Waste Heat Recovery on a Liquefied
Natural Gas Carrier with Tri-fuel Diesel
Electric Propulsion using a Dual Loop
Rankine Cycle
Eleni Lazaratou
Supervisor: Prof. Christos Frangopoulos
Goal
To recover waste heat from a ship power
production system in order to reduce fuel
consumption
2
Goal
To recover waste heat from a ship power
production system in order to reduce fuel
consumption
1. Why is it necessary? How will it be
achieved?
3
Goal
To recover waste heat from a ship power
production system in order to reduce fuel
consumption
1. Why is it necessary? How will it be
achieved?
2. What is the initial installation? How will it
be modified?
4
Goal
To recover waste heat from a ship power
production system in order to reduce fuel
consumption
1. Why is it necessary? How will it be
achieved?
2. What is the initial installation? How will it
be modified?
3. What are the results?
5
Waste heat
recovery
6
Waste heat recovery
Waste Heat Recovery in Industrial Applications
Useable
Energy (5080%)
Waste Heat
(20-50%)
Waste Heat at
Temp <230⁰C
(60%)
The significant cost of energy as well as increasing environmental concerns
make the better utilization of fuel energy a necessity
7
Waste Heat Recovery
Ericsson Cycle
Turbocompounding
Stirling Cycle
Thermoelectric Generator
Rankine Cycle
8
Rankine Cycle
4. 𝐓𝒎𝒂𝒙
𝑄𝐻𝑆 = 𝑚𝐻𝑆 ℎ𝐴 − ℎ𝐵,𝑚𝑖𝑛
𝑄𝐻 = 𝑚 ℎ3 − ℎ2
𝟑. 𝒎
𝑸
𝜼𝑸 = 𝑸 𝑯
Heat recovery efficiency
𝑯𝑺
𝑊𝑛𝑒𝑡 = 𝑊𝑇 − 𝑊𝑃
2.
Evaporation
Pressure
𝜼𝑹 =
1. Condensing
Pressure
𝑾𝒏𝒆𝒕
𝑸𝑯
𝜼𝒕𝒐𝒕 = 𝜼𝑹 ∙ 𝜼𝑸
Thermal efficiency of the
cycle
System overall efficiency
9
Organic Rankine Cycle (ORC)
The working fluid in a classic Rankine cycle is
water.
However, water can only recover energy from
waste heat sources above 100⁰C (its boiling point).
The solution
Replacing water with organic fluids or non-organic
fluids like ammonia which boil at lower
temperatures.
10
ORC Applications
Applications of ORC
Technology
Biomass
20%
1%
48%
31%
Geothermal
Waste heat
recovery
Solar
11
Marine ORC Applications
Enertime
o Feasibility study on a Passenger / Car Ferry: Power production 700 kW, 7.5x2.5x4 m, 25t
o Up to 10% reduction in fuel consumption with a payback period of 6 years
Turboden / Wärtsilä
o Turboden is a well known ORC system producer for on-land applications. Since 2010,
Turboden is cooperating with Wärtsilä to produce a series of ORC systems for Wärtsilä
marine engines
Opcon Marine
o Installed a system on a Ro-Ro ship for electric
power production up to 0.5 MW
o Reported reduced fuel consumption by 4-6%
www.turboden.eu
12
Ship Power
Production System
13
Ship Power Production System
Operating Profile
Liquified natural gas carrier with capacity of 158,000 m3 LNG
Design service speed: 19.5 kn
Operating Profile
Speed Profile
4.79%
15.48%
Laden voyage
37.40%
Ballast
voyage
In port
42.33%
At anchorage
/ idle
Percent of Total Steaming Hours (%)
Laden
Ballast
7%
6%
5%
4%
3%
2%
1%
0%
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Speed Range (kn)
14
Ship Power Production System
Propulsion
Installed power: 4 x 8775 kW (35.1 MW)
15
Ship Power Production System
Waste heat sources
High Temperature
Cooling Circuit ~85⁰C
