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Energy Efficient Compressed Air Systems Workgroup Meeting July 2014 Abdul Qayyum “Q” Mohammed Engineer.

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Presentation on theme: "Energy Efficient Compressed Air Systems Workgroup Meeting July 2014 Abdul Qayyum “Q” Mohammed Engineer."— Presentation transcript:

1 Energy Efficient Compressed Air Systems Workgroup Meeting July 2014 Abdul Qayyum “Q” Mohammed Engineer

2 Why is this important ?  Almost all Manufacturing Facilities use Compressed Air (CA)  These are large systems  Smaller systems draw about 40 kW (50-hp) X 40

3 Expensive Resource  Compressed Air (CA) is a very expensive resource  The most expensive in many cases  About 90% of the input energy is lost through the system Energy In Work Out Only 9% ! Source: David Vanderbeek, 2011 Power Smart Forum Heat Purges And Drains Conversion

4 Why use Compressed Air ? Simple :  Its easy to use  Can be used for a wide variety of applications  All you need is a new hose for a new application  In many cases it is the economically feasible option

5 Well what’s the problem then?  Its ease of use makes it ……. …..the most misused resource

6 CA Fundamentals Before we get into energy savings opportunities lets briefly look at  Types of air compressors  Reciprocating  Screw  Centrifugal  Different control strategies for the compressors  Pros and Cons

7 Reciprocating Compressors  Simplest and oldest compressor type  Size: 1 – 600 hp

8 Recips: Part Load  Good part-load performance  Very close to ideal compressor Ideal

9 Recips: Pros and Cons Pros:  Simplest and oldest compressor type  Comparable full load efficiency  Very good part load efficiency Cons:  Higher maintenance costs compared to the new compressor types (for larger compressors)

10 Screw Compressors  Currently the most commonly used compressor in industry  Sizes 5 – 700 hp

11 Screws: Part Load  Multiple control options Combinations of controls available with each compressor Gives large scope for optimization *VFDs have lower full-load efficiency They are very efficient between 45% to 80% capacity

12 Screw: Pros and Cons Pros:  Low maintenance  Different control options work well within different systems Proper sizing is critical  Large cost range depending on Control options Other additional options (oil free, integrated dryers etc.) Cons:  Optimization is often neglected (or done poorly) which degrades system part-load performance

13 Centrifugal Compressors  Larger compressors (these are dynamic)  Sizes 125 – 6,000 hp

14 Centrifugal: Part Load Can be the most inefficient compressors at part loads Combination of controls are available Control optimization is necessary for efficiency

15 Centrifugal: Pros and Cons Pros:  Very high full-load efficiency Very good for systems that have a high base load Low maintenance if operated properly  Customizable Can be built to match client needs  Oil free Cons:  Slightly higher cost  Can be the worst at part-loads Blow-off should be minimized Dynamic nature limits turn down ratio (to avoid surge)

16 Energy Saving Opportunities  There can be endless opportunities in a system.  It can take couple of hours to go through them all.  So, Let’s just look at the BIG hitters  Inappropriate uses  Leaks  Pressure  Staging  Other opportunities  Air Drying  Storage  Filters  Heat Reclaim These are things we look for when we have limited time with the client.

17 Inappropriate Uses Questions to ask..  Is CA even necessary ? It is a VERY Expensive resource  Is there an alternative that can eliminate CA use?  Is CA being used effectively ?  Can CA use be reduced ? Pressure Timing Let’s look at some examples.

18 In-appropriate use Examples To blow off a product. Good idea? Air Saver nozzles use about 70% less CA

19 CA to cool off product. …. Good Idea? Energy Efficient Process Cooling – Dr. Kissock, University of Dayton In-appropriate use Examples 200x more expensive than cooling towers

20 Personal Cooling (We just saw cooling costs) In-appropriate use Examples Occupational Safety and Health Administration (OSHA) safety violation

21  Drains are used to remove condensate from the system But do we need to lose air? Open valve: Always loosing air. Timed Drain: Timing set for peak, often results in air loss No-loss Drain: Zero air loss In-appropriate use Examples

22 Need low pressure air (20 psig) ? => Use Blowers ! Blowers use about 5x less energy In-appropriate use Examples

23 List of Common Inappropriate Uses Blow-Off Applications Air knives Dust collector purges Cleaning with CA Personal cooling Process cooling Continuous CA Use Applications Aeration Agitation Atomization (mixing) Transport of material Air motors /hoists Diaphragm pumps Air vibrators Electrical cabinet cooling Vacuum generation Vortex coolers Air Cylinders Air Operated vacuum cleaners

24 Energy Saving Opportunities  There can be endless opportunities in a system.  It can take couple of hours to go through them all.  So, Let’s just look at the BIG hitters  In appropriate uses  Leaks  Pressure  Staging  Other opportunities  Air Drying  Storage  Filters  Heat Reclaim These are things we look for when we have limited time with the client.

