The Digital Displacement®
Hydraulic Hybrid Bus
… a globally affordable way of saving fuel
Dr Niall CALDWELL
Managing Director
CENEX LCV 2015
10th September 2015
www.artemisip.com
Hybrid bus market
Global Bus market volumes/year
• Overall bus market is growing
strongly…
• Diesel-electric hybrids are
forecast to increase to 9.7% by
2020
• Why not 100%?
Data from:
“Strategic Analysis of
Global Hybrid and
Electric Heavy-Duty
Transit Bus Market”,
Frost and Sullivan,
October 2013
Growth regions
• Global growth is not driven
by European or North
American demand, where
subsidies are available.
• Do Diesel-Electric hybrids
have a good business case
in markets without subsidy?
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Diesel-Electric buses cost 50% more to buy
and the payback period is too long
Purchase cost = at least 150% of a diesel bus
Source: Frost and Sullivan 2012
A simple financial model…
Purchase price premium = $150,000
Average duty of a city bus = 46,500 miles
Saving per mile = $0.19
Savings per year = $8,835
Running cost = 15% less than a diesel bus
Source: Hallmark and Qiu 2012
Years to achieve cost-neutral vs. cost of
capital: (assuming no battery replacement cost)
17 years @ 0% interest
20 years @ 1% interest
25 years @ 2% interest
Useful life of bus: 10 …. 20 years
• It is unlikely to pay back the
investment without subsidy!
• Diesel electric buses are not a
real business proposition for
most of the market!
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2 . W h y i s E l e c t r i c H y b r i d t e c h n o l o g y ex p e n s i v e ?
Energy Store:
Lithium-Ion Battery
Motor:
Permanent magnet (rare-earth)
Power converter: High-power silicon semiconductor
•Highly-sophisticated
technology
•Expensive/rare materials
•Expensive production
processes
•High capital investment
•High embodied energy
•Poor recyclability
•Special training required
for service
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3. What the world needs…
A hybrid bus which makes business sense
–
–
–
–
–
–
Low capital cost
Low maintenance cost
Substantial fuel consumption reduction
Easy to fit to existing designs
No special training to service
No impact on reliability, noise, passenger space
How about hydraulics?
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Hydraulic Technology?
+ Compact and powerful
+ Tolerance to shock and harsh
environments
+ Continuous control - no gearshifts
+ Low cost vs. electric drives
BUT…..
- Poor energy efficiency
- High-frequency noise
- Difficult to computer control
Limits potential of hydraulic
technology in hybrid vehicles
Is there anything better?
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Rapid development cycle
•
•
•
•
•
Origin: Edinburgh University research
Aquired by Mitsubishi Heavy Industries in 2010
Located in Edinburgh, Scotland
~ 50 employees
Innovation of new technology:
R&D -> Product development -> Product launch
Assignee
Families
Pending
Granted
AIP
54
144
125
MHI
59
149
20
Total
113
293
145
Patents
…NEWS FLASH… 16 July 2015….
Artemis Intelligent Power Ltd. named
as Winner of the the Royal Academy of
Engineering “MacRobert Award 2015”
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AIP: What do we do?
• Develop Digital Displacement® core technology
– Simulation and concept development
– Design: Mechanical, Electronic, Software
– Experimental development and verification
• Develop applications and products with MHI and
partners
– Application demonstration
– Product development
– Manufacturing for pilot production
100 Nm
1 kNm
FM 612199
10 MNm
D i g i ta l D i s p l a ce m e nt ® H y d r a u l i c s
Conventional hydraulics
Controlled by varying the stroke of
the pistons
- Poor energy efficiency
- High-frequency noise
- Difficult to computer control
Digital Displacement® Hydraulics
Controlled by enabling/disabling
cylinders by computer-controlled
valves
+ Efficiency as good as electric motors
+ No high-frequency noise
+ Digital control built-in
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D i g i ta l D i s p l a ce m e nt ® O p e r a t i n g P r i n c i p l e
•
•
•
•
Idle
Low pressure valve is open
Cylinder is depressurised
Parasitic losses are minimal
Ready to respond in ~20ms
Pumping
• Low pressure valve is closed at BDC
• Cylinder is pressurised
• Work is done at high efficiency
…1010101010111111111110000000……
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DD has high part -load efficiency
100
90
DDP
Overall 80
efficiency
% 70
Typical axial-piston
60
50
40
0
10
20
30
40
50
60
70
80
90
100
Relative displacement - %
DD is a dramatic improvement in the efficiency of hydraulic pumps!
