The document provides an overview of a presentation on evaluating regenerative braking systems for urban driving conditions. It discusses the need to study regenerative braking to reduce fuel consumption and emissions from frequent stopping and starting in urban areas. It analyzes braking energy potential from actual bus and vehicle data captured in urban driving. The document compares regenerative braking energy under standard and real-world cycles and evaluates kinetic, electric, and hydraulic regenerative braking technologies based on characteristics like energy storage and conversion efficiency. It also outlines the basic design procedure for a hydraulic regenerative braking system and references on the topic.

1. PDP Session on
Evaluation of Regenerative Braking System
For Urban Driving Conditions
Presented By
Dr. Nityam Oza
Lecturer
Mechanical Engineering Department
Government Polytechnic, Rajkot
31 August 2021 1

2. 31 August
2021
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Content
•Introduction to regenerative braking
•Pros. and Cons. of application of regenerative braking system to the automobile
•Selection criteria for application of regenerative braking system
•Analysis of braking energy potential for real urban driving conditions
•Comparison of regenerative braking energy under standard and actual drive conditions
•Comparison/selection of suitable regenerative braking system for given application
•Design procedure of major components for fixed displacement pump based hydraulic
regenerative braking system
•Integration of hydraulic regenerative braking system to the existing automobile
•Performance evaluation of the regenerative braking system
•Effects of variation in key parameters on performance of the regenerative braking system.
•References

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Content
•Integration of hydraulic regenerative braking system to the existing automobile
•Differential gear - Eaton
•Gear box -
•Operating
•Integrated to brake pedal
•Stand alone

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Content
•Fixed displacement
Variable displacement
Gear pump or piston pump

5. 31 August 2021
Introduction
Need for study – Automotive fuel consumption in India
2012-13 Avg. Growth
Transport sector
share (%)
Gasoline/Petrol
(Million Tonnes)
15.74 7% ~99.6
Diesel
(Million Tonnes)
69.08 5.7% ~73.58
Source: http://www.ppac.org.in/

6. 31 August 2021
Introduction
Need for study – Diesel consumption trend
HCV, LCV &
Buses
3W, Car, UV
Transport sector
share (%)
Diesel 40.80% 32.78% ~73.58
Source: http://www.ppac.org.in/

7. 31 August 2021
Introduction
Need for study – Gasoline consumption trend
Cars 2 wheeler
Transport sector
share (%)
Gasoline/Petrol 34.33% 61.42% ~99
Source: http://www.ppac.org.in/

8. 31 August 2021
Introduction
Need for study – Urban/City Driving conditions
•Frequent start and stop
•Long idling time
•Low avg speed – Significant part load
•High acceleration
•Various class of vehicles

9. 31 August 2021
Introduction
Need for study – Automotive Emissions BS VI –M1 & M2
CO
(mg/km)
NOx
(mg/km)
PM
(mg/km)
Gasoline/Petrol 500 60 4.5
Diesel 1000 80 4.5
Source: https://www.araiindia.com

10. 31 August 2021
Introduction
Need for study – Urban/City Driving conditions

11. 31 August 2021
Introduction
Need for study – Urban/City Driving conditions – MIDC Part I
Acclerations: 0.52 to 1.04 m/s2

12. 31 August 2021
Introduction
Need for study – Urban/City Driving conditions – MIDC Part I
https://dieselnet.com/
Source: https://dieselnet.com/

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Introduction
Need for study – Effect of speed level and acceleration
Speed range
(m/s)
CO (%) HC (PPM) NOx (%)
1.0 m/s2 1.6 m/s2 1.0 m/s2 1.6 m/s2 1.0 m/s2 1.6 m/s2
0-3 0.043 0.4 2.4 3.92 15.66 27.53
3-8 0.006 0.008 1 1.06 2.00 2.46
Above 8 0.29 0.865 5.29 10.49 31.08 44.77
Average tail pipe emissions

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Introduction
Need for study – Basic understanding
• A study shows that average speed under The Delhi driving
condition reduces by 54.2 %, idling time increases by 21%, higher
pollutant emissions and increased braking energy compared to
Modified Indian Driving Cycle 1.
• Average kinetic energy wasted during braking amounts 30.2, 31
and 46% of total tractive- energy under the US: 5U/3H, Europe
NEDC and Japan 10/15 drive cycle respectively2.
• A study on the refuse truck shows that 68% of the total energy
supplied to the wheels is wasted during braking3.
• For no-catalyst gasoline-engined vehicles, the increases in
emissions with average acceleration are very low, and vary from
2% to 7% for most of the pollutants; TWC vehicles are the most

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Introduction
Need for study – Basic understanding
• For no-catalyst gasoline-engined vehicles, the increases in emissions with
average acceleration vary from 2% to 7% for most of the pollutants.
• TWC vehicles are the most sensitive to acceleration variations: CO and HC emissions
increase by about 15% when acceleration increases to 0.5 m/s2 and by 25-30% when
it increases to 0.7 m/s2.
• The fuel consumption increase by 17-18% when the acceleration increases from 0.3
to 0.7 m/s2.
• The whole French car fleet would record emissions increases of 44% (except NO,) for
an acceleration increase from 0.3 to 0.5 m/s2, and increases of about 7-9% for an
acceleration increase up to 0.7 m/s2.