25 Reduce Leaks !  Leaks are lost $$$$$ Air Power Usa

26 Leaks Example  Misconception “We do not have a large leak load..”  On average 30%* of a facility’s compressed air is lost to leaks  Example Facility *U.S. DOE, Compressed Air Fact Sheet #7 Avg. Leak Load = 50% !! In a two compressor system 100 kW in Non- production ~ 100 Homes Weekend

27 Strategy to Reduce Leaks  Strategies we have observed:  Leak reduction programs  Other Methods  Use of Isolation Valves to valve off unused areas  Reduced pressure during non production  Turning off CA system on weekends

28 Goals for Leaks  Can I have Zero Leak Load ? Unfortunately, NO  What should I aim for ? Good rule of thumb is to reduce it by 50% We have observed facilities with leak loads As high as 60% and As low as 7-10% - this was accomplished overtime by reducing leaks and isolating unused areas

29 Energy Saving Opportunities  There can be endless opportunities in a system.  It can take couple of hours to go through them all.  So, Let’s just look at the BIG hitters  In appropriate uses  Leaks  Pressure  Staging  Other opportunities  Air Drying  Storage  Filters  Heat Reclaim These are things we look for when we have limited time with the client.

30 Did we adjust pressures at end use ? Do you need line pressure ? Reduce Pressure at End Use 95 psig Unregulated tool Regulated tool 70 psig ~ 120 acfm ~ 95 acfm ~ 20% reduction ! We recently observed a large manufacturing facility with efficient compressors….. Almost all end uses were unregulated !!!

31 Reduce Pressure at Compressor  Why is a compressor used?  To pressurize the incoming air stream A compressor has to Work harder for higher Pressure Air Compressor Air P1 Air P2 Power kW Heat out

32 Reduce Pressure at Compressor  Common Misconception  “Raising the pressure increases capacity” Reality – It decreases compressor capacity and increases operating costs  Often times other issues are compensated with pressure,  Lack of storage  Improper piping

33 Reduced Pressure - Energy Savings  Rules of Thumb Compressor Efficiency Increases by 1% for every 2 psi reduction in operation pressure

34  Energy savings  Improves compressor efficiency  Reduced leak load  Reduces CA use at applications  Reduced pneumatic equipment fatigue  Increases equipment life Reduced Pressure - Benefits

35 Goals for Reducing Pressure  How low should my system pressure be? Rough rule of thumb, System Press = Min Press + 10  We have observed a large MFG facility with CA system at 75 psig. This was done overtime by addressing system constraints such as adding storage, increasing pipe diameters etc.

36 Energy Saving Opportunities  There can be endless opportunities in a system.  It can take couple of hours to go through them all.  So, Let’s just look at the BIG hitters  In appropriate uses  Leaks  Pressure  Staging  Other opportunities  Air Drying  Storage  Filters  Heat Reclaim These are things we look for when we have limited time with the client.

37 Staging  This is one of THE most important opportunities  Why?  Lets look at an example (worst case)  Compressor – Centrifugal with blow-off only  We just reduced compressed air demand by 50%  How much do we save ?

38 Staging  Centrifugal part load How much do we save ? ZERO !

39 Staging  System Part-Load with Multiple Compressors Very Well staged multiple compressor system Poorly staged multiple compressor system

40 Staging Fundamentals  Points to remember Constant speed compressors are only efficient at full loads Operation at part loads should be minimized. You NEVER* want multiple compressors at part-load *Does not apply in special circumstances with centrifugal and VFD compressors Eliminate (or minimize) blow-off in Centrifugal compressors

41 Complexities in Optimizing Staging  Need to understand  System air flow requirements  Compressor – full load efficiencies  Compressor – individual part-load performance  Effect of combination of different compressors within a system How one staging sequence is different from the other  How ?  Metering the equipment is a start  Analysis of metered data Need to apply knowledge to obtain action items Okay, Let’s not worry about complexities. ** This is where you may want to reach out for technical assistance. Let’s look at a few case studies to understand the potential.

