EVS25

,


Introduction
CITYELEC strategic project was launched October 2009, and with a budget of €19.0 million financed partially by the Spanish Ministry of Science and Innovation, represents a milestone in the vehicle electrification R&D initiatives in Spain.The project gathers the efforts of different companies (automotive and electric), city councils of San Sebastian and Zaragoza, research centres and universities.With duration of four years the project will make possible the development of new concepts of electrical vehicles and recharge infrastructures for urban environments.CITYELEC project arises from the urban sustainable mobility concern today, showing that a large portion of the population limits their daily travel to short / medium distances of less than 80 kilometres, often within urban agglomerations.CITYELEC project is focused on the key elements both in vehicle and infrastructure, for developing new concepts of electrified mobility in urban environment.This approach is carried out from high level specification (urban mobility needs) to low level product definition, with an integrated point of view (taking into account both infrastructure and vehicle), in order to create a electric vehicle fleet optimized for the mobility requirements of the cities participating in the project.The project will last four years (2009 -2012) and will experiment and validate EV on the road for a period of a year (2011).Its aim is to come up with conclusions and recommendations by autumn 2012.In this paper a compilation of the results obtained so far, and the global approach methodology are shown.

High level CITYELEC requirements
CITYELEC global and integrated approach aims to develop an electric vehicle fleet and the required infrastructure, starting from the urban mobility and traffic flow data from cities. Therefore, urban mobility data from two city councils participating in the project has been used for the high level requirements definition.Two type of different city topologies (compact and dispersed), and consequently different urban mobility demands are represented by the two different cities (both in the north of Spain, San Sebastian and Zaragoza).In the following lines the results of the compact city (San Sebastian) will be explained as an example, but the same methodology has been carried out with the dispersed city (Zaragoza).

Urban transport mobility data
San Sebastian is a compact city (185.000habitants) in the north of Spain, and the urban mobility data collected in order to define the high level CITYELEC requirements, illustrate this compact topology.The city has low to medium traffic congestion depending on the daytime, but attending to the data from the traffic authorities, and the collected data from some logged vehicles, rush hours are routine and always associated with the start and end of the working day.Even if the city is less than 60 square km, the private vehicle is used in the 34% of the journeys.Fig. 1 shows the modal city transport distribution.Furthermore San Sebastian city is quite oriented to tourism, and this creates a heavy traffic in the central and flat zones of the city, hence these areas where some of the characteristics of the electrical vehicles are very valuable (no pollution, no noise) have been selected for the definition of the electric vehicle specifications: Fig. 2 shows the city centre map and the logging hardware installed in a electric scooter.

Electric vehicle fleet definition
In order to define the electric vehicle fleet and his benefits, is necessary to estimate the overall CO2 emission reduction (taking into account the energy mix in each country), with the technical specifications and number of units of each type of vehicle on the road.The technical specifications of the vehicle and the infrastructure are quite straightforward to define with the traffic and urban mobility data from the city.Table 1 shows the specifications of CITYELEC vehicles.The CO2 emission reduction of the whole fleet is more complex to obtain, but very valuable because is a reference of the environmental benefits in terms of reduction of CO2 emissions.
Within the CITYELEC project a CO2 emission calculator software has been developed, considering the energy mix of each European country, and giving the possibility of comparing an electric vehicle fleet with a conventional based on internal combustion engine.The software is based on backward modeling of the vehicle to be simulated, and different standardizes driving cycles or user defined.Therefore it permits to launch simulations of electric vehicle fleets, mix of different type of vehicles or define a particular vehicle.With these backward simulations and the data from the city, the electric vehicle fleet (number of vehicles) and the overall CO2 emission reduction can be estimated, and the optimal electric vehicle fleet for the selected city can be defined by iterative simulations.Fig. 3 shows the CO2 emission calculator software which allows estimating the optimal electric vehicle fleet.

