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Introduction
Refrigerated warehouses provide a vital link inthe cold chain from the farmer to the consumer
Refrigerated warehouses operate at -10 to +40F(-25 to +5C)
Electrical energy is used to operate refrigerationequipment
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Introduction
Refrigerated warehouses are significant energyconsumers
USDA (2006) estimates US refrigerated storagecapacity at 3.21 billion ft3(90.9 million m3) andincreasing at the rate of 1% per year
DOE (1999) estimates energy consumption ofUS cold stores to be 17 billion kWh per year
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Project Goal
Increased energy conservation andenvironmental stewardship in the refrigeratedwarehouse industry
Development of a comprehensive best practicesGreenGuide for engineers, contractors, facility
owners and operators
Outreach Program
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A Green, Sustainable, Energy Efficient
Refrigerated Storage Facility
Maintains a safe and appropriate environment for thestorage of perishable food items
Limits its impact on the Earths natural resourcesincluding both energy and water
Employ elegant, simple, passive design and engineering
solutions
Annual refrigeration loads are reduced to the minimum
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A Green, Sustainable, Energy Efficient
Refrigerated Storage Facility
Refrigeration equipment will operate at high energyefficiency
Designed and constructed to be robust Maintainable with minimal effort
Environmentally friendly refrigerants that minimize:
Ozone depletion potential Global warming potential
Annual energy consumption
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Typical Facility Layout
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Typical Facilities
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Contents of the GreenGuide
Sustainable Structure Design
Refrigeration System Design
Natural Refrigerants
Load Calculations
Energy Use and Facility Management
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Sustainable Structure Design
General layout and siting Utilizing the available local natural environment to benefit the facility Reducing the facilitys impact on the environment Building orientation and microclimate; building configuration End-user activities
Traffic flow analysis to optimize material handling systems
Specific aspects of building envelope Walls, roofs, floors, and doors Environmentally preferable building materials Insulation
Vapor retarder Infiltration reduction Thermal mass Cool (high albedo) exteriors Passive solar technologies.
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Building Orientation and Microclimate
Cold stores are usually oriented to present anaesthetically pleasing faade
Little or no regard for the microclimate
Orienting the refrigerated dock so that it doesnot face into the prevailing wind will greatlyreduce:
Infiltration Refrigeration load
Defrost frequency
Energy costs
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Infiltration
Warm, moist ambient air entering the refrigerated facility Sensible and latent heat loads (5 seconds)
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Effects of Infiltration
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Doors and Infiltration
Doors linked directly to productivity and operationalcost
Infiltration: ~50% of the total refrigeration load Minimize energy losses
Minimize door opening/closing cycles Maximize door opening/closing speeds Minimize door opening size Heated door seals
Dock-to-truck seals Infiltration reduction devices: air curtains, vestibules, fast
acting doors
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Air Curtain
Fast-ActingDoor
Vestibule
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Water Vapor Transmission
Building envelope must prevent water vapor migrationfrom outside to inside
Failure to prevent water vapor migration results in: Increased energy cost (more defrost cycles)
Diminished insulating effect
Structural damage
Biological growth
Ice formation
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Vapor Retarder
Prevents moisture migration
Located on the warm side ofthe insulation
Ensureswater vapor pressureremains lower than saturation
pressurethroughout the wall
Must encompass the entirefacility No discontinuities
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Defective Vapor Retarder
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Walls, Ceilings and Insulation
Wall/ceiling materials must be of increasingpermeability toward the cold interior
Moisture that enters wall from outside will migrateto the evaporator surface
Prevents moisture from becoming trapped within
wall
Prevents condensation and ice formation within wall
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Cool Roofs
50,000 ft2roof results in a significant solar load
Cool Roofs can cut solar loads by up to 20%
Reflectance 0.70 and Emittance 0.75
EPDM
single-ply173 F
Cool coating
over BUR108 F
Noon in Sacramento, CA, 89F
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Solar Roof
50,000 ft2roofprovides an excellentopportunity to utilizeroof-mounted
photovoltaic cells
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Refrigerated Dock Design
During loading and unloading of refrigerated trucks, significantenergy savings can be harvested by:
Providing an extended overhanging roof to shade thetruck, reducing its solar load
Using insulated sealing cushions to reduce infiltrationbetween the truck and the dock door
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Refrigeration System Design
Energy required for refrigeration constitutes themajor cost of operating a refrigerated storagefacility
Energy efficient refrigeration technologies andoperating strategies
Efficient piping design to minimize P
Use high efficiency motors and variablespeed drives (compressors, evaporatorand condenser fans, fluid pumps)
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Natural Refrigerants
Ammonia (R-717) Ozone depletion potential, ODP = 0
No global warming potential, GWP = 0
Carbon Dioxide (R-744)
Ozone depletion potential, ODP = 0 Negligible global warming potential, GWP = 1
Ammonia/Carbon Dioxide Cascade Systems Large low-temperature industrial systems (-30C to -50C)
Ammonia (high cascade) confined to machine room
Carbon dioxide (low cascade) circulated to storage spaces and productionareas, where food is being processed and frozen
In case of an ammonia leak, neither the staff nor the food is affected
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Load Calculations
Detailed, comprehensive load calculations rather than peak load Seasonal, hour-by-hour refrigeration load, based on local weather data
Effects of the diurnal cycle as well as weekends and holidays
Time-dependent product loads, both sensible and latent
Sensible heat load transmitted through walls, roof and floor Sensible and latent heat loads due to infiltration through doors and docks
Incremental sizing of compressors, evaporators and
condensers to track variations in the refrigeration load
Computer-based energy management systems to controlthe incremental refrigeration equipment
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Energy Use and Facility Management
Establish and maintain an energy accounting system Monitor how and where energy is being used
Computer-based energy management system
Utility invoices, printouts from time of use meters, recordingsof temperature and relative humidity, submetered data.
