1. Energy Efficiency Project Analysis for 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 considerations in energy efficiency project analysis for supermarkets and arenas
Introduce RETScreen® Energy Efficient Arena & Supermarket Project Model

3. 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
Ice Rink and Bleachers
Photo Credit: Regos Photography/Andrus Architecture
Supermarket Interior

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/losses through 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 refrigeration systems 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 rink heating 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 are distributed around building
Long loops of refrigerant-filled piping connect mechanical room to loads and condenser
Leaks in piping and joints account for 50% of supermarket’s greenhouse gasses
Solution: secondary loops on hot 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 refrigerant charge) that dump heat to the secondary loop

13. Measures for Arenas: Minimize refrigerant leaks with secondary loops
Open compressors and high refrigerant charges lead to significant greenhouse gas emissions
Solution: secondary loops on warm (condenser) side
Small refrigerant load contained 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 exterior air temperature
Solution: Permitting condenser temperature to drop during cold weather improves efficiency and compressor longevity
“Floating head pressure” 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 to temperatures below condensing temperature (subcooling)
Ambient: cold exterior air or rink snow pit
Mechanical: second refrigeration system
Better than simply removing more heat from condenser – second system operates with higher COP

16. Measures for Supermarkets and Arenas: Thermal storage
Storage of rejected heat
Peak demand charges associated with heating 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 or in 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 paints or materials in arenas
Solution: Reduced light intensity where 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 reflectivity into consideration
Solution: Natural lighting
Pleasing ambience
Must avoid solar gains, excessive heat losses or gains through windows
Ice rink with daylighting
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 with low 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. 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 low temperature (≤32ºC) radiant flooring system
Use heat rejected by refrigeration system
Slab heating maintains spectator comfort
Reduce temperature in stands during unoccupied periods
Simulated Temperature

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. 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 direction and then back to header: a two-pass layout
Secondary fluid pump accounts for over 15% of the refrigeration system’s total energy consumption
Secondary fluid pump’s heat adds to refrigeration loads
Solution:
Reduce secondary fluid flow rate according to schedule/occupancy
Two-speed pump, two pumps, or variable speed pump
Piping network that transports fluid four or more passes through slab allows flow rate to be halved
Affects ice uniformity?
Piping in slab
Photo Credit: Marius Lavoie, NRCan

22. 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 mm thick, but can be as high as 75 mm
In most arenas, ~25 mm of concrete above 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 cool storage, reduces capacity requirements
Pouring of slab
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. Supermarkets: Costs of efficiency measures
Secondary Loop
Depending on measures implemented, 0 to 40% higher initial costs than conventional systems
A full range of measures cost additional ~$250,000
Supermarkets often require paybacks of 3 years or less
Additional costs may be offset by 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 want simple 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 system with financially attractive alternative is a 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 be a significant source of annual cost savings
In some provinces, power demand charges account for 40% of electricity invoices

28. Example: Quebec, Canada Repentigny supermarket
Refrigeration systems reject heat to 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 of heat 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
Supermarket Entrance
Vegetable Display

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

30. 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-pass rather than two-pass configuration
Six cascaded 3 hp pumps achieve variable secondary coolant flow rates as required
Floating condenser pressure
Low emissivity ceiling
Efficient lighting (10.5 kW vs 25 kW)
Val-des-Monts Recreational Ice Rink
Photo Credit: Marius Lavoie, NRCan

31. Example: Quebec, Canada Val-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 leaks achieved with sealed units and secondary loops
Refrigerant charge of 36 kg (vs 500 kg in typical system)
Refrigerant with no impact on ozone layer
Autumn start-up and end-of-season shut down require no special skills (where permitted)
Exceptional comfort for spectators

32. RETScreen® Energy Efficient Arena & Supermarket Project Model
Calculates energy savings, life-cycle costs and greenhouse gas emissions 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? www.retscreen.net
Energy Efficiency Project Analysis for Supermarkets and Arenas Module
RETScreen® International Clean Energy Project Analysis Course
For further information please visit the RETScreen Website at