Danfossand Controls for CO2 - Coolmark B.V. · PDF fileDanfossand Controls for CO2 ... pressure ctrl, parallel compressor, etc. AK-PC783 High-end cascade controller, incl. Heat Reclaim,

Optional textDepartment (slide master) Date | 1

Danfoss and Controls for CO2

www.danfoss.com/FoodRetail

CO2

AK-PC 781 introductionDanfoss Electronic Controllers and Services Date 2012-01-12 | 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,


AK-PC781

� AK-PC 781 shown in CO2 trans-critical booster system (MT/LT/IT)

Control of one suction group – including unloaders and speed!

Gas cooler control!Gas by-pass!

Tap water reclaim!Heat reclaim!

Condenser pressure control or gas cooler fan control!

Oil management and control!

IT Parallel compression


AK-PC772

Optimum media temperature out of Gas Cooler via FC 103 or EC-Fan

All transcritical control functions are integrated in AK-PC772

Optimum compressor capacity control via FC 103(or digital scroll)

Heat Reclaim with optimum high pressure control based on actual indoor temperatures

Receiver pressure ctrl by CCM

Optimum pressure in Gas Cooler by CCMT or ICMTS

Second suction group capacity control


AK-PC783

� CO2 for both MT and LT with HFC on top


Improved surveillance using Service Tool - AK-PC781

Click on an icon and you will get – see next slide!


MT

LT

Status and overview - Two Suction groups


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.


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

Sgc_Ref: ( Sc3 + 2K )

PI

Fan capacity

Floating fan control with Sc3 and Sgc temperature sensors


Condensing temp

0

2

4

6

8

10

12

14

16

0 20 40 60 80 100

Compr Cap

con

den

sin

g t

em

p a

bo

ve

Am

b PC780

PC781

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.

� Most compressor run time hours are in the 15% - 50% range

0

2

4

6

8

0 10 20 30 40 50 60 70 80 90 100

Compr cap %

En

erg

y s

av

ings

com

pa

red

to P

C78

0 [%

]

Energy Savings %

(Improved K)


Sub-critical vs. trans-critical CO2

� 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) CO2 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 CO2circuit in order to keep the pressure down in this way avoiding trans-critical operation.

-500 -400 -300 -200 -100 -010

1

102

h [kJ/kg]

P [

ba

r]

0,2 0,4 0,6 0,8

Transcritical

Subcritical


Features:

� Maintain optimal COP in trans-critical areas

� Maintain optimal sub cooling in sub-critical 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

Integrated High Pressure controller


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.

75 80 85 90 95 100 105 110 115 120

Gas cooler pressure [bar]

0.00

0.25

0.50

0.75

1.00

1.25

1.50

Re

frig

era

tin

g c

ap

ac

ity

[k

W]

an

d C

OP

[-] COP

QE

tE = -10 °C, ∆tSH = 10 K

tGC,OUT = 35 °C

OPERATING CONDITION

New

See Next


∆hEVAP ∆hCOMP

COP = 1.90

COP = 2.31

COP = 2.28

Optimal high pressure on trans-critical CO2


Trans-critical vs. sub-critical CO2


+40 °°°°C on gas leaving gas cooler

Trans-critical vs. sub-critical CO2


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 % open3 bar – Pgc max. limit P-band97 bar – Pgc max. limit P-band where valve start to be “forced open”

* Was in T in EKC 326, now in P


Maximum and minimum receiver pressure safety


� MT Pack Configuration

•••

� Use hot gas dumpSelect whether hot gas should be supplied if the receiver pressure falls too low� Prec hot gas dumpReceiver pressure at which hot gas is turned on� Prec gas dump diff.Difference at which hot gas is turned off again

Hot gas dump


Heat reclaim with CO2

� CO2 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.


Heat reclaim with CO2

� Demand for Heat Reclaim becomes more and more relevant due to rising energy costs.

� CO2 applications are getting well known in Food Retail or Industrial systems and they run both sub-critical and trans-critical.

� High discharge temperatures for CO2 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!

x1 x1 kWh

x10 kWh/day

Energy Ratio, kWh

T

60

50

30

Hot Tap Water

Heating

25 ºC35 ºC

5 ºC

MT -10 ºC

40 Bar

80 Bar70 ºC 90 ºC


Achieving higher discharge temperatures

� The gas cooler rejects heat from the evaporator and compressor work

� In practice temperatures between 60-70 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 70-90 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!

