Electric Bus State-of-the-Art ReviewFor the City of Scottsdale, Arizona

IBI GroupJuly 5, 2015

Photo: Proterra Electric Battery Technology buses that are made in the USA

Contents

Electric Bus Technology – A State of the Art Review...................................................................................... 2

1. Introduction ........................................................................................................................................... 2

2. Advantages and Disadvantages of Electric Buses .................................................................................. 3

3. Electric Vehicle Types ............................................................................................................................ 4

Autonomous Electric Buses ............................................................................................................... 5

Battery Electric Bus ........................................................................................................................... 5

Battery Replacement Approach ........................................................................................................ 7

Solar-Augmented Battery Electric Bus .............................................................................................. 7

Fuel cell/battery electric bus ............................................................................................................. 8

Non-Autonomous Electric Buses ....................................................................................................... 9

Electric Bus with Intermittent Overhead Contact Charging ............................................................. 9

Capabus Technology ....................................................................................................................... 10

Electric Bus with Continuous Inductive Power ................................................................................ 11

Electric Bus with Intermittent Induction Charging .......................................................................... 12

4. Electric Vehicle Needs Assessment for the City of Scottsdale ............................................................. 13

5. Study Conclusions and Recommendations .......................................................................................... 14

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Electric Bus Technology – A State of the Art Review

1. Introduction

The City of Scottsdale is interested in exploring the possibility of operating electric transit vehicles in the future. Reasons for exploring electric vehicle (EV) technology include the popularity of environmentally friendly vehicles, particularly with Scottsdale’s millennial generation, and the operating cost savings reported by many operators and manufacturers. This report is a summary of some of the latest electric bus technologies, and presents some recent EV deployments around the world as case-study examples. The EV field is rapidly evolving, and this report is not intended as an all-inclusive catalogue of every electric transit vehicle technology type, combination or manufacturer.

Experiments with EV technology date back to the operation of the first battery-powered electric railway locomotive, developed by Robert Davidson, on the Glasgow and Edinburgh Railway in 1838. At about this same time British inventor Robert Anderson developed a prototype electric carriage.

By the late 1890s, the electric streetcar (‘trams’ in the UK and Europe) became the predominant form of local public transportation in much of the world. These streetcars relied on an externally-generated supply of power provided by an overhead trolley wire; the current through the electric traction motors was returned via the steel running rails.

As early as the 1910s, and then increasingly as the twentieth century drew on, streetcar companies found it uneconomic to re-invest in their rail infrastructure. In 1882, Dr. Ernst Werner von Siemens had demonstrated his "Elektromote" in Germany, and a practical rubber-tired transit EV soon evolved. Many companies turned to the electric trolleybus (ETB), which allowed them to continue to use their overhead power supply and distribution system by the expedient of adding a second overhead wire to provide a current return. ETBs remain the predominant form of highway-based EV in transit service. Cities in North America that have had ETBs in continuous use since conversion from streetcar operations include: Boston, Philadelphia, Dayton, San Francisco, Seattle, and Vancouver.

However, the economics of maintaining the overhead power distribution system for ETBs do not favor this technology for lower-density transit routes. As transit ridership declined after World War II, ETB systems were converted to diesel buses wholesale, with a ‘second wave’ of abandonments in the 1960s and 1970s as the overhead wire systems reached the ends of their service lives.

While ETB use has declined in North America, battery electric buses have been gaining in popularity. Over the past decades, cities in Europe, Australia and Asia have been leaders in embracing electric bus technology for environmental reasons, while American cities’ fleets have remained powered by mostly diesel with a small percentage embracing other alternative fuels including ethanol, methanol, compressed natural gas (CNG) and liquefied petroleum gas (LPG).1

The announcement on June 30th, 2015 that Proterra, a Greenville, South Carolina electric bus manufacturing company, has received funding to build a new factory in City of Industry, California looks to be a turning point for electric bus fleets manufactured in America. The factory, which will double

1 Alternative Fuel Transit Buses, APTA, October 1996.

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Proterra’s production capacity, is expected to be operational by the end of 2015 and will employ 70 people. The factory is also funded by a $3 million grant awarded by the California Energy Commission in April 2014. Falling lithium-ion battery prices, lower repair costs, and long-term fuel savings should allow the buses to compete against diesel-powered models and begin to chip away at transit run on fossil fuels.

