1
ORC and Kalina
Analysis and experience
Páll Valdimarsson
professor of mechanical
engineering
Sabbatical December 2003
Lecture III
2
Energy and energy use
• Energy is utilized in two forms, as heat
and as work
• Work moves, but heat changes
temperature (moves the molecules
faster)
• These are two totally different products
for a power station
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3
Convertability
• Work can always be changed into heat
(by friction since ste stone age)
• Conversion of heat into work is difficult
and is limited by the laws of
thermodynamics. A part of the heat
used has always to be rejected to the
surroundings
4
Heat and work again
• Work is the high quality, high priced
product
• Heat is second class quality, a low
priced byproduct
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5
A power plant
Source
Heat
Fuel
Rejected heat
Losses
Electricity
Sellable heat
Power
plant
6
Single flash - condensing
Production well
Injection well
Separator
Turbine
Cooling tower
Pump
Condenser
Pump
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7
T-s diagram
8
ORC with regenerator
Production well
Injection well
Turbine
Condenser
Pump
Regenerator
Boiler
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9
T-s diagram
-2,0
-1,5
-1,0
-0,5
0,0
0,5
1,0
-50
0
50
100
150
200
250
s [kJ/kg-K]
T
[
°C
]
2300 kPa
1000 kPa
350 kPa
90 kPa
0,2 0,4 0,6 0,8
0
,0
04
5
0
,0
26
0
,0
6
3
0
,1
5
0
,3
7
0
,8
9
m
3/
kg
Isopentane
10
ORC with paralell single flash
Production well
Injection well
Separator
Turbine
Cooling tower
Condenser
Pump
Condenser
Cooling tower
Turbine
Boiler
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11
ORC with serial single flash
Production well
Injection well
Separator
Turbine
Condenser
Cooling tower
Turbine
Boiler
Throttling valve
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15
Rogner, Bad Blumau
• The 250 kW air-cooled geothermal CHP plant
generates electrical power as well as district
heating using a low temperature geothermal
resource.
• One standard containerized ORMAT CHP
module, generating 250 kW electricity and
2,500 kW heat.
• The power plant is in commercial operation
since July 2001.
16
Mokai, New Zealand
• The 60 MW Geothermal Power Plant is
comprised of:
» one 50 MW module operating on geothermal
steam
» two 5 MW units operating on geothermal brine
• The power plant uses air-cooled condensers
and achieves 100% geothermal fluid
reinjection to produce electrical power with
virtually no environmental impact.
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18
Kalina
Production well
Injection well
Separator
Turbine
Condenser
Boiler
Throttling valve
Cooling tower
Regenerator
Pump
Brine hx
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19
Geothermal experience
• Rough surroundings
• Aggressive chemistry
• Simple and reliable solutions
• Geothermal energy - a mayor economic
factor
20
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21
Conversion of heat to electricity
• The Carnot efficiency applies for infinite
heat sources
• The maximum efficiency is lower than
the Carnot efficiency for a source
stream with finite heat capacity
• Kalina reduces entropy generation in
the heat exchange process
22
Carnot efficiency
Hot reservoir
Cold reservoir
Work output
Heat in
Heat out
1
0
1
T
T
Carnot
−
=
η
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23
Maximum efficiency
for a liquid source
−
−
=
2
1
2
1
0
)
(
ln
1
*
T
T
T
T
T
H
E
h
x
1
T
2
T
0
T
0
T
24
What is a Kalina process?
