liquid desiccant technology - ashrae madison€¦ · tons conventional cooling 30 20 reheat system...
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Advantix Systems
LIQUID DESICCANT TECHNOLOGY
Liquid Desiccant: How it works
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What is liquid desiccant?
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Start with a very salty solution…
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…Which will create the “Dead Sea Effect” of absorption
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A two part system enables transport…
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Any imbalance will create a driving force for equilibrating the solutions between the two parts
…and finally adding a heat source creates a continuous dehumidification process
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Basic Function: thermal energy can be derived from many sources
Thermal Transfer Source
• Heat Pump - Electricity only
• Electricity and external hot/cold water
• Hybrid - Heat pump AND external/renewable sources
• Heat Pump models maximize convenience (plug & play) • External hot/cold models take advantage of existing or renewable
thermal sources/sinks to provide maximum possible energy savings
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How it works
Background: The science of humidity control
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A building’s air conditioning load comes from a variety of sources
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External Internal
Thermal (Sensible)
• Heat conduction through envelope
• Fenestration • OA Ventilation (sensible
portion) • Infiltration (sensible portion)
• Lights • Fans & other motors • Office equipment and
electronics • Miscellaneous plug loads • People (sensible portion) • Industrial machinery
Moisture (Latent)
• OA Ventilation (latent portion) • Infiltration (latent portion) • Permeation
• People (latent portion) • Plants • Cooking • Pools, showers, spa • Washing/ Washdowns • Drying processes • Other wet processes
Air conditioning loads require both temperature and humidity control
Primary Sources
Lighting
Thermal conduction
Solar gains
Plug loads
Occupants
Outside air ventilation & infiltration
Occupants
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Reduced directly by absorbing heat into the refrigerant
Conventional A/C Process
Reduced indirectly by overcooling air past condensation point and then adding reheat which demands a lot of energy
Temperature
Humidity
Temperature Control
(sensible load)
Typical Building A/C Load
Humidity Control (latent load)
Though not apparent on the thermostat, humidity control is equally important to temp control for maintaining comfort, indoor air quality, and building integrity
Boston Example Building
The fraction of moisture load in HVAC is substantially increasing in building design standards
Source: TIAX
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3
15
6
13
6 (Btu/ft2)
Increased ventilation
rates
• Greater awareness of IAQ/airborne pathogens
Better energy
efficiency
• Florescent lighting • Insulation / envelope • Low -E glass • Etc.
Continued energy
efficiency
• CFL/LED • White roofs • Plug load reduction • Etc.
ILLUSTRATIVE
Typical building “design” load is currently 20-40% moisture load, but evolving towards 40-60%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1980 1985 1990 1995 2000 2005
Albuquerque
Boston
Atlanta
Miami
ASHRAE Standard Year
Pe
rce
nt
Mo
istu
re L
oad
(1
- SH
R)
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Traditional “design” conditions do not reflect the true challenge of moisture control in modern buildings
Source: TIAX
30 Years Observed Outdoor Air Conditions, Cairns AFB Alabama
Mo
istu
re C
on
ten
t
Temperature
30 Years Observed Outdoor Air Conditions Cairns AFB Alabama
Humidity design
condition
Part load condition
Cooling design
condition
Realistically, the worst-case conditions are already at about 50% - smart designers are increasingly moving away from the “cooling design” load
0%
20%
40%
60%
80%
100%
1980 1985 1990 1995 2000 2005
Pe
rce
nt
Mo
istu
re L
oad
(SH
R)
Shoulder/Part Load Design Conditions
Albuquerque Boston Atlanta Miami
0%
20%
40%
60%
80%
100%
1980 1985 1990 1995 2000 2005
Pe
rce
nt
Mo
istu
re L
oad
(SH
R)
Dehumidification Design Conditions
Albuquerque Boston Atlanta Miami
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… resulting in a difficulty controlling moisture below full load conditions
• Duty cycle, aka “Runtime Fraction” is important for conventional coils • At part load, it is very difficult for standard cooling coil to dehumidify
without over-cooling, or at least large temperature swings (long-cycles) • True for BOTH chilled water and DX coils, when cooling source is removed,
the condensed water will re-evaporate into the air stream
… And can be even more challenging in facilities with more stringent requirements
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High ventilation requirements Low dewpoint requirements
High internal humidity load
Health Care
Supermarkets Indoor pools
Hospitality (hotels, restaurants, auditoriums)
Hospitals (esp. operating rooms)
Food Products/Processing
Schools
Pharmaceutical / Nutraceutical production
Health Clubs
Labs Plastic Molding
Electronics manufacturing
Painting & Printing
Cold / Dry storage
Ice rinks
Any space using chilled beams or VRF systems
Conventional equipment does not sufficiently address the humidity control challenge in modern buildings
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1980 2010
EER 8 10
Refrigerant Ozone-depleting R-22 R-410a, R-407c
environmentally-friendly
Humidity Control/SHR
~20% of load @ full capacity (less at part load)
~20% of load @ full capacity (less at part load)
• Though efficiency has improved, conventional equipment is fundamentally limited in its ability to treat moisture load
• The SHR limits the moisture removal capability required to maintain required IAQ of modern buildings
mold & bacteria
Capacity issues - oversizing - inadequate ventilation
musty odors
maintenance issues
Failure to respond has caused…
ASHRAE best practice design standards call for separate equipment to treat ventilation and/or latent loads
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Return Air Conditioner
ASHRAE Handbook Ch. 6.7: Although most centralized and decentralized systems are very effective at handling the space sensible cooling and heating loads, they are less effective (or ineffective) at handling ventilation air or latent loads. As a result, outside air should be treated separately.
