Surat Municipal Corporation Bus

Electrification Assessment
Cabell Hodge,1 Matthew Jeffers,1 Jal Desai,1 Eric Miller,1
and Varsha Shah2
1 National Renewable Energy Laboratory
2 Sardar Vallabhbhai National Institute of Technology

NREL is a national laboratory of the U.S. Department of Energy Technical Report

Office of Energy Efficiency & Renewable Energy NREL/TP-5400-73600
Operated by the Alliance for Sustainable Energy, LLC May 2019
This report is available at no cost from the National Renewable Energy
Laboratory (NREL) at www.nrel.gov/publications.

Contract No. DE-AC36-08GO28308

 Surat Municipal Corporation Bus
Electrification Assessment
Cabell Hodge,1 Matthew Jeffers,1 Jal Desai,1 Eric Miller,1
and Varsha Shah2
1 National Renewable Energy Laboratory
2 Sardar Vallabhbhai National Institute of Technology

Suggested Citation
Hodge, Cabell, Matthew Jeffers, Jal Desai, Eric Miller, and Varsha Shah. 2019. Surat
Municipal Corporation Bus Electrification Assessment. Golden, CO: National Renewable
Energy Laboratory. NREL/TP-5400-73600. https://www.nrel.gov/docs/fy19osti/73600.pdf.

NREL is a national laboratory of the U.S. Department of Energy Technical Report

Office of Energy Efficiency & Renewable Energy NREL/TP-5400-73600
Operated by the Alliance for Sustainable Energy, LLC May 2019

This report is available at no cost from the National Renewable Energy National Renewable Energy Laboratory
Laboratory (NREL) at www.nrel.gov/publications. 15013 Denver West Parkway
Golden, CO 80401
Contract No. DE-AC36-08GO28308 303-275-3000 • www.nrel.gov
 NOTICE

This work was authored in part by the National Renewable Energy Laboratory, operated by Alliance for Sustainable
Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding
provided by U.S. Department of Energy Office of International Affairs. The views expressed herein do not
necessarily represent the views of the DOE or the U.S. Government.

This report is available at no cost from the National Renewable

Energy Laboratory (NREL) at www.nrel.gov/publications.

U.S. Department of Energy (DOE) reports produced after 1991

and a growing number of pre-1991 documents are available
free via www.OSTI.gov.

Cover Photos by Dennis Schroeder: (clockwise, left to right) NREL 51934, NREL 45897, NREL 42160, NREL 45891, NREL 48097,
NREL 46526.

NREL prints on paper that contains recycled content.

 Acknowledgments
The authors would like to thank Dr. D. N. Basak and Mustafa Sonasath of the Surat Municipal
Corporation for welcoming them to Surat, providing the information necessary to complete this
report, and taking the initiative to consider electrification of their buses. Partha Mishra with the
National Renewable Energy Laboratory (NREL) deserves special thanks for his analysis
of battery lifecycles. In addition, the authors would like to thank Andrew Kotz, Leslie Eudy,
Margo Melendez, and Mollie Putzig at NREL for their contributions and input to the report.
They would also like to thank Shimin Sudhakar and Atlul Vijay Deva with the Sardar
Vallabhbhai National Institute of Technology for assisting with data collection. The work would
not have been possible without the leadership from Russel Conklin and Rudy Kahsar with the
U.S. Department of Energy. Finally, the authors would like to thank Anya Breitenbach for her
diligence, responsiveness, and attention to detail while editing this report.

iii
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 List of Acronyms
AC alternating current
APFC automatic power factor control
BEB battery electric bus
BLAST Battery Lifetime Analysis and Simulation Tool
BRTS bus rapid transit system
BYD Build Your Dreams
C Celsius
capex capital expense
DCFC direct current fast chargers
dLe diesel liter equivalent
DGVCL Dakshin Gujarat Vij Company Limited
DOE U.S. Department of Energy
DRIVE Drive-cycle Rapid Investigation, Visualization, and Evaluation
ESS energy storage system
EVSE electric vehicle supply equipment
FAME Faster Adoption and Manufacturing of Hybrid and Electric Vehicles
FASTSim Future Automotive System Technology Simulator
GCC gross cost contract
GPS Global positioning system
GVWR gross vehicle weight rating
HT high-tension
Hz hertz
kg kilogram
km kilometer
kph kilometers per hour
kW kilowatt
kWh kilowatt-hour
INR Indian Rupees
L liter
LFP lithium iron phosphate
LT low-tension
m million
M million
NCA lithium nickel cadmium aluminum
NMC lithium nickel manganese cobalt oxide
NREL National Renewable Energy Laboratory
OEM original equipment manufacturer
opex operating expense
SMC Surat Municipal Corporation
SOC state of charge
SVNIT Sardar Vallabhbhai National Institute of Technology
U.S. United States
USD U.S. dollars
VCB vacuum circuit breaker

iv
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Executive Summary
This report examines the potential for Surat Municipal Corporation (SMC) to electrify its bus
rapid transit system (BRTS) in Surat, India. Researchers from the National Renewable Energy
Laboratory (NREL) partnered with the Sardar Vallabhbhai National Institute of Technology
(SVNIT) to collect data from SMC, log in-use GPS data of SMC buses, and analyze the results.
The ensuing analysis focuses on the operational feasibility and life-cycle costs of battery electric
buses (BEBs) compared to diesel buses operated on eight BRTS routes out of four bus depots
(Figure ES-1).

Figure ES-1. Map of logged BRTS routes and depot locations

NREL used a backward-looking model to calculate power requirements for a BEB based on
vehicle speed profiles for the BRTS routes. The model uses actual vehicle operation to solve for
the power requirements of the BEB, accounting for regenerative braking, as shown in equation
ES-1 and more fully described in section 3.3.1. Estimated battery power was used to calculate
the required battery size.

Battery  Motor  Transmission  Differential  Wheel  Chassis  Logged Data (ES-1)

Modeled power requirements for each of these routes varied due to distance, time, route
conditions, and driving behavior. In addition, weight of the bus including passenger load and
ambient temperature (assuming that each bus used air conditioning) were significant factors

v
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 contributing to the BEB efficiency. Table ES-1 shows the average calculated BEB efficiency for
a range of vehicle mass and ambient temperatures, as simulated on the Surat BRTS routes. The
ambient temperatures used in the model are representative of the range of operating temperatures
experienced in Surat, and the range of modeled vehicle mass (7,000 kg to 18,000 kg) covers the
estimated vehicle mass for the BEBs with publicly available gross vehicle weight ratings in
India.

Table ES-1. BEB Efficiency by Temperature and Mass (kWh/km)

Mass (kg) Temperature (°C)
25 28 30 35 40
7,000 0.56 0.61 0.64 0.72 0.80
8,000 0.60 0.65 0.68 0.76 0.84
9,000 0.64 0.69 0.72 0.80 0.89
10,000 0.69 0.74 0.77 0.85 0.93
11,000 0.74 0.79 0.82 0.90 0.98
12,000 0.79 0.84 0.88 0.96 1.04
13,000 0.85 0.90 0.94 1.02 1.10
14,000 0.92 0.97 1.00 1.08 1.17
15,000 0.99 1.04 1.07 1.15 1.24
16,000 1.07 1.12 1.15 1.23 1.32
17,000 1.15 1.20 1.23 1.31 1.40
18,000 1.23 1.28 1.32 1.40 1.48

NREL modeled the power requirements for each route using a range of assumptions on vehicle
efficiency, and then estimated the minimum energy storage system (ESS) capacity required to
meet the daily service requirements of each BRTS route.

Figure ES-2 provides an estimated range of ESS sizes per cumulative fraction of BRTS service
met by BEBs. Hashmarks indicate each BRTS route. The bold blue line represents an efficiency
of 1.08 kW/km, which correlates to 14,000 kg and 35°C in Table ES-1. For this modeled average
efficiency, conventional BRTS buses could begin to be replaced by depot-charge BEBs with
250–300 kWh battery capacity.

vi
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Figure ES-2. Cumulative fraction of BRTS bus fleet vs ESS capacity

When calculating the necessary ESS capacity for BEBs, SMC should consider that traction
batteries will degrade over time. Manufacturer warranties often specify 80% or 85% of original
capacity as the level at which batteries should be replaced, suggesting fleet owners should
purchase vehicles with an initial ESS capacity of 17% to 25% over the required energy
consumption. SMC should also consider that stated ESS capacity is sometimes larger than usable
capacity.

NREL modeled battery degradation for three different battery chemistries with the Battery
Lifetime Analysis and Simulation Tool (BLAST). Using the power requirement calculations
described above, the team simulated a 500-kWh battery that was fully charged to 100% of actual
capacity an hour before the start of daily operation. Leaving a lithium-ion battery at 100% state
of charge (SOC) is not optimal for battery longevity. Some manufacturers limit the maximum
and minimum SOC for their batteries in order to improve battery longevity, and operators can
extend lifespan by keeping SOC as close to 50% as possible. NREL recommends securing an
acceptable battery warranty as well.

The Government of India Department of Heavy Industries (DHI) has financial incentives
available for BEBs and charging infrastructure. The Faster Adoption and Manufacturing of
Hybrid and Electric Vehicles (FAME) II program provides a purchase incentive for BEBs of
₹20,000/kWh 1 of battery capacity or 40% of the bus value, whichever is lower. In addition, DHI
has proposed to cover the entire project cost of electric vehicle supply equipment (EVSE) for one

1
The majority of the monetary values in this report are written in Indian rupees (denoted as ₹ or INR) or
derivations as noted (e.g. million INR). NREL used 71.029 INR to 1 U.S. dollar (USD) as the conversion rate in
this report based on Indian Rupee, the Economy Forecast Agency (http://dollarrupee.in/), January 17, 2019.

vii
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 slow charger per bus or one fast charger per every ten buses. This incentive structure is
significantly different from FAME I, but the combined impact to BEBs and EVSE costs is
similar under both programs.

To complete a life-cycle cost comparison, NREL applied several assumptions, including that
BEBs could replace diesel buses at a one-to-one ratio. While this would be accurate in some
cases, longer routes or less favorable conditions could require a greater ratio of BEBs to diesel
buses. NREL used published purchase cost data for four BEBs and two diesel buses available in
India. SMC provided a diesel fuel price of ₹74.3/liter, and NREL calculated the cost of
electricity using DGVCL rates assuming overnight charging at the depots to take advantage of
time-of-use pricing rebates. Maintenance costs were based on three published reports comparing
electric and diesel buses operating within U.S. transit agencies using adjusted labor rates to
account for relative differences between the United States and India. The economic analysis did
not account for on-route charging or swappable batteries due to insufficient information.

Based on these calculations, three of the four BEBs identified were less expensive than the two
reference diesel buses over seven years of ownership (Figure ES-3). However, the BEB with the
largest ESS—which will likely be necessary for Surat BRTS routes—may be slightly more
expensive in the seven-year period when compared to the most affordable diesel bus. If
maintenance costs for Surat BEBs are more similar to the U.S. BEBs under warranty, then even
the 324 kWh bus may be less expensive than the most affordable diesel bus considered.

