Cleanroom Energy Benchmarking

William TschudiJuly 14, 2004WFTschudi@lbl.gov510-495-2417

Today’s session

Present selected cleanroom energy benchmarking findingsFocus on energy efficiency of cleanroom facility systems.Case study involving recirculation air setbackSavings by Design Cleanroom baselinesWhat is the audience background?What industries/institutions are represented?

Business case -facility system optimization

Business case for energy efficiency in cleanroom systems - saving energy puts $$ directly to bottom lineOptimizing facility systems may improve:

Energy performance Production (yields) or Research resultsMaintenance And may Lower capital cost

Some improvements are low or no cost

Benchmarking benefits

Establish Baseline to Track Performance Over TimePrioritize Where to Apply Energy Efficiency Improvement ResourcesIdentify Maintenance and Operational ProblemsOperational Cost SavingsIdentify Best Practices

Plus non-energy benefits

Reliability Improvement Controls Setpoints

Maintenance identificationLeaksMotors, pumps, FansFiltersChillers, boilers, etc.

Safety issues uncoveredHazardous air flow

Chilled Water Pump Power

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Time: Hour, Day; October 2000

Pow

er (k

W)

Chilled Water Pump Power

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Time: Hour, Day; October 2000

Pow

er (k

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Types of Cleanrooms

Each cleanroom is unique – but there are common efficiency opportunitiesMany industries and institutions use cleanrooms for a variety of processesMany different contamination control schemesMany different systems designs

System efficiency vs. production efficiency

Metrics allow comparison of air system efficiency regardless of process – e.g. cfm/kW or kW/cfm

Production metrics can mask inefficient systems – e.g. kW/cm2 (of silicon) or kW/lb of product

LBNL energy benchmarking

Benchmarking Studies available at: http://ateam.lbl.gov/cleanroom/benchmarking/results.html

Energy end-use was determined along with energy efficiency of key systems.

Energy efficiency recommendations were provided to each facility.

Sematech benchmarks

Additional energy benchmarks:

In the mid-ninety’s Sematech benchmarked fourteen semiconductor cleanrooms around the world. Similar metrics were obtained although measurement techniques may have differed.

Energy end-use

Facility 3

Hot Water & Steam

7%

Office (Lights, Plugs)

9%

Process Utilities17%

Cleanrooom Lights

1%

Process35%

Other Misc.6%

Cleanroom Fans11%

Total Chilled Water18%

Facility 1

Hot Water & Steam23%

Chilled Water19%

Cleanroom Fans16%

Other Misc.8%

Process13%

Cleanrooom Lights

1% Compressed Air & Process Vacuum

6%

Office (Lights, Plugs)

9%

Facility 2

Hot Water, Steam and Cafeteria

17%

Total Chilled Water20%

Cleanroom Fans27%

Other Misc.10%

Process9%

Cleanrooom Lights

1% Compressed Air

7%

Office (Lights, Plugs)

9%

What are the costs?

Utility bills from one case study:

Billing days Dollars

Elec 368 38,084,148 kWh $2,549,330

Gas 371 70,203 therms $43,715

approx 20,000 sq ft cleanroom in 68,000 sq ft building w/ $.065 ave. per kW!

Energy intensive systemsair systems in cleanrooms

Process Tools34%

Exhuast Fans7%

Nitrogen Plant7%

Recirculation and Make-up Fans

19%

Chillers and Pumps21%

Support3%Process Water

Pumping4%

DI Water5%

Cleanroom air system metricsAir systems – cfm/kW

RecirculationMake-up Exhaust

Cleanroom air changes – ACH/hrRecirculated, filtered airOutside air (Make-up and Exhaust)

Average room air velocity - ft/sec

Recirculation air comparison

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1000

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3000

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6000

7000

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9000

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11000

Fac. AClass 10

Press.Plen.

Fac. AClass 100

Press.Plen.

Fac. B.1Class 100

Ducted

Fac. B.1Class 100

FFU

Fac. B.2Class 100

Ducted

Fac. B.2Class 100

FFU

Fac. CClass 100

Press.Plen.

