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Optimizing Solutions through Superior Dehumidification Technology SM Humidity Control and Heating and Cooling Applications December 6, 2018
Optimizing Solutions through Superior Dehumidification Technology SM
Humidity Control and Heating
and Cooling Applications December 6, 2018
Today’s Discussion
• Discussion of cooling, heating and
dehumidification loads.
• Importance of zone condition selection on
efficiency.
• Airflow energy impact through HVAC
equipment and room.
• Basic equipment options and energy use.
• Critical importance of commissioning.
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ROOM LOADS
Lights and Water
(and others)
Relative Intensity of Lighting
Relative Intensity of Lighting at
Specific Wavelengths
Relative Intensity of Lighting at
Specific Wavelengths
Lighting Summary
• Even with 45-65 watts / sq. ft. the PAR value is less than full noon summer sun.
• Although plants use a small amount of the light energy in the process of converting water into sugars, starches, and O2, virtually all lighting energy becomes sensible heat load.
• Total input (including ballasts or drivers) is important.
Evapotranspiration
• Latent loads.
• Evaporation highly dependant on irrigation method.
– Drip Irrigation – Low evaporation.
– Flood or Trough Irrigation – Higher rate.
– Spray Irrigation – Extremely high evaporation.
• As much as 300 Btu/hr for large plant in high light.
• Perhaps best estimated by (water in) – (water out); if
known.
Evaporation + Plant Transpiration
Plant Physiology – Water Transport
Transpiration
Evaporative Cooling Effect
• As water evaporates energy is converted.
1060 Btu/lb at typical conditions.
• Plants also use this effect in the transpiration
process to cool themselves. Through
conduction and convection this in turn cools
the air.
• Care must be observed if used to offset
loads. If plants are just emerging, water use
and evaporative cooling effect are small.
Facilities Construction
• Can vary significantly.
• Room within room.
• Structurally insulated panels (or similar).
• Partitioned room.
• Open warehouse.
Typical Rooms
Load Details
Building Skin Loss/Gain – If Applicable
• Insulated (or uninsulated) walls, floors, and
ceilings.
• Heat loss as ambient temperature decreases.
• Heat gain as ambient temperature increases.
• Concrete floors create a heating load.
• Doors and windows have different losses and
gains than the walls.
• Solar load has major impact if it exists.
Ventilation for Plants
• Outdoor air exchange may be required to
maintain CO2 levels for plants.
• Adds (or subtracts) sensible and latent
load.
• Alternative in a “Closed (Sealed) Growing
Environment” is CO2 supplementation.
– Rooms may be kept at higher temperature.
Relative Humidity
…is relative…
It represents the ratio of moisture in the air
relative to when no more can be held in
the air. (Saturated)
…but..
Relative Humidity
Relative humidity is relative to temperature!
Higher temperature air is able to hold more
moisture. Lower temperature hold lesser
amounts before saturation.
Therefore, RH changes with temperature!
Changes in Dry Bulb Temperature Affect Relative Humidity
Changes in Dew Point
Affect Relative Humidity
Relative Humidity is
Relative
Higher Enthalpy(More Energy Rich)
Lower Enthalpy (Lower Total Energy)
Lines of Constant Enthalpy
Transpiration Rates – Lights On
• Leaf temperature determines the vapor
pressure in the leaf.
• Air temperature and humidity determines
the vapor pressure in the air.
• Vapor Pressure Deficit (VPD) drives
transpiration – regulated rates are
important for plant growth and health.
Transpiration Rates – Lights Off
• Stomata closed as no light is being
received. Evapotranspiration continues at
a lower rate during lights off.
• Slowly decreases over 60-90 minutes.
Roughly 30% of full light moisture rate
when full dark.
• This latent load can still be relatively high
as sensible load is negligible.
