compressed air factsheet final

8/4/2019 Compressed Air FactSheet FINAL

1/3www.efficiencyvermont.com 888-921-5990

C O M P R E S S E D A I R S Y S T E M S | F A C T S H E E T

GETTING THE MOST OUT OF YOURCOMPRESSED AIR SYSTEM

Air compressors can account for 10% ofelectricity use in the average industrial facility.Often, a significant amount of energy is wasteddue to undetected air leaks, inappropriate uses,poor control, and inefficient equipment. This can

add up to thousands of dollars in unnecessaryenergy costs per year.

Fortunately, opportunities for savings exist inalmost every compressed air system. In addition tosaving energy and reducing energy costs, a properlyworking, efficient compressed air system can:

improve the quality of the manufacturingprocess, resulting in better quality control;

reduce noise in the plant due to less leakingair in an open blow; and

improve overall system reliability by reducing oreliminating the need for a secondary compressorthrough enhanced performance and improvedair usage.

This fact sheet includes an overview of typicalcompressed air systems, and provides detailedinformation to help you and your compressedair vendor identify energy-saving actions you cantake now, whether youre addressing individualproblems or youre ready to invest in a full-systemupgrade.

TYPES OF COMPRESSOR SYSTEMS

Variable Frequency Drive (VFD) Compressors speed up andslow down in response to load. For a compressed air load thatvaries throughout the day, which describes most loads, a VFDcompressor is typically the best choice for efficiency. However,a VFD compressor is not a good choice for a constant load that

is over 90% of the capacity of the compressor, because the VFDnever gets the opportunity to slow down the compressor,making the VFDand the additional energy it usesunnecessary.

Load/No-Load Compressors are usually screw type, but canalso use rotary vanes. They run continuously, loading andunloading the airend to produce compressed air, or not,in response to changes in plant pressure. Unloading thecompressor saves energy when no air is needed, but theunloading process results in compressed air loss. To minimizeshort cycling, couple the compressor with a large tank.Load/no-load compressors are only efficient if combinedwith a large enough tank.

Multi-Compressor Systems. Load/no-load compressors canbe coupled with VFD compressors. While the load/no-loadcompressor runs continuously as the base load compressor,the VFD unit acts as the trim compressor by speeding up andslowing down. Care must be taken in setting up the controlsso that the compressors do not work against each other.

On/Off Reciprocating Compressors, most common in smallersizes up to 10 or 20 HP, turn on and off in response to pressurein the storage tank. This type of compressor is very efficient.

Modulating Compressors run continuously and modulate

air output in response to load, controlling the incoming airto the compressor by opening or closing a valve. This typeof compressor is often the least expensive to buy, but is alsothe least efficient.

If an ideal compressorexisted, load capacityand input power wouldmatch (e.g., 50% capacity

at 50% input power.)

* Most efficient compressor

type for variable loads

below 90% capacity.

Source: The U.S. Department of Energy (DOE)

110%

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

0%0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

% Capacity (i.e., % Design CFM)

%

InputPower(i.e.,

%

DesignkW)

Input Power at Partial Loads by Compressor Type

Load/No-Load with 1 gal/CFM

Modulating with Blowdown



Variable Frequency Drive*


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C O M P R E S S E D A I R S Y S T E M S | F A C T S H E E T

1 COMPRESSORVariable frequency drive (VFD) compressors are themostefficient option for variable loads below 90%capacity, using less energy than modulatingcompressors. Reciprocating compressors oftencome mounted on a tank (as shown on bottom).

2 FILTERLow-pressure-drop filterssave energyby allowing alowerpressure set point

at thecompressors.

3 DRYERCycling refrigerated dryersrun as determinedby theairflow instead of operatingcontinuously.

4 RECEIVER/STORAGE TANKA properly-sized receiver/storagetank saves energy when coupledwith a load/no-load compressor. Italsoenables a VFD compressor toprovide more stable system pressure.

5 MAIN PLANT MANIFOLDTheplant manifold and pipingshould be properly designed andsized so as not to restrict air floworcause an excessive drop in pressure.

8 AIRHOSE & NOZZLAir-entrainingair nozzlesuseless air to do the sameamount of workas standanozzles.

7 QUICKDISCONNECTHigh-qualitydisconnectsreduceair leaks.

6 NO-LOSS DRAINSNo-loss drains throughout the system only allowcondensate toescapenot valuable compressedair.

SUPPLY-SIDE(Compressor

System)

DEMAND-SIDE(End Use)

Managing System Pressure

Pressureand CFM flowcan havean inverse relationship:Turning up the pressure results in less air flow. Ifyou areshort on air, turning upthe pressurecould be the wrongthing todo. Takeaction todetermineif youare havinga pressureor flowproblemby talking toan expert.In general, you wantto reduce yoursystem pressure aslowas possible tomaximizeair flow andsave energy.Be sure to turn down the pressure slowly overtimeonepsi per dayto make sure that a pressure-reduction doesnot cause problems in the plant. By reducing pressure, youreduce the amount of loss from leaks,therefore reducingartificial demand.

