Green Sustainable Energy Efficient

8/11/2019 Green Sustainable Energy Efficient

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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

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