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

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

Expensive Resource Only 9% ! 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 Heat Conversion Purges And Drains Only 9% ! Work Out Source: David Vanderbeek, 2011 Power Smart Forum

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

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

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

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

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

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)

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

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

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

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

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

Centrifugal: Pros and Cons 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)

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.

Let’s look at some examples. 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.

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

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

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

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

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

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

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.

Reduce Leaks ! Leaks are lost $$$$$ www.logis-tech.co.uk Air Power Usa

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 Weekend Avg. Leak Load = 50% !! In a two compressor system 100 kW in Non-production ~ 100 Homes *U.S. DOE, Compressed Air Fact Sheet #7

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 http://processengineering.theengineer.co.uk/

Goals for Leaks Can I have Zero Leak Load ? What should I aim for ? 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

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.

Reduce Pressure at End Use Did we adjust pressures at end use ? Do you need line pressure ? We recently observed a large manufacturing facility with efficient compressors….. Almost all end uses were unregulated !!! Unregulated tool ~ 120 acfm 0.25” @ 95 psig ~ 20% reduction ! Regulated tool ~ 95 acfm 0.25” @ 70 psig

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 out @ P2 Power kW Air in @ P1 Heat out

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

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

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

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.

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.

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 ?

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

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

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

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.

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

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

Case Study 2 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 Facts: Engineers like factor of safety; Vendors like to sell larger compressors

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

Case Study 3 Manufacturing facility wanted to save energy Pre Post 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

* Could have been achieved the first time if the VFD was sized right. Case Study 3 Savings ~ 24% * Could have been achieved the first time if the VFD was sized right. Big Savings

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

Case Study 4 1. Poorly Staged (Manual) - 8 similar compressors 2. Staged with VFD (Pressure based) - 8 different compressors Facility 1 Facility 2 3. Very well staged. (Demand Based) No VFD - 8 similar but different size compressors. Facility 3

Case Study 4 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

Its time for the Recommendations 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

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

Abdul Qayyum “Q” Mohammed Questions ? Thanks for Listening! Abdul Qayyum “Q” Mohammed Additional Slides are available at the End for Interested Parties www.gosustainableenergy.com 614-268-4263 x308 aqmohammed@gosustainableenergy.com

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 www.wildenpumps.org http://www.winter-pumpen.de/

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

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

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

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

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

Generation: Reclaim Heat Example Installation

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

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 ?”