Exhaust Gas
~400⁰C
Low Temperature
Cooling Circuit ~40⁰C
16
Ship Power Production System
Waste heat sources – Cooling circuits
17
Ship Power Production System
Waste heat sources
High Temperature
Cooling Circuit ~85⁰C
Exhaust Gas
~320⁰C
Engine efficiency:
40-47%
For engines with EBG:
49-52%
Low Temperature
Cooling Circuit ~40⁰C
18
System Modification
Proposed Dual ORC System
High Temperature Cycle Working Fluids
Tcrit (⁰C)
Pcrit (bar)
Tboil (⁰C)
R416a
108.3
39.3
-23.2
Ammonia
132.3
113.3
-33.59
R245fa
154.0
36.5
14.81
Water
374.0
220.1
99.61
Low Temperature Cycle Working Fluid
R134a
Tcrit (⁰C)
Pcrit (bar)
Tboil (⁰C)
101.1
4.06
-26.36
19
System Modification
Optimization Problem
Objective Function
Performance variables
• 𝑀𝑎𝑥 𝑊𝑁𝐸𝑇,2𝑅
• Output power 𝑊𝑁𝐸𝑇,2𝑅
Constraints
• Pinch point > 30⁰C in heat exchanger
with flue gasses
• Pinch point > 5⁰C in other heat
exchangers
Independent variables
• Fluids & Fluid flows 𝑚𝐻𝑇 , 𝑚𝐿𝑇
• Evaporation pressure 𝑃𝑒𝑣𝐻𝑇 , 𝑃𝑒𝑣𝐿𝑇
• Superheating in HT Cycle ΔTsup,HT
• Portion of cooling of the engine system
LT cooling water by the ORC
• Efficiencies
o Thermal: 𝜂𝑅
o Heat transfer: 𝜂𝑄
o Total: 𝜂𝑡𝑜𝑡
• Sizing parameters
o
o
o
o
Ratio of power to flow: 𝑊𝑁𝐸𝑇 /𝑚
Turbine size parameter: SP
Turbine volume flow ratio: VFR
Turbine rotational speed parameter: RSP
Design point: Ballast, 16 kn
20
Results
21
Optimum independent
variables for Dual ORC (1/2)
Power Output for Optimal Dual
Cycles
Power Output (kW)
WNET,LT
1800
1600
1400
1200
1000
800
600
400
200
0
83.1%
Ammonia
- R134a
R245fa R134a
Water R134a
𝒎𝑯𝑻 𝒌𝒈 𝒔
23.2
5.2
20.6
2.0
𝒎𝑳𝑻 (𝒌𝒈 𝒔)
43.0
43.9
42.1
43.4
𝚫𝚻𝐬𝐮𝐩 (℃)
213
207
164
199
𝑷𝒆𝒗,𝑯𝑻 (𝒃𝒂𝒓) 130
150
100
10
𝑷𝒆𝒗,𝑳𝑻 (𝒃𝒂𝒓) 28.30
28.30
27.92
26.23
%𝑳𝑻 𝑪𝑾
0.0%
0.0%
0.0%
WNET,HT
100%
95.7%
905
840
625
741
R416a R134a
738
89.5%
928
732
543
R416a / Ammonia R245fa /
R134a / R134a R134a
Fluid Combinations
Water /
R134a
0.0%
Design point: Ballast, 16 kn
22
Optimum independent
variables for Dual ORC (2/2)
Power Output for Optimal Dual Cycles
with Max Pressure 50 bar
Power Output (kW)
WNET,LT
1800
1600
1400
1200
1000
800
600
400
200
0
928
700
346
795
Ammonia
- R134a
R245fa R134a
Water R134a
WNET,HT
99.0% 100.0%
77.6%
R416a R134a
𝒎𝑯𝑻 𝒌𝒈 𝒔
27.8
20.9
2.0
𝒎𝑳𝑻 (𝒌𝒈 𝒔)
44.9
42.4
43.4
𝚫𝚻𝐬𝐮𝐩 (℃)
158
149
199
𝑷𝒆𝒗,𝑯𝑻 (𝒃𝒂𝒓)
50
50
10
𝑷𝒆𝒗,𝑳𝑻 (𝒃𝒂𝒓) 28.33
27.85
26.23
%𝑳𝑻 𝑪𝑾
0.0%
0.0%
757
543
R416a / Ammonia R245fa /
R134a / R134a R134a
Water /
R134a
Fluid Combinations
0.0%
Design point: Ballast, 16 kn
23
Results
Output of Dual Water-R134a Cycle
MGEs
Dual Rankine Cycle
Reduction in fuel energy consumption
35
6.78%
6.94%
Power (MW)
30
25
20
15
10
5
6.78%
6.72%
6.76%
6.74%
4.6%
5.5%
14.4%
4.7%
13
14
15
16
6.59%
6.48%
7.10%
11.6%
5.5%
5.6%
6.2%
6.4%
19
20
21
0
17
18
Ship speed (kn)
40%
35%
30%
25%
20%
15%
10%
5%
0%
Reduction in Fuel Energy Consumption
Ballast Power Production with Water-R134a Dual
Rankine Cycle
24
Results
Output of Dual Water-R134a Cycle
MGEs
Dual Rankine Cycle
Reduction in fuel energy consumption
35
6.55%
Power (MW)
30
7.10%
25
20
15
10
5
6.87%
5.69%
5.70%
6.74%
6.60%
6.49%
11.65%
4.52%
5.40%
14
15
4.66%
5.43%
7.73%
5.62%
1.76%
0
16
17
18
Ship speed (kn)
19