Figure ES-3. Total cost of ownership comparison

NREL recommends subsequent analysis to verify the operational results model with a pilot
deployment of BEBs. SMC could validate the power requirements for various routes at various
ambient temperatures, precipitation conditions, and passenger loads in order to determine how
many routes could be electrified without impacting BRTS service. The economic analysis will
take longer to verify—particularly maintenance costs, which can vary significantly from year to
year with small-scale vehicle deployments. However, this report indicates that several Surat
BRTS routes could be electrified using BEBs currently available in India, and SMC could
benefit from significantly reduced operational costs.

viii
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Table of Contents
Executive Summary .................................................................................................................................... v
1 Introduction and Background ............................................................................................................. 1
1.1 Partner Organizations .................................................................................................................... 1
1.1.1 NREL ............................................................................................................................... 1
1.1.2 SVNIT .............................................................................................................................. 1
1.1.3 SMC ................................................................................................................................. 2
1.2 Surat, India .................................................................................................................................... 2
1.3 Surat Transit System ..................................................................................................................... 4
1.3.1 Transit Business Model .................................................................................................... 4
1.3.2 BRTS Background ........................................................................................................... 5
1.3.3 Surat Transit System Operations ...................................................................................... 5
1.4 Smart Cities ................................................................................................................................... 8
2 Battery Electric Bus Market ............................................................................................................... 10
2.1 Policies and Incentives ................................................................................................................ 11
3 Approach ............................................................................................................................................. 13
3.1 Data Collection ............................................................................................................................ 13
3.2 BRTS Route Characterization ..................................................................................................... 14
3.3 ESS Model Description ............................................................................................................... 15
3.3.1 Model Description .......................................................................................................... 15
4 Operational Assessment Results ..................................................................................................... 18
4.1 BRTS Route Profiles and Statistics ............................................................................................. 18
4.2 BEB Modeling Results ................................................................................................................ 23
5 Battery Life Longevity ........................................................................................................................ 32
6 Life-cycle Cost Comparison .............................................................................................................. 36
6.1 Capital Expense ........................................................................................................................... 36
6.1.1 Bus Costs ........................................................................................................................ 36
6.1.2 EVSE Costs and Considerations .................................................................................... 39
6.2 Operational Costs ........................................................................................................................ 42
6.2.1 Fuel Costs ....................................................................................................................... 42
6.2.2 Maintenance Costs ......................................................................................................... 43
6.2.3 Life-cycle Operating Costs............................................................................................. 44
6.3 Total Cost of Ownership ............................................................................................................. 45
7 Conclusion .......................................................................................................................................... 47

ix
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 List of Figures
Figure ES-1. Map of logged BRTS routes and depot locations .................................................................... v
Figure ES-2. Cumulative fraction of BRTS bus fleet vs ESS capacity....................................................... vii
Figure ES-3. Total cost of ownership comparison ..................................................................................... viii
Figure 1. Location of Surat, India ................................................................................................................. 3
Figure 2. BRTS bus in Surat ......................................................................................................................... 5
Figure 3. Map of Surat transit system ........................................................................................................... 6
Figure 4. Average diesel fuel economy by daily driving distance for all routes........................................... 8
Figure 5. SMC Smart City Centre ................................................................................................................. 9
Figure 6. Trip Recorder 747 ProS ............................................................................................................... 13
Figure 7. Motor efficiency map .................................................................................................................. 16
Figure 8: Comparison of modeled results to measured results ................................................................... 17
Figure 9. Map of logged BRTS routes and depot locations ........................................................................ 18
Figure 10. Example daily drive cycle - Route 11 ....................................................................................... 19
Figure 11. Kinetic intensity vs driving average speed for BRTS routes ..................................................... 22
Figure 12. Characteristic acceleration vs aerodynamic speed for BRTS routes ......................................... 22
Figure 13. Example speed profile for a measured conventional bus and the modeled electric bus ............ 23
Figure 14. Instantaneous power requirement and cumulative energy use .................................................. 24
Figure 15. Sankey diagram displaying the dissipation of battery energy for a BEB on Route 11,
normalized by route distance ................................................................................................. 25
Figure 16. Sankey diagram displaying the dissipation of fuel energy for a conventional bus on Route 11,
normalized by route distance ................................................................................................. 25
Figure 17. Fuel economy by BRTS route for baseline diesel buses (measured in-use data) and BEBs
(modeled results) .................................................................................................................... 26
Figure 18. Impact of ambient temperature on BEB energy consumption rate ............................................ 27
Figure 19. Impact of vehicle mass on BEB energy consumption rate ........................................................ 29
Figure 20. Cumulative fraction of BRTS bus fleet vs ESS capacity........................................................... 31
Figure 21. ESS charge and discharge profile for model ............................................................................. 33
Figure 22. Ambient temperature profiles for model ................................................................................... 33
Figure 23. Quoted rates for electric buses - gross cost contract (GCC) ...................................................... 37
Figure 24. Quoted rates for electric buses - outright purchase ................................................................... 38
Figure 25. EVSE connection types ............................................................................................................. 39
(a) handheld conductive (b) automatic conductive (c) automatic wireless ................................................. 39
Figure 26. Single line diagram of electrical upgrades to support BEBs ..................................................... 41
Figure 27. Total estimated cost of ownership ............................................................................................. 46

x
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 List of Tables
Table ES-1. BEB Efficiency by Temperature and Mass (kWh/km) ............................................................ vi
Table 1. Average Meteorological Conditions for Surat ................................................................................ 4
Table 2. Overview of Surat Transit System .................................................................................................. 6
Table 3. Surat Transit Depots and Operators ................................................................................................ 7
Table 4. Overview of Surat BRTS Routes .................................................................................................... 7
Table 5. Key Specifications for Battery Electric Buses Available in India ................................................ 11
Table 7. BRTS Route Summary Statistics from Logged Data.................................................................... 20
Table 8. BEB Efficiency by Temperature and Mass (kWh/km) ................................................................. 30
Table 9. Years to Reach 80% Charge Capacity .......................................................................................... 34
Table 10. Bus Purchase Costs Before and After FAME Incentives............................................................ 38
Table 11. Utility Setup Charges for 600 and 1,000 kVA Transformers ..................................................... 41
Table 12. Distribution Transformer Costs .................................................................................................. 41
Table 13. Fuel Cost Per Bus ....................................................................................................................... 43
Table 14. Maintenance Costs for Electric and Diesel Buses from NREL Evaluations .............................. 44
Table 15. Life-cycle Operating Costs ......................................................................................................... 45

xi
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 1 Introduction and Background
This study examines current operations, transit assets, and infrastructure of the Surat Bus Rapid
Transit System (BRTS) in the Indian state of Gujarat and assesses the operational and economic
feasibility of transitioning from diesel buses to battery electric buses (BEBs). It includes
assessments of BEB range under various scenarios and potential battery life for different
chemistries, as well as life-cycle cost comparisons. The analysis leverages advanced vehicle
modeling and analysis tools developed by the National Renewable Energy Laboratory (NREL) to
identify candidates for fleet electrification at reasonable costs. This report outlines a range of
potential outcomes that could be validated through future pilot studies of BEBs on Surat roads.

1.1 Partner Organizations

Researchers from the U.S. Department of Energy's (DOE) NREL partnered with Sardar
Vallabhbhai National Institute of Technology (SVNIT) Surat to conduct an operational
feasibility and economic analysis of Surat BRTS vehicles.

1.1.1 NREL
NREL helps U.S. and international fleet operators assess the operational and economic feasibility
of alternative fuel vehicles (AFVs) including BEBs. NREL has developed a suite of tools and
resources to assist fleets in quantifying efficiency benefits of AFVs. 2

NREL was asked to provide unbiased, objective analysis to the Surat Municipal Corporation
(SMC) on the feasibility of BEBs. NREL's experience in evaluating, measuring, and verifying
fleets’ deployment of advanced medium- and heavy-duty vehicle technologies has illustrated the
relationship between vocational duty cycle and efficiency for different fuel types, as well as the
potential impacts on life-cycle costs, barriers to implementation, and commercial viability. 3
NREL used fleet analysis tools and validation experience to estimate the fuel economy, auxiliary
load, required battery capacity, and economic feasibility for the SMC on BRTS routes.

1.1.2 SVNIT
SVNIT was founded in 1961with a focus on higher education for civil, mechanical, and electrical
engineering. It has since expanded to electronics, computer, production, and chemical
engineering, and the electrical engineering department has developed expertise in the utility and
automotive sectors. NREL partnered with SVNIT in the development of this assessment to
leverage the institute’s knowledge of the Surat utility structure and relationships with the SMC.
SVNIT played an instrumental role in the collection of data and coordination of responsibility. 4
Varsha Shah, an SVNIT professor of electrical engineering, also assisted NREL by developing
an estimate of transformer costs to support electric vehicle supply equipment (EVSE) in Surat
BRTS parking areas (Section 6.1.2).

2
NREL. 2018 “Transportation Research: Data and Tools.” https://www.nrel.gov/transportation/data-tools.html.
[Accessed: September 21, 2018].
3
Kotz, et al. 2018. National Park Service Bus Electrification Study Interim Report. Unreleased
4
http://www.svnit.ac.in/index.php. [Accessed: January 17, 2019].

1
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 1.1.3 SMC
SMC is the local governing body of the Surat district. It was established in 1966. SMC carries
out all the tasks and functions with the mission “to make Surat a dynamic, vibrant, beautiful,
self-reliant and sustainable city with all basic amenities, to provide a better quality of life.” 5
There are nine main departments in the SMC: engineering, health, support revenue, social
welfare, secretary, fire and emergency services, culture, and watch and ward. SMC is the key
stakeholder in this project, along with the residents of Surat. The BRTS division of the
engineering department oversees the BRTS transportation within Surat district. SMC coordinated
with SVNIT and NREL, provided BRTS route and bus information, and provided access to the
conventional BRTS buses for installation and monitoring of loggers.

1.2 Surat, India

Surat is located on the western side of India (Figure 1). It is one of the major cities in the Gujarat
state. In 2011, Surat district had a population of 4.5 million, 6 making it the second-largest city in
Gujarat and ninth-largest in India. 7 Due to Surat’s geographical location, many large industries
including textile, trade, diamond cutting and polishing, Zari 8 works, chemical, petrochemical,
and natural gas-based businesses have developed there.

The tropical climate in Surat—with a high average daily temperature of 31.3°C in May and a low
of 22.8°C in January—impacts the viability of BEBs in two ways. First, air conditioning is a
significant auxiliary load requiring larger battery capacity. Second, high temperatures negatively
impact the longevity of lithium-ion batteries. 9

5
Surat Municipal Corporation. 2019. “Corporation Introduction.”
https://www.suratmunicipal.gov.in/Corporation/Introduction. [Accessed: January 17, 2019].
6
Surat Municipal Corporation. 2019. “City Introduction.” https://www.suratmunicipal.gov.in/TheCity/Introduction.
[Accessed: January 17, 2019].
7
WikiTravel. 2019. “Surat.” https://wikitravel.org/en/Surat. [Accessed: January 17, 2019].
8
Utsavpedia. 2019. “Zari.” https://www.utsavpedia.com/motifs-embroideries/zari-the-ultimate-precious-metal-
weaving-art/. [Accessed: January 17, 2019].
9
Pesaran, et al. 2013. “Addressing the Impact of Temperature Extremes on
Large Format Li-Ion Batteries for Vehicle Applications.” https://www.nrel.gov/docs/fy13osti/58145.pdf

2
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Figure 1. Location of Surat, India 10

10
Google Maps. 2019. “Surat, Gujarat, India.”
https://www.google.com/maps/place/Surat,+Gujarat,+India/@22.6669265,70.5465757,4.99z/data=!4m5!3m4!1s0x3
be04e59411d1563:0xfe4558290938b042!8m2!3d21.1702401!4d72.8310607. [Accessed: January 17, 2019].

3
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Table 1. Average Meteorological Conditions for Surat 11

Average Temperature
Annual Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
°C 27.6 22.8 24.3 28 30.4 31.3 30.3 28.2 27.8 28.2 29.2 26.8 24
Average High Temperature
Annual Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
°C 33.4 30.9 32.4 35.8 37.2 36.2 33.8 30.8 30.4 31.8 35.3 34.3 32
Average Low Temperature
Annual Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
°C 21.7 14.7 16.2 20.1 23.6 26.3 26.7 25.5 25.1 24.6 23 19.2 15.9
Average Number of Days Above 32°C
Annual Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Days 173 3 9 22 27 28 21 6 3 11 23 16 5
Average Precipitation
Annual Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
mm 1117 2.1 1 0.8 2.2 6.4 212.8 440.8 233.4 169.7 33.5 12.4 2.1

1.3 Surat Transit System

Surat has a well-connected transport system, with 275 city buses and an additional 127 BRTS
buses operating on multiple routes within the city. The BRTS buses have access to dedicated
lanes (Figure 2), where they travel fixed routes at set times without traffic concerns impeding
their predictability. The reliability of these routes makes them good candidates for BEBs, which
are primarily constrained by driving range and recharge time. A countervailing consideration is
that BRTS buses currently offer air conditioning, which can add a significant auxiliary load on
the BEB energy storage system (ESS), reducing the effective driving range. The set routes could
also provide convenient locations for extreme fast charging, especially where the BRTS routes
overlap.

