The document evaluates applying an Electric-Turbo-Compound system to recover waste heat from marine diesel engines. Modeling shows a system with an expansion ratio of 1.5 and engine design point of 85% could generate 490kWe per engine on a frigate, saving 43 tons of fuel annually and reducing payback time to 4.2 years with projected 2021 costs. Overall, the analysis found waste heat recovery via Electric-Turbo-Compound can provide cost-effective emissions reductions on certain vessel types.

1. Evaluation of Electric-Turbo-Compound applied to Marine
Diesel-Engines for Waste Heat Recovery
October 4th, 2018
Prof Richard Bucknall (UCL)
Presenter: Dr Santiago Suárez de la Fuente (UCL)
Dr Shinri Szymko (Bowman Power Group Ltd.)
Will Bowers (Bowman Power Group Ltd.)
Alastair Sim (Rolls-Royce)
Presenter: Keith Douglas (Bowman Power Group Ltd.)

2. Contents
• Introduction
• Objectives
• Electric-Turbo-Compound (ETC)
• Case Study – Frigate
• Modelling
• Results
• Conclusions

3. Introduction
Innovate UK project [101987]: Vessel efficiency at sea, Marine ETC
Lead Partner: Bowman Power Group Ltd
Partners: Lloyd’s Register, Rolls-Royce and UCL
Length: 30 months (between 2015 and 2018)
Objectives:
• To develop a new, marine-capable ETC system for 4-stroke diesel engines
(< 4 MW);
• To develop a market study for the new ETC system;
• To model the ETC system performance on different ships, layouts and
operational profiles; and
• To open new development roads for the marine ETC.

4. Objectives
• Model and test different ETC designs for the Frigate’s diesel
engines and quantify:
• ETC electric power output
• Fuel savings
• CO2 emission reductions
• Secondary impacts  Cylinder backpressure
• Initial cost
• Payback time
What are the benefits and secondary impacts when
installing an ETC system on-board a Frigate?

5. • Exhaust gas, with high temperature and pressure flows
from the engine and enters the ETC 1000
• The stationary Nozzle Guide Vanes (NGV) direct and
accelerate the flow toward the rotating rotor blades
downstream
• The flow from the NGV transfers the exhaust energy (high
temperature and high pressure) to the turbine blades and
rotor
• The gases exit the ETC 1000 at close to the exhaust stack
• The rotor is connected to the high speed alternator
producing a non-stable AC current, which is exported to the
Power Electronics unit
• This AC input current is converted to DC before final
conversion to 3 phase AC grid quality (50/60Hz) output
(Can also be used to power site auxiliaries or charge
batteries for hybrid solutions)
KEY COMPONENTS
Turbo
Generator
Power
Electronics
1
2
3
4
5
1
2
3
4
5
6
6

6. EXAMPLE ETC SYSTEM SET UP
1: TURBO GENERATOR
Located downstream of the
engine’s turbocharger to recover
further energy. Produces
electricity typically > 1000 Hz
3: POWER ELECTRONICS
The high frequency electricity is
converted to grid quality
electricity at 50/60 Hz
Also available in single system
set up
2: TURBOCHARGER
To maintain engine performance
this is re-matched to work with
the turbo generator
2
1
3

7. ELECTRIC TURBO-COMPOUNDING (ETC)
ETC is currently applied: 1 - In-line with the engine’s turbocharger as shown:
1. ETC power is increased by decreasing the TG NGV, thus increasing back pressure on
the TC, slowing it and dragging down the air fuel ratio (AFR)
 Increased combustion & exhaust temperatures and pumping losses
2. This is offset by decreasing the TC NGV, increasing TC speed and AFR
 Further increased pumping losses, residual fraction & firing pressures
1
2
TG & TC NGV’s optimised together to maximise ETC power within engine limits

8. EFFECT ON ENGINE PERFORMANCE
0
100
200
300
400
500
600
700
Temperature
(°C)
Engine Baseline
System Optimisation
50
150
250
350
450
Pressure(kPa)
1. Increased dP across engine leads to pumping
losses. At constant fuel consumption this results in
a decrease in engine power
2. Increased engine out pressure results in increased
expansion ratio for turbocharging system and more
power extracted from exhaust gases
 Increased system power
Typical pressures and temperatures for
ETC application
2
1
2
1
1
2

