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Energy Efficiency Project Analysis for Supermarkets and Arenas Clean Energy Project Analysis Course

Energy Efficiency Project Analysis for Supermarkets and Arenas Clean Energy Project Analysis Course. Objectives. Review basics of advanced refrigeration systems & energy efficiency measures for supermarkets and arenas

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Energy Efficiency Project Analysis for Supermarkets and Arenas Clean Energy Project Analysis Course

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  1. Energy Efficiency Project Analysisfor Supermarkets and Arenas Clean Energy Project Analysis Course

  2. Objectives • Review basics of advanced refrigeration systems & energy efficiency measures for supermarkets and arenas • Illustrate key considerationsinenergy efficiency project analysis for supermarkets and arenas • Introduce RETScreen® Energy EfficientArena & Supermarket Project Model

  3. Ice Rink and Bleachers Supermarket Interior What do energy efficiency measures & advanced refrigeration systems provide? • Refrigeration and cooling in supermarkets and arenas • Space, ventilation air, and water heating; dehumidification …but also… • Reduced energy consumption • Reduced power demand charges • Reduced refrigerant leaks • Reduced greenhouse gas emission • Reduced maintenance costs • Improved comfort Photo Credit: Regos Photography/Andrus Architecture

  4. Supermarkets:Background • Among most energy-intensive commercial buildings • 5,000 MWh-eq/year for electricity in large supermarket (>1,000 m2) • Over 5,000 large supermarkets in Canada • Refrigeration accounts for 50% of energy costs; lighting, 25% • $150,000/year for refrigeration in large supermarket • Energy costs are ~1% of sales • But this is approximately same as store profit margin! • Conventionally have very high refrigerant charges • Average store has 1,300 kg of refrigerant • Long piping runs result in leakage of 10 to 30% of charge per year • Synthetic refrigerants are potent greenhouse gases (GHG) • Can have over 3,000 times the effect of CO2

  5. Arenas: Background • Typical arena in Canada: • ~ 1,500 MWh-eq/year consumption • ~ $100,000/year energy cost • Major consumer of energy • 2,300 skating rinks in Canada • 1,300 curling rinks in Canada • Conventionally have high refrigerant charges • Average arena has 500 kg of refrigerant • Open compressor results in significant leakage • Synthetic refrigerants: potent greenhouse gases • Can have over 3,000 times the effect of CO2 Energy Consumption for Typical Arena in Canada

  6. The building as a system • Supermarkets and arenas are systems with purchased energy inputs… • Electricity, natural gas, etc., • …that satisfy simultaneous heating and refrigeration loads… • …in proximate warm and cold zones.

  7. Heating and refrigeration loads • Influenced by… • Gains/losses through building envelope • Gains/losses in ventilation fresh and exhaust air (sensible + latent) • Gains from occupants (sensible + latent) • Gains from equipment (e.g. lighting) • Gains/losses in mass flows (e.g. hot water down drain, ice making) • Gains/lossesthrough floor • Solar gains • …and heat transfer from heated to cooled areas!

  8. Where are improvements possible? • Control according to activity & environmental conditions • Reduce heat transfer from warm to cold zones • Reduce unwanted gains and losses • Process integration: transfer heat from cold to warm zones • Use heat rejected by refrigerationsystems to satisfy heat loads • Improve HVAC&R equipment efficiency • Reduce refrigerant charge and leakage • Major reduction in greenhouse gases

  9. Review of vapour-compression refrigeration cycle

  10. Supermarkets and Arenas:Problem: Heat transfer from warm to cool zones • Heat draining from warm zones to cold zones accounts for majority of refrigeration load • Majority of heat dumped to outside air by condenser • Heating system must make up for some of this rejected heat • Heat rejected by refrigeration system generally exceeds heating load Typical Canadian skating rinkheating load and heat rejected by refrigeration system, by month