1.3.1 Transit Business Model

City and BRTS buses operate on a cross cost model. In this partnership, private firms operate the
buses under the control of SMC. All operating expenses such as maintenance, fuel, and driver
salaries are incurred by the operator. SMC pays an agreed price per kilometer to the operator to
cover these expenses, and in return, SMC collects all the bus fare proceeds. An agreement
between SMC and the operator identifies a set daily distance that each bus must run, irrespective
of the number of passengers on board. In addition, the contract specifies the number of years that
each operator shall operate the buses.

11
WeatherBase. 2019. “Surat, India.”
https://www.weatherbase.com/weather/weather.php3?s=4824&cityname=Surat-Gujarat-India&units=metric.
[Accessed: January 17, 2019].

4
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 1.3.2 BRTS Background
Development and operation of BRTS for the city of Surat is managed by Surat Sitilink Limited, a
wholly owned subsidiary of SMC. SMC defines BRTS as, “A multifaceted project which
integrates land use and transport, various forms of public transport services as well as other
motorized and nonmotorized modes through various physical, operational and policy
interventions to achieve the objective of making Surat an accessible and competitive city.” 12

The Surat BRTS includes roadways that are dedicated to buses as shown in Figure 2. The buses
have priority at the intersections where they interact with other traffic.

Figure 2. BRTS bus in Surat 13

1.3.3 Surat Transit System Operations

SMC provided information about Surat’s transit bus system to NREL to begin this evaluation
with a characterization of the current transit operations. Figure 3 displays the span of transit
routes across the geographic area of Surat, and Table 2 provides a brief overview of the BRTS
and city portions of the transit service.

12
Surat Municipal Corporation. 2019. “BRTS Cell Introduction.”
https://www.suratmunicipal.gov.in/Departments/BRTSCellIntroduction. [Accessed: January 17, 2019].
13
Times of India. 2017. “City buses, 3 BRTS routes await inauguration.”
https://timesofindia.indiatimes.com/city/surat/city-buses-3-brts-routes-await-
inauguration/articleshow/57456944.cms. [Accessed: January 17, 2019].

5
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Figure 3. Map of Surat transit system 14

Table 2. Overview of Surat Transit System

BRTS City Total
Buses 127 275 402
Routes 8 33 41
Depots 3 3 6
Operators 3 2 5

The number of buses for BRTS and city routes are listed by depot and operator in Table 3. Of the
402 transit buses operating in Surat, 127 are on dedicated BRTS routes, operating out of three of
the six depots.

14
Surat Sitilink Ltd. 2018. Provided by Mustafa Sonasath, Assistant Manager of Operations at Surat Sitilink Ltd. in
personal correspondence with authors.

6
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Table 3. Surat Transit Depots and Operators
Depot Operator BRTS Buses City Buses
Bhestan Prasanna Purple 66 -
Pal RTO Adinath 50 -
Kosad Hansa Hansa Travels 11 -
Kosad CSPL Chartered SPL - 1
LP Savani Chartered SPL - 199
Bhestan Garden Maruti - 75

Table 4 lists the number of buses scheduled for each of the eight BRTS routes, along with the
number of daily trips and daily distance traveled, according to SMC data. Route 18 requires only
four buses and has the smallest daily distance at 186 km/bus. All other BRTS routes have 12 or
more buses each scheduled to travel at least 209 km/day.

Table 4. Overview of Surat BRTS Routes

Number Daily Daily

BRTS Daily Trips, Daily Trips, Daily Trips,
of Distance, Distance,
Route Peak Off Peak Total
Buses Total [km] Per Bus [km]
11 13 119 152 271 3,147 242
12 26 145 183 328 6,469 249
14 20 80 164 244 4,856 243
15 16 78 140 218 4,212 263
16 18 100 146 246 3,788 210
17 20 64 136 200 4,180 209
17e 12 103 86 189 3,024 252
18 4 64 46 110 743 186

Figure 4 shows the average fuel economy of the baseline buses––all of which are diesel-fueled––
by daily distance traveled for each BRTS bus route. The routes are identified as BRTS or city
routes, and the size of the data marker indicates the number of buses operating on each route.
BRTS routes have four to 26 buses operating on a route, while the city routes range from two to
14 buses per route. Except for one city route, all buses travel between 150 km and 275 km daily.
It is clear from the figure that BRTS routes generally have the most buses per route, traveling the
greatest daily distance with the poorest fuel economy. This indicates opportunities to improve
efficiency and reduce of emissions with the introduction of electrified transit buses.

7
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Figure 4. Average diesel fuel economy by daily driving distance for all routes

SMC plans to electrify a large percentage of its fleet over the next several years, starting with a
pilot program using 10 to 15 BEBs on BRTS routes. NREL has been engaged to identify existing
bus routes where BEBs could operate and to estimate the life-cycle costs of the replacement
BEBs in comparison to acquiring new diesel buses, including an estimate of charging
infrastructure costs.

1.4 Smart Cities

Surat was selected in the first round of applications in 2016 by the Indian Ministry of Housing
and Urban Affairs as one of 20 Indian cities to be developed as a “Smart City” under the
Government of India's Smart Cities Mission. Launched in 2015, the Smart Cities Mission
promotes sustainable development, transit electrification, and improved urban transport
options. 15,16

SMC, Special Purpose Vehicles, Surat Sitilink Limited, and Surat Smart City Development
Limited worked with Google to add real-time bus information in Google Maps, making it

15
Times of India. 2015. “Full list of 98 smart cities.” https://timesofindia.indiatimes.com/india/Full-list-of-98-smart-
cities/articleshow/48694723.cms?from=mdr. [Accessed: January 17, 2019].
16
Government of India. 2019. "Smart Cities Mission." http://smartcities.gov.in/content/innerpage/smart-city-
features.php. [Accessed: January 17, 2019].

8
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 possible for commuters to more easily plan their trips. Surat is the first city in Gujarat and second
in India to launch real-time transit information with Google Maps. 17, 18

SMC has used smart technology to increase bus ridership from 3,000 riders per day in August
2016 to 65,000 per day by November 2017. 19 The focus of this technology has included real-
time monitoring at the SMC Smart City Center (Figure 5) to ensure bus reliability and improve
the rider experience.

Figure 5. SMC Smart City Centre 20

17
Surat Smart City. 2017. "Real Time Transit Launch."
http://www.suratsmartcity.com/PressNote/RealTimeTransitLaunch. [Accessed: January 17, 2019].
18
Commuters can download the web application “Surat Sitilink” to track buses and pay for tickets at
https://www.suratmunicipal.gov.in/EServices/SuratSitilinkApp. [Accessed April 12, 2019].
19
Dash. 2017. “How Surat got people to ditch autorickshaw rides, opt for buses,”
https://timesofindia.indiatimes.com/city/delhi/how-surat-got-people-to-ditch-autorickshaw-rides-opt-for-
buses/articleshow/61611309.cms. [Accessed: January 17, 2019].
20
Desai. 2019.

9
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 2 Battery Electric Bus Market
There appear to be at least seven automotive manufacturers currently offering or planning to
offer BEBs to the India market, but NREL researchers were only able to obtain data on offerings
from three manufacturers at the time of writing this report: BYD (partnered with Goldstone
Infratech Ltd.), Tata Motors Ltd., and Ashok Leyland. 21, 22, 23 Considering the size of the bus
market in India, the aggressive incentive programs available from the Indian government for
adoption of BEBs, and the growing international market of BEB manufacturers, it is likely that
more electric options will be offered in the near future.

Based on the available information, two different models of BEBs are offered by each of the
three automotive manufacturers. Table 5 summarizes and compares the key specifications across
the three established manufacturers. Currently, none of the manufacturers are offering BEBs with
on-route charging capability, although Ashok Leyland offers a swappable battery pack.

21
Government of India, DHI. 2018. “Recommendations of the Committee Constituted to Decide Benchmark Price
for Electric Buses to be Procured by Different STUs, for Release of Demand Incentives.”
https://dhi.nic.in/writereaddata/UploadFile/Benchmark%20price%20for%20Electric%20Buses63666299596397561
6.pdf. [Accessed: January 17, 2019].
22
Singh, Saluja. 2018. “Goldstone-BYD, Tata Motors grab E-Bus contracts.”
https://economictimes.indiatimes.com/goldstone-byd-tata-motors-grab-e-bus-
contracts/articleshow/63406325.cms?utm_source=contentofinterest&utm_medium=text&utm_campaign=cppst.
[Accessed: January 17, 2019].
23
UITP. n.d. “Electric Buses Procurement In India – Indian Cities Got The Viable Rates.”
https://india.uitp.org/sites/default/files/documents/Procurement%20of%20Electric%20buses%20in%20India%20-
%2020032018.pdf. [Accessed: January 17, 2019].

10
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Table 5. Key Specifications for Battery Electric Buses Available in India

Goldstone Goldstone Tata Motors Tata Motors

OEM Ultra Electric Ashok Leyland
-BYD -BYD Starbus Electric
BEB model Circuit-F and Circuit-S
K7 K9 6/9 EV 9/12 EV

GVWR (kg) 13500 18000 10200 16200 —

Size (mm -
8900 x 12000 x 9000 x 12000 x 9400 x
length x 2465 x 2520 x 2340 x 2570 x 2600 x
width x 2930 3340 3380 3700 900
height)
Passenger 26 + driver 40 + driver 23–39 seated
31 + driver 39 + driver
Capacity + 13 standees + 22 standees + 23–30 standing
250 kW (peak)
145 kW 145 kW
Motor 150 kW (continuous)
Maximum 180 kW 180 kW
Power Operating range: Operating range:
0–2,500 rpm 0–2,500 rpm Torque: 900 Nm (peak)
360 Nm (continuous)
Battery Size 256 kWh or
162 kWh 324 kWh — —
(kWh) 64 kWh (swappable)
Electrical
Available Available Available Available Available
Regeneration
Up to 200 Up to 250 215 km 151 km
Range (km) —
km km (as per CMVR) (as per CMVR)
6–7 hours 6–7 hours
(slow option) (slow option)
Charging
2–3 hours 4–5 hours Less than 3 hours
Time (hours)
2.5–3 hours 2.5–3 hours
(fast option) (fast option)

2.1 Policies and Incentives

SMC is interested in deploying BEBs to reduce pollution in the Surat urban area as part of a
broader strategy coordinated by the Indian national government. India has prioritized BEBs
through an incentive program known as Faster Adoption and Manufacturing of Hybrid and
Electric Vehicles (FAME).

The original FAME I program provided incentives for up to 60% of the purchase cost of BEBs
and capped those incentives at ₹10M or ₹8.5M depending on the percentage of localization
(or the percentage of bus manufacturing within India). 24, 25 FAME I offered an incentive for

24
The majority of the monetary values in this report are written in Indian rupees (denoted as ₹ or INR) or
derivations as noted (e.g. million INR). NREL used 71.029 INR to 1 U.S. dollar (USD) as the conversion rate in this
report based on Indian Rupee, the Economy Forecast Agency (http://dollarrupee.in/), January 17, 2019.
25
One lakh = 100,000 INR. One crore = 10,000,000 INR.

11
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 BEB charging infrastructure as well, providing an additional 10% on top of the total bus
incentive. 26, 27

The Government of India superseded FAME I with a proposal for the FAME II program in April
2019. The FAME II proposal provides BEB incentives based on the size of the energy storage
system (ESS). Every kWh of ESS in a BEB qualifies for ₹20,000 in grant funding up to 40% of
the cost of the vehicle. 28 In addition, FAME II will cover up to 100% of the project costs of one
slow charger per BEB or one fast charger for every ten buses. 29

Indian policies such as the National Auto Fuel Policy 2003 and the Auto Fuel Vision & Policy
2025 require diesel buses to produce fewer emissions. The National Green Tribunal, which
resolves environmental disputes involving multidisciplinary issues, has passed a ruling that
heavy diesel vehicles in the Delhi National Capital Region that are more than 10 years old must
be retired. In addition, the Bureau of Energy Efficiency Star Ratings is setting higher fuel
economy standards for buses. The additional emission controls increase the cost of diesel bus
acquisition and maintenance. As a result, many bus operators are beginning to favor the adoption
of BEBs.

