Electric Taxis in Berlin – Analysis of the Feasibility of a Large-Scale Transition [original]

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Bischoff, J.; Maciejewski, M. (2015). Electric Taxis in Berlin – Analysis of the Feasibility of a Large-Scale

Transition. Tools of Transport Telematics, 343–351. https://doi.org/10.1007/978-3-319-24577-5_34

Joschka Bischoff, Michal Maciejewski

Electric Taxis in Berlin – Analysis of the

Feasibility of a Lar

e-Scale Transition

Accepted manuscript (Postprint)Dokumententyp |

Electric taxis in Berlin – Analysis of the feasibility of a

large-scale transition

Joschka Bischoff1, Michal Maciejewski1,2

1Technische Universität Berlin

Department of Transport Systems Planning and Transport Telematics

Berlin, Germany

{bischoff, maciejewski}@vsp.tu-berlin.de

2 Poznan University of Technology

Division of Transport Systems

Poznan, Poland

michal.maciejewski@put.poznan.pl

Abstract. Battery operated electric vehicles (BEVs) offer the opportunity of

running a zero-emission car fleet. However, due to their current range

constraints, electric vehicle operations are mainly attractive for inner-city

transport, such as the taxi business. This paper is bringing together facts and

assumptions about Berlin’s taxi transport and the current conditions of BEVs in

Germany to provide the scope of electrification. Firstly, the necessary amount

of fast chargers is determined taking general constraints of Berlin’s taxi

business into account. For charging, especially busy days during cold winter

days will be critical. Furthermore, a pricing scheme for fast charger usage is

introduced. Based on this, operating operation costs of a hybrid electric vehicle

and a battery electric vehicle are compared. The authors conclude that BEV

operation will only pay off if the vehicle’s battery life can be warrantied over a

long span or costs of electric energy in Germany drops.

Keywords: Berlin, BEV, electric taxis, fast charging infrastructure, electric cars

1 Introduction

Battery electric vehicles (BEVs) are on the top list of currently discussed topics

concerning private transport. Research in BEVs is driven both privately and by the

public with huge investments. At the same time, however, the general public looks

rather sceptical at electric cars. Especially, the short range is a restraint that prevents

people from switching to BEVs. Therefore, it seems a plausible idea to evaluate BEVs

in those fields of usage where the vehicle range is not of major importance. Inner city

taxi services are one of them. Each single task is usually short so that the vehicle

range does not prevent taxis from fulfilling single requests. On the other hand, the taxi

overall daily mileage is comparably high, so that they would have to be re-charged at

some time of the day. Moreover, the use of BEV as taxis has the potential to reduce

inner city greenhouse gas emissions, especially since conventional taxis have

relatively high share in these emissions. At the same time, taxis may be seen as a

lighthouse project for BEV usage in general: Taxi passengers will gain the

opportunity to try out an electric car on the passenger seat and some may get

convinced to buy one at a later stage if they are satisfied with the quality of the

electric taxi service.

This study aims to provide an overview about possible impacts of using BEV for

Berlin’s taxi business on a large scale. To provide a high quality service, there are

several issues that have to be addressed prior to the introduction of electric taxis.

Among them is the question of where and when taxi drivers should recharge their

vehicles’ batteries and how many chargers are needed to warrant a smooth service.

With the Berlin taxi business being highly competitive, it is also of major importance

to determine the impact of BEV usage the taxis’ operating cost.

2 Related work and current real-world appliance

The usage of BEVs in taxi fleets has rapidly increased over the last years. In Europe,

the biggest fleet has been announced to operate in Amsterdam using 167 Tesla

Model S.

Worldwide, Shenzhen has the largest fleet with roughly 1000 operative

vehicles.

Electric taxis may now also be found in regions with colder climate

conditions, such as several cities in Estonia.

Several authors see taxi operators as

potential buyers of BEV [8].

For New York City, a large-scale feasibility study comes to the conclusion that

BEV operations for one third of the city’s yellow-taxi taxi fleet would require at least

300 fast chargers and cost 20 million $ annually that could only partly be recovered

by user costs [11]. The study also comes to the conclusion that one fast charging

outlet is required per 13 taxis.

The authors have evaluated possibilities of electric taxis in smaller cities [3] using

a microscopic simulation approach [7, 10]. It could be shown that electric taxi

operation works well under ordinary demand conditions, yet conventional powered

taxi fleets are capable to serve sudden peaks in taxi demand better.

3 General context

Using BEV as taxis leads to some constraints that come both from the taxi business as

such, as well as from the current state-of-the-art technology.

Currently, some 8000 taxi vehicles are licensed to operate in Berlin. These are

operated by around 18000 taxi drivers [5]. Taxi fares are regulated by the city

authority and mainly depend on distance rather than time. During a typical 8-hour

shift, a taxi drives between 100 and 120km in total and yields between 100 to 120 e of

metered fares. A recent study by the authors shows that under normal conditions taxis

are idle (either standing at ranks or cruising) around 50 percent of their online

time [4]. However, during trade fairs and similar events, yields and driving distances

see http://cleantechnica.com/2014/10/21/amsterdam-airport-enlists-167-tesla-taxis/

see http://www.tdm-beijing.org/files/news/Factsheet_GoodPracticeChina_ElectricTaxi_20130409.pdf

see http://www.elektritakso.ee/

for part of the fleet may be twice as high, as it was the case during a railway strike in

October 2014 [9].