In another notable development, Tesla’s massive giga-factory near Reno, Nevada will have the capacity to produce 50 gigawatt-hours of battery packs a year once it’s complete, and is already having an effect on electric bus prices. The first phase of Tesla’s gigafactory is expected to be ready next year. The new batteries are doubling the distance from 100 miles to an expected 200 miles between charges, which is significant given the typical duty-cycles of Scottsdale’s transit fleet.

2. Advantages and Disadvantages of Electric Buses

The advantages of electric traction for buses have prompted considerable research and development into electric bus technology that does not require investment in the continuous overhead contact system (OCS) required for ETBs.

These advantages include:

Reduction of the total energy consumption and associated operating costs Greatly reduced or non-existent local (tailpipe) emissions of greenhouse gases Lowest achievable noise levels for a transit bus No idling motor energy losses when stopped at bus stops, traffic signals Less vibration that results in a smoother and more attractive journey experience for passengers,

similar to rail transit vehicles Faster acceleration that offers potential travel time savings for routes with frequent stops and/or

traffic signals, and for bus operators, faster journeys reduce the fleet size and the number of trolleybus

Fewer moving parts and the 'slide out / slot in' modularity of the electric traction packages make for simpler and cheaper maintenance

The potential for regenerative braking allows electric buses to use their motors as generators and recycle energy either into batteries, capacitors, or overhead wires instead of wasting it as friction / heat. Typically regenerative braking brings energy savings of around 25% - 30%, depending on vehicle, duty cycles, and other conditions

The potential for lower overall lifetime costs - higher initial capital costs may be recaptured from operating and maintenance cost savings over a longer vehicle service life

There are of course disadvantages associated with electric buses.

For ETBs the disadvantages include:

The initial costs of constructing an OCS system for Electric Trolley Buses The annual costs of maintaining an OCS system - Specialist staff or contractors are required, and

can be cost-ineffective for a small or low-density system Limitations on passing (‘leapfrogging’) other ETBs or operating for extended distances off-route;

but these limitations have become less severe with recent developments in battery technology The occasional nuisances and delays associated with coming detached from the overhead wires

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For transit properties operating substantial motorbus fleet there is a need to staff up for mechanics and other specialists to maintain electric traction motors, which is present for all electric buses

Buses that rely on batteries for traction power have their distinct disadvantages, including: o The need for specialists in traction motors, as for ETBs o Increased vehicle weight and often a loss of interior space for batteries o Expensive batteries with a shelf life that is shorter than the vehicle’s life, which therefore

need to be replaced and recycled properly o Potential for additional staff time switching out and recharging batteries o A limitation on the operational range dependent on the capacity of the batteries, but

with a potential to alleviate this issue with en-route recharging of batteries

3. Electric Vehicle Types

An electric bus is a bus powered by electricity, i.e. which relies on electric traction motors as a prime mover but does not rely on an internal combustion engine (ICE) to generate power for those motors. This definition excludes the hybrid bus technology, which couples electric motors with power generation by an ICE. There are two basic classes of electric bus, autonomous (with an on-board power source) and non-autonomous (requiring a physical connection to an external power source). The non-autonomous class can be further divided into continuous contact and intermittently-charged categories, depending on the form of the external power source. The autonomous vehicle can be divided into those that simply store energy obtained externally and those that have some capability to generate power on-board from a source other than internal combustion.

There are advantages and disadvantages to each type of technology, requiring some analysis to determine the right choice of technology for Scottsdale’s climate, topography, size and budget. Conventional continuous-contact ETB technology offers a high level of performance that other technologies strive to achieve without the expense of a continuous OCS. Recent advances in battery and capacitor technology have made alternatives to the conventional ETB more practical.