26
Government of India, Ministry of Heavy Industries and Public Enterprises, DHI. 2017. Minutes of the 9th Meeting
of the Project Implementation and Sanctioning Committee Held Under the Chairmanship of Secretary Heavy
Industry on 20th December 2017. https://dhi.nic.in/writereaddata/UploadFile/dhi-didm-MOM9-meetingPISC.pdf.
[Accessed: January 17, 2019].
27
This report uses 71.029 USD to INR as the conversion rates per “Indian Rupee: The Economy Forecast Agency,”
http://dollarrupee.in/. [Accessed: January 17, 2019]. 1 lakh = 100,000 INR; 1 crore = 1,000,000 INR.
28
Government of India, DHI. 2019. Operational Guidelines for Delivery of Demand Incentive under FAME India
Scheme: Phase - II - regarding. https://dhi.nic.in/writereaddata/UploadFile/DHI%20FAME%20PHASE-
II22March2019.pdf. [Accessed April 8, 2019].
29
Government of India, DHI. 2019. Notification: Scheme for Faster Adoption and Manufacturing of Vehicles in
India Phase II (FAME Phase II). https://www.fame-india.gov.in/WriteReadData/userfiles/file/FAME-
II%20Notification.pdf. [Accessed April 12, 2019].

12
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 3 Approach
In June 2018, NREL researchers traveled to Surat to collect data on BRTS and city bus
operations, and to meet with the SMC commissioner, staff, and partners at SVNIT Surat. The
primary purpose of this trip was to gather second-by-second data on bus operation, including
velocity and location, which NREL then distilled into operation statistics to estimate BEB
feasibility.

3.1 Data Collection

NREL worked with SMC and SVNIT Surat to compile information on the Surat BRTS and city
buses. In its Surat Smart City Center, SMC collects data on key operational characteristics of its
buses (Figure 5) such as number of trips, distance traveled, fuel consumed and arrival/departure
time for all routes. SMC also collects GPS data on its buses at a rate of one sample every three to
five seconds.

In addition to utilizing the sample data provided by SMC, NREL installed data loggers on
existing baseline buses to develop a detailed characterization of each BRTS route, beyond
scheduled stop times and average speed data available from SMC. NREL used Trip Recorder
747 ProS GPS recorders (Figure 6) to instrument 16 buses operating on BRTS routes and 24
buses operating on City routes. The trip recorders logged latitude, longitude, elevation, and
vehicle speed at a frequency of one hertz (Hz) when the instrumented buses were in motion. The
data were collected over four days in June 2018.

Figure 6. Trip Recorder 747 ProS

Although data were collected on city bus routes as well, NREL focused on the BRTS routes
where SMC intends to begin its deployment of BEBs. The collected data were analyzed for
quality and for adherence of each bus to the planned route. Minimal data processing was
necessary to eliminate a few outliers from the dataset, and a vehicle speed of less than 0.5
kilometers per hour (kph) was considered to be zero for the purpose of this analysis, due to
known GPS scatter at low speeds. Extraneous trips not adhering to the planned BRTS route for
each bus were removed from the dataset. In addition, because this analysis focused on the
requirements for full days of transit service on each route, partial days of operation were not
included in the analysis. Except for Route 18, which has a scheduled daily distance of 186 km
per bus, a daily distance traveled of 200 km or more per bus was considered a full day of service

13
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 for the BRTS routes. Due to the short logging duration and the variability of operation for some
of the instrumented buses, the installed data loggers captured between one and four full
workdays for each of the eight BRTS routes, for a total of 19 days of operation.

3.2 BRTS Route Characterization

NREL has developed a suite of tools that characterize vehicle drive cycles and analyze driving
behavior for a wide variety of vehicle types, weight classes, and vocations. One of these tools—a
component of the Drive-cycle Rapid Investigation, Visualization, and Evaluation (DRIVE)
analysis toolset 30—uses vehicle speed data with a sampling frequency of one Hz or higher to
calculate an extensive set of route statistics. The route-specific metrics calculated from these
driving speed profiles are independent of vehicle size, type, or powertrain, allowing the routes to
be characterized and compared objectively and quantitatively. Examples of the metrics include
maximum and average driving speeds, acceleration and deceleration rates, stop durations, and
number of stops per kilometer.

Two notable route metrics are the characteristic acceleration, ã, and aerodynamic speed, νaero,
described by O’Keefe, et al., and derived from the energy-based road load equation. 31 Dividing
characteristic acceleration by the square of aerodynamic speed (Equation 1) defines kinetic
intensity (ki), another important metric that represents the ratio of specific inertial energy
required to propel a vehicle to the specific energy lost to aerodynamic drag. Kinetic intensity is a
measure of the aggressiveness or driving intensity of a route and is a reliable indication of the
suitability for electric/hybrid powertrains.
𝑐𝑐ℎ𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 ã
𝑘𝑘𝑘𝑘 = (𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠)2
= (𝜈𝜈 2 (1)
𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 )

The collected speed data for each of the 19 full BRTS work days were fed into the NREL
analysis to create a detailed characterization of each BRTS route for further comparison.
Statistics for routes that had more than one valid day of collected data were averaged across all
valid days to establish one set of representative statistics for each BRTS route—eight in total.

NREL has also developed the Fleet DNA database with detailed commercial vehicle drive-cycle
data. 32 This extensive collection of real-world driving profiles and aggregated summary statistics
enables researchers and analysts to evaluate operational characteristics and vehicle performance
considerations for dozens of different vehicle types, vocations, weight classes, locations, and
powertrains, leading to optimized vehicle-route combinations. Transit bus data available in the
FleetDNA database were used in NREL’s analysis of the Surat BRTS routes.

30
NREL. 2018. “DRIVE: Drive-Cycle Rapid Investigation, Visualization, and Evaluation Analysis Tool.”
https://www.nrel.gov/transportation/drive.html. [Accessed: January 21, 2019].
31
O’Keefe, et al. 2007. “Duty Cycle Characterization and Evaluation Toward Heavy Hybrid Vehicle Applications.”
SAE World Congress and Exhibition. https://www.nrel.gov/docs/gen/fy07/40929.pdf. [Accessed:
32
NREL. 2018. “Fleet DNA: Commercial Fleet Vehicle Operating Data.”
https://www.nrel.gov/transportation/fleettest-fleet-dna.html. [Accessed: January 18, 2019].

14
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 3.3 ESS Model Description
3.3.1 Model Description
With GPS speed as the only available in-use data, NREL developed a variation of the FASTSim
modeling tool to analyze the power requirements and battery size for the Surat electric buses. 33
FASTSim and the derivation used for this report are backward-looking models, meaning that
with knowledge of the vehicle state (i.e., speed, acceleration, vehicle characteristics, etc.), it
solves to find the power requirement necessary to achieve that state. Inputs to the model are
vehicle speed, road grade, and the data sampling increment (timestep). Each component takes a
backwards step in series, with the model using logged data to calculate the power to or from the
battery. Diagram 1 shows the chronology of the simulation.

Battery  Motor  Transmission  Differential  Wheel  Chassis  Logged Data (1)

In Equation 2, recorded data are used to calculate the total force necessary from the vehicle in
order to meet the driving profile. The road load equation is simpler for a vehicle tested on a
dynamometer, as the road grade is held constant at zero.
𝑑𝑑𝑑𝑑
𝐹𝐹𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟 = + 𝐶𝐶𝑑𝑑𝑑𝑑 𝑣𝑣 2 + 𝑚𝑚𝑚𝑚𝑚𝑚𝑟𝑟𝑟𝑟 (2)
dt

The wheel model converts linear force, 𝐹𝐹, and speed, 𝑣𝑣, to torque, 𝜏𝜏, and rotational speed, 𝜔𝜔,
respectively, using the radius of the tire, 𝑟𝑟𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 , in Equations 3 and 4.

𝜏𝜏𝑤𝑤ℎ𝑒𝑒𝑒𝑒𝑒𝑒 = 𝐹𝐹𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟 𝑟𝑟𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 (3)

𝑣𝑣𝑣𝑣𝑣𝑣ℎ𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖
𝜔𝜔𝑤𝑤ℎ𝑒𝑒𝑒𝑒𝑒𝑒 = (4)
𝑟𝑟𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡

Components with gears will modify the speed and torque using Equations 5 and 6, respectively,
using knowledge of the gear ratio, 𝑟𝑟𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔 . The component efficiency, 𝜂𝜂, is used to divide the
−1 +1
torque in traction (𝜂𝜂𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 ) and multiply the torque in regeneration (𝜂𝜂𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 ).

𝜔𝜔𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 = 𝜔𝜔𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 𝑟𝑟𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔 (5)

𝜏𝜏𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 ±1
𝜏𝜏𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 = 𝜂𝜂𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 (6)
𝑟𝑟𝑔𝑔𝑔𝑔𝑔𝑔𝑔𝑔

Rotational speed and torque are multiplied and divided by gear ratios and efficiencies in the
driveline until the motor, where the electrical power requirement is calculated in Equation 7.

𝑃𝑃𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏 = 𝜏𝜏𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 𝜔𝜔𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 𝜂𝜂𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 (𝜏𝜏𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 , 𝜔𝜔𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚 ) ±1 (7)

33
NREL. 2018. “FASTSim: Future Automotive Systems Technology Simulator.”
https://www.nrel.gov/transportation/fastsim.html. [Accessed: January 18, 2019].

15
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Motor efficiency is a function of speed and torque. The motor map used in the model is shown in
Figure 7. This efficiency map was derived from electric transit bus data stored in NREL’s
FleetDNA database.

Figure 7. Motor efficiency map

The model was validated using data from BEBs operating in California. In most cases, measured
and modeled daily consumption matched within 10% (as seen in Figure 8), indicating that the
model is a good approximation of real-world transit bus operations. However, the authors did not
have access to the buses specifically available in India. Additionally, the data collected in
California included road grade. Elevation data collected in Surat was deemed not sufficiently
accurate for road-grade estimation; thus, energy consumption was simulated without road grade.
The model will under-predict energy consumption when road grade is not included, with only
limited effect as Surat is a relatively flat city.

16
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Figure 8: Comparison of modeled results to measured results

17
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 4 Operational Assessment Results
Following the approach outlined in Section 3, the logged vehicle data were analyzed to
characterize each BRTS route. The speed profiles from all 19 BRTS bus days were applied to
NREL’s model to determine the daily BEB energy requirements for each route. Researchers also
investigated temperature and mass sensitivities. The results show that the high kinetic intensity
of Surat BRTS routes translates to significant efficiency improvements by using BEBs.
Depending on temperature and mass, the results indicate that a significant portion of the Surat
BRTS fleet could be replaced by BEBs currently available in India.

4.1 BRTS Route Profiles and Statistics

The map in Figure 9 shows the paths of all eight BRTS routes and the locations of the depots
where the BRTS buses are housed. The BRTS system operates along major corridors and spans a
wide portion of Surat’s geographic area. Significant sections of the routes overlap, utilizing
shared depots and bus lanes. These areas of overlap could be effective locations for on-route fast
chargers, which could supplement depot chargers or serve as primary power sources. Individual
BRTS route maps are available in Appendix A.

Figure 9. Map of logged BRTS routes and depot locations

18
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Figure 10 provides an example of a typical speed profile for BRTS routes, showing more than 14
hours of total daily operation with a vehicle speed fluctuating frequently between 0 kph and 50
kph. The Route 11 bus accumulated approximately 240 km during this day.

Figure 10. Example daily drive cycle - Route 11

NREL generated detailed driving statistics from all 19 speed profiles for analysis of the BRTS
routes. Statistics for routes which had more than one full day of collected data were averaged. A
selection of the average summary statistics is listed in Table 7.

A typical full day of service for a bus operating on a BRTS route covers 200–280 km during 10–
15 hours of operation. Route 18 is an exception, having a smaller total distance due to the slower
average speed and shorter route length, yet it still covers nearly 180 km in 12.8 hours. Most
routes have a daily driving time (when the vehicle is moving) of 9–11 hours and a driving
average speed of 22–28 kph. Route 11 and 18 have slower speeds, at 16.0 and 17.5 kph,
respectively. Average stops per kilometer for the BRTS routes range from a low of 1.72 for
Route 17 to a high of 4.00 for Route 18.