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DD hybrid bus system
Energy Storage
High pressure Nitrogen
filled accumulator
FEAD
High power, low cost belt drive.
Energy Capture / Recovery
Digital Displacement® intelligently controlled
hydraulic machine capable of highly efficient
Pumping and Motoring – DDPM®
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Round-trip efficiency of energy recovery
Transmission
loss
15%
Engine
accessories
29%
Drag - 3%
Rolling
resistance
21%
Braking – 32%
Hydraulic
Accumulator
Ein
Eout
Energy Storage
Efficiency=Eout/Ein
Digital Displacement®
Pump/Motor
Measured round-trip efficiency
In high-power KERS = 73%
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Hoses
Valves
Accumulators
Mechanism
Mineral oil
Mass
Base Vehicle: 8140kg
Hybrid system: 200kg
+2.4%
Digital
Displacement®
Control Module
Belt drive
(Steel, oil, rubber,
aluminium)
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Digital Displacement® pump -motor
• Machine can operate continuously at
peak power (no limit to duty cycle)
• Made from common low-cost materials
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Baseline Vehicle
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Baseline Model Development
Coastdown A,B,C
Physical parameters
Baseline
vehicle
model
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City of Edinburgh: in -ser vice data collection
Route 12
Baseline model was validated with test data
=> 32% of the engine output energy is wasted in the brakes!
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Model based design => sizing
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Model-based design => control system
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Installation
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Drive cycle characteristics
MLTB
LB 12
Drive cycle
Braking MJ / km
Braking energy as % of wheel energy
MLTB
1.42
58%
LB 12
1.05
56%
*MLTB: ‘Millbrook London Transport Bus’ – drive cycle used in Low Carbon bus certification in UK
*LB 12: Lothian Buses route 12
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Ve h i c l e te st i n g – fo r ca l i b r a t i o n o f m o d e l
Route
Avg. acceleration [m/s^2]
Avg. deceleration [m/s^2]
MLTB
0.5
-0.8
Route 12
0.6
-0.5
Saw Tooth
0.5
-1
Vehicle speed
Gear number
Accumulator pressure
Fuel flow-rate
No. Cycles
Total Distance [m]
Total Fuel [cc]
Fuel [l/100km]
KERS
9
2189
675
31
Non-KERS
10
2431
903
37
Fuel Saving
17%
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Outlook – by validated simulation
30
% Fuel Saving
25
20
15
10
5
0
LB Route 12
MLTB
Drive cycle
• Next generation
• 420 bar max
• No Torque limit
+ Non-Voith Gearbox
+ Stop / Start
MLTB
11.1%
19%
27%
LB 12
8.2%
12%
20%
27% “fuel saving” (l/100km) => +37% “fuel economy increase” (MPG)
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Summar y
• Digital Displacement® Hydraulic Hybrid
• 27% fuel saving forecast for Euro 6 bus
• Low capital and maintenance cost
 2…3 years pay back on investment with
no subsidy
•
•
•
•
•
No rare materials
Inexpensive production
Easy to integrate
Easy to recycle
Easy to maintain
Digital Displacement® Hydraulic Hybrid
A Globally Affordable way to Save Fuel!
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Please visit our stand for more information or to
arrange a demonstration.
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