Photo: First electric bus service in Seoul,

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Autonomous Electric Buses

Electric buses which operate independent of any wayside infrastructure include:

Battery Electric Bus

A battery electric vehicle (BEV) is a type of electric vehicle (EV) that uses chemical energy stored in rechargeable battery packs. BEVs use electric motors and motor controllers instead of ICEs for propulsion. Several manufacturers worldwide make battery-powered electric buses, though they are all challenged by the same problem of limited battery life that is exhausted fairly quickly in large vehicles that operate all day and every day, along with additional power needs to climb hills, run air conditioning, or operate long-haul routes. The battery capacity to provide a full day’s operation under some duty cycles may require giving up some seating capacity. The additional power drain of air conditioning makes battery-only electric vehicles somewhat impractical for desert climates with the current state of battery technology. However, the state of the art in batteries continue to advance quickly. BEVs are usually recharged at operating garages of depots, often overnight; this often requires about 6 hours. Battery packs can also be configured to be manually switched out to fresh batteries at regular intervals during the operating day. BEVs are commercially available.

Optare PLC of the UK manufactures a range of fuel-efficient buses and BEVs in sizes typically required by transit operators. BEVs have been supplied to: the state of Queensland, Australia and Inverness, Scotland. Range on a single charge is reportedly 95 miles on a charge requiring 6 hours to complete.

BYD Motors of China is offering for sale a 40-foot transit bus product (C9) that reportedly has a range of 190 miles on charge requiring about 2 hours to accomplish.

On April 28, 2015, the Long Beach Transit (LBT) Board of Directors authorized the purchase of 10 battery-electric buses and supporting charging systems. The LBT Board approved up to $11,069,319, which also includes training and required equipment in support of the purchase. BYD Motors offered a 12-year warranty on major components of the propulsion system, including the battery. Twelve years is considered the useful life of a public transit bus, and is the minimum time the Federal Transit Administration expects a transit agency to maintain a bus.

LBT plans to operate these initial battery-electric buses on the Passport route in downtown Long Beach starting fall of 2016. Expansion will be considered in the future as the transit agency has an option to purchase 14 more of the buses at a later date with Board approval.

Optare Group Ltd Hurricane Way South, Sherburn in Elmet Leeds North Yorkshire, LS25 6PT, United Kingdom Web: www.optare.com

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Proterra, Inc., US electric bus manufacturer, now offers an extended-range BEV; for a 40-foot bus charged in less than two hours, a range on the order of 110 miles appears attainable for the duty cycle expected for the Scottsdale Trolley. Proterra has delivered prior versions of its BEV to twelve North American transit agencies. The buses can be customized to suit each transit agency’s needs, including an extended range product line that can go up to 200 miles on a single charge. Company directors believe orders will only accelerate as battery prices continue to fall and as the company expands into the corporate fleet market this year. Proterra will focus its corporate fleet efforts on the Bay area first. The company is targeting Fortune 500 companies, universities, and theme parks as potential clients.

Proterra claims to have 110 orders for its buses, which can cost up to $800,000 for customers who buy the battery packs that have the maximum battery configuration. Customers can buy a bus and lease the batteries for about $550,000. The 60 first generation buses have already been delivered and are on the road in Los Angeles and San Joaquin counties in California, as well as San Antonio, Texas and Nashville, Tennessee. Another 50 of its 40-foot second-generation buses will be produced and delivered this year. Seattle, Washington, Louisville, Kentucky, and Stockton, California are also slated to receive electric buses this year.2

As one example, Foothill Transit operates three 35-foot, 35-passenger Proterra buses. Each relies on batteries that supply 72 kilowatt-hours and runs on a 17-mile-long loop that handles 5 percent of the yearly ridership. At specially built fast charging stations in the Pomona Transit Center, the buses can fill up within 10 minutes on their normally scheduled layover, meaning they never have to travel more than 17 miles between full charges, which is about half of what their rated battery capacity can provide.

2 “This Startup is Gearing Up to be the Tesla of Electric Buses” Fortune Magazine, June 30, 2015.