19
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Table 6. BRTS Route Summary Statistics from Logged Data
BRTS Route 11 12 14 15 16 17 17e 18
Daily Total Distance [km] 239.2 255.8 226.4 276.0 206.5 242.5 223.2 178.3
Daily Total Time [hrs] 14.5 14.9 11.0 14.5 11.5 10.8 11.9 12.8
Daily Driving Time [hrs] 10.0 10.3 9.2 11.0 9.1 8.9 9.3 10.2
Maximum Speed [kph] 52.9 58.5 62.2 64.7 62.4 55.6 59.7 58.7
Total Average Speed [kph] 16.4 17.2 20.6 19.0 18.0 22.4 18.8 13.9
Driving Average Speed [kph] 24.0 24.8 24.7 25.1 22.7 27.2 24.0 17.5
Average Acceleration [m/s ] 2
0.30 0.32 0.41 0.33 0.39 0.35 0.43 0.36
Average Deceleration [m/s2] -0.60 -0.72 -0.53 -0.54 -0.51 -0.43 -0.47 -0.41
Average Stop Duration [sec] 25.7 22.9 11.4 18.8 14.1 16.2 15.5 12.9
Median Stop Duration [sec] 8.0 8.0 5.0 6.0 5.5 4.0 6.0 4.0
Stops per Kilometer [1/km] 2.66 2.74 2.52 2.42 2.92 1.72 2.64 4.00
Kinetic Intensity [1/km] 2.08 2.09 2.17 1.85 2.21 1.54 1.83 2.79

20
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Figure 11 plots the kinetic intensity and driving average speed of each route. The kinetic
intensity is a measure of the aggressiveness or intensity of driving on a route, as detailed in
Section 3.2. Routes with frequent stops and higher kinetic intensity are generally good
candidates for vehicle electrification, because they can capitalize on the use of efficient electric
motors and ample opportunities to recuperate inertial energy through regenerative braking.

Route 18 has a low driving average speed and the highest kinetic intensity at 2.79 km-1, and
Route 17 has the highest driving average speed and the lowest kinetic intensity at 1.54 km-1. If
considering only the ability to recapture energy from braking, Route 18 would be the best
candidate for electrification. However, both routes have relatively high kinetic intensity
compared to the high-speed long-haul applications common among tractor trailers.

Overlaid on the chart for reference are corresponding transit bus data from NREL’s FleetDNA 34
database of real-world drive cycles. These data points show the relationship between ki and
driving average speed for transit buses operating at various locations throughout the United
States. As this figure represents primarily city transit routes, it is not expected that these data
necessarily will match the characteristics of the BRTS routes, but it is worth noting that the
BRTS routes fall on the lower-speed side of the data cluster and tend to have above average
kinetic intensity for this type of vehicle operation, relative to the selection of U.S. transit buses.

Figure 12 shows the relationship between the characteristic acceleration and the aerodynamic
speed, with lines of constant kinetic intensity included for reference. The BRTS routes are
clustered around a kinetic intensity of 2 km-1, which is slightly higher than most of the FleetDNA
data points.

34
NREL. 2018. “Fleet DNA: Commercial Fleet Vehicle Operating Data.”
https://www.nrel.gov/transportation/fleettest-fleet-dna.html. [Accessed: January 18, 2019].

21
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Figure 11. Kinetic intensity vs driving average speed for BRTS routes

Figure 12. Characteristic acceleration vs aerodynamic speed for BRTS routes

22
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 4.2 BEB Modeling Results
The electric transit bus model described in Section 3.3 was used to simulate BEB operation on
all eight BRTS routes. Input to the model was an entire day of logged vehicle speed data for each
route—the same speed profiles used to develop the route statistics. Where multiple days of
operation were recorded for a route, all days were simulated independently—19 in all. The
model calculates the energy required for a BEB to drive the route in exactly the same way it was
driven by the conventional vehicle, as demonstrated in Figure 13, where the “measured” trend
line is recorded data from a conventional bus and the “modeled” line is the speed achieved by the
electric bus model.

Figure 13. Example speed profile for a measured conventional bus and the modeled electric bus

The driving speed profile is used to estimate instantaneous power required from the vehicle
battery as shown in Figure 14. If the model is able to complete the route without deviating
significantly from the speed profile of the conventional vehicle—that is, the simulated electric
bus meets the required driving performance for the route—then the battery power estimate can
be integrated over an entire day to calculate the total energy used by the vehicle.

23
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Figure 14. Instantaneous power requirement and cumulative energy use

The Sankey diagram in Figure 15 shows an example of the flow path of energy through the BEB
as simulated on Route 11. In the BEB model, electricity is converted to rotational power used to
overcome drag and friction forces and to accelerate the vehicle. When the brakes are applied, a
portion of that energy is recaptured and returned to the battery through the electric motor during
regenerative braking. By recapturing energy through regenerative braking, electrified drivetrains
(hybrids included) partially recharge their batteries using energy that would otherwise be
dissipated as heat from conventional brake pads. Absent from the diagram is energy used by the
bus to climb hills. Elevation data logged from Surat was not accurate enough to approximate the
grade of the road for modeling purposes. However, Surat is a relatively flat city.

In contrast, the flow of energy for a nonhybrid conventional bus is unidirectional, and none of
the kinetic energy of the bus can be recaptured (Figure 16). For both bus types, the model
incorporates energy losses due to aerodynamic drag, rolling resistance, mechanical friction, and
thermal losses in vehicle components, as well as energy used for auxiliary vehicle loads such as
air conditioning and on-board electronics. Notably, most inefficiencies are the same for electric
and diesel buses, such as rolling resistance and aerodynamic drag, but an electric motor can
operate at a much higher average rate of efficiency than is possible for a diesel engine. This is
largely a factor of diesel buses losing significant amounts of energy due to heat rejection from
combustion and engine losses.

24
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Figure 15. Sankey diagram displaying the dissipation of battery energy for a BEB on Route 11,
normalized by route distance

Figure 16. Sankey diagram displaying the dissipation of fuel energy for a conventional bus on
Route 11, normalized by route distance

25
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Using the results of the vehicle model, Figure 17 compares the fuel economy of the diesel buses
and BEBs for each BRTS route. The diesel bus results are averages of data from the existing
diesel buses in service as provided by SMC. The BEB fuel economy values are modeling results
assuming a vehicle mass of 14,000 kg, a constant ambient temperature of 28°C, and dry road
conditions. The electrical energy consumption (kWh) for the BEBs was converted to diesel liter
equivalent (dLe) fuel consumption using a conversion factor of 9.94 kWh/dLe. The modeled
results for BEBs were generally three to five times more fuel efficient than the conventional
diesel bus fuel records for the relevant routes. This benefit is especially pronounced on routes
with low average speed and more stops per mile.

Figure 17. Fuel economy by BRTS route for baseline diesel buses (measured in-use data) and
BEBs (modeled results)

A chief concern when adopting electric vehicles is driving range. Assuming that BEBs will be
required to drive the same routes for the same distance between recharging events as the
conventional buses, a minimum battery size can be estimated. The required battery size will be
determined by the daily distance and the average energy consumption rate (kWh/km) of the bus.

In addition to route characteristics (average speed, driving intensity, etc.), the two factors that
most significantly impact the energy consumption rate include vehicle mass (vehicle +
passengers) and weather conditions. Heavier buses consume more energy, vehicle air-
conditioning systems require a significant amount of energy in Surat’s extremely hot climate,
and the city’s monsoon season could impact bus energy consumption as well.

Figure 18 shows the impact of daily average ambient temperature on the energy consumption
rate of the electric bus. The BEB was modeled on each BRTS route with the daily average
temperature ranging from 15°C to 40°C. As the temperature increases, more energy is required
to run auxiliary air conditioning loads, which increases the BEB’s overall energy consumption
rate by approximately 0.08 kWh/km for every 5°C of temperature increase. The average ambient

26
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 temperature in Surat is 28°C. Ambient temperature was used primarily to estimate power
consumption by the vehicle’s air conditioning system.

Figure 18. Impact of ambient temperature on BEB energy consumption rate

Road wetness influences vehicle efficiency as well. Ejsmont, J., et al. found that a 0.8 mm water
film could increase the rolling resistance of tires traveling at 30 km/hr by 30% compared to dry
conditions. 35 These tests took place in Denmark in October and may not be perfectly applicable
to Surat's climate. The report authors noted that tires cooled off more on wet roads, partially
deflating them, which accounted for an undetermined percentage of the impacts to rolling
resistance. In addition to this confounding factor, driving speeds are likely to decrease on wet
roads, potentially mitigating the impact of impaired rolling resistance. Furthermore, the monsoon
season in Surat typically takes place from July to September, when average daily high

35
Ejsmont, J., et. al. 2015. "Influence of Road Wetness on Tire-Pavement Rolling Resistance." Journal of Civil
Engineering and Architecture 9. http://www.davidpublisher.org/Public/uploads/Contribute/566e64a472e9f.pdf.

27
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 temperatures and air conditioning needs tend to be lower than average, but not as low as average
October temperatures in Denmark. Road testing on Surat roads or a similar climate during dry
and wet conditions would be the best way to determine these effects. Driving through deep
flooding may also present safety and functionality concerns for BEB traction batteries.

The energy consumption rate (or efficiency) of the BEB is sensitive to the total vehicle weight—
the sum of the vehicle curb weight and weight of passengers—which should not exceed the gross
vehicle weight rating (GVWR). The starting curb weight of a bus can vary significantly between
models based on overall size and construction, ESS capacity and other factors, yet is essentially
constant for the life of the bus. The total weight of the bus in operation varies continuously based
on passenger loading.

Figure 19 highlights the impact of the vehicle weight on the BEB’s energy consumption rate.
Assuming an ambient temperature of 28°C, the BEB was modeled on each BRTS route with
vehicle mass settings swept from 7,000 kg to 18,000 kg. This represents the estimated range of
vehicle mass from the commercially-available BEBs described in Table 5, according to
specifications of GVWR and passenger loading. The range of estimated vehicle mass
corresponding to each BEB in the table is shown at the bottom of Figure 19.

28
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Figure 19. Impact of vehicle mass on BEB energy consumption rate

As a point of comparison, Table 8 outlines a range of efficiencies that can be expected at any
given point in time, depending on temperature and bus mass including the passenger load. For
context, the GVWR of the Tata 9-meter BEB is 10,200 kg, and the GVWR for the BYD 12-
meter BEB is 18,000 kg (Table 5).

29
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Table 7. BEB Efficiency by Temperature and Mass (kWh/km)
Temperature (°C)
Mass (kg)
25 28 30 35 40
7,000 0.56 0.61 0.64 0.72 0.80
8,000 0.60 0.65 0.68 0.76 0.84
9,000 0.64 0.69 0.72 0.80 0.89
10,000 0.69 0.74 0.77 0.85 0.93
11,000 0.74 0.79 0.82 0.90 0.98
12,000 0.79 0.84 0.88 0.96 1.04
13,000 0.85 0.90 0.94 1.02 1.10
14,000 0.92 0.97 1.00 1.08 1.17
15,000 0.99 1.04 1.07 1.15 1.24
16,000 1.07 1.12 1.15 1.23 1.32
17,000 1.15 1.20 1.23 1.31 1.40
18,000 1.23 1.28 1.32 1.40 1.48

Identifying the appropriate ESS capacity for BEBs can be challenging. It is important that the
buses have sufficient range to meet the daily service requirements of the BRTS routes without
significantly oversizing the ESS, which would increase bus mass and incur unnecessary capital
costs.

The minimum size of battery required for the BEB to meet the daily service needs of BRTS
routes is determined by the energy consumption rate of the BEB and the daily distance traveled.
Energy consumption rates could range from a low of approximately 0.74 kWh/km for a lighter
(10,000 kg) bus operating on a mild-temperature (28°C) day, ) to a high of approximately 1.32
kWh/km for a heavy (16,000 kg) bus operating on a hot (40°C) day in Surat. Factoring in the
daily distance variation for BRTS routes results in a wide range of potential minimum ESS sizes.

It is helpful to consider how much of the existing BRTS bus fleet could be electrified (replaced
by BEBs) for each increase in ESS capacity. Each BRTS route has a different daily range
requirement, which means service on different routes could be achieved by BEBs with different
ESS capacities. Each of the eight routes also has a different number of buses operating every
day, adding up to the total BRTS fleet of 127 buses.