Simplified CO2 refrigeration cycle

25 ºC water return40 ºC

5 ºC

-10 ºC

40 Bar

Heat to Evaporator Work to Compressor

Heat to Gas Cooler

Heat Reclaim

95 ºC

65 ºC

80 Bar

Gas Cooler

Heat Reclaim

Log P

h

MT -10 ºC


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


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 offsetand Gas Cooler by-pass

� This makes it possible to reclaim almost all heat and provide sufficient heat to most supermarkets in order to cover ALL the heat demand!

25 ºC water return HR

40 ºC water return TW

5 ºC

-10 ºC

40 Bar

Heat reclaim Hot Tap Water

95 ºC

80 BarGas Cooler

Heat Tap water

Log P

h

Offset

MT -10 ºC

Pgc


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.

20 ºC water return HR

40 ºC5 ºC

-10 ºC

40 Bar


95 ºC

80 BarGas Cooler

Heat Tap water

Log P

h

Offset

MT -10 ºC

Pgc


Heat consumers 0-10V signal:0-2 V: Variable pump speed1-6 V: Variable offset (Pgc)5-8 V: Reduce fan speed7-10 V: By-pass gas cooler.

Gas Cooler by-pass= increasing

compressorrunning capacity


Values

� Same energy efficiency (COP) as traditional HFC refrigeration systems

� CO2 does not effect the ozone layer

� CO2 has up to 4.000 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)


CO2 and Heat reclaim in Supermarkets

� Two stage Heat Reclaim

1. Hot Tap Water, with 3-way valve

2. Heat Reclaim, with 3-way valve

� 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

Save 10% on CO2 How to make Heat Reclaim


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.


TIME

0

2

4

6

8

10

12

14

16

18

Actual superheatSuperheat set point

Su

pe

rhe

at

in K

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!

S2 Pe

AKV 10

SS U RE

NS MITT ER

AKS 33

0G 21 03

Pe : - 1 - 34 bar

-14.5 - 49 3 ps ig

/ MW P 5 80 p sig

10 - 3 0 V d.c.

4 - 20 m A

+ SU PP LY VO LTA GE

- C O MMO N

SH = S2 - Te


FR inject function


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 CO2)

0

2

4

6

8

10

12

14

16

18

Actual superheat

Superheat set point



� CO2 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


Evaporator design


ADAP-KOOL® monitoring modules

Temperature monitoring Multi purpose ctrl COP monitoring

AK-LM 340

Value

Application

AK-LM 330

AK-LM 350

Refrigeration performance, ADAP-KOOL


AK-LM 3xx function overview

AK-LM330 AK-LM340 AK-LM350

Thermostats w. defrost interlock 10 5 5

Pressostats functions 5 5 5

Voltage input functions 5 5 5

Digital alarm input functions 16 16 16

Utility / Pulse meter input functions 4 8 8

Alarm relay outputs 2 2 2

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



Why COP and what is it?

How can we measure if a refrigeration works good enough?

Can we compare refrigeration plants, regarding energy consumption?

Are there any useful key numbers for refrigeration plants?

PowerUsed

energyObtainedCOP

_

_=



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!

idealMT

MT

IdealMTPower

QCOP

,

,0

,=



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!

idealMT

MT

IdealMTPower

QCOP

,

,0

,=



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 performingIf Valid % data < 50%, you need to investigate, and COP could also be low

Refrigeration performance, KPIs


• When it is possible to provide data from the supermarkets, it is possible to evaluate:

• Power consumption

• Energy consumption

• Costs

• Heat reclaim

• Operating patterns

• Plant efficiency

• Cooling load pr. M display case

Ideal

actual

COP

COPiencyPlanteffic =

Frontend—Comparing Supermarkets


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 pricesfor electricity at varoiusgeographical sites, and size of supermarket.

AND…..valve lifetime is degradingfastAND…...compressors is switchingfast, thus wearing down faster.


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)

Refrigeration performance, reports

Shop City Plant

efficiency

Pot.

Savings

pr day

kWh

P-MT

[kW]

P-LT

[kW]

COP-MT COP-LT Pct Valid

Shop1 City 1 0.86 0 6.14 0.98 4.11 3.34 63.2

Shop2 City 2 0.85 3.98 17.33 1.17 3.49 2.13 9.18

Shop3 City 3 0.78 102.50 46.22 13.16 2.67 1.53 45.68

Shop 4 City 4 0.64 27.75 4.46 0.84 4.17 3.58 64.34


End

Documents

Danfossand Controls for CO2 - Coolmark B.V. · PDF fileDanfossand Controls for CO2 ... pressure ctrl, parallel compressor, etc. AK-PC783 High-end cascade controller, incl. Heat Reclaim,