Calculating TCO for Biological Safety
Cabinets – Replace vs. Service
Decisions
Molly Love
Commercial Manager
September 29, 2010
Recent Press: Energy Efficiency in Lab Design
• Laboratories consume 3-8 times more energy than typical office buildings1
• Annual energy costs range from $2 to $16 per square foot per year
• A 100,000 square foot laboratory building could cost up to $1.6M per year to operate
• An analysis of 26 lab projects showed that over-sizing of cooling systems
averaged 80% (with a range of 40% to 300%)2
• Mills and Sartor3 report that a single fume hood can consume more energy
than three homes in the U.S.
Minimizing carbon footprint is at the forefront of new building
design and renovation discussions
1 NREL
Climate Neutral Research Campuses, www.nrel.gov (excerpt from Labs21 benchmarking data)
Martin, J. (2004) “Filling a Scientific Void in Laboratory Planning and Design. A case for Probability Case Analysis.” Syska Hennesy Group, San Diego, CA.
3 Mills and Sartor, “Energy Use and Savings Potential for Laboratory Fume Hoods.” Energy 30 (2005) 1859-1864
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2
Fume Hoods and BSCs – Close Cousins
• Fume Hoods and BSCs are all safety devices
• Inflow air velocity acts as a barrier to the user
• Similar to Fume Hoods, ducting to external exhaust is required of
BSCs for certain applications
• 24 hour per day operation may be required in some instances
Fume Hoods have long been considered the largest
consumer of energy of a laboratory – BSCs should be as well
3
Volatile Chemical Applications Require BSC Exhaust
BSC Exhaust
Air
Recirculation
Allowed for work with volatile
toxic chemicals and
radionuclides required as adjunct
to microbiological studies*
Class II, Type A1 or A2
To Room
Mixed
Not Suitable
Class II, Type A2 (thimble
duct)
External through
thimble
Mixed
Only minute quantities
Class II, Type B1 (direct
duct)
External through
Direct Connection
Partial
Only minute quantities
Class II, Type B2 (direct
duct)
External through
Direct Connection
None
Suitable
Volatile toxic chemicals should only be used in a ducted BSC
* Recommendations from NSF/ANSI 49
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Ducted BSCs Consume as Much Energy as Fume Hoods
Assuming 4 foot cabinet in operation 24 hours per day, 365 days per year:
Fume
Hood
Class II, A2
BSC
Class II, A2
BSC
Class II, B1
BSC
Class II, B2
BSC
(recirculated)1,2
(thimble ducted)1,2
(direct ducted)1
(direct ducted)2
Energy Consumed (W)
22
564
564
863
449
Heat Output (BTU)
05
1,924
05
05
05
485
0
438
350
754
Annual Cost of Energy
Consumed
$29.41
$753.85
$753.85
$1,153.49
$600.14
Annual Cost of Heat
Removal
$0.005
$257.22
$0.005
$0.005
$0.005
Annual Cost of Exhaust
$2,182.50
$0.00
$1,611.00
$1,237.50
$3,117.00
Est. Total Annual
Energy Cost
$2,211.91
$1,011.07
$2,364.85
$2,390.99
$3,777.14
Exhaust (CFM)
1
Assumes 8” working height of front sash
Assumes use of AC motors
3 Assumes $0.153 per kW-hr for MA http://www.eia.doe.gov/cneaf/electricity/epm/table5_6_b.html
4 Mills and Sartor, Energy 30 (2005) 1859-1864, $4.50/CFM
5 The heat output of exhausted unit is exhausted and does not add to the room.
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BSC Use and the Cost of Operation
• Non-Operational Electricity – 41%
• The amount of energy consumed when the
BSC is left ON but not in use
• Non-Operational Exhaust – 37%
• The amount of exhaust consumed when
the BSC is left ON but not in use
• Operational Exhaust – 12%
• The amount of exhaust consumed when
the BSC is ON during operation
• Operational Electricity – 10%
• The amount of electricity consumed whent
the BSC is ON during operation
Up to 80% of energy may be consumed when BSC is not in use
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Chart above taken from Biological Safety Cabinets: Energy Efficiency
Saves Resources, BIOforum Europe, May 2009, pp 34-36
Operating Costs of BSCs
• Ask these questions regarding your current BSC:
•
•
•
•
•
Does the BSC use DC motors?