Figure 20 shows how the minimum ESS capacity corresponds to the cumulative percentage of
BRTS fleet that could be electrified, for a range of average efficiencies. The left trend line in the
figure represents conditions of higher efficiency (an average energy consumption rate of 0.74
kWh/km for a 10,000 kg bus at 28°C), and the right trend line represents lower fuel efficiency
conditions (an energy consumption rate of 1.32 kWh/km for a 16,000 kg bus at 40°C). The thick
blue trend line in the middle corresponds to an average efficiency of 1.08 kWh/km for a 14,000
kg bus at 35°C. As the ESS capacity increases, each step change in the trend lines represents the
number of buses operating on one of the eight routes, in order of increasing daily route distance,
thereby showing the cumulative percentage of the BRTS service met by BEBs.

30
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 For example, assuming an average efficiency of 1.08 kWh/km (thick blue line), BEBs with 250
kWh of energy storage could replace over 40% of the BRTS buses—those operating on Routes
18, 16, 17e, and 14. BEBs with ESS capacity of at least 280 kWh could replace almost 90% of
the fleet. Electrifying 100% of the BRTS fleet with buses of a single type or size would require
BEBs with ESS capacity of 300 kWh or greater, for this middle efficiency case.

Because the BRTS bus fleet will not be electrified all at once, SMC can use this relationship to
plan the acquisition of each additional group of BEBs based on the routes to be electrified, the
expected efficiency, the size of ESS available, and the number of buses being purchased. To
begin, SMC could acquire the first four BEBs with an ESS capacity of approximately 200 kWh
and operate them exclusively on Route 18 as an initial pilot program. SMC may also benefit
from piloting a small number of BEBs along various routes to test the actual range under various
real-world conditions.

When calculating the necessary ESS capacity for BEBs, SMC should consider that rated battery
capacity may be larger than usable capacity and that traction batteries will degrade over time.
Manufacturer warranties often specify 80% or 85% of original capacity as the level at which
batteries should be replaced, correlating to a required increase in initial ESS capacity of 17% to
25%. As a point of reference, 312.5 kWh of usable ESS degraded to 80% will provide the
equivalent range of a 250 kWh ESS.

Figure 20. Cumulative fraction of BRTS bus fleet vs ESS capacity

31
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 5 Battery Life Longevity
Battery lifetime and rate of degradation depend on several factors, including battery chemistry,
age, temperature, the rate of charge and discharge, and the constantly varying state of charge
(SOC). While a full analysis of battery longevity would exceed the scope of this report, NREL
researchers investigated the potential degradation of generic versions of the battery chemistries
under consideration: lithium nickel manganese cobalt oxide (NMC) specified by Ashok Leyland,
lithium iron phosphate (LFP) specified by BYD, and lithium nickel cadmium aluminum (NCA),
which is another common battery technology. Real-world results will vary based on the
percentage and configuration of elements used by each manufacturer, pack-cooling technology,
and other factors, such as the amount of time the battery packs are fully charged each day, which
puts additional stress on the battery.

NREL conducted an analysis using the Battery Lifetime Analysis and Simulation Tool (BLAST)
to examine battery degradation. 36, 37 The analysis highlighted the sensitivity of battery lifetime to
differences in chemistry and temperature impacts, rather than predicting the actual battery
lifetime for BEBs that may be acquired by SMC. Therefore, several assumptions were made to
simplify the analysis. The team modeled batteries with 500 kWh capacity for the analysis to
ensure there was excess charging capacity to meet the service requirements of all BRTS routes.
The batteries were modeled to be discharged according to the power requirements of each route,
determined by the vehicle power requirements model. They were charged nightly, beginning
when the bus returned to the depot from each route, and scheduled to charge at a fixed rate
necessary to reach 100% capacity one hour before the beginning of operation the following day.
Figure 22 shows the modeled state of charge during a 24-hour period for each BRTS route.

The analysis also considered three temperature scenarios—labeled “Min.”, “Max.”, and
“Avg.”—where it was assumed that the battery pack temperature matched one of the ambient
temperature profiles shown in Figure 23. The three profiles are averages of the weekly minimum,
maximum, and average ambient temperatures, respectively. Without any active battery pack-
cooling, battery temperatures could be significantly higher, which would reduce the lifetime of
the batteries. Active cooling would maintain lower temperatures, which would extend the battery
lifetime.

36
NREL. “BLAST: Battery Lifetime Analysis and Simulation Tool Suite”.
https://www.nrel.gov/transportation/blast.html. [Accessed: October 22, 2018].
37
Neubauer, J., Wood, E. 2014. Thru-life impacts of driver aggression, climate, cabin thermal management, and
battery thermal management on battery electric vehicle utility.
https://www.sciencedirect.com/science/article/pii/S0378775314002766

32
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 100

90

80

70

R#11
SOC, %

60 R#12

R#14

R#15

50 R#16

R#17

R#17e
40 R#18

30
0 5 10 15 20 25

Hours

Figure 21. ESS charge and discharge profile for model

40

35

30
°C

25

20
Temperature,

15

10 Monthly Avg.

Weekly Avg.

5 Weekly Max.

Weekly Min.

0
0 10 20 30 40 50

Weeks

Figure 22. Ambient temperature profiles for model 38

Weatherbase. “Surat.” 2019. https://www.weatherbase.com/weather/weather.php3?s=4824&cityname=Surat-

38

Gujarat-India&units=metric. [Accessed: January 17, 2019].

33
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 The analysis considers 20% an acceptable degradation factor. Battery degradation accelerates as
the overall percentage of nominal capacity is lost, and approximately 80% of nominal capacity is
a common cutoff level for original equipment manufacturer (OEM) battery warranties.

Based on the assumptions described above, Table 8 displays the estimated number of years of
operation it will take the various battery technologies to deplete to 80% of their original capacity.
The results vary based on the technology used, battery temperature, and the daily battery
depletion along each route. Routes 12 and 15 require the most daily energy, and therefore the
batteries are more fully depleted, while Route 18 reflects the lowest daily depletion.

Table 8. Years to Reach 80% Charge Capacity

NMC LFP NCA Max ∆SOC

Route Avg. T Max. T Min. T Avg. T Max. T Min. T Avg. T Max. T Min. T 10 Years
11 5.3 1.4 >10 3.5 2.3 5.6 5.6 3.4 9 57.6%
12 3 1 9.4 3.5 2.3 5.6 5.2 3 7.6 67.6%
14 5.8 1.6 >10 3.5 2.3 5.6 5.8 3.5 9.5 53.5%
15 2.9 1 9 3.5 2.3 5.6 5.2 3 7.6 68.3%
16 5.8 1.6 >10 3.5 2.3 5.5 5.7 3.5 9.4 53.9%
17 5.9 1.6 >10 3.5 2.3 5.5 5.8 3.5 9.4 53.0%
17e 6 1.6 >10 3.5 2.3 5.5 5.8 3.5 9.5 52.4%
18 9.5 3 >10 3.5 2.3 5.6 6.2 3.9 >10 43.0%

The biggest takeaway from the battery lifetime analysis is that SMC should require a battery
warranty acceptable to Surat BRTS as part of the solicitation process. This could include battery
replacement coverage for the seven-year operational period and 500,000 km that SMC buses are
likely to run, but SMC will need to work with OEMs to negotiate terms. SMC should also work
to implement effective smart charging solutions in tandem with the deployment of electric buses
to maximize battery life.

Actual performance will vary based on several factors, including the actual depth of discharge
allowed by the vehicle manufacturer. For example, Transpower limits the battery SOC range of
its electric truck batteries to improve the longevity. If the total energy used from batteries is
limited to 80% of their capacity, they can cycle 2,000 to 3,000 times, but if they are limited to
70% of their total energy, they can cycle 5,000 times. 39 Operators can also improve battery life
by maintaining a battery SOC closer to the middle of its range, rather than fully charging or fully
discharging. SMC could consider minimizing battery depletion by operating BEBs along shorter
routes on days when air conditioning loads are expected to peak or on particularly wet days when

39
Transpower USA. Electric Class 8 Truck Product Description. 2014.
http://www.transpowerusa.com/downloads/Electric-Class-8-Truck-Description-TransPower-08-08-14.pdf.
[Accessed: January 22, 2019].

34
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 road conditions may reduce efficiency. Using multiple BEBs along a longer route in adverse
conditions could achieve the same purpose.

Because of these considerations, battery lifetime represents a significant risk factor to the
economic feasibility of converting the SMC transit fleet to BEBs. The cost of battery
replacement is another major economic challenge. While electric vehicle battery pack costs in
2017 were approximately $219/kWh (₹15,555/kWh) in the United States, the DOE goal for pack
costs is $100/kWh (₹7,103/kWh) by 2022, and $75/kWh (₹5,327/kWh) in the long term. 40
Assuming these goals are achieved in India, and batteries need to be replaced in 2022, they will
cost less than half of what they currently cost. In addition, the government of India reduced the
goods and services tax on lithium-ion batteries from 28% to 18% in July 2018, although the
import duty was raised from 10% to 20%. This will reduce the pack costs for batteries produced
in India, but the costs will remain the same for imported batteries. 41

40
DOE Vehicle Technologies Office. 2018. Batteries: 2017 Annual Progress Report.
https://www.energy.gov/sites/prod/files/2018/06/f52/Batteries_FY2017_APR_Final_FullReport-webopt.pdf.
[Accessed: January 17, 2019].
41
Rajeshwari. 2018. Mercom India. “GST on Li-Ion Batteries Reduced from 28 to 18 Percent”.
https://mercomindia.com/gst-li-ion-batteries-reduced-from-28-to-18-percent/. [Accessed: January 17, 2019].

35
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 6 Life-cycle Cost Comparison
The economic feasibility of BEBs depends on several factors, which can be summarized as a
combination of capital expense (capex) and operating expense (opex). The capex includes
purchase of the bus itself as well as charging equipment, while the variable opex consists mostly
of fuel and maintenance costs. Insurance and accident costs are assumed to be equal for diesel
and electric buses, and therefore are not factored into the life-cycle cost comparison.
Furthermore, the analysis does not include the cost of diesel fueling stations; the authors
assumed that the diesel infrastructure is already in place or the buses fuel at publicly available
stations, whereas the electric charging equipment must be installed to support new BEBs. This
section also assumes that BEBs would replace diesel buses at a ratio of one to one. However, to
electrify routes with a longer range without on-route charging or battery swapping, Surat may
need to acquire additional BEBs.

6.1 Capital Expense

Capex for BEBs can be divided into bus purchase costs and installed EVSE costs. Both the
vehicle and charging equipment costs for BEBs are subsidized by the FAME program. The
proposed FAME II program was introduced in April 2019. Under the plan, BEBs qualify for
incentives equaling ₹20,000/kWh up to 40% of the cost of the vehicle, and one slow charger per
BEB or one fast charger for every ten BEBs will be funded through the grant program. 42 The
following calculations are based on the FAME II proposal, assuming that it is formalized in its
current form.

6.1.1 Bus Costs

The Department of Heavy Industry (DHI) committee that oversees the FAME program set
FAME I incentive amounts for BEBs based on benchmark prices using the lowest bid among
nine cities for each bus category. 43 Bus categories were based on bus length, seating capacity,
battery capacity, and floor height. This report uses those categories and prices as an
approximation of prices that Surat could secure in its bid for BEBs. However, actual costs may
differ.

To highlight the wide range of potential BEB purchase costs, Figure 24 and Figure 25 show the
submitted bid prices for BEBs from seven OEMs to solicitations from municipal corporations in
10 Indian cities. 44 Some cities requested gross cost contract (GCC) bids, which include opex, and
others requested outright purchase contracts. Therefore, the charts are divided into GCCs
(INR/km) and outright purchase bids (INR Million), and cover 9-meter and 12-meter BEBs

42
Government of India, DHI. 2019. Operational Guidelines for Delivery of Demand Incentive under FAME India
Scheme: Phase - II - regarding. https://dhi.nic.in/writereaddata/UploadFile/DHI%20FAME%20PHASE-
II22March2019.pdf. [Accessed April 8, 2019].
43
Government of India, DHI. 2018. Recommendations of the Committee Constituted to Decide Benchmark Price for
Electric Buses to be Procured by Different STUs, for Release of Demand Incentives.
https://dhi.nic.in/writereaddata/UploadFile/Benchmark%20price%20for%20Electric%20Buses63666299596397561
6.pdf. [Accessed: January 17, 2019].
44
UITP. 2018. Electric Buses Procurement in India - Indian Cities Got the Viable Rates.
https://india.uitp.org/sites/default/files/documents/Procurement%20of%20Electric%20buses%20in%20India%20-
%2020032018.pdf. [Accessed: January 17, 2019].

