Danfoss and Controls for CO2

Transcription

1 Danfoss and Controls for CO2 CO 2 Department (slide master) Optional text Date 1

2 Controllers for various CO2 applications Some examples of Danfoss controllers suited for CO2: AK-PC781 High-end multipurpose pack controller, incl.heat Reclaim, High pressure ctrl, parallel compressor, etc. AK-PC783 High-end cascade controller, incl. Heat Reclaim, high pressure ctrl, etc. AK-PC772 High-end limited to 3+2 compressors, 2 suction group controller, limited HR, parallel compressor, etc. Intended for small to medium sized supermarkets AK-CC550A FR-inject algorithm specially suited for CO2, Date

3 AK-PC781 AK-PC 781 shown in CO2 trans-critical booster system (MT/LT/IT) Control of one suction group including unloaders and speed! Condenser pressure control or gas cooler fan control! Gas cooler control! Gas by-pass! IT Parallel compression Tap water reclaim! Heat reclaim! Oil management and control! Date

4 AK-PC772 All transcritical control functions are integrated in AK-PC772 Heat Reclaim with optimum high pressure control based on actual indoor temperatures Optimum compressor capacity control via FC 103 (or digital scroll) Second suction group capacity control Receiver pressure ctrl by CCM Optimum pressure in Gas Cooler by CCMT or ICMTS Optimum media temperature out of Gas Cooler via FC 103 or EC-Fan Date

5 AK-PC783 CO 2 for both MT and LT with HFC on top Date

6 Improved surveillance using Service Tool - AK-PC781 Click on an icon and you will get see next slide! Date

7 Status and overview - Two Suction groups MT LT Date

8 Ease of use improved - Smart Settings Smart Settings allow fast setup of complex high pressure settings. Select just one Smart value for the High Pressure side, approx. 15 bar below Safety Valves, and the rest of parameters are calculated. Select just one Smart value below the receiver design pressure, to do the second calculation. Unused functions are hidden. E.g. if you deselect Receiver. Values can be changed after calculation, if preferred. Date

9 Floating fan control with Sc3 and Sgc temperature sensors Ref (for Sgc) temp. = Sc3 + tm + (dim-tm x cap/100) Sgc reference is mostly 2K above ambient temperature as dim and tm is set to equal values Sgc_Ref: ( Sc3 + 2K ) PI Fan capacity Sgc Date

10 Condenser improvements Improved floating condenser set point function compared to former AK-PC 780 Rule of thumb indicates 3 % energy savings on every 1 K on the condenser. condensing temp above Amb Condensing temp Compr Cap Energy savings compared to PC780 [%] Most compressor run time hours are in the 15% - 50% range PC780 PC Compr cap % Energy Savings % (Improved K) Date

11 Sub-critical vs. trans-critical CO 2 P [bar] 10 2 Subcritical Transcritical ,2 0,4 0,6 0, h [kj/kg] A trans-critical booster system can run both sub- and trans-critical. At lower temperatures than 31ºC the system runs sub-critical with a very good COP. At temperatures higher than the critical temperature (31ºC) CO 2 cannot condense therefore the system must run trans-critical with poorer COP as consequence In warmer climates a cascade system is often preferred because it has an advantage here. Cascade system has an extra cooling circuit, which can be used to cool the CO 2 circuit in order to keep the pressure down in this way avoiding trans-critical operation. Date

12 Integrated High Pressure controller Features: Maintain optimal COP in trans-critical areas Maintain optimal sub cooling in subcritical areas Safe transition between trans-critical and subcritical operation Optimum COP gas cooler control using the ICMTS or CCMT valve, Vhp Control of receiver pressure using the CCM (or ETS) valve, Vrec Heat reclaim with by pass of Gas Cooler, V3gc Use of radiometric pressure transmitters Supports 60, 100 and 160 bar pressure transmitters AKS 2050 Improved EKC 326a functionality Date

