Compressed Air SystemsScott Wetteland, CEM, DNV GL
July 2018
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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
Free technology
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
Participation requirements
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SolarGenerations
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SolarGenerations incentives
Expected Performance- Performance-BasedBased Buydown 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
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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)
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
Instructor Scott Wetteland
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
Today’s agenda
Fundamentals of Compressed Air
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Compressed air…it’s not rocket science
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Total life cycle costs of an air compressor
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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
Used in 70% of manufacturing facilities
Blowing
Clamping
Conveying
Injection molding
Mixing
Packing
Stamping
Apparel
Automotive
Chemicals
Food
Metal
Plastics
Textiles
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Variety of applications
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
Compressed air definitions
Types of Compressors and Controls
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Types of air compressors
http://www.nrcan.gc.ca/energy/products/reference/14968
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Single acting, reciprocating compressor
http://nuclearpowertraining.tpub.com/h1018v2/css/h1018v2_85.htm
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Double acting, reciprocating compressor
http://nuclearpowertraining.tpub.com/h1018v2/css/h1018v2_85.htm
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Single stage, oil floodedrotary screw compressor
http://www.aircompressorworks.com/blog/index.pHP?mode=post&id=20http://www.gellertco.com/oil-free-nirvana/
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Single stage, oil floodedrotary screw compressor
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Two stage, oil floodedrotary screw compressor
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Two stage, oil floodedrotary screw compressor
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Two stage, oil freerotary screw compressor
http://www.aircompressorworks.com/blog/index.pHP?mode=post&id=20http://www.gellertco.com/oil-free-nirvana/
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Two stage, oil freerotary screw compressor
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Single stage, oil lessrotary scroll compressor
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Single stage, oil lessrotary scroll compressor
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Three stage centrifugal compressor
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Three stage centrifugal compressor
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Compressor controls types
http://www.nrcan.gc.ca/energy/products/reference/14970
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
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Compressor controls types
http://www.nrcan.gc.ca/energy/products/reference/14970
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
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Compressor controls types
VFD
Variable Capacity
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Replacing load/unload compressor with a VSD compressor
Example
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
Replacing load/unload compressor with a VSD compressor
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Typical compressed air system
http://www.nrcan.gc.ca/energy/products/reference/14968
Air Compressor 1
Air Compressor 2
Air Intake
Air Intake Aftercooler
Zero Air Drain
Aftercooler
Zero Air Drain
Wet Receiver
Air Dryer
Dry Receiver
Filter
Pressure Control Air
distribution pipes to
plant
End Use Equipment
End Use Equipment
Zero Air Drain
Zero Air Drain
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Better compressed air system
http://www.nrcan.gc.ca/energy/products/reference/14968
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Best compressed air system
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
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
Difference between dryers
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
Quiz #1
Compressed Air System Management
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 system45
Spotting inefficiencies
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
Inappropriate use of compressed air
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
Compressed air leaks
Leaks reduce output
Continuous drain on power
Leakage rate increases exponentially with diameter
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Find, fix air leaks*
*Compressed Air System Leaks Compressed Air System Fact Sheets
Identifying Energy Efficiency Opportunities
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
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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
Replace air tools with electric
* Improving Compressed Air Energy Efficiency in Automotive Plants Nasr Alkadi, Kelly Kissock
A 15-HP electric pump can do the job replacing a 100-HP air compressor
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
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Small changes, big savings
Air Compressor 1
Air Compressor 2
Air Intake
Air Intake Aftercooler
Zero Air Drain
Aftercooler
Zero Air Drain
Wet Receiver
Air Dryer
Dry Receiver
Filter
Pressure Control Air
distribution pipes to
plant
End Use Equipment
End Use Equipment
Zero Air Drain
Zero Air Drain
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Switch desiccant to refrigerated dryer
http://www.elliott-scott.com/h000212.htm
Use refrigerated rather than desiccant dryer
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
Other measures?
Great energy, cost savings potential
Reduce downtime
Eliminate maintenance crises
Increase competitive advantage
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Benefits
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
Quiz #2
Solutions
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
Identifying opportunities for improvement
Check the system pressure against plant required pressure
http://universalmasterproducts.com/products/the-endocube/installation/
Check pressure
Performing air audits Reviewing compressed air end use in the plant
Air audits
http://www.onsetcomp.com/files/AirCompressorMonitoring-WP.pdf
Simultaneous flow and power measurement
Short and long metering intervals
http://www.onsetcomp.com/files/AirCompressorMonitoring-WP.pdf
Injection molding facility upgraded their existing compressed air system consisting of a 75 HP air compressor to a 75 HP VFD
NV Energy success story 1
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
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 success story 2
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
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 non-synthetic 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
Rules of thumb
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Questions