36
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 either with or without air conditioning (AC or non-AC). The life-cycle cost comparison in this
report uses the benchmark outright purchase figures with adjustments for electricity prices
available in Surat and additional assumptions regarding charging equipment. The life-cycle costs
over seven years for BEBs calculated in this report amount to between ₹26/km and ₹40/km,
placing the report estimates on the low end of the range shown in Figure 24. There is
significantly more variation within the submitted bids for GCCs, which might include accident
and insurance costs.

Figure 23. Quoted rates for electric buses - gross cost contract (GCC)

37
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Figure 24. Quoted rates for electric buses - outright purchase

Table 10 compares the original purchase cost and the cost after FAME II incentives for
benchmark BEBs and two diesel buses sold in India. 45 As additional points of reference, a report
from the Lawrence Berkley National Laboratory includes production cost estimates of
approximately ₹2M for 9-meter diesel buses, ₹6M for 12-meter diesel buses, ₹5M for 9-meter
BEBs, and ₹10M for 12-meter BEBs. 46

Table 9. Bus Purchase Costs Before and After FAME Incentives

Battery Cost After
Fuel Length Passenger Purchase FAME II
Manufacturer Capacity FAME II
Type (m) Capacity Cost Incentive
(kWh) Incentive
Tata Electric 9 31 125 ₹7,490,000 ₹2,500,000 ₹4,990,000
Tata Electric 12 40 125 ₹8,800,000 ₹2,500,000 ₹6,300,000
BYD Electric 9 31 162 ₹12,297,600 ₹3,240,000 ₹9,057.600
BYD Electric 12 40 324 ₹17,519,400 ₹6,480,000 ₹11,039,400
Tata Diesel 12 44 - ₹3,300,000 ₹ - ₹3,300,000
Volvo Diesel 12 32 - ₹8,800,000 ₹ - ₹8,800,000

45
Global Green Growth Institute and Center for Study of Science, Technology, and Policy. 2015. Electric Buses in
India: Technology, Policy and Benefits.
http://www.cstep.in/uploads/default/files/publications/stuff/CSTEP_Electric_Buses_in_India_Report_2016.pdf.
[Accessed: January 17, 2019].
46
Khandekar, et. al. 2018. The Case for All New City Buses in India to be Electric. http://eta-
publications.lbl.gov/sites/default/files/india_electric_city_buses.pdf. [Accessed: January 17, 2019].

38
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 While the purchase costs of BEBs are higher than those of the diesel buses, after accounting for
FAME incentives they are more competitive.

6.1.2 EVSE Costs and Considerations

The FAME II program proposes to provide grants for up to 100% of the cost of one slow charger
per BEB and one fast charger for every ten BEBs. 47 Slow and fast EVSE were not defined in the
DHI notification; the authors assumed that a unit capable of charging a BEB overnight would be
considered slow in the context of FAME II, and an on-route charger would be considered fast.
Assuming the Surat BRTS qualifies for the 100% EVSE project cost incentive, there will be no
cost associated with EVSE. This differs significantly from the FAME I program, which offered
10% of the bus costs as an incentive for EVSE.

There are multiple depot-charge or on-route charge strategies that Surat could employ. If SMC
elects to purchase a depot-charge bus, it could rotate high-power direct current fast charger
(DCFC) ports overnight among multiple BEBs or install a slower, dedicated EVSE port to each
vehicle. Alternatively, SMC could acquire a BEB with on-route ultra-fast charging (typically
employing an automatic conductive coupler such as a pantograph or wireless charging pads) or
swappable batteries. The types of charging are illustrated in Figure 25.

(a) (b) (c)

Figure 25. EVSE connection types

(a) handheld conductive (b) automatic conductive (c) automatic wireless
None of the BEBs identified in this report as available in India currently offer on-route charging
options. However, Ashok Leyland offers a BEB with swappable batteries that could function in a
fashion similar to that of on-route ultra-fast-charging, with designated locations along a bus route
to swap the depleted batteries with fully charged batteries. This minimizes the wait time for bus
operators, but it requires designated locations for BEB battery exchange. The company operating
the swapping would then use one of the strategies outlined in Figure 25 to charge the depleted
batteries. Costs for battery swapping in India were not available publicly, but the GCC bids in
Bangalore and Ahmedabad might include those costs (Figure 24).

As an example of a depot-charge option, BYD buses can charge using the GB/T standard DCFCs
or IEC 62196 Type 2 alternating current (AC) connectors. 48 GB/T DCFC currently can provide

47
Government of India, DHI. Notification: Scheme for Fast Adoption and Manufacturing of Electric Vehicles in
India Phase II(FAME India Phase II). https://www.fame-india.gov.in/WriteReadData/userfiles/file/FAME-
II%20Notification.pdf
48
Song, N. BYD Auto Asia-Pacific Auto Sales Division. 2018. “Personal Communication with Author.”.

39
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 up to 237.5 kW of charging power, 49 although 150-kW chargers appear more common on
clearinghouse sites such as Alibaba. Type 2 AC EVSE can charge at up to 43 kW on 63A three-
phase power (415 V). In order to provide up to 324 kWh between 11:00 p.m. and 6:00 a.m.
(which would fully charge the battery of a BYD 12-meter BEB overnight), the EVSE must
provide 52 kW of continuous power (assuming 10% efficiency loss from the EVSE to battery).
Although the batteries are unlikely to be fully depleted every day, EVSE units do not always
provide the maximum rated power listed by the manufacturer, especially as ESS capacity
approaches 100%. Therefore, Surat may want to consider a 60 kW DCFC.

In case SMC does not qualify for the full EVSE project costs, an approximation of unit and
installation costs may prove useful. The authors could not ascertain cost data on EVSE units sold
in India, and installation expenses depend heavily on power availability, electrical upgrades, and
surface disruptions such as trenching through concrete. In a 2015 report on nonresidential U.S.
EVSE costs, the DOE estimated 24–90 kW DCFC unit costs between ₹710,000 – ₹2,800,000
and average installation costs of about ₹149,000. 50 Assuming an average unit purchase price of
₹178,000 for a 60 kW charger in addition to the installation cost, unsubsidized EVSE would cost
₹3,270,000. SMC may be able to achieve lower costs by installing Type 2 AC EVSE if 43 kW is
sufficient and the BEBs can accept 43 kW AC, or by installing 150 kW DCFC and rotating
charging among three buses overnight. However, rotating the charging cords or moving the
buses throughout the night would increase labor costs. Detailed electrical and labor assessments
at the depots would be necessary to determine the optimal charging strategy.

It is unclear whether the FAME II definition of EVSE project costs will include upgrades to the
distribution transformer. Therefore, SVNIT Surat analyzed the costs of installing a distribution
transformer to provide apparent power at up to 800 kVA (standard transformer size with more
than enough capacity for 10 BEBs charging at 60 kW) or 1,250 kVA (more than enough capacity
for charging 15 buses at 60 kW or 10 BEBs at 100 kW). While the transformers are specified at
standard sizes, the analysis used 600 kVA and 1,000 kVA respectively for setup charges because
they more accurately reflect likely power requirements for 10 or 15 BEBs at 60 kW. As shown in
Table 11, the expected charges from the utility include a refundable security deposit, which
accounts for over 75% of the total charges.

49
Kane. 2018. “China is Developing New GB/T Fast Charging Standard at 900 kW.” Inside EVs.
https://insideevs.com/china-new-gb-t-fast-charging-standard-900-kw/. [Accessed: January 17, 2019].
50
DOE. 2015. Costs Associated with Non-Residential Electric Vehicle Supply Equipment: Factors to consider in the
implementation of electric vehicle charging stations.
http://www.afdc.energy.gov/uploads/publication/evse_cost_report_2015.pdf. [Accessed: January 17, 2019].

40
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Table 10. Utility Setup Charges for 600 and 1,000 kVA Transformers
Setup Charges 600 kVA 1000 kVA
Registration Charges ₹6,000 ₹10,000
Service Connection Charges ₹10,400 ₹16,000
Pro Rata Charges ₹690,000 ₹1,150,000
Security Deposit (refundable) ₹3,294,000 ₹5,553,000
Line Charges (approximate) ₹350,000 ₹350,000
Total ₹4,350,400 ₹7,079,000

In addition, there would be costs associated with installing the distribution transformer. SVNIT
estimates that the total costs associated with an 800-kVA transformer would be ₹2,730,000,
while a 1,250-kVA transformer would cost ₹3,320,000.

Table 11. Distribution Transformer Costs

Equipment Type 800 kVA 1250 kVA
BIS 1180 Level, 2 (11/433), ₹1,280,000 ₹1,570,000
OLTE Tap, ONAN, Copper
Wound
11 kVA Switchyard ₹325,000 ₹325,000
1250 A VCB and High-Tension ₹325,000 ₹325,000
Cable
LT Main PCC Panel with APFC ₹550,000 ₹750,000
Panel (approximate)
Cabling and Other Accessories ₹250,000 ₹350,000
Total ₹2,730,000 ₹3,320,000

SVNIT diagrammed the installation of the high-tension (HT) vacuum circuit breaker (VCB),
transformer, low-tension (LT) bus, and LT panel with automatic power factor control (APFC) as
shown in Figure 26.

Figure 26. Single line diagram of electrical upgrades to support BEBs

41
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Sufficient detail was not available to isolate electrical upgrades within the overall installation
cost estimates provided in the DOE 2015 cost report. 51 However, the total costs associated with
electrical upgrades, including the charges for new service and the security deposit, total
₹7,080,400 for ten 60-kW EVSE, or ₹708,040 per unit. Excluding the security deposit—which
can be refunded as a bill credit—the total would be ₹3,786,400. This is approximately one
quarter of the ₹1,491,609 estimated for overall EVSE installation costs. It is likely that the
balance of installation costs—such as trenching, pouring a concrete pad, and configuring the
EVSE—would not equal three times the cost of the electrical upgrades, suggesting that the DOE
installation cost estimates for the United States are higher than SMC's costs would be.

As noted above, the FAME II program proposal includes a provision to pay for 100% of the cost
of EVSE. Therefore, it is likely that all of the EVSE costs for the Surat BEBs will be reimbursed.
However, they could be as high as 15 lakh per EVSE without incentives.

6.2 Operational Costs

The two primary opex factors assessed in this report are fuel and maintenance. BEBs are
significantly more efficient than diesel buses on the basis of energy content. Combined with low
electricity costs in Surat, fuel costs for BEBs are far less than those for diesel buses. However,
the maintenance cost comparisons are not as clear.

6.2.1 Fuel Costs

BEBs achieve significantly higher fuel efficiency than conventional diesel buses—modeled at
approximately two to five times higher in this report (see Figure 17 for estimates along Surat
BRTS routes). NREL performed an analysis to estimate the costs for depot-charging BEBs based
on available tariff schedules from Dakshin Gujarat Vij Company (DGVCL). 52 The HTP-1 tariff
was applied for high-tension electricity supply above 100 kVA. This tariff includes energy
(consumption) charges, demand changes, a power factor adjustment, and time-of-use rebates. For
power availability between 500 and 1,000 kVA, the energy charge is ₹4.2/kWh. The demand
charge for 612 kVA (10 x 60 kW EVSE units with a 98% power factor) is ₹104,184 per month.

SMC should be able to take advantage of adjustments for maintaining power factor above 95%
(₹0.0006/kWh for 98% power factor), as well as time-of-use rate rebates (₹0.40/kWh for
charging between 10:00 p.m. and 6:00 a.m.). In total, monthly energy costs for charging 10
BEBs at 293 kWh/night (which includes a 10% efficiency loss) would be ₹438,650. For a BEB
fuel efficiency of 1.12 kWh/km (16,000 kg at 28° C, Table 8), this equates to ₹6.20/km. At lower
tension (<100 kVA, for 1–2 EVSE only), the rate for EV charging is simply ₹4.1/kWh, which
equates to ₹4.59/km using the same efficiency.