Proterra’s Corporate Office 1 Whitlee Court Greenville, South Carolina 29607 Phone: (864) 438-0000

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London Replaces Double Decker Fleet with Zero Emission Electric Vehicles The world’s first purpose-built purely electric double-decker bus will enter passenger service in London this year, Mayor Boris Johnson announced July 2015, as he hosted representatives and major bus manufacturers from across the globe for the first ever global Clean Bus Summit. As part of his Ultra Low Emission Zone (ULEZ) proposals, Mayor Johnson has committed that by 2020 all 300 single-deck buses in central London will be zero emission at tailpipe. Furthermore, all 3,300 double deck buses in central London will be Euro VI electric hybrid, with the exception of a small number of Euro V Routemasters that nearly meet the Euro VI standard. Scottsdale may be interested in the double-decker buses due to their attractiveness to tourist travel markets, owing to the great views from the top deck. Another market well-served by double-decker buses is college campuses. Double-decker buses have been in constant use on the UC Davis campus for some 40 years. Students love the fun design that enables riders to easily jump on and off the buses.

Battery Replacement Approach

One approach to dealing with the range limitations of batteries sees the batteries being removed from the vehicle for recharging. If several sets of batteries are available, then immediately replacing them with a fully charged set of batteries would mean that the bus could be back in service within minutes without having to wait for the removed batteries to be recharged.

Solar-Augmented Battery Electric Bus

BEVs have successfully been outfitted with solar panels to recharge batteries while operating, thereby extending the operating range of the vehicles.

As part of an industrial development project in Heilongjiang province in 2010, and in pursuit of the Chinese government's program for the clean transport sector, the Lianfu Group joined with the Heilojiang government and the city of Qiqihar to develop a prototype solar-electric hybrid bus in 2012. Its engine is powered by lithium-ion batteries that are fed by solar panels installed on the bus roof. It was claimed that the bus consumed 0.6 to 0.7 kilowatt-hours of

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electricity per kilometer and could transport up to 100 people, and that the use of solar panels prolongs the batteries' lifetime by 35 percent. The Lianfu Group offers a commercial product (LHJ6110BEV) based on this prototype, a 35-foot vehicle with an operating range of 110 miles.

Austria's first solar-powered buses (Solarbus) were put in operation in the villages of Perchtoldsdorf and Hornstein in 2011. Powertrains, operating strategy, and design specifications were optimized in view of the planned services for both a 35-passenger fixed route bus and a 9-passenger paratransit vehicle. A cooperative effort of Kutsenits Busconstruction, two Austrian universities, two Austrian state governments and ‘green’ energy supplier Ökostrom, the project has not resulted in a commercially available vehicle.

Fuel Cell/Battery Electric Bus

BEVs have also been equipped with hydrogen fuel cells designed to provide a steady charging current to on-board batteries. The batteries provide the power for the traction motors and can capture regenerative energy from braking. On-board storage of a hydrogen supply is required, as well as the fuel cell equipment to generate the charging current.

Historically, the size and cost of the fuel cell and equipment have been prohibitive, but recent developments suggest that this is changing. New Flyer Industries is developing a prototype 40-foot Xcelsior® test bus under the California Energy Commission’s Alternative and Renewable Fuel and Vehicle Technology Program for operation by Connecticut Transit. Hydrogenics will supply a fuel cell power plant intended to be smaller, lighter and lower in cost than previous models. The Siemens ELFA drive system, common to other electric buses of the Xcelsior® line, will be employed. This vehicle is not as of yet commercially available.

Solar Bus (Austria) Mobility Department - Claudia Hable Phone: +43 505 50-6322 Email: claudia.hable@ait.ac.at Web: www.ait.ac.at/mobility

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Non-Autonomous Electric Buses

Non-autonomous electric buses are of two types; those that use a continuous supply of electric power along their route, and those that recharge intermittently at fixed wayside locations. Continuous contact systems include conventional ETBs and systems relying on induction to effect a wireless transmission of power.

Conventional Electric Trolleybus. ETB is the well-established baseline technology that was described in the introduction. There are many ETB manufacturers worldwide offering a wide range of vehicles in terms of size, seating configuration, and other particulars.