• A modified Rankine cycle, or rather:
•
a reversed absorption cycle
• Ammonia - water working fluid
• Patented by Exergy Inc and A. Kalina
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25
The characteristics
• Heat is added in a combined boiling and
separation process
» at a variable temperature
• Heat is rejected in a combined
condensation and absorption process
» as well at a variable temperature
26
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
60
80
100
120
140
160
180
200
220
240
T
e
m
p
e
ra
tu
re
[
°C
]
Ammonia mass fraction [-]
Mixture boiling at 30 bar
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27
Heat addition - boiler
Source
Kalina
ORC
28
The working fluid
• Ammonia has a molar mass of 17, so
steam turbines can be used
• The mixture properties are more
complex, usually three independent
properties are needed for the
calculation of the fourth
• Therefore the cycle is more flexible, and
can be closely optimized to the source
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29
The benefit
• The working fluid is almost at the
temperature of the source fluid when
leaving the boiler
• The variable heat rejection temperature
makes regeneration possible
30
Kalina vs. ORC
• Kalina is better when the heat source
stream has a finite heat capacity
• ORC and Kalina are similar when the
source is condensing steam
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31
Boiling curves for Húsavík
0
200
400
600
800
1000
1200
20
30
40
50
60
70
80
90
100
110
120
T
e
m
p
e
ra
tu
re
[
°C
]
Enthalpy [kJ/kg]
Water
Kalina
ORC
32
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33
34
Kalina again
Production well
Injection well
Separator
Turbine
Condenser
Boiler
Throttling valve
Cooling tower
Regenerator
Pump
Brine hx
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37
38
0
200
400
600
800
1000
1200
1400
1600
0
50
100
150
200
Enthalpy [kJ/kg]
T
e
m
p
e
ra
tu
re
[
°C
]
T - h diagram
6.5
6.5
6.5
6.
5
31
31
31
31
6.5
6.5
6.5
6.5
31
31
31
31
6.5
6.5
6.5
6.
5
31
31
31
31
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39
Comparison
Power
[kW]
1. law
2. law
Max
liquid
eff.
Volum e
to
turbine
[m
3
/s]
Kalina
2000
0,13
0,45
0,56
0,57
ORC
1589
0,10
0,36
0,45
2,06
Flash cycle
1589
0,10
0,36
0,45
22,4
Themoelectricity
720
0,05
0,16
0,20
0
40
Comparison of Kalina and ORC
• Heat (10MW) is available down to 80°C
• Cooling water (120kg/s) is available at
20°C
• Heat exchangers have a pinch of 3°C
• Condensers have a pinch of 10°C
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90
95
100
105
110
115
120
125
130
135
140
0
0.05
0.1
0.15
0.2
0.25
Temperature [C]
E
ff
ic
ie
n
c
y
[
-]
Carnot
Liquid
Kalina
ORC
42
Húsavík geothermal
power plant
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43
General design parameters
44
Summary
• Commissioned in the summer 2000
• Running at ~1500 kW net 2000 - 2001
• Running at ~1700 kW net since
November 2001
• Final acceptance certificate issued
• Total investment cost 3,7 MEUR
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45
Process
diagram
G
121 °C
80 °C
90 kg/s
1950 kW
5 °C
24 °C
118 °C
31 bar
a
5,5 bar
a
12 °C
67 °C
16,3 kg/s
173 kg/s
0,81 NH
3
130 kW
11,2 kg/s
46
The power plant
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47
Design
• Standard industrial components
• Turbine-generator from KKK, Germany
• Electrical components CE marked
• Heat exchangers from USA
• Most of the tanks made in Iceland
• Installed by a local contractor
48
Equipment
• Evaporator, shell and tube, 1600 m
2
• Separator
• Turbine
• Recuperators
• Condenser, plate, 2 x 750 m
2
• Hotwell
• Circulation pump
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49
Auxillary equipment
• Ammonia storage tank
• Demineralized water tank
• Blow down tank
50
Thermal equilibrium
Power output
Power input
14.000 kW
Cooling water
1.700 kW
Electricity, net
15.700 kW
Brine
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51
Start-up problems
• Separator
• Evaporator
• Axial sealing of the turbine, ammonia leakage
• Condensers
• Miscellaneous
» Main pump
» Safety valves
» Magnetite
52
Separator
• Difficult to measure the performance of
the separator
• Mist eliminator module wrongly installed
• New separator installed November 2001
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53
Evaporator
• Ammonia leaking into the hot water
• All tubes rolled again in November
2001, no leakages since
54
Axial sealing
• One axial sealing on the low pressure
side
• N
2
used in the sealing
• The sealing has been replaced once
• Leakage caused by carry-over from
separator
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55
Condensers
• Plate heat exchangers
• Important to mix liquid and vapor
• Spraying nozzles modified
• Increase power output by improving
performance of the condensers
56
Miscellaneous
• Safety valves, leakage
• Circulation pump, seals and
guides/bushings for shaft
• Improvment of spraying system in
recuperator 2
• Magnetite (Fe
3
O
4
)
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57
Turbine corrosion
• Ferritic material in the turbine corrodes
• Austenitec material is unharmed
• Corrosion is from the turbine control
valve until abt 1 metre after the turbine
• Influence of rotor magnetic field?