42 Case Study 1  Pre:  Two new 900-hp centrifugal compressors are operated in base trim manner Project cost ~ $800,000  Both of them can modulate and then blow-off  Post:  Compressors are operated in parallel so that Only one compressor blows-off first

43 Case Study 1 (Cont) Savings ~ $50,000/year

44  A facility has two compressed air systems that were put in place for two different systems  Pre  As often seen Both systems were oversized  What's interesting is both systems operate at 95 psig.  Post  Combine the two compressed air systems Case Study 2 Facts: Engineers like factor of safety; Vendors like to sell larger compressors

45 Compressor Optimization: Case Study 2 In the new case only one compressor is part- loaded instead of two. Savings ~ 20%

46  Manufacturing facility wanted to save energy  They thought VFD compressor is a good idea (it is, but..)  Pre  They bought a Oversized (215 hp) VFD compressor Why ? Sales person recommendation ? Lack of analysis ?  Issue: the VFD could not trim Used a 250 hp load/unload as the trim instead Not good  Post  Bought appropriately sized (125 hp) VFD compressor Compressor Cost ~ $150,000  And changed the control sequence Case Study 3

47 Big Savings Savings ~ 24% * Could have been achieved the first time if the VFD was sized right.

48  Multiple facilities with multiple compressors  Are more compressors better ?  Is a control system better ?  Is a VFD better ? Case Study 4

49 Facility 1 Facility 2 Facility 3 1. Poorly Staged (Manual) - 8 similar compressors 2. Staged with VFD (Pressure based) - 8 different compressors 3. Very well staged. (Demand Based) No VFD - 8 similar but different size compressors.

50  Most of the savings can be achieved by effective staging Control systems are vital for optimization in large systems  A VFD compressor can help improve your part-load performance Typically only one effective VFD is required per system If sized correctly Case Study 4

51 Summary  We discussed  Importance of compressed air Why its an expensive resource  Different types of compressors and their controls Reciprocating Screw Centrifugal  Largest Energy savings opportunities In-appropriate uses Leaks Pressure Staging  We looked at a few case studies Its time for the Recommendations

52 Recommendations  Pursue all the low-cost no-cost opportunities  In-appropriate uses  Leaks  Reducing pressure  Staging with available control systems Consult experts to evaluate best strategy with available controls  Consult technical experts before Investing Capital The last thing you want is invested capital and no savings.  New compressor installation  Control system upgrade

53 Questions ? Thanks for Listening! Abdul Qayyum “Q” Mohammed x308 Additional Slides are available at the End for Interested Parties

54 End Use: CA Diaphragm Pumps Facilities use CA Diaphragm Pumps. Needed for extremely corrosive or volatile fluids However, in many cases diaphragm pumps are used for fluids that can be moved with a regular centrifugal pump Motor Operated pumps use about 4x less energy

55 End Use: Dust Collector Purges CA is used in dust collector for purges. These purges can use significant amount of air if not optimized properly. Control CA with solenoids to appropriately time purges Bag house uses ~ 40% of system capacity

56 Distribution: Storage  Used to eliminate (or dampen) the variation of pressure within the system.  Particularly important in systems with load/unload compressors Storage improves part load performance of a system with load/unload compressors “Improving Compressed Air System Performance: A Sourcebook for Industry.” – US D.O.E, Nov 2003

57 Distribution: Storage (Cont.)  How much storage should I have ?  Rule of thumb 3 to 5 gal/cfm of compressor output Actual requirement depends on fluctuations in CA demand and types of compressors

58 Optimize Compressed Air Drying Appropriate drying technologies should be used Common drying technologies in order of decreasing efficiency  Refrigerant Dryers Cycling Non-Cycling  Desiccant Dryers Heat of Compression* (HOC) Heated desiccant Heated with Blower purge Heated with CA purge Heatless desiccant * HOC dryers are more efficient than refrigerated dryers

59 Generation: Reclaim Heat  ~ 80% of input energy is lost as heat  Heat can be used for various purposes For space heating during winter For process use throughout the year

60 Generation: Reclaim Heat  Example Installation

61 Generation: Compress Outdoor Air  Outdoor air is typically cooler than a mechanical room  Cooler air is denser hence easier to compress  Fraction savings ~ 2% per 10 F reduction  Note: Savings are realized in oil free compressors only In oil lubricated compressors the air is mixed with hot oil before compression. This eliminates savings. Considerations should be made to avoid freezing temperatures

62 What's the benefit of Energy Savings?  We reduce emissions  Helps slow down global warming Helps Protect Out planet  What are we talking about ?  Lets rephrase “What is MY benefit ?”


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