Electric Bus with Intermittent Overhead Contact Charging Intermittent overhead charging is a direct outgrowth of conventional ETB technology, aimed at reducing the cost and aesthetic impact of continuous overhead catenary wires by building the charging infrastructure at only a few key station locations, where the charging elements can be blended into the overall station design. It evolved by adding high-capacity batteries (and later capacitors) to the buses and charging them at stops and terminals. Fixed wayside overhead charging facilities have two overhead conductors, allowing most of the current collection provisions on board to be straightforward variants of conventional ETB technology. Wayside power distribution elements (e.g. substations) also resemble those for ETBs. Three manufacturers have intermittently-charged products with some operation in service.

ABB Sécheron Ltd, a company of the Swiss ABB Group, has developed the TOSA (Trolleybus Optimisation Système Alimentation) ‘flash-charging’ system.

A bus with TOSA begins its route with a fully-charged battery. At every third or fourth stop, a charging mechanism on the roof of the bus engages an overhead receptacle installed at the stop. The charging mechanism is mounted on a movable arm, and is able to line itself up

with the receptacle using a laser guidance system. Once the two devices are coupled, the receptacle delivers a 15-second-long 400-kilowatt boost to the batteries. This takes place as passengers are getting on and off of the bus. At the end of its route, the bus takes three to four minutes to completely top off its batteries. This is compatible with the layover time typically scheduled at route termini. Working with Geneva’s public transport company (TGP), the office for the Promotion of Industries and Technologies, and the Geneva power utility SIG, ABB have completed, as a pilot project in which TOSA was tested on, an articulated 135-passenger bus equipped with regenerative braking. That bus ran on a route from the Geneva airport to the Palexpo exhibition center. Plans are to expand the use of TOSA to equip the entire route between the airport and industrial zone of the Plan-les-Ouates community (ZIPLO).

TOSA (a group owned by parent company ABB Ltd.) Affolternstrasse 44 CH-8050 Zurich, Switzerland Phone: +41 (0) 43 317 7111 Fax: +41 (0) 43 317 4420

Photo: The conventional electric trolleybus is the most widely deployed electric transit

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The Chinese firm, Sinautec Automobile Technology, LLC has developed the ‘Capabus’ technology for intermittent contact charging. This grew out of the extensive and long Chinese experience with conventional ETBs, especially in Beijing, where some ETB routes have extended sections without OCS, and larger-than-typical batteries have been employed to operate over them.

‘Capabus’ vehicles use power stored in large onboard electric double-layer capacitors (EDLCs), which are quickly recharged whenever the vehicle stops at any bus stop (under so-called ‘electric umbrellas’), and like TOSA are fully charged at the terminals. The buses are basically a variant of conventional ETBs with high-capacity batteries and a two-contact power collector in place of the trolley poles. The wayside contact elements at the ‘umbrellas’ are static and resemble a short section of conventional OCS; the bus operator positions the bus correctly and uses a button to raise the contacts. During a typical passenger stop, the bus can transfer enough energy to operate about three miles.

Previously-discussed US manufacturer Proterra also uses a fast-charging system.

In addition to these suppliers, Volvo Bus Corporation has prototyped and tested contact-charged electric transit buses in both Sweden and Germany. The firm plans to launch a full line of all-electric buses in 2017. Like TOSA, its system relies on a movable element on the wayside infrastructure that ‘seeks’ the contacts on the vehicle beneath it.

The intermittent-contact technology can be considered reasonably well established, and there is relatively little risk that it will become obsolescent. It is presently not mature, however, and further evolution should be expected. Because the contact elements will likely remain proprietary, linkages between specific technologies and specific vehicle manufacturers may become prevailing practice, although in principle this is not a necessary development.

Photo: Proterra’s fast-charger at the Pomona Transit Center

Sinautec Washington D.C. 3801 Connecticut Avenue, N.W. Suite 614 Washington, D.C. 20008 Phone: (202) 224-5178 Email: dan.ye@Sinautecus.com

Volvo Bus Corporation SE-405 08 Göteborg, Sweden Phone: +46 31 668000

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Electric Bus with Continuous Inductive Power

Electric induction offers a way of supplying energy to vehicles without actual contact, from devices placed within the roadway. At least two such technologies have been developed.