Does the BSC have a 8”, 10”, or 12” window opening?
Do users turn off the BSC’s fluorescent lights at night?
Does the BSC offer a UV light timer (or is UV left on overnight)?
Does the BSC offer reduced motor speed when the sash is closed?
• Minimizing operational costs require care to:
• Select the proper BSC at time of purchase
• Train laboratory staff to initiate the built-in cost-saving features
Newer BSCs make it easier for the user to manage day-to-day
operational costs
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AC vs. DC Motors in BSC Design
Comparison of watts consumed in AC and DC BSCs:*
Nominal 4 ft Width
Nominal 6 ft Width
DC Motor
with 10”
window
AC Motor
with 10”
window
AC Motor
with 8”
window
AC Motor
with 10”
window
DC Motor
with 10”
window
DC Motor
with 10”
window
AC Motor
with 8”
window
AC Motor
with 10”
window
Blower(s)
Operational
142
780
725
602
346
185
1,034
883
Blower(s)
Reduced Flow
66
N/A
N/A
N/A
119
68
N/A
N/A
Fluorescent
Lights only
67
61
N/A
62
62
72
N/A
76
Germicidal
Light only
26
N/A
59
N/A
N/A
41
94
N/A
Off
6
2
4
0
3
6
2
0
Blowers and fans consume the most energy;
DC motors reduce energy consumption by as much as 80%
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* Webber, B. A. (2008 September) University of Michigan field study of Class II biological
safety cabinet energy consumption costs. American Biotechnology Laboratory; 2005; 26(9):2224
Cooling Costs are Directly Proportional to Energy Consumption
• Energy consumed is turned into a proportional amount of heat
(measured in BTU/h)
• Cooling costs should be considered part of the TCO
Comparison of cooling costs of 4 BSCs at the University of Michigan:*
Survey Location #1
Survey Location #2
Survey Location #3
Survey Location #4
Electricity Price Rate
$0.085 per kWh
$0.085 per kWh
$0.071 per kWh
$0.0986 per kWh
Cooling Price Rate
$17.63 per MMBTU
$7.58 per MMBTU
$7.58 per MMBTU
Assumes AC SEER of 13
Annual Electrical Cost for 764 watt BSC
used 2000 hours
$129.88
$129.88
$108.49
$150.66
Annual Cooling Cost for 764 watt BSC used
2000 hours
$91.92
$39.52
$39.52
$39.54
Total Annual Cost of Operation
$221.80
$169.40
$148.01
$190.21
Cost of cooling as % of Electrical Cost
71%
30%
36%
26%
Cooling costs can add up to as much as 70% of the total
energy cost of a BSC
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* Webber, B. A. (2008 September) University of Michigan field study of Class II biological safety
cabinet energy consumption costs. American Biotechnology Laboratory; 2005; 26(9):22-24
BSC Usage has Greatest Impact on TCO
Comparison of BSC Operating Costs Over 15
Years Based on Hours of Use per Year
•
Traditional AC BSC
• BSC 2
•
DC Motor BSC
• BSC 3
•
Optimized DC Motor BSC
Cost of Operation Over 15 Years of Use
• BSC 1
$30,000
BSC 1
$25,000
BSC 2
BSC 3
$20,000
$15,000
$10,000
$5,000
$0
Hours of Use per Year
The more the cabinet is used, the greater the impact newer
BSC designs have on TCO
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* Assumes simple TCO calculation (A2 BSC recirculating into laboratory, no reduced flow, SEER of 13). Formulas will
change when exhaust or reduced flow mode is added into the calculation.
Summary of BSC Operating Costs
• Minimize the number of BSCs requiring exhaust
• Avoid direct ducted BSCs
• Share BSCs for volatile toxic applications across labs within a building
• Select a BSC that uses DC motors to minimize energy
consumption and cooling costs
• Utilize energy-saving BSC features during periods low use
• Close front sash for reduced airflow
• Turn off fluorescent lighting
• Use only timed UV lights for disinfection
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Molly Love, Tel: 813.855.7360
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