13 Benefits of integrated High Pressure controller High pressure systems can maintain either maximum COP or maximum system capacity for any given ambient condition Intermediate pressure is controlled independently and maintained on the required level All valve positions, measured temperatures and pressures are visible on the controller (one device) If required by Heat Recovery demand, the high pressure can be changed. Changeover is only allowed if several conditions are fulfilled, which makes a safe system (flow, temperatures, pressures, timers). A safe High Pressure operation has priority over other functions. Trans-critical optimum is a curve made by several tests and measurements Gas cooler pressure [bar] Date Refrigerating capacity [kw] and COP [-] New See Next COP QE OPERATING CONDITION t E = -10 C, t SH = 10 K t GC,OUT = 35 C

14 Optimal high pressure on trans-critical CO 2 COP = 1.90 COP = 2.31 COP = 2.28 h EVAP h COMP Date

15 Trans-critical vs. sub-critical CO 2 Date

16 Trans-critical vs. sub-critical CO C on gas leaving gas cooler Date

17 High Pressure system The Smart Settings make it easy to setup several HP settings by entering a single number. See Bold numbers and fig. Design criteria define levels. Safety valve and cut out switch ICMTS valve has 140 bar working pressure (0-10V control) CCMT valve has 140 bar working pressure (Stepper control) 120 bar Design pressure and setting of safety valve 115 bar High pressure switch cut-out (compressors) 103,5 bar Pc max limit (safety on Pack/Rack) 3 bar 100,5 bar Pc max start to make capacity reduction 100 bar Pgc Max, High pressure valve 100 % open 3 bar Pgc max. limit P-band 97 bar Pgc max. limit P-band where valve start to be forced open * Was in T in EKC 326, now in P Date

18 Maximum and minimum receiver pressure safety Date

19 Hot gas dump MT Pack Configuration Use hot gas dump Select whether hot gas should be supplied if the receiver pressure falls too low Prec hot gas dump Receiver pressure at which hot gas is turned on Prec gas dump diff. Difference at which hot gas is turned off again Date

20 Heat reclaim with CO 2 CO 2 has some excellent properties which can be utilized in heat reclaim High temperatures of the gas on the compressor outlet High enthalpy on the gas on the compressor outlet High density Good heat conductivity Heat reclaim can really be utilized above the critical temperature because gas rejects heat at higher temperatures with steady reduction in temperature through the heat exchanger. Above the critical temperature pressure and temperature can be controlled individually, which is an advantage in connection with heat reclaim. Date

21 Heat reclaim with CO 2 Demand for Heat Reclaim becomes more and more relevant due to rising energy costs. CO 2 applications are getting well known in Food Retail or Industrial systems and they run both subcritical and trans-critical. High discharge temperatures for CO 2 compression cycle is normal, often > 70 ºC This provide hot tap water (typically around 60 ºC) And low temperature heating for floor heating, radiators, air unit heater, etc. The Heat ratio is often x10 between hot tap water and heating A superior control strategy is necessary! 5 ºC 80 Bar 40 Bar T ºC MT -10 ºC 35 ºC Hot Tap Water x1 kwh Heating x10 kwh/day Energy Ratio, kwh 70 ºC 90 ºC Date

22 Achieving higher discharge temperatures The gas cooler rejects heat from the evaporator and compressor work In practice temperatures between ºC even with minimum compressor load can be achieved Heat reclaim between 25 and 65 ºC gives only a limited amount of heat If Pgc is raised when demand is present temperatures will increase to ºC Heat reclaim down to 25 ºC can now reject a large amount of heat The gas cooler will then only reject a small part of the heat Only little extra compressor work is needed! Log P 80 Bar 40 Bar -10 ºC 5 ºC 40 ºC 25 ºC water return Gas Cooler Heat to Gas Cooler MT -10 ºC Heat Reclaim Heat to Evaporator Heat Reclaim Work to Compressor Simplified CO2 refrigeration cycle 65 ºC 95 ºC h Date

23 Two stage Heat Reclaim integrated Features Control of hot Tap Water temperature Control of additional Heat reclaim source e.g. floor heating By pass valve for TW, HR and Gas Cooler Additional input (0-10V) from up to 5 heat consumers VSD (AKD, 0-10V) control of fans and water pumps to control water temperature Independent control of each subsystem, including safety conditions Date

