Download liquid desiccant technology

LIQUID DESICCANT TECHNOLOGY
Advantix Systems
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…
Any imbalance will create a driving force for
equilibrating the solutions between the two parts
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…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
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Background: The science of humidity control
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A building’s air conditioning load comes from a variety of
sources
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) • People (latent portion)
• Infiltration (latent portion)
• Plants
• Permeation
• Cooking
• Pools, showers, spa
• Washing/ Washdowns
• Drying processes
• Other wet processes
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Air conditioning loads require both temperature and humidity
control
Conventional A/C Process
Primary Sources
Typical Building
A/C Load
 Lighting
 Thermal conduction
 Solar gains
 Plug loads
 Occupants
 Outside air ventilation
& infiltration
 Occupants
Temperature
Control
(sensible load)
Humidity Control
(latent load)
Temperature
Reduced directly by
absorbing heat into
the refrigerant
Humidity
Reduced indirectly by
overcooling air past
condensation point
and then adding
reheat which demands
a lot of energy
Though not apparent on the thermostat, humidity control is equally important to
temp control for maintaining comfort, indoor air quality, and building integrity
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The fraction of moisture load in HVAC is substantially
increasing in building design standards
Percent Moisture Load (1- SHR)
Boston Example
Building
(Btu/ft2)
100%
ILLUSTRATIVE
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15
13
3
6
6
Albuquerque
90%
Boston
80%
Atlanta
Miami
70%
Typical building
“design” load is
currently 20-40%
moisture load,
but evolving
towards 40-60%
60%
50%
40%
30%
20%
10%
0%
1980
ASHRAE Standard
Year
1985
1990
2000
Increased
ventilation
rates
• Greater awareness
of IAQ/airborne
pathogens
Source: TIAX
1995
2005
Better
energy
efficiency
•
•
•
•
Florescent lighting
Insulation / envelope
Low -E glass
Etc.
Continued
energy
efficiency
•
•
•
•
CFL/LED
White roofs
Plug load reduction
Etc.
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Traditional “design” conditions do not reflect the true
challenge of moisture control in modern buildings
Dehumidification Design Conditions
Moisture Content
Cooling
design
condition
Temperature
Part load
condition
Realistically, the worst-case conditions are already at about 50% - smart
designers are increasingly moving away from the “cooling design” load
Source: TIAX
Percent Moisture Load (SHR)
100%
80%
60%
40%
20%
0%
1980
1985
Albuquerque
1990
Boston
1995
2000
Atlanta
2005
Miami
Shoulder/Part Load Design Conditions
Percent Moisture Load (SHR)
AirAir
Conditions
30 Years
YearsObserved
ObservedOutdoor
Outdoor
Cairns
AFB
Alabama
Conditions, Cairns AFB Alabama
Humidity
design
condition
100%
80%
60%
40%
20%
0%
1980
1985
Albuquerque
1990
Boston
1995
2000
Atlanta
14
2005
Miami
… 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
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… And can be even more challenging in facilities with more
stringent requirements
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
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Conventional equipment does not sufficiently address the
humidity control challenge in modern buildings
1980
2010
Failure to respond has caused…
Capacity issues
- oversizing
- inadequate ventilation
musty odors
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
mold & bacteria
maintenance issues
• The SHR limits the moisture removal capability
required to maintain required IAQ of modern
buildings
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ASHRAE best practice design standards call for separate
equipment to treat ventilation and/or latent loads
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
Return Air
Conditioner
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Dealing with the latent load
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Basic approaches to humidity control
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
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An example to compare the approaches
Approach
Dedicated Outside Air System (DOAS)
Example 1: treating 100% outdoor air
Solid Desiccant
Requirements: bring 3000 CFM of
humid outdoor air to room-neutral
conditions
Liquid Desiccant
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Mechanical dehumidification/DOAS equipment
Advantages
Limitations
• Meets moisture load without
overcooling the space
• Energy intensive
• Refrigerant-based systems
familiar to contractors and
consumers
• Latent degradation at part load
• High maintenance requirements
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Adding reheat enables humidity control with mechanical
refrigeration, but at a cost
Example 1: bringing 3000 CFM of
humid outdoor-air to room-neutral
Approach 1: Mechanical
refrigeration + reheat
217 MBH
(18 tons)
74 MBH*
Total: 291 MBH
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Solid desiccant wheel dehumidification
Advantages
Limitations
• Able to reach extremely low
dew points (< 10 gr/lb)
• Expensive
• Energy intensive
• High maintenance requirements
• Usually requires pre-cooling
and/or post cooling equipment
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A desiccant wheel also requires significant excess energy input
* A portion, not all, can be condenser heat
Example 1: bringing 3000 CFM of
humid outdoor-air to room-neutral
Method 2: Solid desiccant
252MBH*
MBH*
252
(For
(Forregeneration)
regeneration)
Note: Pre + Post cool configuration
(not shown) requires similar energy
input
Total: 445 MBH
193 MBH
(16 tons)
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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
Example 2: bringing 3000 CFM of
humid outdoor-air to room-neutral
Approach 3: Liquid Desiccant
Note: Desiccant regeneration