  11. Measures for Supermarkets and Arenas: Process Integration makes use of heat rejected by refrigeration system • Capture rejected heat in a secondary loop • Secondary loop facilitates heat distribution • Desuperheater at outlet of compressor • Recovers up to 15% of rejected heat– good for hot water • Further heat recovery before condenser • Heat can be used for space, ventilation air, and water heating • Heat pumps raise temperature of heat from secondary loop as necessary • Excess heat can be… • Stored for later use • Heat under ice rink slab • Snow pit melting • Export to nearby buildings • Sidewalk, parking lot, street heating • Dump any surplus to outside air

  12. Measures for Supermarkets:Minimize refrigerant leaks with secondary loops • Refrigeration loads aredistributed around building • Long loops of refrigerant-filled pipingconnect mechanical room to loads and condenser • Leaks in piping and joints account for 50% of supermarket’s greenhouse gasses • Solution: secondary loops onhot and cold sides • Secondary loop with water, glycol mix, brine, CO2, methanol, etc.: not potent GHGs like synthetic refrigerant • Small refrigerant load contained in hermetic unit • Low temperature loads: use autonomous refrigeration sub-units (with low refrigerantcharge) that dump heat tothe secondary loop

  13. Measures for Arenas:Minimize refrigerant leaks with secondary loops • Open compressors and high refrigerant charges lead to significantgreenhouse gas emissions • Solution: secondary loops on warm (condenser) side • Small refrigerant loadcontained in hermetic unit • Water or glycol mix in loop: no GHG’s

  14. Measures for Supermarkets and Arenas: Tailoring HVAC&R equipment to cold climates • Equipment is conventionally designed for warm climates • Condensers typically operate at high temperature,regardless of the exteriorair temperature • Solution: Permitting condensertemperature to drop duringcold weather improvesefficiency and compressorlongevity • “Floating headpressure” operation • COP can double, (e.g. from 3 to 6) • Reduces usefulness of rejected heat • Must optimize operating temp.

  15. Measures for Supermarkets and Arenas: Mechanical/ambient refrigerant subcooling • Conventionally, output of condenser feeds directly into expansion valve • Capacity and efficiency can be improved by cooling liquid exiting condenser totemperatures below condensing temperature(subcooling) • Ambient: cold exterior air or rink snow pit • Mechanical: second refrigeration system • Better than simply removing moreheatfromcondenser– second systemoperates with higher COP

  16. Measures for Supermarkets and Arenas: Thermal storage • Storage of rejected heat • Peak demand charges associatedwithheating can be reduced • Short-term: water tanks of 2,000 litres for several hour storage (e.g. night) • Seasonal: underground storage with horizontal/vertical heat exchanger • Arenas can also store“cold” under slab orin reservoir • Reduce peak demand charges by extracting cold from storage during times of peak load • Reduce design capacity of refrigeration equipment • Increase in COP through use of heat pump to produce heat and cooling simultaneously

  17. Ice rink with daylighting Measures for Supermarkets and Arenas: Efficient lighting and daylighting • Artificial lighting augments refrigeration loads • Solution: More efficient lighting technologies • Solution: Highly reflective ceilings– reduce lighting needs by 30% • Can be combined with low-e paintsor materials in arenas • Solution: Reduced light intensitywhere permissible • Multi-light level intensity lamps • Vary number of operating lamps • Consider activity and occupancy level • Reduce height of fixtures and ceiling,taking ceiling and wall reflectivityinto consideration • Solution: Natural lighting • Pleasing ambience • Must avoid solar gains, excessive heat losses or gains through windows Photo Credit: Skating Club of San Francisco

  18. Measures for Arenas: Ceilings that radiate less heat • Infrared radiation from ceiling: up to 30% of the ice sheet refrigeration load • Ceiling gets hot from space heating, solar gains and artificial lighting • Common materials have high emissivity index (e = 0.80 to 0.95) • Solution: use materials withlow emissivity • Low-e aluminized cloth(e=0.03 to 0.08) • Aluminium-based low-e paint or other low-e paints • Additional Benefits • Reduced condensation • Improved acoustics • Reduce lighting requirements Reflective, Low-e Ceiling Photo Credit: Marius Lavoie, NRCan