24 Heat Reclaim There are 4 different heat reclaim control solutions in the system: Hot tap water Heat Reclaim, no HP offset (Pgc) Heat Reclaim, fixed HP offset Heat Reclaim, variable HP offset and Gas Cooler by-pass Log P 80 Bar 5 ºC 40 ºC water return TW 25 ºC water return HR Gas Cooler Heat reclaim Hot Tap Water Offset 40 Bar Pgc Heat Tap water 95 ºC This makes it possible to reclaim almost all heat and provide sufficient heat to most supermarkets in order to cover ALL the heat demand! -10 ºC MT -10 ºC h Date

25 Tap Water and Max Heat Reclaim mode Max Heat reclaim mode will control Pump speed Variable reference offset (Pgc) AND reduce fan speed AND finally gas cooler by-pass Up to 5 different heat consumers can give their reflected heat demand by a 0-10V signal, and the highest will determine the load on the system. The Ultimate heat reclaim is when Gas Cooler is by-passed. This will result in the red line. Which will increase running compressor capacity thus generating more heat. COP is decreased close to 1. Log P Gas Cooler by-pass = increasing compressor running capacity 80 Bar Offset 40 Bar -10 ºC 5 ºC 20 ºC water return HR Gas Cooler 40 ºC Heat reclaim Hot Tap Water Pgc MT -10 ºC Heat consumers 0-10V signal: 0-2 V: Variable pump speed 1-6 V: Variable offset (Pgc) 5-8 V: Reduce fan speed 7-10 V: By-pass gas cooler. Heat reclaim Hot Tap Water Heat Tap water 95 ºC h Date

26 Values Same energy efficiency (COP) as traditional HFC refrigeration systems CO2 does not effect the ozone layer CO2 has up to times lesser direct emission impact on global warming compared with traditional HFC refrigerants Produce high temperature tap water. (over 55 ºC/130 ºF) Produce heat in the store instead of rejecting the heat to the ambient Just one integrated electronic controller doing: Compressor and condenser capacity control High pressure control as well as heat recovery (CO2) Oil management and multi speed control (Compressor, fan, pump) Proven reliability of ADAP-KOOL controllers This controller is essential to make trans-critical systems work All former HFC functions are still available (as in AK-PC 740/780) Date

27 CO2 and Heat reclaim in Supermarkets White paper can be found in DILA 1. Save energy in your Supermarket with a CO2 Refrigeration system 2. Highly efficient heat reclaim with CO2 Two stage Heat Reclaim 1. Hot Tap Water, with 3-way valve 2. Heat Reclaim, with 3-way valve Save 10% on CO2 How to make Heat Reclaim Date

28 AK-CC 550A Case controller New functions in AK-CC 550A compared with AK-CC 550 S1 has been deleted Injection is controlled using Pe (Po) & S2 New Injection algorithm (FR-Inject) * Adaptive Defrost with skip function * The opening degree is reduced more rapidly, if liquid is detected after the Evaporator or low SH. Security function ensures that the valve closes if the SH get below the set limit. Department (slide master) Optional text Date 28

29 SS U RE NS MITT ER AKS 33 0G Pe : bar ps ig / MW P 5 80 p sig V d.c m A + SU PP LY VO LTA GE - C O MMO N AK-CC 550A Case controller FR inject function The superheat is reduced until the signal becomes unstable. Search speed is 0,25 K per 8 minutes. Then superheat is increased a bit until stability is found followed by a new reduction, and so on! AKV 10 S2 P e SH = S2 - T e Superheat in K TIME Superheat set point Actual superheat Department (slide master) Optional text Date 29

30 AK-CC 550A Case controller FR inject function Advantages: Integrated solenoid valve Adaptive adjustment Optimum utilisation at all load conditions Insensitive to operation conditions Compensate low Pc with higher opening degree Typical 5 10 % energy savings (TEV s are not available for CO 2 ) Superheat set point Actual superheat Department (slide master) Optional text Date 30