In contrast to other cities, there is no standard type of vehicle operating in Berlin.

Both vehicles from the upper and lower end of the car market may be found. Diesel is

still the preferred fuel for taxis, but both hybrid-gasoline as well as natural gas

powered cars may be found. Especially the usage of natural gas was subsidized in the

past.

The amount of available BEV models on the market which are suitable for taxi

usage has increased substantially. Volkswagen (e-Golf), Renault (Kangoo Z.E.),

Nissan (Leaf), Mercedes-Benz (B-Klasse Electric Drive), Ford (Focus Electric) and

Tesla (Model S), all offer potential candidates for taxicabs in different price ranges.

With the exception of the Model S, all vehicles come with a nominal battery capacity

of 20 to 28 kWh, of which around 80% are usable at moderate temperatures and only

around 70% at -20°C.

There are also several case studies for designated electric taxi vehicles. Some of

them focus rather on comfort, high battery capacities and ultra-fast charging [2],

while others are rather proposing more light-weight concepts [1].

Calculations in this paper are based on the Nissan Leaf, mainly because it is the

most popular BEV on the European market. Moreover, it has been on the market long

enough so that detailed consumption statistics exist. An energy consumption of

11 kWh / 100 km at city conditions was measured [6] as a realistic value for a Leaf

without any auxiliary power consumers such as lights, radio or climate control. In

every day operations, a value of 15 kWh / 100 km at an outside temperature of 15 °C

is more realistic.

Auxiliary devices, heating and cooling further increase

consumption, typically between 1 and 3 kW, depending on the weather conditions.

4 Energy consumption and battery charging

To evaluate the effects of satisfying all short-haul taxi demand in Berlin using BEVs,

the whole currently operative fleet is considered. Long-distance taxi trips are

generally not part of this paper, mainly because they are very rare (e.g. 20+ km long

trips account for about 1% of all trips [5]; moreover, trips 50+ km long follow

different taxation rules and do not count as a form of public transport. Several

scenarios taking into account different outside conditions in terms of demand for taxi

trips and the weather have been developed. Table 1 provides an overview about the

mileage and drive times assumed [5, 10].

In the default scenario, all cars are able to charge at a rate of 50 kW under standard

conditions (the rate of the currently available fast charging standards CHAdeMO and

CCS), vehicles are operating 16 hours a day, split into two 8-hour shifts, and their

average driving speed is 30 km/h.

see http://www.spritmonitor.de/de/uebersicht/33-Nissan/1296-Leaf.html?powerunit=2

see http://www.fleetcarma.com/electric-vehicle-heating-chevrolet-volt-nissan-leaf/

Table 1 Assumptions about average daily mileage per vehicle during ordinary and busy days

Standard demand

Increased demand

Work time [h]

Busy mileage [km]

150

225

Idle mileage [km]

Overall mileage [km]

225

300

Average speed [km/h]

Drive time [h]

7.5

Idle time [h]

8.5

It is assumed that taxis start their first shift fully charged and end the second one

discharged, so additional (slow) charging may take place during off-shift time. The

detailed energy consumption under different scenarios is provided in Table 2.

4.1 Standard conditions

With standard climate conditions (i.e. neither air conditioning nor heating in constant

use) and a typical demand for taxi trips (225 km of travel distance a day, of which 70

km are without any customers on board) roughly 42 kWh of electric energy per

vehicle will be consumed, of which at least 26 kWh need to be supplied by fast

chargers during the day. This would require about 30 minutes of charging, separated

at least into two cycles. Considering the moderate Berlin climate conditions, this

scenario represents around half of the year.

4.2 Hot and very hot summer conditions

During hotter summer days, constant usage of air conditioning while driving will

increase the overall energy usage to 57 kWh per vehicle and day. Thus, almost 50

minutes of charging will be required per car (divided into at least three sessions). If

taxi drivers keep on using air conditioning also when standing, energy consumption

climbs to 70 kWh and fast charging time to over 1 h. The car would therefore most

likely need to charge four times during a day. However, climate conditions in Berlin

usually do not require such behaviour.

4.3 Cold and very cold winter conditions

Wintertime operations are somewhat more extreme. Battery charging is highly

temperature dependent and the lower the temperature, the longer the charging process

takes. Charging power may drop to 25 kW and below [2]. At the same time, vehicle

heating increases battery usage. Heating vehicles only during drive time will raise the

average daily energy consumption to 64 kWh. If charging can now only take place at

25 kW, each vehicle would likely need to charge for almost two hours during work

shifts. Should drivers require vehicle heating also during breaks, energy consumption

will rise even further (106 kWh per vehicle), which requires a sizeable charging

infrastructure.

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