Database of past energy usage
Identify energy conservation opportunities
Commissioning and periodic re-commissioning
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Commissioning
Verify performance of each system versus design specifications Check refrigeration system for leaks prior to charging with refrigerant.
Check vapor retarder seals for integrity
Check floor heating system, door threshold heaters and all trace heating
Check lighting and emergency lighting
Check fire/smoke detection systems/refrigerant leak sensors Check manual and automatic doors for their operation
Verify refrigeration equipment start-up procedure andtemperature pull-down rate Ensure that thermal expansion and contraction does not become a
problem
Thermographic Scan
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Thermographic Scan
Infrared thermal imaging survey
Qualitative measure of the thermal performanceof the insulated envelope
Identify areas of high or low thermal emission
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Example Thermgraphic Scans
Roof/Wall Junction
Loading Dock
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Energy Strategies and Alternatives
Use hot gas from compressor discharge for heating Under-floor heating
Space heating of offices, shops and docks in the winter
Set the temperature of refrigerated storage facilities only as low
as required Remove lamps or reduce lamp wattage in the refrigerated space
Minimize the use of material handling equipment which is storedoutside and used inside
Minimize evaporator defrost time and frequency Provide evaporator fan controls (on/off and/or variable speed)
Only load cold product into the storage facility
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Design Essentials for Refrigerated
Storage Facilities
This book provides engineers in the food refrigeration industry with acomprehensive design guide that addresses the various issues surrounding thedesign of refrigerated storage facilities. The design guide covers those areaswhere ASHRAE is uniquely qualified, and includes a thorough treatment ofthe current, established trends in refrigerated facility design. Chapter topics
include storage facility specifications, structure design, and management. Thisguide is the result of ASHRAE Research Project 1214.
AUTHORS: Bryan Becker, Ph.D., P.E.; Brian Fricke, Ph.D.ISBN/ISSN: 1-931862-74-5
NO. OF PAGES: 192PUBLISH DATE: 2005PUBLISHER: ASHRAEUNITS: Dual
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Support Structure
Performance of the insulated envelope, especially joints,depends upon the deflection of the support structure:
Snow, wind, rain, seismic loads
Mechanical equipment: evaporators, piping, ice/frost loads
Two basic refrigerated facility construction techniques:
External frame/internal insulation
Internal frame/external insulation
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External Frame/Internal Insulation
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Internal Frame/External Insulation
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Water Vapor Transmission
Due to vapor pressure difference across the insulated envelope.
Condensation begins when water vapor pressure and saturationpressure, based on the temperature, are equal.
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Frost Heaving
Occurs when ground below a cold store freezes
Moisture in the ground freezes and expands Floor buckles
Support columns move, damaging roof and support structure Can be prevented with under floor heating system
Prevent the subsoil from freezing
A note about insulated floors:
Insulation does not inhibit heat flowit only slows the rateof heat transfer
An insulated floor may be damaged by frost heave
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Floor Heating: Liquid Circulation
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Venting
Substantial indoor/outdoor pressuredifferentials
Caused by evaporator defrosting, warm product
influx, facility cool-down, rapid barometricpressure change
Can result in movement of insulated panels,
disruption of vapor retarders, structural damageAlleviated by inflow/outflow hinged vent pairs
(not on opposing walls)
Eff f I d V i
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Effects of Inadequate Venting