Compressed Air Systems:Opportunities to Cut Energy Use and Operating Costs

Presented by: Jonathan Thibeault

Energy Consultant, Efficiency Vermont

SEPTEMBER 18, 2019

Thank you to our sponsors!

Agenda

1. Leaks

2. Shut-It-Off

3. Inappropriate Uses

4. Pressure Modifications

5. Distribution System

6. Dryer Options

7. Compressor Technology

8. Heat Recovery

Invisible Money

Compressed Air – The 4th Utility “Powers” equipment and processes

Units of operation, psi, cfm, NOT kWh, Btu

Ignores the energy required to compress and deliver air

5 scfm = 1hp or 0.7457kW

~1500 kWh (single shift)

~$225/hp-year

ex. 250 scfm @ 2,000 hrs/yr= $11,250/yr

The Cost of Leaks

• Leaks often account for 20-30% of a compressor’s output

• Common locations for leaks include couplings, fittings, joints, flanges, disconnects, valves, filters, regulators, and traps.

• Leak rate is pressure dependent

• Ex: 1/8” hole @ 100psi, 2000 hrs/yr, & $0.15/kWh

25.22 𝑐𝑐𝑐𝑐𝑐𝑐 ×1 ℎ𝑝𝑝

5 𝑐𝑐𝑐𝑐𝑐𝑐×

0.7457 𝑘𝑘𝑘𝑘1 ℎ𝑝𝑝

×2000 ℎ𝑟𝑟𝑟𝑟

𝑦𝑦𝑟𝑟×

$0.15𝑘𝑘𝑘𝑘ℎ

= $1,128/𝑦𝑦𝑟𝑟

EVT Standard Offers

• Incentives available for leak remediation:

• Leak Audit Service Providers Active in Vermont: – American Plant Maintenance– Compressor Energy Services – Fastenal– Reynolds & Sons– Check with your Compressed Air Vendor

Close the Door

• If: Air is supplied to applications that do not run 24/7

• And: Your compressed air system is charged 24/7

VALVE IT OFF!

• Best Practice: Install solenoid valve that is connected to machine switch

• Examples of equipment: remote optical sensors, spindles, parts washers, packaging lines, CNC machines

• Install no-loss drains!

Use it Wisely

Compressed air should only be used if pressurized air is required.

If flow is the requirement, a blower may be satisfactory and would use less power

Potentially inappropriate uses of compressed air include: Open blows, sparging, aspirating, atomizing, material

transport, vacuum generation, cooling, cleaning, motors & pumps

Engineered Nozzles!

Eliminate Artificial Demand

“Excess volume of air that is consumed when supplyinghigher pressure necessary for applications”

- Improving Compressed Air System Performance: A Sourcebook For Industry

Air pressure is unregulated at the point of use Commonly 30-50% of air demand Solution: Pressure Regulators

Air pressure is regulated higher than necessary Solution: Adjust pressure set point Caution: Analysis of network pressure may be needed

Pressure = Energy Rule of thumb: +2 psig discharge pressure = +1% energy use

Eliminate Traffic Jams

Air distribution network critical to equipment performance and set points

Identify pinch points in supply and correcto Air Velocity should

never surpass 50ft/s

Install storage local to sources of high demand (intermittent, rapid discharge)

o Pressure drop should not exceed 10% between the compressor and end use

How Dry Do you Need It?

• Lower Dew Point = More Energy

• Dry only to the dew point required• 38°F Dew Pt. satisfactory for many applications• Consider environmental influences

• Dew Pt. ≥ 38°F = Cycling refrigerated dryers

• Dew Pt. < 36°F = Desiccant dryers• High operating cost – Generally uses 10-18%

of air produced• Purge air controllers available

• Savings Opportunity - Seasonal decommissioning of Desiccant Dryers

• CAGI Sheets now available for dryers!

Pay Attention to Operating Cost

H.O.C.

Heatless Desiccant

Heated Blower Purge Desiccant

H.O.C. Zero Purge

Illustrations provided here were published by manufacturers and have not been verified by Efficiency Vermont. True performance and cost may vary.

Heart of the Operation

Reciprocating- Single & Double

acting- Air and/or water

cooled- Generally low hp- 15-24 kW/100 cfm

Rotary Compressors

- Variable output- Air and/or water

cooled- ~ 15hp +- 15-22 kW/cfm

Centrifugal- High volume, poor

turn down - Compact, multiple

stages possible- ~150hp +- 16-20 kW/cfm

Load Profile and Control is Critical

Energy efficiency dependents upon air demand and compressor performance!

Part-load Control Schemes: On/Off Load/No Load Modulation Variable Displacement Speed Control (VSD) Blow-off/purge (centrifugal only)

Not All Losses are Equal

Heat Recovery Opportunities

• 80-93% electrical energy used by an air compressor is converted to heat

• Rule of thumb: – 50,000 Btu / 100 cfm (at full load)

• Heat recovery via free-air:– Increase air temp 20-40°F– Recovery efficiency 80-90%

• Heat recovery via water:– Additional heat exchanger needed– Recovery efficiency 50-60%– Temperature of available heat is lower– Uses: Radiant heat, domestic hot

water, boiler feedwater preheating, process heating

But Wait There’s More!

• Dedicated supply for equipment that operates 24/7

• Master controller for multiple compressors

• Account for operational changes and/or growth

• Knowledge is power – Meter it!

Questions?

SEPTEMBER 18, 2019

Interested in Compressed Air Training? CAC Level 1 Training sign-up sheet at the back of the room!