PRICE CHOPPER SARATOGA, NY First cascade supermarket system in North America Installed and Started March of 2008
Why did we choose CO2? Meets Corporate sustainability initiatives Looking for ways to reduce our carbon footprint (reduced carbon footprint by???) GWP of 1 versus 1,300 to 3,900 for HFC s Questionable future of HFC refrigerants Reduced copper line sizing and component size Refrigerant costs $1.00/pound versus $8.00/pound Timing!
Pro s Low Global Warming Potential (GWP =1) Chemically inactive, non-flammable Not toxic, it s in your soda and BEER! High volumetric refrigerating capacity Subcritical: 6 to 8 times higher than for R22, R404A or NH 3 Low refrigerant mass flow It s NOT new! Used until 1940 s when man made refrigerants of the 30 s replaced CO2
Con s Higher pressures Operating pressures of 220psig for suction pressure and 420psig for discharge pressure Max pressures for low and high side for safety is 350psig and 575psig safety aspects (regulations, UL) and component design Lower practical limit in air than with HFCs (3.5 to 6 times less) CO 2 is odourless for closed rooms this requires special safety and detection systems
Key Properties of Refrigerants Refrigerant CFC's / HCFC's HFC's HC's R12 R22 R134a R410A R407C R404A R290 R600a R717 R744 Propane Isobutane Ammonia Natural ODP 1 0.05 0 0 0 0 0 0 0 0 GWP (100 yr) 10,600 1,500 1,300 1,725 1,525 3,900 20 20 2 1 Flammable No No No No No No High High Low No Toxic No No No No No No No No Yes No CO2 Pressure (psia) 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0-60 F 0 F Low Temp. Sub Critical CO 2 60 F 0 F -20 F -40 F -60 F 40 F 20 F 60 F 80F 100 F S=0.20 s=0.25 s=0.30 140 F 200 F -50 0 50 100 150 200 Enthalpy (Btu/lbm) 300 F s=0.35 s=0.40 s=0.45
1200 Critical temperature [88F] 31.06 C 1000 800 Pressure [p si] 600 400 CO 2 R404A 200 R22 0-75 -50-25 0 25 50 75 100 125 150 175 Temperature [ F]
Our LT CO2 DX Cascade System 250,000Btu/Hr of Low-Temperature CO2 Refrigeration Uses POE Oil (supplied by compressor manufacturer) R-404A on Upper-Cascade also chills 125,000Btu/Hr Medium-Temperature loads with PG secondary coolant system Stepper EEV s on are used on CO2 evaporators Most components designed for R-410A can be applied to CO2 cascade systems US component manufacturers slow to introduce equipment for CO2 Equipment footprint reductions compared with CO2 secondary Recommended Coleman grade CO2 99.99% pure. Readily available BUT long lead times.
AIR-COOLED CONDENSER RECEIVER MT Secondary Load: 145 kbtu/hr LT CO2 Cascade Load: 242 kbtu/hr UPPER-CASCADE (MT) WITH R-404A COMPRESSORS COAXIAL SLHE GLYCOL PUMP PARALLEL CONDENSER-EVAPORATOR HEAT EXCHANGERS MEDIUM-TEMPERATURE LOADS RECEIVER ELECTRONIC EXPANSION VALVES ON ALL CONDENSER-EVAPORATORS AND GLYCOL CHILLER SOLENOID VALVES ON ALL GLYCOL HEAT EXCHANGERS PLATE SLHE LOWER-CASCADE (LT) WITH CO2 COMPRESSORS LOW-TEMPERATURE LOADS ELECTRONIC EXPANSION VALVES ON ALL CO2 EVAPORATORS LEGEND R-404A Discharge R-404A Liquid R-404A Suction Glycol Return Glycol Supply CO2 Discharge CO2 Liquid CO2 Suction
Notes on System Design Concentration of CO 2 in air In closed rooms appropriate safety and monitoring devices (CO 2 detectors available) Inhalation of higher CO 2 concentrations can lead to unconsciousness and suffocation! Threshold Limit Value-Time Weighted Average of 5,000ppm compared to 3,000ppm for R404A and 507. This is for 8hrs per day, 40hrs per week. CO 2 is odourless and colourless and can therefore not be perceived directly in case of emission. (sensors required in closed areas)
General Comment on Refrigerants No single refrigerant (or group) ideal for all applications CO 2 technology promising in various applications but no general solution for the substitution of HFC s HCs and NH 3 - Convincing in thermodynamic properties but strongly limited in application due to safety aspects
Operational Experiences Reduced copper lines as compared to R404A Training required for installation crew and in house service technician s (follow up training required as well) Installation and startup was no big deal according to contractor. Just follow the requirements Leak detectors are expensive. Availability of Coleman grade CO2 is limited. Long lead times requires full charge on site.
Operational Experiences cont d Have had numerous leaks on Threaded fittings for Relief valve, gauges, etc. Leaks found on ball valves. Discussing with manufacturer for solution. Sporlan controller used for liquid stepper valves on heat exchangers. Requires pre-load spares be available. Even with backup auxiliary condensing unit, we had pressure relief valves release. Need to review with manufacturer.
Other Improvements ECM fan motors on all new cases. Noise issue LED lighting in all Reach-in cases Variable speed fans on condenser early failure on 2 fans Changed existing refrigeration systems from R22 to R404A. Replaced all HVAC units with New AAON units
What s Next? New LEED project store that will have a total refrigerant charge 300 pounds for the whole store using CO2 secondary and glycol medium temp.