accomplished entirely through
condenser heat
143 MBH
(12 tons)
Total: 143 MBH
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Liquid Desiccants Do Less Work for the Same Task
Base
processes
Units: MBH
Process
Work required
With
“site”energy
recovery
Conventional
Solid desiccant
Overcool
Reheat
Desiccant wheel
dehumidification
217
74
252
Liquid desiccant
Postcooling
Liquid desiccant cooling
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
Total Energy
445
Base case
291
Optimized
217
245
142
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There are also non-energy, IAQ considerations to compare
between approaches
The conventional approach
contributes to IAQ issues
Cooling coil
Fungi
In contrast, tests and field data
demonstrate liquid desiccant’s
positive effect on IAQ
• Laboratory testing shows
desiccant solution killing 99%+ of
microorganisms it contacts
Bacteria
Viruses
Wet coils & condensate system
form a veritable petri dish that the
treated air flows over
Advantix Systems
• Field testing shows 89-98%
reduction in airborne
microorganisms after install
• Allergens, particulates, and odor
causing molecules also captured
by the process
Smarter dehumidification and cooling
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Flexible in installation: Good for both new build and retrofits
series install
(rooftop)
industrial ventilation
(rooftop)
thermal-driven renewable
(mechanical room)
parallel install
(rooftop)
“tight-spaces”
(indoors)
commercial ventilation
(pad-mounted)
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Save green by going green – superior economics of LDAC
By dealing with moisture more efficiently:
Energy costs
(opex)
First costs
(capex)
•
30-40% lower energy consumption than conventional
mechanical systems
•
30-60% lower energy consumption than desiccant
wheels
•
Comparable (or less) upfront cost to alternative
equipment
•
Systems sized more efficiently by handling more
humidity removal than conventional units
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A viable, sustainable solution for many global brands…
Hospitality
Healthcare
Other Commercial
Pharma
Food & Beverage
Other Industrial
Advantix Systems
Smarter dehumidification and cooling
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How to Apply LDAC
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Application: flexible in installation (1/5)
Commercial (School), Pad mounted
Outdoor air, in parallel
OA
LDAC
RTU
conditioned
space
Commercial (Restaurant), Rooftop
Industrial Ventilation (Food Processing) Pad
mounted
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Application: flexible in installation (2/5)
Commercial (Multifamily), Rooftop
Outdoor air, in series
OA
LDAC
AHU
AHU
conditioned
space
Industrial Ventilation (Food processing)
Rooftop
Commercial (Hospital), Rooftop
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Application: flexible in installation (3/5)
Internal latent load, in parallel
LDAC
Commercial (Retail), Rooftop
OA
RTU
conditioned
space
Industrial (Plastic Molding)
Indoor
Commercial (Fitness Center), Indoor
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Application: flexible in installation (4/5)
Internal latent load, in series
LDAC
Commercial (Restaurant)
Pad mounted
AHU
conditioned
space
Commercial (School) Rooftop
Industrial (Pharma) Mechanical Room
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Application: flexible in installation (5/5)
Thermally-Driven
Renewable
(Office Building)
Other Common Installations
Cafeteria
Hotel, Ballroom
Problem
Spaces
Cold/Dry
Storage
Indoor
Pool
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LIQUID DESICCANT
AIR CONDITIONING
Saves energy, Controls humidity, Cleans air
Advantix Systems
www.advantixsystems.com
Case Studies
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Pharma Production
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Environmental control example – neutral conditions
• 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
OA
AHU
LDAC
Design Requirements:
AHU
75 ̊F, 50% RH
Ambient Conditions:
88 ̊F, 80% RH
conditioned
space
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LDAC solution is less expensive in first cost and operating costs
Conventional A/C System
Liquid Desiccant System
Tons Conventional Cooling
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20
Reheat System (kW)
21
-
-
Liquid Desiccant Unit
Hourly Operating Cost
$5.10
$3.60
Annual Operating Time (hours)
5,000
5,000
$25,500
$18,000
None
$7,500
Liquid Desiccant System
Annual Operating Cost
Annual Operational Savings
Liquid Desiccant equipment was less expensive than the
more energy-intensive outdoor air unit it replaced
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Powder Processing
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Low humidity – industrial process example
• 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
Design
Requirements:
81 ̊F, 20% RH
Ambient Conditions:
88 ̊F, 80% RH
LDAC
OA
AHU
AHU
conditioned
space
AHU
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Operating cost advantage is even greater for low humidity
Solid Desiccant Wheel &
Chilled Water
Tons of Conventional Cooling
Liquid Desiccant &
Chilled Water
93
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$74,400
$26,400
10,000 CFM desiccant wheel
3 x Liquid Desiccant Units
$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
$2,156,787
$1,064,874
Approx. Cost of Conventional Equip.
Desiccant Equipment
Cost of Desiccant Equipment
5-Year Total Cost
-51%
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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
OA
Liquid
Desiccant
RTU
door
infiltration
door
conditioned
space
50
Systems for comparison
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
~$255,000
~$275,000
Overcooling to achieve
target conditions
Overcooling not required to
achieve target conditions
Total Equipment Cost
Humidity Control
Projected Savings
$15,000-35,000/year
For a 9% premium in equipment costs,
payback is under 1 year
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