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

Energy Efficiency Project Analysisfor Supermarkets and Arenas

Clean Energy Project Analysis Course

Objectives

Review basics of advanced refrigeration systems & energy efficiency measures for supermarkets and arenas

Illustrate key considerationsin energy efficiency project analysis for supermarkets and arenas

Introduce RETScreen® Energy Efficient Arena & Supermarket Project Model

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

What do energy efficiency measures & advanced refrigeration systems provide?

Supermarket Interior

Ice Rink and Bleachers

Photo Credit: Regos Photography/Andrus Architecture

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

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

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.

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!

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

Review of vapour-compression refrigeration cycle

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

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

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

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


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 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.


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


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


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

Ice rink with daylighting


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

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) radiantflooring system

Use heat rejected by refrigeration system

Slab heating maintains spectator comfort

Reduce temperature in stands during unoccupied periods

Simulated Temperature


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


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 over 15% of the refrigeration system’s total energy consumption

Secondary fluid pump’s heat adds torefrigeration 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 flowrate to be halved

Affects ice uniformity?


Piping in slab


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 coolstorage, reduces capacity requirements

Pouring of slab



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

Supermarkets:

Costs of efficiency measures

Depending on measures implemented, 0 to 40% higher initial costs thanconventional systems A full range of measures cost

additional ~$250,000

Supermarkets often requirepaybacks of 3 years or less

Additional costs may be offsetby elimination of combustion heating system

Standard DX system Secondary

loop system

Secondary Loop

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

Thermal storage

Cold-climate adaptionsPower factor correction

Process integrationSnow PitOptimize ice thickness

Efficient lightingDehumidificationNighttime setbacks

Low-e ceilingDesuperheaterBetter controls

Major InvestmentModerate InvestmentMinor Investment

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 systemwith financially attractive alternative isa convincing argument

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

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

Vegetable Display

Supermarket Entrance

Example: Quebec, Canada Repentigny supermarket (results)

No boiler or backup heating installed! All heating provided by waste heat from refrigeration system

Energy consumptionreduced 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


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 thantwo-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



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 leaksachieved with sealed units andsecondary 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

RETScreen® Energy Efficient Arena & Supermarket Project Model Calculates energy savings, life-cycle

costs and greenhouse 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

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

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

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

Documents

Transcript of Energy Efficiency Project Analysis for Supermarkets and Arenas Clean Energy Project Analysis Course.