» Elimination of ferritic material in the steam
side of the turbine
58
Operating experience
• Maximizing the output by optimizing the
strength of the NH
3
– H
2
O solution
• Prevent air entering the system
• Improvement of flushing and filters
• The system is stable in operation
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59
Lessons learned
• The technology is proven
• Standard equipment has been adjusted
• The plant is running according to specs
• Individual equipment still may be
improved to increase output
• Engineering details will improve future
plants
60
What do we have?
• New thermodynamic cycle with better
efficiency in particular when the heat source
cooled down while heat is extracted
• Theoretical and technical descriptions of the
processes involved.
• Mathematical models that have been tested
up against Husavik Plant
• Known media and known machinery
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61
The knowledge
• Real experience and know how from the
Husavik plant
• Mathematical models and ,,steam
tables”, worked out in cooperation with
University of Iceland.
• Over 30 years of experience in electrical
generation from low and mid heat
sources (Geothermal)
62
Kalina references
• Canoga Park, USA, demonstration plant
3 – 6 MW, 1991-1997
• Fukuoka, Japan, incineration plant, 4,5
MW, 1999
• Sumitomo, Japan, waste heat recovery
from a steel plant, 3,1 MW
• Husavik, Iceland, geothermal plant, 2,0
MW, 2000
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Krafla 1970, 60 MWel
Svartsengi 1980, 37 MWel, 60 MWdh
Nesjavellir 1990, 90 MWel, 250 MWdh
64
Were does it fit?
• Temperature above 150°C and good
size stands on its own.
• Cogeneration of electricity and water for
district heating.
• Good cold end helps
• Environmental issues and subsidizing
changes these values
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65
Budgetary unit price
• Budgetary price for 500 kW unit
720.000 USD
• Equals 1440 USD/kW
• Turbine/generator most costly unit (30-
35%)
• Presuming cooling water available
66
Opportunities
Where there may be hot water or other
fluid/gas available at temperatures
between 120 and 300°C
• Geothermal
• Waste heat
» Industrial processes
» Gas and diesel engine exhaust
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67
Kalina plant benefits
• Energy cost efficient
• Environmental issues
• Green energy
• Reduced emissions
• Standard off the shelf equipment
68
General market
conditions
• General market price 4 eurocents/kWh
• General pay-back time 4 years required
• General investment 1000 USD/kW
• So how can 1440 USD/kW be
competitive?
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69
German law
“Green” electrical power generation bonus
• 2002-2004 1,74 eurocents/kWh
• 2005-2006
1,69 eurocents/kWh
• 2007-2008 1,64 eurocents/kWh
• 2009-2010 1,59 eurocents/kWh
Provided plant in operation before end of 2005
70
Competitive investment ?
• Given 1,65 eurocents/kWh bonus
• 4 year pay-back period
• Additional investment acceptable for
“green” energy USD 528.000/MW
• Total acceptable investment cost thus
USD 1.528.000/MW
or 764.000 USD for
our 500 kW unit
.
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71
“Green” energy?
• Is waste heat recovery=green energy?