Eliminating System Leaks

Leaksin your compressed airsystemcan addup tothousands ofdollars a yearin wasted energy, so itsimportant tocheck your system regularlyto identifyandfixleaks as quickly aspossible. Leaks can be estimated bymeasuringcompressedair flowor compressor powerduringtimeswhen no compressed air is beingused in theplant, such as on nights or weekends.Al ternatively, aprofessional auditor can conduct a leakaudit, typically byusingan ultrasonic listening device, to identify andtagleaks, and providean estimateof the volumeandvalueof the escaping air. A leak auditcanusuallybecompletedin a dayor two.

Conducting System AuditsA system audittakes a comprehensive look at thecompressedair systemboth the supplyside and thedemand sideto identify if inefficiencies exist. Thisapproach requires an experiencedauditor to meterthecompressorsfor a week or more, andto conduct extensiveanalyses and calculations to determine the magnitude ofthe costs andsavings of proposed improvement projects.Theresult?A written report that will help you prioritizeopportunitiesbased on savings,simple payback,investmentrate-of-return, and any other business goalsor metrics yourequest.

Identifying and fixing leakssaves valuablecompressed air, and saves you energyandmoney.

Your compressedair system might also haother,larger savings opportunities beyondleaks. To finda compressed air contractorconsultant, or vendor nearyou, visitthe online Business Marketplace atwww.efficiencyvermont.com.

For additional information, call

Efficiency Vermont toll-free at888-921-5990.

A TYPICAL COMPRESSED AIR SYSTEM


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www.efficiencyvermont.com 888-921-5990

WHEN ITS TIME TO REPLACEOR UPGRADE YOUR EQUIPMENT

Rebates are available through Efficiency Vermont forpurchasing select energy-efficient compressed air systemequipment that is installed in your facility.

Visit the Business Rebate Center to download a rebateform or the Business Marketplace to find a compressed air

contractor, consultant, or vendor near you; both online atwww.efficiencyvermont.com.

To obtain information on additional custom incentives,low-cost financing, or other approaches that may beavailable to you, contact Efficiency Vermont toll-free at888-921-5990.

SAVINGS OPPORTUNITIES

The most cost-effective approach to reducing compressed air energy use is to optimize your entire system;both the supply side (compressor system) and the demand side (end use). Below, youll see typical ways thatenergy savings can be achieved.

SUPPLY-SIDE SAVINGS

Heat Recovery: Approximately 80%

of the energy used by a compressorturns into heat, which can be recoveredand used to warm a building. This can save heating fuel.

Pressure Drops: Its a common misconception thatturning up the pressure at the compressor will meanmore airflow and fewer problems in distributionpiping. In fact, the higher the pressure the fewercubic-feet-per-minute (CFM) the compressor canproduce. If pressure drops and flow chokepoints occur,identify and fix their causes rather than increasingpressure or using a bigger compressor. Minimize sharp

bends and elbows in distribution piping, use aclosed-loop header layout, install distribution piping ofa sufficient diameter, and maintain filters regularly.A low-pressure-drop filter saves energy by allowing alower pressure set point at the compressor.

Compressor Control: Proper control of multiplecompressors on the same system is critical for efficientoperation. This can be achieved with a single set ofcontrols for all compressors or with individualcompressor controls that are carefully set to maintainsystem-wide pressure without excess compressor cycling.

Compressor Operation: For a load that variesthroughout the day, VFD compressors use less energythan modulating compressors.

Cycling Refrigerated Dryers: Cycling refrigerated dryersturn on and off in response to demand rather thanoperating continuously, making them more efficientthan standard refrigerated dryers.

Desiccant Dryers: If extremely dry air is required forend use, a desiccant dryer may be needed. However, adesiccant dryer uses more energy than a refrigerateddryer and often consumes so much air that it becomes asignificant air load on the system. Be sure to choose themost efficient dryer that fits your needs.

Storage: Reduce demand spikes by installing additionalreceivers/storage tanks close to high-volume/short-durationpoints of use. A properly sized receiver/storage tank of fouror five gallons per CFM of air flow saves energy whencoupled with a load/no-load compressor. It also enables aVFD compressor to provide more stable pressure.

No-Loss Drains: No-loss drains allow only condensateto escapenot valuable compressed airby onlyopening a valve when signaled by the condensate levelcontrol. Timed drains waste air by operating for a fixed

time, even when there is no condensate to drain.

DEMAND-SIDE SAVINGS

Leak Detection/Correction: Air

leaks can significantly increase theenergy demands of a compressed air systemand can be extremely costly. Put a regular leak-detectionand fixing program into place. Listen for leaks when thefacility is quiet, such as during off hours, or considerpurchasing and using an ultrasonic leak detector.

Regulated Use: When compressed air runs continuouslyeven when it is not requiredenergy and money arewasted. Turn compressed air on and off as needed tocomplete a task or use a solenoid valve to shut air downautomatically when not needed.

Appropriate Use: Using compressed air when a task canbe accomplished by other meanssuch as a broom, avacuum pump, an electric motor, or a bloweradds upto higher electricity costs. Using compressed air to coola bearing or an electric panel, for instance, is not cost-effective; identify and fix the underlying problem instead.

Quality Disconnects: Reduce pressure drops and air leaksby using long-lasting, high-quality disconnects made ofhardened steel or plated brass with six or more ball bearing

Air Nozzles: Standard handheld and fixed air nozzles usecompressed air to clean or dry things. In comparison,

air-entraining air nozzles use less compressed air bygrabbing or entraining atmospheric air to do the sameamount of work.

compressed air factsheet final

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