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Introduction
Need for study – KE lost during MIDC part I
Speed Velocity KE KE Car KE Bus
Distance (km) 1.013 KMPH m/s ½ v2
m=1200 kg m=20000 kg
Deceleration 1 1 15-0 4.17 8.69 10.43 173.8
Deceleration 2 2 32-0 8.89 39.52 47.42 790
Deceleration 3 3 50-35 13.88-9.72
96.33-47.24
=49.09
58.91 982
Deceleration 4 4 32-0 8.89 39.52 47.42 790
164.18 kJ 2736 kJ
W to w Effi= 20% 821 kJ 13679 kJ
Fuel wasted
(ml/km)
26 375
Idle waste (ml/km) 60 sec 0.2 ml/sec 1.11 ml/sec 12.11 68
Total fuel
waste(ml/km)
38.11 443

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Introduction
Regenerative Braking – Basic understanding
Regenerative braking is a process, in which, a portion of the kinetic energy of the
vehicle is stored by a short term energy storage system.
Energy normally dissipated in the brakes is directed by a power transmission
system to the energy store during deceleration.
That energy is held until required again by the vehicle, whereby it is converted
back into kinetic energy and used to accelerate the vehicle/power auxiliaries.
The magnitude of the portion available for energy storage varies according to the
duty cycle, type of storage, drive train efficiency, inertia weight etc.

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Pros. & Cons.
Regenerative braking - Advantages
Improved fuel economy - dependent on duty cycle, power train design, control
strategy and the efficiency of the individual components.
Reduced pollutants – Pollutants emissions reduced by engine decoupling, reducing
total engine revolutions and total time of engine operation (engine on - off strategy).
If recovered energy is used to assist engine power (or Hybrid)/run auxiliary systems
improved performance - in terms of acceleration, average speed and trip duration.
Engine down-sizing – down-size engine can be used as some of the power supplied is
now delivered through regenerated energy.
Improved fuel economy – engine operation shifts to optimum efficiency range. (Engine
switch off during deceleration, idling, down the slope(over bridge) sluggish traffic etc.)
Reduction in brake wear - reducing cost of replacement brake linings, cost of labor to
install them and vehicle down time.
Improved operating range.

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2021
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Pros. & Cons.
Regenerative braking - Disadvantages
Added weight/bulk - extra components can increase weight increasing fuel
consumption, offset by smaller engine operating at its best efficiency.
Complexity - control necessary for operation of regenerative braking system.
Cost - of components, engineering, manufacturing and installation. Mass production
bring costs down to a more reasonable level
Safety - Primary concern with any energy storage unit of high energy density. There
must be very little chance of failure during vehicle operation.
Noise - dependent on system
Size and packaging constraints - most important for cars.
Added maintenance requirement - dependent on complexity of design.

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Content
•Introduction to regenerative braking
•Pros. and Cons. of application of regenerative braking system to the automobile
•Selection criteria for application of regenerative braking system
•Analysis of braking energy potential for real urban driving conditions
•Comparison of regenerative braking energy under standard and actual drive conditions
•Comparison/selection of suitable regenerative braking system for given application
•Design procedure of major components for fixed displacement pump based hydraulic regenerative
braking system
•Integration of hydraulic regenerative braking system to the existing automobile
•Performance evaluation of the regenerative braking system
•Effects of variation in key parameters on performance of the regenerative braking system.
•References
Emissions during acceleration of different vehicles
Braking energy in different drive cycles
•Introduction
•Pros. and Cons. of application of regenerative braking system
to the automobile
•Need - Brake Energy Regeneration Potential
•Regenerative Braking Technologies
•Basic Design procedure
•References

21. 31 August 2021 21
Selection criteria
Regenerative Braking – Selection criteria
Sr Criteria Kinetic Electric Hydraulic
1 No. of Energy Conversion and
storage
+++ ++ ++
2 Integration and Control
Complexity
-- --- -
3 Power and storage density ++ + +++
4 Bulk -- - ---
5 Mass/Weight - -- ---
6 Safety -- --- --
7 Noise -- - --
8 Added cost - -- ---
9 Maintenance - - --
10 Application Light Light Heavy
11 Available Technology + +++ ++

22. Brake energy regeneration potential
Basics of braking – Tractitive and braking energy of the vehicle with mass of 1200 kg
31 August 2021 22
Tractive-Energy : Acceleration + aerodynamic drag + rolling resistance +
Gradient
Braking-energy: Kinetic energy - Rolling friction - Aerodynamic drag

23. Brake energy regeneration potential
BRTS bus – Trip data captured with Qstarz sports
31 August 2021 23

24. 31 August 2021 24
Brake energy regeneration potential
School van - Data captured with Qstarz

