Post on 25-Sep-2020
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
0
10
20
30
40
50
60
12:0010/12
12:1510/12
12:3010/12
12:4510/12
13:0010/12
13:1510/12
13:3010/12
13:4510/12
14:0010/12
Time: Hour, Day; October 2000
Pow
er (k
W)
Chilled Water Pump Power
0
10
20
30
40
50
60
12:0010/11
12:0010/12
12:0010/13
12:0010/14
12:0010/15
12:0010/16
12:0010/17
Time: Hour, Day; October 2000
Pow
er (k
W)
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
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
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
0
500
1000
1500
2000
2500
3000
3500
4000
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
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
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
0
200
400
600
800
1000
1200
1400
1600
1800
2000
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
0
500
1000
1500
2000
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
0
100
200
300
400
500
600
700
3 10 11 12 13 14 15 16 17 18 19 20 21 22Cleanroom ID
Air
Cha
nge
Rat
e (1
/hr)
-10
10
30
50
70
90
110
130
150
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
0
100
200
300
400
500
600
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
0
20
40
60
80
100
120
140
160
180
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
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
WaterCooled 42F
Air Cooled42F
Air Cooled40F
Air Cooled48F
Air Cooled50F
WaterCooled 40F
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
0
20
40
60
80
100
0 20 40 60 80 100
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
1 5 . 0 0
2 0 . 0 0
2 5 . 0 0
/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