The on-line electric vehicle (OLEV) has been developed by the Korea Advanced Institute of Science and Technology (KAIST). Electric power strips are buried about 12 inches under the ‘electric road’ surface and connected to the national grid. Pick-up equipment underneath the vehicle then collects power through non-contact magnetic induction which is used either to power the vehicle prime-mover or for battery charging. The demonstration system is a trackless train with an electric tractor hauling three passenger cars.

Beginning in 1998, Ansaldo experimented with a substantially similar system, Sistema di Trasporto Elettrico and Attrazione Magnetica (STREAM) in Trieste, Italy, with modified ETBs. The continuous roadway elements were visible as shown. The system was not expanded or implemented elsewhere, and the in-street installations were removed in 2012.

There are no commercially available systems of this type at present. Its principal advantage over a continuous overhead installation is the reduced visual impact. Access to the continuous elements is complicated by their being installed below the pavement.

Given the advancements in on-board battery or capacitor power storage, including rapid or ‘flash’ charging, it is possible that this technology will not be advanced farther. However, the Volvo Group is planning to have a 300- to 500-meter electric road for test operations in Gothenburg completed in 2015. The benefit of such a system is of course that buses could remain in operation while charging.

KAIST University Research Campus, South Korea KAIST 291 Daehak-ro (373-1 Guseong-dong) Yuseong-gu Daejeon 305-701 Phone: 042-350-2114 Fax: 042-350-2210 (2220)

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Electric Bus with Intermittent Induction Charging

For operators concerned with the visual impact of overhead installations, even if limited to stops or terminals, intermittent induction charging provides an alternative. Power transfer occurs at fixed wayside points, but the infrastructure is under the pavement, and the transfer occurs by electromagnetic induction rather than by electrical contact.

This can be considered an established technology, and there are several suppliers of the inductive charging technology.

Bombardier is promoting its PRIMOVE inductive charging system for both bus and light rail transit use Conductix-Wampfler’s IPT Charge (France) and previously-described Chinese BEV manufacturer BYD Motors also supplies this technology.

Prototype combinations of vehicles and inductive charging have also been developed by Proterra and in South Korea and Utah.

This technology, although proven in service, does not seem to be quite as mature as intermittent contact charging. This application of induction charging has raised questions in some quarters regarding health risks or relative maintenance costs versus contact charging, which have not been definitively explored or

resolved. The need to locate induction power transfer elements on the vehicle does introduce an element of technological risk that is not present with intermittent contact charging; this may diminish as the cumulative experience with this technology grows. There is therefore some risk of technological obsolescence, should the market not continue to grow. At this point, however, these do not appear reasons to exclude it from consideration.

Because the elements of vehicles which are not part of the inductive charging technology are essentially the same as ETBs, it is possible in principle to ‘mix and match’ vehicles and charging technology. It is too early to know whether this will occur in the marketplace, or whether specific charging systems will become associated with particular manufacturers (except, likely, for Bombardier).

IPT Charge location on ELFO bus route Turin, Italy

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4. Electric Vehicle Needs Assessment for the City of Scottsdale

According to data the 2013 National Transit Database (NTD) and Scottsdale Trolley’s website, the agency had a fleet of 21 vehicles, 17 of which were needed for peak service. The average fleet vehicle was scheduled for 2,560 revenue service hours per vehicle annually, covering 29,400 miles per vehicle annually, for an average commercial speed of 11.5 mph. Scottsdale Trolley presently operates three routes, which are classified as ‘neighborhood circulators’ by Valley Metro.

In the future, the Trolley service may grow overall, and may well grow to be more of a trunk fixed route system than a circulator. The Miller Road Route may be indicative of this. It is also possible that the span of service for the system as a whole would develop to resemble Valley Metro’s, with evening service becoming the norm. The Miller Route Trolley, which was formerly covered by Valley Metro route 76, could be considered as a duty cycle that should be accommodated in the future.

In terms of vehicle size, the requirement is not likely that a high-capacity vehicle (e.g. an articulated bus) would be required. The 2013 average vehicle occupancy according to the NTD was 4.5 persons. The 29-foot GIllig trolley replicas ordered in 2013 are likely adequate for their service life. It is likely that the successor electric buses would be single-unit vehicles not exceeding 35 feet in length.