VPD at 1.3 kPa (0.39” Hg) at various DB/WB/RH
Different operation, but same drive for growth
Larger Equipment/Higher Energy Use
Smaller Equipment/Lower Energy Use
Calculation Methods for Latent Load
Net Watering Rate given or calculations
Derivations of Penman-Monteith equation or similar
Total Loads and Control - HIDDesign Conditions –3,500 ft2, 2,000 plants,
63 watts/sq ft. (85% BE), 318 gal/day net water – Early Veg
500 CFM Ventilation - Lights On
Description Sensible (Btu/hr) Latent (Btu/hr)
Lighting and Appliance 852,500 0
Doors 445 0
Ceiling 5,331 0
Walls 4,564 0
Infiltration -320 -199
Ventilation -6,510 -7,770
Evapotranspiration 0 150,404
Evaporative Cooling Effect -150,404 -
Total 705,606 142,435
Compiled using ACCA Manual N Form N1 and ASHRAE Dehumidification Weather Data
705,606/(142,435 + 705,606) = 0.83 SHR
Total Loads and Control - LEDDesign Conditions –3,500 ft2, 2,000 plants,
25 watts/sq ft. (95% DE), 318 gal/day net water – Early Veg
500 CFM Ventilation - Lights On
Description Sensible (Btu/hr) Latent (Btu/hr)
Lighting and Appliance 314,078 0
Doors 445 0
Ceiling 5,331 0
Walls 4,564 0
Infiltration -320 -199
Ventilation -6,510 -7,770
Evapotranspiration 0 150,404
Evaporative Cooling Effect -150,404 -
Total 167,184 142,435
Compiled using ACCA Manual N Form N1 and ASHRAE Dehumidification Weather Data
167,184/(142,435 + 167,184) = 0.54 SHR
Total Loads and Control - HIDDesign Conditions –3,500 ft2, 2,000 plants,
63 watts/sq ft. (85% BE),954 gal/day net water–Early Flower
500 CFM Ventilation - Lights On
Description Sensible (Btu/hr) Latent (Btu/hr)
Lighting and Appliance 852,500 0
Doors 445 0
Ceiling 5,331 0
Walls 4,564 0
Infiltration -320 -199
Ventilation -6,510 -7,770
Evapotranspiration 0 526,414
Evaporative Cooling Effect -526,414 -
Total 326,596 518,445
Compiled using ACCA Manual N Form N1 and ASHRAE Dehumidification Weather Data
326,596/(326,596 + 518,445) = 0.32 SHR
Total Loads and ControlDesign Conditions – 3,500 ft2, 2,000 plants,
954 gal/day net water - Flower
500 CFM Ventilation - Lights Off
Description Sensible (Btu/hr) Latent (Btu/hr)
Lighting and Appliance 1,203 0
Doors 445 0
Ceiling 5,331 0
Walls 4,564 0
Infiltration -320 -199
Ventilation -6,510 -7,770
Evapotranspiration 0 175,471
Evaporative Cooling Effect -175,471 -
Total -170,758 167,502
No cooling required. Dehumidification Only Load.Compiled using ACCA Manual N Form N1 and ASHRAE Dehumidification Weather Data
Lights On
Lights Off
Air conditioner and dehumidifier
Lighting Load
Air conditioner and dehumidifier
Lighting Load
Reheating
Energy use and control
• Traditional dehumidifiers heat the air when it may not be needed.
– Cooling needs to work “harder.”
• Some equipment has less than full capacity reheat or electric reheat only.
– “New” energy needs to be added.
– Not considered here.
• “All-in-one” environmental control is best practice.
Multiple Units Serving a Space
Multiple Units Serving a Space
• Partial capacity during
maintenance/service.
• Redundancy possible.
• Footprint and layout advantages.
• Enhanced staging capability.
– Energy efficiency.
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Control coordination is critical
Economizers
• Number of hours where OA is possible is variable depending on the location and time of year.
• More care required for filtering with air economizer. May introduce more spores and pests.
• Both the temperature and humidity are affected if economizer is used. This must be approached carefully.
• CO2 Enhanced grows impractical with OA economizer.
Outdoor Air Too Warm in Lights On
Outdoor Air Too WarmFew Hours in Lights Off
Outdoor Air too Humid
Will require more energy to heat or humidify.
May not be able to properly cool or dehumidify
Target76° Dry Bulb
45% RH
IMPACTS OF AIRFLOW
Affinity Laws Working for Energy Efficiency
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Affinity Laws (Fan Laws)
Affinity Laws (Fan Laws)
Affinity Laws (Fan Laws)
For example, reduction in the airflow (shaft speed) to ½ of the peak flow rate in a given system results in
1/8 of the peak power at the fan shaft.
Importance of Air MovementPlant Leaf Boundary Layer
• Water vapor builds at leaf boundary layer.
• Creates higher relative humidity and vapor pressure at leaf
surface.
• Buildup can happen under canopy.
– Dicots have most stomata on underside of leaf.
– 20-30% higher relative humidity under canopy if airflow is too
low.
Slowly moving canopy is goal
Δ 7.8 Btu/lb
10-tons Capacity (120,000 Btu)3400 CFM
Δ 17 grains/lb
Moisture Removed = (3400 CFM *17 grains per lb) / 1555 = 37.2 lbs Water Removed
Δ 22°F
Sensible Cooling= (3400 CFM *Δ 22°F TD) * 1.08 = 80,784 Btu/h
Δ 15.6 Btu/lb
10-tons Capacity (120,000 Btu)1700 CFM
Δ 44 grains/lb
Moisture Removed = (1700 CFM *44 grains per lb) / 1555 = 48.1 lbs
Δ 34°F
Sensible Cooling= (1700 CFM *Δ 34°F TD) * 1.08 = 62,424 Btu/h
COMMISSIONING
Critical Steps in Ensuring Success
Commissioning
• Startup by factory trained technicians who know the equipment.
• Equipment and facility in operation.
– Challenge with this application.
– A project manager with timeline is key.
• Have operators/facility people available during startup for Owner Training.
• Have local Service Technicians aligned for PM and ready in case of any issues.
Continuous Commissioning
• Periodic Maintenance for this type of
equipment is key.
• Complete a “Start-up” on a yearly basis.
• Review trends to determine if there is an
issue.
• “An ounce of prevention is worth a pound
of cure.”
Sensor Locations and
Central Control
79°/55%
72°/65%
76°/50%
85°/35%
60°/11% 76°/55%
Controls Tuning
Tune Changes
Remote Monitoring
• Remote monitoring.
– E-mail and SMS alerts.
– Cloud-based service.
– Real-time data and logging.
– Allows a team to review together quickly.