20
21
40%
35%
30%
25%
20%
15%
10%
5%
0%
Reduction in Fuel Energy Consumption
Laden Power Production with Water-R134a Dual
Rankine Cycle
25
Results
Output of Dual R245fa-R134a Cycle
MGEs
Dual Rankine Cycle
Reduction in fuel energy consumption
35
7.61%
7.92%
Power (MW)
30
25
20
15
10
5
6.78%
6.96%
4.6%
5.7%
13
14
7.05%
7.41%
7.30%
7.11%
8.09%
12.1%
14.6%
5.3%
6.0%
6.3%
6.9%
7.1%
19
20
21
0
15
16
17
18
Ship speed (kn)
40%
35%
30%
25%
20%
15%
10%
5%
0%
Reduction in Fuel Energy Consumption
Ballast Power Production with R245fa-R134a Dual
Rankine Cycle
26
Results
Output of Dual R245fa-R134a Cycle
MGEs
Dual Rankine Cycle
Reduction in fuel energy consumption
35
7.64%
Power (MW)
30
25
7.06%
20
15
10
5
5.95%
6.03%
4.50%
5.40%
14
15
6.04%
7.07 %
6.94%
7.23%
12.20%
5.10%
6.00%
8.40%
6.30%
1.80%
0
16
17
18
Ship speed (kn)
19
20
21
40%
35%
30%
25%
20%
15%
10%
5%
0%
Reduction in Fuel Energy Consumption
Laden Power Production with R245fa-R134a Dual
Rankine Cycle
27
Natural boil-off rate
Environment +25⁰C
Evaporation
-160⁰C
Insulation
The amount of the cargo
which will naturally
evaporate depends on the
quality of the insulation.
For every ship, a nominal
«Natural Boil off Rate»
(NBOR) is defined which
gives the percentage of
cargo evaporating each
day.
The evaporated cargo is
used as fuel in the main
engines.
28
Natural boil-off speed
Laden Energy Requirements vs
Energy from NBOG
80
80
70
70
Worst insulation
NBOR = 0.150% ∙ Vcargo/day
60
50
40
30
Best Insulation
NBOR = 0.090% ∙ Vcargo/day
20
Energy (MW)
60
Energy (MW)
Ballast Energy Requirements vs
Energy from NBOG
50
40
30
20
10
10
0
0
5
10
15
Ship speed (kn)
20
Worst insulation
Best insulation
5
10
15
Speed (kn)
20
29
Results
Fuel savings
Yearly fuel savings
Water-R134a
R245fa-R134a
1200
1000
(t LNG)
800
600
400
200
0
0.090%
0.100%
0.110%
Natural Boil-off Rate
0.125%
0.150%
30
Results
Economic analysis
Net Present Value of WaterR134a Dual Cycle
NBOR
0.090%
0.100%
0.125%
0.150%
Net Present Value of R245faR134a Dual Cycle
0.108%
NBOR
40
30
20
10
0
-10
0.100%
0.125%
0.150%
0.108%
50
NPV (million USD)
NPV (million USD)
50
0.090%
40
30
20
10
0
0
20
40
60
80
LNG fuel unit price (USD / MMBtu)
-10
0
20
40
60
80
LNG fuel unit price (USD / MMBtu)
31
Results
Economic analysis
Dynamic Payback Period of
Water-R134a Dual Cycle
0.090%
0.100%
0.125%
0.150%
0.108%
NBOR
DPP (Years)
DPP (Years)
NBOR
Dynamic Payback Period of
R245fa-R134a Dual Cycle
25.0
20.0
0.100%
0.125%
0.150%
0.108%
25.0
20.0
15.0
15.0
10.0
10.0
5.0
5.0
0.0
0.0
0
20
40
60
80
LNG fuel unit price (USD / MMBtu)
0.090%
0
20
40
60
80
LNG fuel unit price (USD / MMBtu)
32
Conclusions
1. In industrial applications, 20-50% of fuel energy is lost as
waste heat, heat which can be utilized with Organic
Rankine Cycles.
2. In the present study, ORC technology was applied to an
LNG ship propulsion system. A dual cycle was used with
the HT cycle recovering exhaust heat and the LT cycle
recovering heat from the engine cooling water system.
3. In the optimal system, which proved to be the dual
Water-R134a cycle, the yearly fuel savings reached 1133
t LNG.
33
Thank you for your attention
34