31 AK-CC 550A Case controller Evaporator design CO 2 has different properties than other refrigerants due to the high pressure Density of the gas is approximately 3 to 10 times higher than conventional refrigerants and therefore getting gas velocities high enough is a problem in evaporators Pressure drop has only very little influence on the evaporation temperature Long pipes in one sling gives long reaction time for the control Use small diameter and a pressure drop of ½-1 bar. Avoid long pipes To low velocity and surface is dry High velocity and wet surface Date

32 Refrigeration performance, ADAP-KOOL Value ADAP-KOOL monitoring modules AK-LM 350 AK-LM 340 AK-LM 330 Application Temperature monitoring Multi purpose ctrl COP monitoring Date

33 Refrigeration performance, ADAP-KOOL AK-LM 3xx function overview AK-LM330 AK-LM340 AK-LM350 Thermostats w. defrost interlock Pressostats functions Voltage input functions Digital alarm input functions Utility / Pulse meter input functions Alarm relay outputs PI controls advanced 10 Thermostat w. 2 sensor inputs 10 Temperature alarms 10 Difference thermostat 10 Differential pressostat 10 Pressure alarms 10 COP monitoring - CO2 boost, / cascade/one stage 1 Department (slide master) Optional text Date 33

34 Refrigeration performance, ADAP-KOOL Why COP and what is it? How can we measure if a refrigeration works good enough? Can we compare refrigeration plants, regarding energy consumption? COP = Obtained _ energy Used _ Power Are there any useful key numbers for refrigeration plants? Department (slide master) Optional text Date 34

35 Refrigeration performance, ADAP-KOOL What is an ideal COP? When calculating a COP for a refrigeration, it is possible to calculate an ideal COP, which can never be achieved. But, calculating the ratio between actual COP and ideal COP, tells how efficient the refrigeration plant is. Qo is the cooling removed at the MT level, and the ideal power consumption is calculated! When trimming/optimizing the refrigeration plant, one should try to lift the actual COP as much as possible! COP MT, Ideal = Q Power 0, MT MT, ideal Department (slide master) Optional text Date 35

36 Refrigeration performance, ADAP-KOOL What is an ideal COP? When calculating a COP for a refrigeration, it is possible to calculate an ideal COP, which can never be achieved. But, calculating the ratio between actual COP and ideal COP, tells how efficient the refrigeration plant is. Qo is the cooling removed at the MT level, and the ideal power consumption is calculated! When trimming/optimizing the refrigeration plant, one should try to lift the actual COP as much as possible! COP MT, Ideal = Q Power 0, MT MT, ideal Department (slide master) Optional text Date 36

37 Refrigeration performance, KPIs KPIs Service tool picture from a live installation. As can be seen various averages is calculated - 1 minute - 1 hour - 24 hour - All data can be collected by ADAP- KOOL system. Please NOTE: Valid flag (OK) shows if calculation is valid. One should calculate how many % valid data is present. If Valid % data > 70%, plant is stable and performing If Valid % data < 50%, you need to investigate, and COP could also be low Date

38 Frontend Comparing Supermarkets When it is possible to provide data from the supermarkets, it is possible to evaluate: Planteffic iency = COP COP actual Ideal Power consumption Energy consumption Costs Heat reclaim Operating patterns Plant efficiency Cooling load pr. M display case Date

39 Frontend Comparing Supermarkets Whats the reason for the low plant performance? And just as important: What is the cost of low plant efficiency? The cost of TOO low performance for inst.2 is calculated to: App. 336 Euro pr week Note: Depends upon prices for electricity at varoius geographical sites, and size of supermarket. AND..valve lifetime is degrading fast AND...compressors is switching fast, thus wearing down faster. Date

40 Refrigeration performance, reports Important info from COP Below table is a report generated in Danfoss Demo tool, on 4 actual supermarkets. Different info is available: - Potential savings pr day - Percent valid calculations(very important because it indicates if there is loose sensors, bad settings in controllers, etc, below 70% it could be necessary to check the plant) - COP for individual sites(should be at a certain level) Shop City Plant efficiency Pot. Savings pr day kwh P-MT [kw] P-LT [kw] COP-MT COP-LT Pct Valid Shop1 City Shop2 City Shop3 City Shop 4 City Department (slide master) Optional text Date 40

41 End Date