on peak and $0.10 for on peak kwh savings The prescriptive incentive and first year savings will typically cover the incremental cost between a standard and VFD air compressor purchase price
Rules of thumb 3-5 gallons of storage for each actual CFM or 15 to 25 gallons per compressor HP For industrial applications (100 PSIG) ~4 to 4.5 CFM per HP The more CFM per HP the less energy used Air receiver size (The more air storage the less energy used) Modulating control = 1 gallon per CFM (very inefficient) On-line/off-line = 3 to 5 gallons per CFM Stop-Start/Variable Speed = 2 to 5 gallons per CFM
Rules of thumb Air piping size by CFM and pressure drop (the less pressure drop, the less energy used): Compressor room header---0.25 PSIG pressure drop per 100 feet of piping Main line = 0.1 PSIG pressure drop per 100 feet of piping Loop line = 0.1 PSIG pressure drop per 100 feet of piping Branch line = 0.5 PSIG pressure drop per 100 feet of piping Lowering compressor pressure settings 2 PSIG will result in a 1% energy savings Lowering compressor inlet air temperature 10 F will result in a 2% energy savings The average energy cost to operate an air compressor is approximately $0.10 per HP per hour
Rules of thumb Compressed air system leaks totaling the size of a 1/4" orifice, at 100 PSIG, running 24 hours a day will waste approximately $15,000 worth of electrical energy a year Using synthetic compressor lubricants can save you up to 9% of the energy cost of operating your compressor as compared to using a nonsynthetic lubricant Size compressed air line filters to be twice your compressor CFM flow rate This will lower your pressure drop 2-3 PSIG and save an additional 1% on electrical energy costs Elements will last twice as long and this can save on your maintenance costs
Questions 72