Danfoss and Controls for CO2
CO2
www.danfoss.com/FoodRetail
Department (slide master)
Optional text
Date
|1
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,
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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!
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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)
Receiver pressure ctrl
by CCM
Optimum media
temperature out of
Gas Cooler via
FC 103 or EC-Fan
Second suction group
capacity control
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Optimum pressure
in Gas Cooler by
CCMT or ICMTS
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AK-PC783
CO2 for both MT and
LT with HFC on top
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Improved surveillance using Service Tool - AK-PC781
Click on an icon and you will get
– see next slide!
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Status and overview - Two Suction groups
MT
LT
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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.
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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
Fan capacity
Sgc_Ref: ( Sc3 + 2K )
PI
Sgc
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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
Condensing temp
14
12
10
PC780
8
PC781
6
4
2
0
0
20
40
60
Compr Cap
80
Energy savings
compared to PC780 [%]
condensing temp above
Amb
16
100
8
6
Energy Savings%
4
(Improved K)
2
0
0
10
20
30
40
50
60
70
80
90
100
Compr cap %
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AK-PC 781 introduction
Date 2012-01-12 | 10
P [bar]
Sub-critical vs. trans-critical CO2
10
2
Transcritical
Subcritical
0,2
1
10
-500
-400
0,4
-300
0,6
0,8
-200
-100
-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) 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 CO2
circuit in order to keep the pressure down in this way avoiding trans-critical operation.
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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
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Date 2012-01-12 | 12
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.
Refrigerating capacity [kW] and COP [-]
1.50
COP
1.25
1.00
QE
0.75
0.50
0.25
OPERATING CONDITION
tE = -10 °C, ∆tSH = 10 K
tGC,OUT = 35 °C
0.00
75
80
85
90
95
100
105
110
115
120
Gas cooler pressure [bar]
New
See Next
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Date 2012-01-12 | 13
Optimal high pressure on trans-critical CO2
COP = 1.90
COP = 2.31
COP = 2.28
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∆hEVAP
AK-PC 781 introduction
∆hCOMP
Date 2012-01-12 | 14
Trans-critical vs. sub-critical CO2
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Trans-critical vs. sub-critical CO2
+40 °C on gas leaving gas cooler
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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
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Maximum and minimum receiver pressure
safety
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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
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•
•
•
AK-PC 781 introduction
Date 2012-01-12 | 19
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.
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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 subcritical 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!
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5 ºC
80 Bar
25 ºC
35 ºC
70 ºC
90 ºC
40 Bar
AK-PC 781 introduction
MT -10 ºC
T
60
50
Hot Tap Water
x1
kWh
Heating
x10 kWh/day
30
Energy Ratio, kWh
Date 2012-01-12 | 21
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
Log P
40 ºC
25 ºC water return
5 ºC Gas Cooler
Heat Reclaim
80 Bar
95 ºC
Heat Reclaim
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!
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Heat to Gas Cooler
40 Bar
65 ºC
-10 ºC
AK-PC 781 introduction
MT -10 ºC
Heat to Evaporator
Work to
Compressor
h
Simplified CO2 refrigeration cycle
Date 2012-01-12 | 22
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
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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
40 ºC water return TW
25 ºC water return HR
Log P
5 ºC
Gas Cooler
80 Bar
Heat reclaim
Heat
Offset
40 Bar
This makes it possible to reclaim
almost all heat and provide sufficient
heat to most supermarkets in order to
cover ALL the heat demand!
Hot Tap Water
Tap water
95 ºC
Pgc
-10 ºC
MT -10 ºC
h
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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.
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.
Gas Cooler by-pass
= increasing
compressor
running capacity
20 ºC water return HR
Log P
Heat reclaim
40 ºC
5 ºC
Gas Cooler
80 Bar
Heat reclaim
Hot Tap Water
Heat
Offset
40 Bar
Hot Tap Water
Tap water
95 ºC
Pgc
-10 ºC
MT -10 ºC
h
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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)
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CO2 and Heat reclaim in Supermarkets
White paper can be found in DILA
1. Save energy in your Supermarket
with a CO2 Refrigeration system
Two stage Heat Reclaim
1. Hot Tap Water, with 3-way valve
2. Heat Reclaim, with 3-way valve
2. Highly efficient heat reclaim with
CO2
Save 10% on CO2
How to make Heat Reclaim
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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
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!
Superheat in K
18
16
14
12
10
8
6
4
2
0
S2
AKV 10
SS U RE
NS M ITT ER
AKS 33
0G 21 03
Pe :
- 1 - 34 bar
-14.5 - 49 3 ps ig
/ M W P 5 80 p sig
10 - 3 0 V d.c.
4 - 20 m A
+ SU PP LY VO LTA GE
- C O MM O N
SH = S2 - Te
TIME
Superheat set point
Actual superheat
Department (slide master)
Optional text
Pe
Date | 29
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 CO2)
18
16
14
12
10
8
6
4
2
0
Superheat set point
Actual superheat
Department (slide master)
Optional text
Date | 30
AK-CC 550A – Case controller
Evaporator design
CO2 has different properties than
other refrigerants due to the high
pressure
To low velocity
and surface is dry
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
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High velocity
and wet surface
Date 2012-01-12 | 31
Refrigeration performance, ADAP-KOOL
Value
ADAP-KOOL® monitoring modules
AK-LM 350
AK-LM 340
AK-LM 330
Application
Temperature monitoring
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Multi purpose ctrl
AK-PC 781 introduction
COP monitoring
Date 2012-01-12 | 32
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
Department (slide master)
1
Optional text
Date | 33
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
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.
COPMT , Ideal =
Q0,MT
PowerMT ,ideal
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!
Department (slide master)
Optional text
Date | 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.
COPMT , Ideal =
Q0,MT
PowerMT ,ideal
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!
Department (slide master)
Optional text
Date | 36
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 ADAPKOOL 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
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Date 2012-01-12 | 37
Frontend—Comparing Supermarkets
•
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
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Plantefficiency =
COPactual
COPIdeal
AK-PC 781 introduction
Date 2012-01-12 | 38
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.
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Date 2012-01-12 | 39
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 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
Department (slide master)
Optional text
Date | 40
End
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AK-PC 781 introduction
Date 2012-01-12 | 41