Dedicated Outdoor Air System
Dealing with the latent load
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Basic approaches to humidity control
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Approach Technology
Dedicated Outside Air System (DOAS)
• Overcools as above, has packaged hot gas reheat • Specialized coils to allow greater moisture removal
Solid Desiccant • Hygroscopic chemistry adsorbs moisture • Heat addition necessitates pre-cooling and/or post-cooling of
air
Liquid Desiccant • Hygroscopic chemistry absorbs moisture • Cools and dries air simultaneously
An example to compare the approaches
Example 1: treating 100% outdoor air
Requirements: bring 3000 CFM of humid outdoor air to room-neutral
conditions
Approach
Dedicated Outside Air System (DOAS)
Solid Desiccant
Liquid Desiccant
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Mechanical dehumidification/DOAS equipment
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Advantages • Meets moisture load without
overcooling the space
• Refrigerant-based systems familiar to contractors and consumers
Limitations • Energy intensive
• Latent degradation at part load
• High maintenance requirements
Adding reheat enables humidity control with mechanical refrigeration, but at a cost
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Approach 1: Mechanical refrigeration + reheat
Example 1: bringing 3000 CFM of humid outdoor-air to room-neutral
217 MBH (18 tons)
74 MBH*
Total: 291 MBH
Solid desiccant wheel dehumidification
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Advantages • Able to reach extremely low
dew points (< 10 gr/lb)
Limitations • Expensive
• Energy intensive
• High maintenance requirements
• Usually requires pre-cooling and/or post cooling equipment
A desiccant wheel also requires significant excess energy input
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Method 2: Solid desiccant
Example 1: bringing 3000 CFM of humid outdoor-air to room-neutral
252 MBH* (For regeneration)
Total: 445 MBH
Note: Pre + Post cool configuration (not shown) requires similar energy
input
* A portion, not all, can be condenser heat
252 MBH* (For regeneration)
193 MBH (16 tons)
Alternate path of solid desiccant – some energy savings possible
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To reach San Diego from Miami, why would you connect through Anchorage?
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Only liquid desiccant can use the thermodynamic minimum energy in low-SHR tasks
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Approach 3: Liquid Desiccant
Example 2: bringing 3000 CFM of humid outdoor-air to room-neutral
Note: Desiccant regeneration accomplished entirely through
condenser heat 143 MBH (12 tons)
Total: 143 MBH
Liquid Desiccants Do Less Work for the Same Task
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Base processes
With “site”energy
recovery
Total Energy
291
142 217 245
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Base case
Optimized
445
Units: MBH Conventional Solid desiccant Liquid desiccant
Process Overcool Reheat Desiccant wheel dehumidification
Post-cooling Liquid desiccant cooling
Work required 217 74 252 193 142
Total energy 291 445 142
Optimization Condenser hot-gas reheat Condenser heat for regen on-site heat sink
MBH savings -74 -200 -70
Advantix Systems Smarter dehumidification and cooling
There are also non-energy, IAQ considerations to compare between approaches
• Laboratory testing shows desiccant solution killing 99%+ of microorganisms it contacts
• Field testing shows 89-98% reduction in airborne microorganisms after install
• Allergens, particulates, and odor causing molecules also captured by the process
In contrast, tests and field data demonstrate liquid desiccant’s positive effect on IAQ
The conventional approach contributes to IAQ issues
Cooling coil Fungi
Bacteria
Viruses
Wet coils & condensate system form a veritable petri dish that the treated air flows over
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Flexible in installation: Good for both new build and retrofits
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series install (rooftop)
thermal-driven renewable (mechanical room)
“tight-spaces” (indoors)
commercial ventilation (pad-mounted)
parallel install
(rooftop) industrial ventilation
(rooftop)
Save green by going green – superior economics of LDAC
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Energy costs (opex)
First costs (capex)
• Comparable (or less) upfront cost to alternative equipment
• Systems sized more efficiently by handling more humidity removal than conventional units
• 30-40% lower energy consumption than conventional mechanical systems
• 30-60% lower energy consumption than desiccant wheels
By dealing with moisture more efficiently:
Advantix Systems Smarter dehumidification and cooling