Fac. DClass 10Ducted

Fac. EClass 100

FFU

Fac. EClass 100

Press.Plen.

Fac. FClass 10

Press.Plen.

Fac. FClass 10

Press.Plen.

Fac. FClass 10

Press.Plen.

Fac. FClass 10k

CFM

/ kW

(hig

her

is b

ette

r)

Averages (cfm / kW)FFU: 1664

Ducted: 1733Pressurized Plenum: 5152 Average 3440

Recirculation efficiency –Sematech study

Recirculation Efficiencies

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1 2 3 4 5 6 7 8 9 10 11 12 13 14Facility

CFM

/kW

Average 1953 cfm/kW

Using benchmarks to set goals

Building Owners and Designers can use benchmark data to set energy efficiency goals.

Cfm/KW

KW/ton

System resistance – i.e. Pressure drop

Face velocities

Etc.

Recirculation air comparison

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11000

Fac. AClass 10Press.Plen.

Fac. AClass100

Press.Plen.

Fac. B.1Class100

Ducted

Fac. B.1Class100 FFU

Fac. B.2Class100

Ducted

Fac. B.2Class100 FFU

Fac. CClass100

Press.Plen.

Fac. DClass 10Ducted

Fac. EClass

100 FFU

Fac. EClass100

Press.Plen.

Fac. FClass 10Press.Plen.

Fac. FClass 10Press.Plen.

Fac. FClass 10Press.Plen.

Fac. FClass10k

CFM

/ kW

(hig

her

is b

ette

r)

Averages (cfm / kW)FFU: 1664

Ducted: 1733Pressurized Plenum: 5152

System Performance Target

Hypothetical operating cost comparison

Annual energy costs - recirculation fans (ISO Class 5, 20,000sf)

-

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

450,000

Ann

ual k

Wh

Cos

t bas

ed o

n $0

.10/

kWh,

$

Make-up Air System Comparison

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Facility AClass 10

Facility AClass100

FacilityB.1

Class100

FacilityB.2

Class 10

FacilityB.2

Class100

Facility CClass100

Facility DClass 10

Fac.E.1.1Class100

Fac.E.1.2Class100

Fac. F.2Class 10

*

Fac. F.3Class 10

Fac. F.1Class 10

CFM

/ kW

(hig

her i

s be

tter)

Average 972

Make-up air system efficiency Sematech study

Make-up Air Energy Efficiency

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2500

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Facility

cfm

/kW

Average 946

Make-up system efficiency

Adjacency of air handler(s) to cleanroomResistance of make-up air pathPressurization/losses/exhaustAir handler face velocityCoil Pressure DropDuct/plenum sizing and layoutFan and motor efficiencyVariable Speed Fans

Recirculation air change rates and average velocities

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3 10 11 12 13 14 15 16 17 18 19 20 21 22Cleanroom ID

Air

Cha

nge

Rat

e (1

/hr)

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Ave

rage

Cle

anro

om A

ir Ve

loci

ty (f

pm)

Air Change Rate ave Vel

Air-change and velocity choicesNot an exact science…

The Institute of Environmental Sciences and Technology (IEST) provides recommended recirculation air-change rates

Most semiconductor firms have their own criteria

Studies have shown that more airflow is not necessarily better

Philosophy of ceiling filter coverage varies

Pressurization/losses can have a large impact

Air changes also need to match cleanroom protocol

Recirculated air change ratesISO class 5

LBNL Cleanroom Benchm ark Data ISO Class 5 (Class 100) Cleanroom s

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Facility A Facility B Facility C Facility D Facility E Facility F Facility G Facility H

Mea

sure

d A

ir C

hang

e R

ate

(AC

/hou

r)

TYPICAL RECOMMENDED DESIGN RANGE

Recommended ranges from Cleanroom Design, second ed., W. Whyte

Component efficiencies also vary

Average Outlet Velocity, m/s0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Flow