9. ELECTRIC TURBO-COMPOUNDING (ETC)
ETC is currently applied: 1 - In-line with the engine’s turbocharger as shown:
Engine size
Fuel
Type
Typical fuel saving and /
or Power uplift
Typical ROI payback (months)
0.5 – 2.5MWe
Natural Gas 3 – 5%
18 - 30Bio Gas / Low BTU 5 – 7%
Diesel 4 – 7%

10. WASTEGATE VARIANT
Engine size
Fuel
Type
Typical fuel saving and /
or Power uplift
Typical ROI payback (months)
10 - 20MWe Natural Gas 1 – 3 % 24 - 36
ETC is currently applied: 2 - Parallel to the engine’s turbocharger as shown:

11. OTHER ADVANTAGES
Downsizing the engine’s turbo brings through increased AFR at idle, low speeds and loads:
• Better transient response and acceleration
• Lower transient emissions (NOx and PM)
• Reduced Methane slip / UHC emissions (SI gas engines)

12. Case Study - Frigate
• Propulsion layout = CODLOG
• Engines = 4 x MTU4000 (20 cylinder each)  16 MW
• Electrical Generator Efficiency = 91%
• Gas Turbine = 1  36 MW (Out of the scope of this work)
• Hotel Demand = 1.9 MWe (Assumed constant)
• Fuel (Diesel engines) = F76 (42,700 kJ/kg)
[CF = 3.206 t CO2/t of fuel ]
[Cost = £392.9/t – average between April 2017 and April 2018]
[1]

13. Case Study - Frigate
Power Curve  Assumed a cubic relationship

14. • Propulsion layout = CODLOG
• Engines = 4 x MTU4000 (20 cylinder each)  16 MW
• Gas Turbine = 1  36 MW (Out of the scope of this work)
• Hotel Demand = 1.9 Mwe (Assumed constant)
• Fuel (Diesel engines) = F76 (42,700 kJ/kg)
• Maximum Speed Diesel only (kn) = 20.0
• Maximum Speed (kn) = 30.0
• Operational time (days) = 215 (59% of a year)
Case Study - Frigate
[1]

15. Case Study - Frigate
Operational Profile

16. Marine Engine Model + ETC
aFour-stroke diesel engine

17. Approach
A sensitivity analysis was performed:
• ETC Design Expansion Ratios
(ER):
• 1.1 – 1.7 in steps of 0.2
• 4-stroke diesel engine Design
Point (DP):
• 75% & 85% MCRe
• Operational Point (OP):
• 57% to 95% MCRe  9 points
• One year operation
[2]

18. Results
ETC Electric Power Output (per engine)
18
Larger design ER produce more electrical
power.
• 680 KWe (ER 1.7) vs 220 kWe (ER 1.1)
Higher DP loads produce less electrical power
for the same loading condition and ER.
• ER 1.7: 680 kWe vs 600 kWe
• Better efficiencies and higher ER when
the DP is set at 75% MCRe
Low design ER do not produce electrical
power when:
• DP is @ 75% MCRe and OP < 65% MCRe
• DP is @ 85% MCRe and OP < 70% MCRe.

19. Results
Pressure before the TC turbine
Low DP and ER reduce the
backpressure at low loads
• Better TC efficiency
High ER for any DP can reach a change
above 40% at any loading condition
(Max. 68% change)
• This will be an important issue with respect
to NOx formation  Engine recertification
may be needed
• Exhaust gas leaking to intake manifold 
combustion temperature increase

20. Results
Mechanical Power Reduction per Cylinder
20
Drop in mechanical power:
• Increase in cylinder backpressure 
Pumping losses rise
• Lower electrical demand due to ETC
operation
Larger change happens with larger ER &
lower loading at DP and larger OP
Larger ETC Power = Larger Mechanical
Power Reduction