The City of Scottsdale’s expressed desire is to avoid the visual clutter of an overhead contact system in highly visible City streets where no trees exist to camouflage it.

The Scottsdale Trolley’s frequency and traffic density are also not high enough to be in the range where an OCS is economically justifiable, even if ridership were to grow substantially. This rules out conventional ETBs. Similarly, the costs of installing and maintaining a continuous infrastructure for inductive transmission preclude that as a technology.

The Scottsdale Trolley operation is not large, and is therefore not an ideal place to assume technological risks; the scale of operation is small enough that a technological misstep could have relatively large consequences. The inclusion of electric traction for buses will be a significant step in terms of maintenance staffing in and of itself. Each additional element of recently developed proprietary technology may have to be supported to some degree by specialist talent from ‘outside’ or an added in-house skillset that may not be optimally utilized. These elements include wayside intermittent contact charging infrastructure and both wayside and vehicle-borne induction charging elements.

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Based on the limited information on solar power augmentation for BEVs, it does not appear that the addition of this technology markedly extends the operating range of the buses. It creates one additional systems interface and specialty for maintenance. If solar power is considered something that should be part of the picture, given Scottsdale’s climate, then the ‘solar’ approach pursued in sunny Adelaide, Australia beginning in 2007. The "Tindo" (Kaurna word for sun) is a BEV, equipped with a regenerative braking system and air conditioning which can carry up to 40 persons, 25 of whom are seated.

The bus itself is not equipped with solar panels; rather it is charged from a photovoltaic system on Adelaide's central bus station. The vehicle has been hailed as the world's first bus service powered exclusively by solar power; a similar claim has been made for the Calgary (Canada) light rail system being ‘wind-powered’ because all its operating power is purchased from source using wind to generate power. This indirect approach is likely a more cost-effective one for incorporating solar power as an energy source.

The choice between vehicles relying solely on batteries while operating (BEVs) and intermittently-charged electric buses with substantial battery or capacitor energy storage capability depends on the service or duty cycle requirements of the service. The constantly moving technological frontier, especially in terms of energy storage and charging capacity, also means that a decision made at one point in time might prove to be less compelling later.

5. Study Conclusions and Recommendations

As the report has shown, the electric bus industry is rapidly evolving, most dramatically in terms of battery range. During the writing of this report, electric battery operating ranges doubled from 100 miles to 200 miles between charges, owing largely to the advancements in battery technology by the Tesla Corporation. Since the City of Scottsdale does not envision purchasing new buses for at least another seven years, it is not worthwhile to make a hard-and-fast recommendation at this point.

When Scottsdale is ready to go to market, it should reassess two key points:

o The expected duty cycle of its routes o The range offered by manufacturers at the time

If the City’s anticipated duty cycles are expected to exceed battery range, the City should consider en-route charging and solar-power enhancement.

If Scottsdale circulator routes continue to operate at less than 100 miles per day in the future, battery powered electric vehicles may be the right technology choice for the City. If Scottsdale can take advantage of battery powered vehicles without the added expense of building charging stations (either into the ground or in overhead charging facilities), this would be the lowest initial cost and lowest maintenance option as well.

On the other hand, if the City wishes to operate longer routes (in miles and/or service-hours) in the future, it should give some consideration to intermittent charging at stations (either direct-contact or inductive) and to adding solar panels to the tops of the vehicles and in the central maintenance facility as an extended power source, taking advantage of the natural abundance of sunshine in Arizona. The extra

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charge provided by the solar panels would add more miles to the battery life and provide extra protection for the power drain of running air conditioning.

At the appropriate time, the City of Scottsdale should consider a smart performance-based procurement to include wayside infrastructure maintenance if intermittent charging and/or solar panels are selected as the backup power system. Consider adding training for operations and maintenance staff on the new technology as part of the contract. Seeking battery life warranties to match the operational life of the vehicle is another way to protect Scottsdale’s investment in electric vehicle technology buses.

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