Inte

nsity

, CM

M /

kW

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200FFU AFFU BFFU CFFU DFFU EFFU FFFU GFFU HFFU I-1FFU I-2FFU JFFU KFFU LFFU MFFU NERL FFU (AC)ERL FFU (ACS)ERL FFU (DC)FFU P-1FFU P-2

4'X2' FFU2800 cfm/kW

Source: Industrial Technology Research Institute, Taiwan

Chilled Water Systems Efficiencies

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WaterCooled 42F

Air Cooled42F

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Air Cooled50F

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WaterCooled 38F

WaterCooled 36F

WaterCooled 44F

WaterCooled 43F

Fac. A Fac. B.1 Fac. B.2 Fac. B.2 Fac. B.2 Fac. C Fac. D Fac. E.1 Fac. E.2 Fac. F

kW /

ton

(low

er is

bet

ter)

Cooling TowerCW PumpsCHW PumpsChiller

UPS Efficiency

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Load Factor (% )

Effic

ienc

y (%

)

Within each system…Efficiency choices can be made

System pressure drop – face velocity, duct/pipe velocity, chase sizing, plenums vs. duct, adjacency, layout – changes of direction

Air change rates

Ceiling coverage

Equipment – fans, motors, controls, filters, floor systems

Cleanroom benchmarking highlights some important issues

Contamination control can often be achieved with reduced air change rates

Cleanliness ratings are often higher than needed

Rule of thumb criteria should be examined

(e.g.: 90ft/min, air changes, filter coverage etc.)

Overcooling and subsequent reheat can be excessive

Chilled water pumping is often an opportunity

Chilled water temperature often is lower than needed

Many owners don’t know how they compare

Best practices/conclusions

Minimize clean spaceSize for real loadCorrect cleanliness classification for contamination control problemAir-change rate can be optimizedMinimize pressure dropMost systems benefit from variable speed devicesExhaust minimization

Case study

Good news/Bad news

Recirculation setback at night and on weekends was successfully utilized and dramatically saved energy

Unfortunately air-change rates were very high and the system had a high pressure drop (resistance to airflow)

Ducting to HEPA filterscreated more pressure drop

Case study – recirculation setback

Based Solely on Timeclock, 8:00 PM -6:00 AM setbackNo reported process problems or concerns from process engineers60% – 70% Power Reduction on turndown

R A H - Z P o w e r

0 . 0 0

5 . 0 0

1 0 . 0 0

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/0 4 0 :0 0

3 /1 6 /0 4 0 :0 0

3 / 1 7 / 0 4 0 : 0 0

3 /1 8 /0 4 0 :0 0

3 /1 9 /0 4 0 :0 0

3 /2 0 /0 4 0 :0 0

3 /2 1 /0 4 0 :0 0

3 / 2 2 / 0

D a t e

C h a n . 1C h a n . 2C h a n . 3

T o t a l k W

Case study – energy savings

Annual fan savings from daily and weekend setback:1,250,000 kWhapproximately $138,000

Cooling load reduction when setback:234 kW65 tons

ISO 14644-4

ISO 14644-4

(Its OK to save energy!)

Case study - recommendation

Air change rates exceeded IEST recommendations during daylight operation.Further large reductions in energy use are possible by reducing air change rates and should not affect the process within the room.

Savings By Design

Cleanroom baseline criteriaRecirculation system

Metric: Watts/cfmDetermine watts by measurement or from design BHPW = BHPx746

0.91

Determine flow from balance report or design documentsBaseline value is 0.43 W/cfm (2,325 cfm/kW)Annual savings=(Baseline - Efficiency metric) x Annual cfm

Savings By Design

Cleanroom baseline criteriaMake-up air system

Metric: Watts/cfmDetermine watts by measurement or from design BHPW = BHPx746

0.91Determine flow from balance report or design documentsBaseline value is 1.04 W/cfm (961 cfm/kW)Annual savings=(Baseline - Efficiency metric) x Annual cfmwhere annual cfm = .7 x design cfm

Run redundant stand-by units in parallel

Savings By Design

Cleanroom baseline criteria

Additional criteria for:Chilled water systemHot water productionCompressed air