• Waste heat recovery reduces emissions
• CO
2
quotas pricing as high as 20-25
USD/tonCO
2
• Average emission 800 gCO
2
/kWh in
fossil fuel plants
• Equals values of 1,8-2,2 eurocents/kWh
72
Summary
• Given green energy bonuses or CO2
evaluation the investment in a Kalina waste
heat recovery electrical generating plant is
feasible
• The investment is competitive to other
investments for industrial improvements
• Pay-back time of 4 years in a green energy
technology is short
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73
Introduction
• Finite source heat capacity lowers this upper
bound due to the reduction of the source
temperature as heat is removed from the
source
• This results in high cost for such low
temperature power plants, as they have to
handle large heat flows
• The Kalina cycle is a novel approach to
increase this efficiency
74
The Models
• It is assumed that a fluid is available at
temperatures ranging from 100 to 150°C
• A heat customer is assumed for the primary
outlet water at the temperature of 80°C
• Primary flow of 50 kg/s is assumed
• Cooling water source is assumed at 15°C,
and cooling water outlet is fixed at 30°C
• It is assumed that a cooling water pump has
to overcome a pressure loss of 1 bar on the
cooling water side in the condenser
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75
Solution
• The software Engineering Equation Solver (EES) is
used to run the models
• The cost model keeps the logarithmic mean
temperature difference for each heat exchanger at
the same value as found in the cycle data for the
tenders for the Husavik power plant
• Estimated cost figures for individual components
were then added together in order to obtain the final
cost value
76
Process assumptions
• The OCR model is based on a system
without regeneration
• Isopenthane is assumed as a working
fluid
• A Kalina cycle for generation of
saturated vapour for the turbine is used
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77
ORC flow sheet
Production well
Injection well
Turbine
Condenser
Pump
Boiler
78
Kalina flow sheet
Production well
Injection well
Separator
Turbine
Condenser
Boiler
Throttling valve
Cooling tower
Regenerator
Pump
Brine hx
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79
Kalina assumptions
• This cycle will be limited by the dew point of the mixture,
that is when the boiling of the mixture is complete, and
no liquid remains at the boiler outlet
• The bubble temperature of the mixture has to be lower or
equal to the primary fluid outlet temperature to ensure
safe operation
• The feasible region will be in the area between the 70
and 80°C bubble contours
• The feasible area regarding the dew temperature is
limited to a value some 2-4°C lower than the maximum
temperature of the primary fluid
Bubble temperature
10
20
30
40
0.6
0.8
1
20
40
60
80
100
Pressure [bar]
Bubble temperature
Ammonia ratio [-]
B
u
b
b
le
t
e
m
p
e
ra
tu
re
[
°C
]
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Dew temperature
10
20
30
40
0.6
0.8
1
50
100
150
200
Pressure [bar]
Dew temperature
Ammonia ratio [-]
D
e
w
t
e
m
p
e
ra
tu
re
[
°C
]
Bubble contours
10
15
20
25
30
35
40
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
Pressure [bar]
A
m
m
o
n
ia
r
a
ti
o
[
-]
Bubble temperature contours
3
0
4
0
4
0
5
0
5
0
6
0
6
0
70
7
0
7
0
8
0
8
0
80
90
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Dew contours
10
15
20
25
30
35
40
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
Pressure [bar]
A
m
m
o
n
ia
r
a
ti
o
[
-]
Dew temperature contours
80
90
100
100
11
0
110
110
12
0
120
120
120
13
0
13
0
130
130
140
140
14
0
14
0
150
150
15
0
160
16
0
16
0
170
17
0
180
19
0
84
More Kalina
• Both high pressure level and ammonia content are
design variables in the Kalina cycle
• This gives flexibility in the design of the cycle, and
requires as well a certain design strategy
• The plant can be designed for maximum power
• or with strong demands on the investment cost
• The cost is 100 for the lowest cost, and the power
100 for the highest power
• An x denotes an infeasible solution, the cycle will not
be able to run at these ammonia content – pressure
combinations
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Cost contours
15
20
25
30
35
40
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
Pressure [bar]
A
m
m
o
n
ia
r
a
ti
o
[
-]
Cost contours, 100°C source
10
1
101
101
1
0
2
102
1
0
2
10
2
10
3
103
10
3
10
3
103
104
104
10
4
104
105
105
1
0
5
105
10
6
10
6
1
0
6
106
10
7
10
7
1
0
7
10
7
107
10
8
10
8
1
0
8
1
0
8
10
9
109
1
0
9
1