21. Results
Annual Overall Fuel Savings
Frigate annual fuel consumption  680 t (633 t from the 4-stroke & 47 t gas
turbine)
CO2 emissions  2,180 t (2,030 t from the 4-stroke & 150 t gas turbine)
• 60 t of fuel reduced (More than what the GT consumes)
• And 190 t of CO2
• And £23,500
• But there is an important increment in backpressure
ETC Expansion Ratio
(-)
Engine Design Point
(% MCRe)
1.1 1.3 1.5 1.7
75 2.1% 5.2% 7.3% 8.8%
85 1.0% 4.2% 6.4% 7.9%

22. Results
Initial and Running Costs (Best estimated)
• ETC (110 kWe kit)
• Specific cost = £700/kWe (Today)  Target 2021 = £350/kWe
• Running cost = £0.30/h
• Lowest overall cost = £0.39 million (DP 85% MCRe & ER 1.1)
• 2 - 110 kWe ETC per engine
• Highest overall cost = £1.55 million (DP 75% MCRe & ER 1.7)
• 7 - 110 kWe ETC per engine
£0.19 million
£0.78 million
2021

23. Results
Carbon Emission Reduction Costs
•Assuming an operative life of 25 years, reducing CO2
emissions could cost:
• DP 85% MCRe & ER 1.1 (Lowest total cost) = £620/t CO2
• DP 85% MCRe & ER 1.5 (Mid total cost) = £190/t CO2
• DP 75% MCRe & ER 1.7 (Highest total cost) = £200/t CO2
[3]
£95/t CO2
£100/t CO2
2021
£310/t CO2

24. Results
Payback Time
Shortest payback time is 8.4 years  DP 85% MCRe with ER 1.5
• Lower initial cost
• Frigate navigates only 59% of the year and the 4-stroke diesel + ETC just 31%

25. Results
Payback Time (Other ships)
Ship Type DWT
ETC
Location
Number of ETC
per Engine (-)
Ship Fuel
Savings (%)
Payback Time
(Years)
Coastal Cargo 6,500 ME 1 3.2 3.9
Dry Bulk 96,140 AE 2 7.4 5.2
PSV (Small) 1,315 AE 2 7.3 5.2
PSV (Medium) 4,470 AE 3 5.2 7.5
Passenger (Small) 527 ME 2 3.0 9.0
Passenger (Medium) 5,770 AE 4 5.6 7.1
Tanker 363,280 AE 2 1.2 2.3
Optimum payback time depends on:
• Ship utilisation
• How the ship is being operated (ETC utilisation)
• Complexity

26. Results
Payback Time (Other ships)
Ship Type DWT
ETC
Location
Number of ETC
per Engine (-)
Ship Fuel
Savings (%)
Payback Time
– 2021 Costs
(Years)
Coastal Cargo 6,500 ME 1 3.2 1.8
Dry Bulk 96,140 AE 2 7.4 2.6
PSV (Small) 1,315 AE 2 7.3 2.6
PSV (Medium) 4,470 AE 3 5.2 3.8
Passenger (Small) 527 ME 2 3.0 4.5
Passenger (Medium) 5,770 AE 4 5.6 3.6
Tanker 363,280 AE 2 1.2 1.2
Optimum payback time depends on:
• Ship utilisation
• How the ship is being operated (ETC utilisation)
• Complexity

27. Conclusions
Performed ETC sensitivity analysis and found that the
frigate will benefit from an ETC with a:
Design point at 85% MCRe with a design ER of 1.5
• Initial cost of £1.1 million 5-110 kWe ETC per engine
• Max. electrical power output per engine (kWe) = 490
• Max. cylinder backpressure change (kPa) = 116 (40%)
• Annual fuel savings (t) = 43 (140 t CO2)
• Cost CO2 reduction (£/t CO2) = 195
• Payback time (years) = 8.4
• Payback time (years, specific costs 2021) = 4.2 years

28. Contact Details
LinkedIn:
https://www.linkedin.com/in/santiagosuarezdlf/
https://www.linkedin.com/in/keith-douglas-9a6772158
Webpage:
https://www.bowmanpower.com/
Thank you
Any Questions?

29. Images References
1. https://ukdefencejournal.org.uk/the-type-26-frigate-could-be-the-most-
capable-royal-navy-warship-in-decades-if-funded-properly/
2. https://www.lynda.com/Data-Science-tutorials/least-squares-
approach/664827/702911-4.html
3. https://www.conservationinstitute.org/co2-to-ethanol/