CITYELEC vehicle electric propulsion system
Results and methodology used to obtain the electric propulsion system specifications of the CITYELEC battery electric vehicles (city-car, citybus, and city-motorbike) will be presented.Results of the previous section were used as input and Model Based Design (MBD) as the methodology.
A vehicles backward modeling and simulation tool in combination with an iterative optimization technique was developed in order to obtain the best specifications of the CITYELEC vehicle"s electric propulsion subsystems.Some targets including the energy efficiency, size & weight, reliability, cost and alignment with international R&D automotive programs and technological road maps were considered on the search and definition of the electric propulsion functional specifications.Different electric propulsion architectures have been evaluated such us: (1) stand alone or propulsion power centralized (electric machine with gear box & differential) and (2) "in wheel motor" or propulsion power distributed (electric machines integrated into the wheels).As an example, table 2 shows the specifications obtained for the electric propulsion system with stand alone architecture of the CITYELEC battery electric vehicle (BEV-City-car).Simulations results corresponding to the iteration from which these specifications were chosen are shown in figure 4. Standard USA FTP-75 driving cycle was used as input.Electric drive operation points (speed, torque) are displayed over the continuous and maximum torque vs. speed characteristic of the electric drive.Most of the operation points are placed below the continuous torque vs. speed characteristic and also concentrated in high efficiency zones.A compromise between functional and cost & reliability targets was also considered.Some R&D actions have been initiated with some Spanish industrial partners with the aim to fulfill the specifications obtained for the different electric propulsion subsystems.Figure 5 shows some results related with the conceptual design of a Permanent Magnet Synchronous Machine (PMSM) for the BEV-city-car with stand alone configuration.In the figure 6, the conceptual design related with the integration of a ten kilowatts axial flux PMSM into the wheel, is presented.

CITYELEC electric infrastructure
In this section, the results and methodology used to size and define the characteristics of the electric infrastructure needed in the cities, under the CITYELEC approach, will be presented.Main objective resides on the design and the sizing of the electric infrastructure subsystems needed to support the CITYELEC vehicles" fleet.Electric infrastructure will be designed and introduced in an environment friendly way, according with the characteristics of the CITYELEC model approach.Some infrastructure subsystems are being developed, with next operational objectives:

Intermediate Energy Store System (IESS):
Intermediate energy store systems between the primary energy source and the electric vehicles" fleet.They will have a great energy & power capacity to guarantee the vehicles" fleet energy supply.This accumulated energy will help on the balancing of the power grid.Electric vehicles could be recharged even during peak hours without increasing the grid power consumption.At off-peak hours the IESS could be recharged, helping on the power plants and electrical system balancing.Thus, they could also attenuate the variability of the renewable power plants.

BEV Recharge Points with Bidirectional
Communication System: Aspects such us: power consumption measurements, user credentials, rate-settings, recharge management, security, etc., should be implemented, controlled and supervised in all the recharge points.A bidirectional communication system between the recharge points and the energy distribution management system is mandatory.

Integration of renewable energy in the cities:
The BEV is as clean as the primary energy used for his recharge.Our cities have some particular restrictions for the introduction of micro grids based on renewable energy.Evaluation studies of the most appropriated technologies for his introduction on the cities are being done in order to develop some prototypes.

Conclusion
An example of global solution approach for the electrification of urban mobility in Spain has been presented in this paper, showing that the optimal sizing of both electric vehicleinfrastructures requires a comprehensive approach, taking into consideration the city topology and urban mobility issues, that will be the electric vehicles and infrastructure defining input data.

Figure 2 :
Figure 2: San Sebastian city centre map and logging hardware installed in an electric scooter.

Fig. 3
Fig. 3 CO2 emission calculator software and backward models inside.

Figure 5 :
Figure 5: Conceptual design of a radial flux PMSM for CITYELEC-BEV city-car with stand alone configuration.

Table 1 :
CITYELEC vehicle specifications for the city of San Sebastian.