25. 31 August 2021 25
Brake energy regeneration potential
Actual driving conditions - Data captured with Qstarz
Parameters
MIDC Part I
(Equivalent)
BRTS Bus (156
Trips)
Distance covered
during cumulative trips
(km)
3824.4 3824.4
Total no. of braking
episodes
15094 12774
Cumulative braking
energy (MJ)
9816.5 13139.9
Average Braking
episodes per km
3.95 3.34 18.3
Braking energy per
km (MJ/km)
2.567 3.436 33.8

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Brake energy regeneration potential
BRTS bus data analysis– Initial braking speed
Initial Braking Speed Span
(kmph)
Braking Energy
MIDC Part I
(MJ)
Braking Energy
Actual
(MJ)
10-20 622.5 8.9
20-30 0.0 1672.0
30-40 5666.3 2896.3
41-50 0.0 4111.3
50 & above 3527.6 4451.4
Distribution of the braking energy according to an initial speed at braking

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Brake energy regeneration potential
Actual driving conditions - Data captured with Qstarz
Braking energy distribution according to initial braking speed

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kinetic energy is
stored in the form
of kinetic energy
using flywheel and
CVT.
Single energy conversion
high level efficiency
Fuel savings of up to
59% for city bus
average in service
drive cycle.
Applications
Light Weight
Vehicles
Problems of Low
storage and
windage loss.
Energy stored
mass and speed of
flywheel.
Regenerative Braking Technologies
Kinetic Regenerative Braking – System and basics

29. 2. Electric Regenerative Braking
31 August 2021 29
Energy stored – Size
and Material of
battery.
Problems–Power, Slow
Charging, SoC &
Cooling Requirement,
Environment, Safety
Applications - Two
wheeler, Car, Bus
kinetic energy is in the
form of chemical
energy.
Two energy
conversion- Less
efficient
Efficiency of the range
of 36% for bus under
city drive conditions
Regenerative Braking Technologies
Electric Regenerative Braking – System and basics

30. 31 August 2021 30
Energy stored – Size of
Accumulator
Problems– specific
storage, Noise,
Environment, Safety
Applications – Vehicle
with frequent stop &
Go
Efficiency of the range
of 68 % for bus under
optimized conditions
Two energy
conversion- Less
efficient
kinetic energy is
stored in the form of
Pressure energy.
Regenerative Braking Technologies
Hydraulic Regenerative Braking – System and basics

31. 31 August 2021 31
Regenerative Braking Technologies
Hydraulic Regenerative Braking – System and basics

32. 31 August 2021 32

33. 31 August 2021 33
Basic Design procedure
Kinetic Regenerative Braking – Comparison
Flywheel Electric Hydraulic
Storage ½ Iω2 VIt 𝚫PV
Power ω I V
Storage 3 1 2
Power 2 3 1

34. 1. Sachin Chugh, Prashant Kumar, M Muralidharan, Mukesh Kumar B, M Sithananthan, Anurag Gupta, Biswajit Basu and Ravinder Kumar
Malhotra. (2012). “Development of Delhi driving cycle: a tool for realistic assessment of exhaust emissions from passenger cars in Delhi.” SAE
technical papers, Pages: 1-8, ISSN: 0148 7191
2. Gino Sovran and Dwight Blaser. (2006). “Quantifying the potential impacts of regenerative braking on a vehicle’s tractive-fuel consumption for
the US, European and Japanese driving schedules.” SAE Technical paper, Pages: 1-18, ISSN: 0148 7191
3. Andrej Ivanco, Rajit Johri and Zoran Filipi. (2012). “Assessing the regeneration potential for a refuse truck over a real-world duty cycle.” SAE
International Journal of commercial vehicles 5(1): 364–370.ISSN 1946 3928.
4. M. Andre and C. Pronellot (1997) "Relative influence of acceleration and speed on emissions under actual driving conditions", Int. J. of Vehicle
Design, Vol. 18, Nos. 3/4 (Special Issue).
5. P.S. Bokare, A.K. Maurya and Sharad Gokhale,(2022) "Effect of speeding behaviour of passenger cars on tailpipe emissions", International
journal for traffic and transport engineering, 12(1): 78 - 93
William JB Midgley and David Cebon, “Comparison of regenerative braking technologies for heavy goods vehicles in urban environments”, Proceedings of the
Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 2012 226: 957, published 14 March 2012
2 Amy Y. HU et al. “Characteristics of Emissions and Vehicular Operations of Buses in Taipei’s Exclusive Bus Lanes”, Proceedings of the Eastern
Asia Society for Transportation Studies, Vol.9, 2013
3
4 Gabrielle String, “Feasibility of a Regenerative Braking System for a School Bus”, A Thesis Proposal, Clarkson University, March 12, 2010
5 Farhad Sangtarash,” Effect of Different Regenerative Braking Strategies on Braking Performance and Fuel Economy in a Hybrid Electric Bus
Employing CRUISE Vehicle Simulation”, 2008 SAE International, 2008-01-1561
6 Er. Amitesh Kumar,” Hydraulic Regenerative Braking System”, International Journal of Scientific & Engineering Research Volume 3, Issue 4,
April-2012
31 August 2021 34
References