0
9
11
0
11
0
110
1
1
0
110
Power contours
20
25
30
35
40
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
Pressure [bar]
A
m
m
o
n
ia
r
a
ti
o
[
-]
Power contours, 100°C source
90
90
90
90
90
90
90
90
90
9
0
9
0
90
90
90
91
91
9
1
91
91
91
91
91
91
91
91
91
91
92
9
2
92
92
92
92
92
92
92
92
92
92
9
3
93
93
93
93
93
93
93
93
93
93
94
94
9
4
94
94
94
94
94
94
94
94
95
95
95
95
95
95
95
95
95
95
96
96
96
96
96
96
96
96
97
97
9
7
97
97
97
97
97
98
98
98
98
98
99
99
99
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Cost surface
10
20
30
40
0.6
0.8
1
0
200
400
600
Pressure [bar]
Cost function
Ammonia ratio [-]
C
o
s
t
Power surface
10
20
30
40
0.6
0.8
1
0
50
100
Pressure [bar]
Power function
Ammonia ratio [-]
P
o
w
e
r
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89
Discussion
• The best power and best cost points are
different
• The lowest cost is at 32 bar, 92% ammonia, but
highest power is at 34 bar and 88% ammonia
• This leads to the definition of two different Kalina
cycles, the best power and the best cost cycles,
with different pressure and ammonia content
15
20
25
30
35
40
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
Pressure [bar]
A
m
m
o
n
ia
r
a
ti
o
[
-]
Cost contours, 120°C source
10 1
10 1
1
0
1
10
2
10 2
102
10
2
10 2
10 2
10 3
10
3
1
0
3
10 3
10 3
10
4
10
4
1
0
4
10 4
10 4
105
1
0
5
1
0
5
10 5
10 5
10 6
1
0
6
1
0
6
10 6
10 7
1
0
7
1
0
7
10 7
10
8
10 8
10 8
1
0
8
10
8
10 9
10 9
1
0
9
1
0
9
11 0
1
1
0
1
1
0
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22
24
26
28
30
32
34
36
38
40
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
Pressure [bar]
A
m
m
o
n
ia
r
a
ti
o
[
-]
Power contours, 120°C source
7
0
7
0
7
2
7
2
7
4
7
4
76
7
6
7
6
7
8
7
8
78
8
0
8
0
80
8
2
8
2
82
8
4
8
4
84
84
8
6
86
86
8
8
88
88
9
0
90
90
9
1
91
91
9
2
92
92
9
3
93
93
94
94
9
5
95
9
6
96
97
98
9
9
18
20
22
24
26
28
30
32
34
36
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
Pressure [bar]
A
m
m
o
n
ia
r
a
ti
o
[
-]
Cost contours, 150°C source
10 1
10
1
101
10 2
1
0
2
102
10
3
10
3
10 3
10 3
10 4
1
0
4
10 4
10 4
10 5
1
0
5
10 5
10 6
1
0
6
10 6
10
7
1
0
7
10 7
10 8
1
0
8
1
0
8
10 8
10 9
1
0
9
1
0
9
1
1
0
1
1
0
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22
24
26
28
30
32
34
36
38
40
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
Pressure [bar]
A
m
m
o
n
ia
r
a
ti
o
[
-]
Power contours, 150°C source
7
0
7
0
7
2
7
2
7
4
7
4
7
6
7
6
7
8
7
8
8
0
8
0
8
2
8
2
8
4
8
4
8
6
8
8
9
0
9
1
9
2
9
3
9
4
9
5
9
6
9
7
94
Comparison
• Two ORC companies made a tender in
the Husavik bid
• Manufacturer A offered a high power,
high cost power plant, where
manufacturer B took a more
conservative approach
• Following is a comparison with both the
low cost and high power Kalina power
plants
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48
Cost comparison
100
110
120
130
140
150
1000
1200
1400
1600
1800
2000
2200
2400
Source inlet temperature [°C]
N
e
t
c
o
s
t
[$
/k
W
]
Kalina vs ORC cost comparison
ORC B
ORC A
Kalina HP
Kalina LC
Power comparison
100
110
120
130
140
150
0
500
1000
1500
2000
Source inlet temperature [°C]
N
e
t
p
o
w
e
r
[k
W
]
Kalina vs ORC power comparison
Kalina HP
Kalina LC
ORC A
ORC B
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97
Results
• The maximum power generated for a
given source is greater for the Kalina
cycle
• Kalina cycle is well positioned against
an ORC cycle for applications with high
utilization time, a base load application
98
Results II
• A heat consumer is beneficial for the ORC
cycle as it results in less temperature change
of the primary fluid during the boiling process
• The Kalina cycle has the boiling or
vaporization of the fluid happening over a
temperature range up to 100°C, which is
beneficial when the primary fluid return
temperature has to be minimized
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50
99
The debate
• The theoretical efficiency and cost/production
ratio are better for Kalina as shown above
• Other arguments like difficulties with
machinery and lesser operational security or
uptime are only temporary discussion items,
as always for a new technology
• These arguments were exactly the same
between conventional flash cycle and ORC
when the latter popped up 30 years ago with
better efficiency but little track record
100
Conclusion
• The Kalina cycle is thermodynamically
superior or equal to the ORC cycle
• There is no black magic behind the
Kalina cycle
• The startup problems that have either
been solved, or are solvable
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