  19. Simulated Temperature Measures for Arenas:Reduce heat losses from stands • Space heating in stands adds to refrigeration load • Air temperature in spectator stands may be as high as 15 to 18ºC • Typically adds 20% to the refrigeration load • Solutions: • Heat stands with lowtemperature (≤32ºC) radiantflooring system • Use heat rejected by refrigeration system • Slab heating maintains spectator comfort • Reduce temperature in stands during unoccupied periods

  20. Measures for Arenas: Optimize ice temperature • Rinks normally maintain ice temperature around –6ºC • Refrigeration load can be reduced by letting ice temperature rise • During figure skating: -3 to -4ºC • During free skating: -2 to -3ºC • During unoccupied periods (e.g. night): -1 to -2ºC • Stop secondary fluid pump during unoccupied periods,and restart only when infrared sensor indicates ice temperature has risen to a preset maximum allowable temperature

  21. Piping in slab Measures for Arenas:Reduce refrigerant pumping energy • Ice cooled by secondary fluid circulating in concrete slab • Piping network transports secondary fluid across ice in one directionand then back to header: a two-pass layout • Secondary fluid pump accounts for over15% of the refrigeration system’s totalenergy consumption • Secondary fluid pump’s heat adds torefrigeration loads • Solution: • Reduce secondary fluid flow rateaccordingto schedule/occupancy • Two-speed pump, two pumps, orvariablespeed pump • Piping network that transports fluid fouror more passes through slab allows flowrate to be halved • Affects ice uniformity? Photo Credit: Marius Lavoie, NRCan

  22. Pouring of slab Measures for Arenas:Optimize ice and concrete slab thickness • Heat transfer from secondary fluid to ice surface reduced by thick ice and thick layer of concrete above tubes • Lower heat transfer results in higher refrigeration energy consumption • In most arenas, ice 25 to 40 mmthick, but can be as high as 75 mm • In most arenas, ~25 mm of concreteabove embedded tubes • Solution: • During construction or renovation,ensure concrete slab should be≤ 25 mm above tubes • Keep ice thickness at 25 mm, where permitted • In combination with under slab coolstorage, reduces capacity requirements Photo Credit: Marius Lavoie, NRCan

  23. Measures for Arenas: Different dehumidification approaches • Dehumidification normally involves stand-alone cooling unit • Heat rejected to ice rink and adds to refrigeration load • Solution: Reject heat from dehumidifier to condenser-side secondary loop of principal refrigeration system • Rejected heat can be used for space heating, etc. • Solution: Desiccant dehumidification system

  24. Secondary Loop Supermarkets:Costs of efficiency measures • Depending on measures implemented, 0 to 40% higher initial costs thanconventional systems • A full range of measures costadditional ~$250,000 • Supermarkets oftenrequirepaybacksof 3 years or less • Additional costsmay beoffsetby elimination of combustion heating system Standard DX system Secondary loop system

  25. Arenas:Costs of efficiency measures • Major rink renovation every 25 years: ~$700,000 • $175,000 (single pad) or $200,000 (multipad) for efficiency measures • Owners and operators generally wantsimple payback of 5 to 8 years or less • Process integration of heating and refrigeration typically has 3½ year payback in new construction, 5 to 8 years in retrofit Minor Investment Moderate Investment Major Investment Better controls Desuperheater Low-e ceiling Nighttime setbacks Dehumidification Efficient lighting Optimize ice thickness Snow Pit Process integration Power factor correction Cold-climate adaptions Thermal storage

  26. Supermarkets:Project considerations • Systems must demonstrate very high reliability • A one day refrigeration system failure is extremely costly in terms of lost revenue and produce • Incorporate advanced refrigeration innovations in new buildings and during major equipment overhauls • Supermarket refrigeration systems overhauled every 8 years on average • In existing supermarkets, new systems may need to be installed and brought on-line while supermarket is operating • Rejected heat from refrigeration system can supply all heat required for supermarket • Elimination of combustion heating systemwithfinancially attractive alternative isa convincing argument