A viable, sustainable solution for many global brands…
Other Industrial Food & Beverage
Healthcare
Pharma
Hospitality Other Commercial
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How to Apply LDAC
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Application: flexible in installation (1/5)
Commercial (School), Pad mounted
Commercial (Restaurant), Rooftop Industrial Ventilation (Food Processing) Pad mounted
Outdoor air, in parallel
conditioned
space
OA LDAC RTU
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Application: flexible in installation (2/5)
Commercial (Multifamily), Rooftop
Industrial Ventilation (Food processing) Rooftop
Commercial (Hospital), Rooftop
Outdoor air, in series
OA LDAC
AHU
AHU
conditioned space
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Application: flexible in installation (3/5)
Commercial (Retail), Rooftop
Industrial (Plastic Molding) Indoor
Commercial (Fitness Center), Indoor
Internal latent load, in parallel
LDAC
conditioned space
RTU
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OA
Application: flexible in installation (4/5)
Commercial (Restaurant) Pad mounted
Commercial (School) Rooftop Industrial (Pharma) Mechanical Room
Internal latent load, in series
LDAC
conditioned space
AHU
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Application: flexible in installation (5/5)
Thermally-Driven Renewable
(Office Building)
Other Common Installations
Problem Spaces
Indoor Pool
Cold/Dry Storage
Cafeteria Hotel, Ballroom
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Advantix Systems
LIQUID DESICCANT AIR CONDITIONING Saves energy, Controls humidity, Cleans air
www.advantixsystems.com
Case Studies
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Pharma Production
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Environmental control example – neutral conditions
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• Compression area requires moderate humidity with strict control during the production process
• Existing conventional A/C system had high
operating costs, owner was seeking a more
economical solution for the plant’s air
treatment
• Owner requested that replacement be done
with minimum modification to the existing
system and no compromise over the desired
conditions
Design Requirements:
75 ̊F, 50% RH
Ambient Conditions:
88 ̊F, 80% RH
OA LDAC AHU
AHU
conditioned space
LDAC solution is less expensive in first cost and operating costs
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Conventional A/C System Liquid Desiccant System
Tons Conventional Cooling 30 20
Reheat System (kW) 21 -
Liquid Desiccant System - Liquid Desiccant Unit
Hourly Operating Cost $5.10 $3.60
Annual Operating Time (hours) 5,000 5,000
Annual Operating Cost $25,500 $18,000
Annual Operational Savings None $7,500
Liquid Desiccant equipment was less expensive than the more energy-intensive outdoor air unit it replaced
Powder Processing
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• 65,000 sq. ft plant
• Powder production / packaging line
• Powder processing requires low and precise humidity control,
• Initial design called for a solid desiccant wheel in additional to conventional A/C (chilled water system) to reach desired environmental control
Low humidity – industrial process example
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Design Requirements:
81 ̊F, 20% RH
Ambient Conditions:
88 ̊F, 80% RH
OA
LDAC
AHU AHU conditioned space
AHU
Operating cost advantage is even greater for low humidity
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Solid Desiccant Wheel & Chilled Water
Liquid Desiccant & Chilled Water
Tons of Conventional Cooling 93 33
Approx. Cost of Conventional Equip. $74,400 $26,400
Desiccant Equipment 10,000 CFM desiccant wheel 3 x Liquid Desiccant Units
Cost of Desiccant Equipment $86,000 $70,000
Total First Cost $160,400 $96,400
Annual Energy Consumption (kWh) 2,348,690 1,139,381
Annual operating costs $399,277 $193,695
5-Year Total Cost $2,156,787 $1,064,874
-51%
Big Box Store
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Economics still favorable replacing inexpensive packaged DX
Before: 280 tons conventional
After: 150 tons + 18,000 CFM LDAC
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Liquid Desiccant
conditioned space
RTU
infiltration
door
door
OA
Systems for comparison
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Conventional Rooftop DX Units
Liquid Desiccant Units + Rooftop DX Units
Tons of Conventional Cooling 280 150
# of Conventional Rooftop Units
13 7
# of Liquid Desiccant Units - 6
Total Equipment Cost ~$255,000 ~$275,000
Humidity Control Overcooling to achieve
target conditions Overcooling not required to
achieve target conditions
Projected Savings $15,000-35,000/year
For a 9% premium in equipment costs, payback is under 1 year