51
DOE 2015. Costs Associated with Non-Residential Electric Vehicle Supply Equipment: Factors to consider in the
implementation of electric vehicle charging stations.
http://www.afdc.energy.gov/uploads/publication/evse_cost_report_2015.pdf. [Accessed: January 17, 2019].

52
Paschim Gujarat Vij Company Limited. 2018. Truing up for FY 2016-17 and Determination of Tariff for FY
2018-19. http://www.gercin.org/uploaded/document/3667c615-84ea-44ff-9eb7-ee58fe742fd5.pdf. [Accessed:
October 20, 2018].

42
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 The diesel fuel prices reported by SMC were ₹74.30/liter. As shown in Table 13, for a fuel
efficiency of 3.50 km/liter, this results in fuel costs of ₹21.23/km; for 2.20 km/liter, fuel costs
would be ₹33.77/km.

Table 12. Fuel Cost Per Bus

Fuel Price Fuel Efficiency
Charging Fuel Cost
Bus (INR/energy (km/energy
Efficiency (INR/km)
unit) unit)
Tata 9m 125 kWh Electric ₹5.73 1.45 0.90 ₹4.38
Tata 12m 125 kWh Electric ₹5.17 1.04 0.90 ₹5.55
BYD 9m 165 kWh Electric ₹5.38 1.19 0.90 ₹5.02
BYD 12m 324 kWh Electric ₹4.98 0.89 0.90 ₹6.20
Tata 12m Diesel ₹74.30 3.50 N/A ₹21.23
Volvo 12m Diesel ₹74.30 2.20 N/A ₹33.77

6.2.2 Maintenance Costs

Available data on BEB maintenance costs in India are limited because few BEBs had been
deployed in the country as of 2018. However, NREL completed three U.S. BEB evaluations
from 2017 to 2018, including maintenance cost comparisons between electric and conventional
(diesel and CNG) buses. 53,54,55 In the reference reports, NREL standardizes labor rates at
$50/hour (or ₹3,551/hour) to estimate maintenance costs. For this economic analysis, the authors
converted the labor rates based on relative average wages between India and the United States to
₹299/hour. 56 Parts costs were assumed to remain the same in either country. Although the actual
bus manufacturing and labor rates may be different, these results provide a levelized approach
for comparison and constitute the best data available. The sample size is limited to 21 BEBs and
10 diesel buses.

Many of the buses studied by NREL were under warranty for the duration of the evaluations. In
these cases, NREL has no insight into the cost of work performed by the warrantors. One
exception is the 2014 Proterra 35-foot Catalyst bus, which concluded the warranty period during
the bus evaluation and carried significantly higher overall maintenance costs and propulsion-
specific costs (three to six times higher) than any other set of buses analyzed. This evaluation
may be indicative of BEB maintenance costs in the period immediately following warranty,
when bus operator technicians are learning to troubleshoot electric propulsion system problems.

53
Eudy, Jeffers. 2018. Foothill Transit Agency Battery Electric Bus Progress Report.
https://www.nrel.gov/docs/fy19osti/72207.pdf. [Accessed: January 17, 2019].
54
Eudy, Jeffers. 2018. Zero-Emission Bus Evaluation Results: King County Metro Battery Electric Buses.
https://www.transit.dot.gov/sites/fta.dot.gov/files/docs/research-innovation/115086/zero-emission-bus-evaluation-
results-king-county-metro-battery-electric-buses-fta-report-no-0118.pdf. [Accessed: January 17, 2019].
55
Eudy, Jeffers. 2018. Zero-Emission Bus Evaluation Results: County Connection Battery Electric Buses.
https://www.nrel.gov/docs/fy19osti/72864.pdf. [Accessed: January 17, 2019].
56
Nation Master. "Country vs. Country: India and United States Compared: Labor Stats."
https://www.nationmaster.com/country-info/compare/India/United-States/Labor. [Accessed January 30, 2019].

43
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 However, these buses also suffered from low-voltage battery failures due to accessories such as
fareboxes and cameras drawing power continuously from batteries instead of switching off.

Excluding the set of 35-ft Proterra BEBs would yield BEB total maintenance costs of ₹3.02/km,
considerably less than the total maintenance costs of ₹11.76/km with those particular BEBs
included. This difference when excluding the outlier is enough to impact the overall life-cycle
cost comparison between BEBs and diesel buses. Table 14 provides a summary of maintenance
costs (converted to INR/km) from the U.S. BEB evaluations.

Table 13. Maintenance Costs for Electric and Diesel Buses from NREL Evaluations
Number
Fuel Total Maintenance Propulsion System
Bus of
Type (INR/km) Maintenance (INR/km)
Buses
Gillig 29 ft BAE Systems 2016 Electric ₹3.86 ₹1.56 4
Proterra 35 ft Catalyst 2014 Electric ₹18.32 ₹8.65 12
Proterra 40 ft Catalyst 2016 Electric ₹2.98 ₹1.56 2
Proterra 40 ft Catalyst 2015 Electric ₹1.92 ₹0.23 3
Gillig 40 ft Cummins ISL 2015 Diesel ₹5.18 ₹2.26 3
Gillig 29 ft Cummins ISL-9 2014 Diesel ₹7.77 ₹3.09 7
Weighted Average Electric ₹11.76 ₹5.42 21
Weighted Average Diesel ₹7.00 ₹2.84 10

The weighted average of maintenance costs across the evaluations are similar between electric
and diesel buses, but there is significant deviation within each category. In addition to the
limitations described above, these costs do not account for battery replacements that may be
necessary as the electric buses age, or diesel engine rebuilds that are typical at the midlife point
of these buses in the United States.

6.2.3 Life-cycle Operating Costs

Total operational costs are based on the fuel costs shown in Table 12 and the weighted average
maintenance costs shown in Table 13. Average daily driving distance was based on a weighted
average of BRTS route distance (distance of each route multiplied by the number of buses
assigned to each route per SMC). This equated to 236 km/day. NREL assumed that both diesel
and electric buses were available 85% of the time based on U.S. industry standards and that they
would operate for at least seven years based on recent proposed contract periods by other major
Indian cities. 57 Table 15 shows the inputs for and results of these calculations.

57
UTIP. 2018. “Electric Buses Procurement in India -Indian Cities Got the Variable Rates.”
https://india.uitp.org/sites/default/files/documents/Procurement%20of%20Electric%20buses%20in%20India%20-
%2020032018.pdf. [Accessed: January 17, 2019].

44
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Table 14. Life-cycle Operating Costs
Fuel Maintenance Daily Travel Daily Lifetime
Years of
Bus Cost Cost Distance Operating Availability Operating
Operation
(INR/km) (INR/km) (km/day) Cost Cost
Tata 9m
125 kWh ₹4.38 ₹11.76 236 ₹3,806 85% 7 ₹8,264,729
Electric
Tata 12m
125 kWh ₹5.55 ₹11.76 236 ₹4,081 85% 7 ₹8,863,977
Electric
BYD 9m
162 kWh ₹5.02 ₹11.76 236 ₹3,958 85% 7 ₹8,594,739
Electric
BYD 12m
324 kWh ₹6.20 ₹11.76 236 ₹4,235 85% 7 ₹9,198,202
Electric
Tata 12m
₹21.23 ₹7.00 236 ₹6,655 85% 7 ₹14,453,775
Diesel
Volvo 12m
₹33.77 ₹7.00 236 ₹9,613 85% 7 ₹20,877,633
Diesel

6.3 Total Cost of Ownership

Total cost of ownership is calculated by summing all of the inputs described in sections 6.1 and
6.2 As noted earlier, NREL did not attempt to calculate insurance or accident costs under the
assumption that they would not differ between diesel and electric buses. The analysis does not
account for the benefits from reduced emissions or local economic impacts.

Figure 27 shows the total cost of ownership of each bus examined in Section 6. In most cases,
the BEBs are less expensive to own and operate than the diesel buses over seven years, although
the larger battery size of the most expensive BEB may be necessary to support Surat BRTS
routes. This is largely a function of the lower fuel cost per km for BEBs, as well as of the
incentives provided under the FAME program. The total estimated cost of ownership for the
BYD 324 kWh BEB is ₹20,237,602, while the Tata Starbus diesel bus is ₹17,753,775. However,
if the maintenance costs are more in line with the BEBs under warranty in NREL's U.S. reports
(see Section 6.2.2), the 324 kWh BEB life-cycle cost drops to ₹15,761,821.

45
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Figure 27. Total estimated cost of ownership

46
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 7 Conclusion
Bus electrification promises improved efficiency and reduced operating costs for the Surat
BRTS, but there are several considerations to make before deploying BEBs along all BRTS
routes. As described in Section 4.2, the NREL model predicts vehicle efficiency to vary
significantly depending on vehicle mass and ambient temperature, among other factors. SMC
should carefully weigh factors affecting battery degradation when sizing ESS capacity, planning
BEB operations, and negotiating warranties.

Available BEB options appear to allow SMC to begin electrification of the BRTS fleet with
favorable results. Assuming an efficiency of 1.08 kWh/km or better, depot-charge BEBs with
ESS capacity of 250 kWh or greater could replace conventional buses for half of the BRTS
routes. Factoring in 20% battery degradation before replacement, the initial ESS requirement for
those buses would be at least 312.5 kWh of usable capacity. On particularly hot or wet days,
BEB efficiency will be reduced.

With an ESS of that size, BEB costs are comparable to diesel buses available in India.
Depending on whether the estimates include outlier maintenance costs for a limited sample size
of U.S buses past the warranty period, a 324 kWh BEB could cost 14% more or 11% less than
the more affordable diesel bus considered (see Section 6.2.2 for details).

The FAME II program proposes to cover the entire EVSE cost of one slow charger per BEB or
one fast charger per 10 BEBs. Although it appears that EVSE installation costs will be covered
by these incentives, Section 6.1.2 includes cost considerations for depot-charging EVSE.

On-route charging is not currently available for the BEBs identified in this report, and therefore
was not yet analyzed with respect to BRTS bus service, but this charging strategy could be an
effective way to reduce BEB battery size. On-route fast-charging BEBs with smaller battery
packs may prove to be a more suitable option than that of extended-range depot-charging BEBs
for the longest BRTS routes. This should be investigated as manufacturers in India begin
offering the technology. Important considerations for on-route strategies include access to land
and power supply, electrical demand charges incurred by high-power fast chargers, planning for
layover time at charging stations, and battery lifetime impacts of high-powered charging. Battery
replacement and vehicle maintenance warranties are important considerations regardless of
charging strategy.

SMC would benefit from a small deployment of BEBs to validate the operational model and
financial projections against actual conditions in Surat. This would minimize Surat's risk
exposure and allow SMC to work through technical challenges. A strategy employed in the
United States is to purchase a specified number of BEBs pending a short-term test trial of one to
five buses. This could involve shadowing a diesel bus operation along actual routes with a
dummy payload and auxiliary loads operating to simulate real service. The test trial could
measure performance in hot, cold, dry, and wet conditions. A long-term trial will be necessary to
understand maintenance costs, and validating propulsion battery lifetime in-situ will take several
years.

Securing a favorable warranty from the manufacturer for the bus and battery can shift some of
the maintenance risk to the OEM, reducing barriers for early adopters of the technology and

47
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 further encouraging other municipal corporations to deploy BEBs. An in-service evaluation to
compare diesel and electric buses once deployed would provide a more comprehensive
understanding of the performance and cost differences between the two technologies. 58

BEBs hold great promise for improving fleet efficiency and reducing operational costs. This
report illustrates that several Surat BRTS routes could begin operating BEBs currently available
in India. Subsequent analysis of those buses in operation can refine ESS capacity estimates for
longer routes and extreme weather as well as determine how much money Surat could save
through bus electrification in the long term. As SMC begins realizing benefits, Surat bus
operators will gain valuable experience, and the lessons learned can inform the adoption of BEBs
throughout India and the world.

58
A description of this type of evaluation and several example reports are available at
https://www.nrel.gov/hydrogen/fuel-cell-bus-evaluation.html.

48
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 Appendix A. BRTS Maps by Route Number

11 12

14 15

16 17

49
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
 17e 18

50
This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.