  27. Arenas:Project considerations • Incorporate advanced refrigeration innovations in new buildings and during major equipment overhauls • Arena refrigeration systems overhauled on 25 year basis (30 to 40% of Canadian rinks presently operating beyond projected life span) • Many arenas close for 1 to 2 months per year when retrofits can be done • Rejected heat from refrigeration system is three times heating energy requirement on annual basis • But for short periods in winter heat load may exceed reject heat • Reduction in power demand charges can bea significant source of annual cost savings • In some provinces, power demand charges accountfor 40% of electricity invoices

  28. Supermarket Entrance Vegetable Display Example: Quebec, Canada Repentigny supermarket • Refrigeration systems reject heatto two secondary loops • Medium temperature refrigeration system loop provides up to 250 kW of space and air heating • Low temperature loop provides up to 220 kW ofheat to heat pumps (2nd function: air conditioners) • Desuperheater meets hot water needs • Medium temperature cold side secondary loop used to subcool low temperature refrigerant by 30ºC at output of condenser • Evaporator (cold) side secondary loops • Condenser temperature/pressure floats according to building heating requirement and outdoor air temperature

  29. Supermarket Interior Example: Quebec, CanadaRepentigny supermarket (results) • No boiler or backup heating installed! • All heating provided by waste heat from refrigeration system • Energy consumption reducedby 20% • On-going monitoring • GHG emission reduction of 75% anticipated • Due to reduced natural gas consumption and reduced refrigerant leaks • Minimal commissioning: system functionedwell from start • No problems since April 2004

  30. Val-des-Monts Recreational Ice Rink Example: Quebec, Canada Val-des-Monts recreational ice rink • Heat rejected by refrigeration system recovered in secondary loop • Radiant floor heating (stands and space heating)reduces refrigeration load • Service hot water and resurfacing hot water(with heat pump) • Under slab heating • Snow pit melting • Excess heat to nearby community centre • Thermal storage • Short term: 2,000 litre water tank for heat • Short term: Under pad storage for cold • Seasonal: Horizontal loop underground • Circulation of secondary coolant in five-passrather thantwo-pass configuration • Six cascaded 3 hp pumps achieve variablesecondary coolant flow rates as required • Floating condenser pressure • Low emissivity ceiling • Efficient lighting (10.5 kW vs 25 kW) Photo Credit: Marius Lavoie, NRCan

  31. Example: Quebec, CanadaVal-des-Monts recreational ice rink (results) • 60% reduction in energy compared with model building code reference rink • 50% reduction in power demand compared with average rink • Power demand and energy savings of $60,000 annually • Greater than 90% reduction in GHG emissions • Mainly due to reduced refrigerant leaksachieved with sealed units andsecondaryloops • Refrigerant charge of 36 kg(vs 500 kg in typical system) • Refrigerant with no impact on ozone layer • Autumn start-up andend-of-season shut downrequire no special skills (where permitted) • Exceptional comfort for spectators

  32. RETScreen®Energy Efficient Arena & Supermarket Project Model • Calculates energy savings, life-cyclecosts andgreenhouse gasemissions reductions • For supermarkets & ice rinks • Process integration (waste heat recovery) • Secondary loops to reduce refrigerant losses • Lighting and ceiling improvements • Floating condenser pressure • Ice and concrete slab thickness • Other efficiency measures • Also includes: • Multiple currencies, unit switch, and user tools

  33. Conclusions • Cost-effective energy efficiency measures, as well as improvements to refrigeration systems in supermarkets and arenas, can greatly reduce energy consumption and greenhouse gas (GHG) emissions • Through process integration, heat rejected by refrigeration system can satisfy most or all of supermarket/arena heating load and, in certain cases, eliminate fossil-fuel combustion heating systems • RETScreen® calculates energy savings and greenhouse gas emission reductions for a wide range of energy efficiency measures for supermarkets and ice rinks • RETScreen® provides significant preliminary feasibility study cost savings

  34. Questions? Energy Efficiency Project Analysisfor Supermarkets and Arenas Module RETScreen® International Clean Energy Project Analysis Course For further information please visit the RETScreen Website at www.retscreen.net

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