Case Study Pilot project: Performance of Electric vehicles on small island and in small cities

Case study 1:   Pilot  project:  Performance  of  Electric  vehicles  on  small  island  and  in  small cities (Klaus-Dieter Merz / Joseph Cilia Abertax)

The ongoing pilot project has been running since 2002 on the archipelago Malta, Gozo and Comino, three small islands located in the central Mediterranean. The test areas are made up of low hills, steep-sided valleys and  small  areas  of  plain.  The  total  length of  a  line  trending  NW  to  SE covering the three islands is 50 km.

The EV fleet consists of 20 Reva cars. As the daily distances traveled are limited to a few tens of km, the islands are an ideal place for EV use as a means of reducing emissions and energy use in transport. The cars are used by a variety of owners but it became clear during the test that domestic use for commuting to work and back became dominant.

Figure 1 Reva cars used for daily use and as a field test facility of battery accessories in Industry

No serious accidents were reported and the max car speed of 65km/hr was adequate on the Maltese roads were speed is generally limited to 60 km/hr with some exceptions going up to 70km/hr. Acceleration at traffic lights and roundabouts which is essential is very good and better than that of a similar size of car. Speed drops to about 40 km/hr on most hills and this was found to be somewhat limiting.

Figure 2 Sector Vs average km /car

Motor controlled by a four quadrant DC controller. The heart of the system is an energy management system, which controls the drive and charger while sending the necessary critical information to the driver’s display. The same car today has better performance due to the use of AC drive technology which is highly encourage for a number of reasons;The technology of the cars used is very basic and is still using the DC drive technology. The cars are equipped with a 48V 200Ah tubular plate flooded lead acid battery pack and a separately excited DC

1. cheaper and more robust
2. no maintenance
3. higher efficiency
4. higher peak power to size ratio

  

The range of the car varied from 55km to 65 km depending on the journey and way of driving. The economy switch which limits the current to 200A was very useful especially to ensure a good range when the batteries start to age. The batteries lasted up to 8 years and covered up to 40,000km (approx 800cycles if you take an average of 50km per charge which consumes 9kWhr of electricity i.e. 180Whr/km) for very careful drivers who made regular use of the economy switch. However there were also some surprises especially with lower quality batteries. The cost of the disturbance, disappointment of customers and guarantee claims is surely much more than the cost difference between the lowest and highest quality batteries together with a sophisticated management unit. In our pilot project an online BMU with internet data access was added to each car and this improved the battery performance enormously as we could detect what was the cause of any trouble. Most of the battery problems occurred during winter time and hardly anything during summer. One has to point out here that in this region the  lowest winter temperatures is around 8deg while the highest is around 40deg. Most of the year the temperature is between 20 and 30deg. Colder countries experienced much more trouble.

This pilot project has shown that EVs are economically viable and even the lead acid technology can be ideal for daily transport on small islands or cities worldwide. In order to improve the reliability and reduce maintenance,  AC drives and the use of the highest quality batteries with a proper management unit are a must. Obviously the setting up of the right infrastructure including high technical servicing facilities is vital for the success of EVs.

The EV trend line in figure 3 ranges from 310Wh/km down to 160Wh/km.  These can be compared to 450Wh/km for a petrol engine vehicle with a consumption of 5litres/100km.  From the point of view of emissions, the absence of tailpipe emissions from vehicles moving on the narrow streets of maltese towns and villages offers a great advantage. Transferred emissions from the EV go from 300g CO₂/km to 155g CO₂/km, taking a Malta value of 970g CO₂/kWh delivered to the grid.  The upper value is higher than the CO₂ emissions from current models of small cars but it does represent a situation where one covers less than 5km/day in the EV.  A more realistic daily distance of 15km/day gives a CO₂ emission of 218g CO₂/km, which is similar to current ICE models but higher than the average (120gCO₂/km) Euro5 standard. These emission advantages are further enhanced in cases where a significant fraction of the car fleet carries no catalytic converters or short distances make catalytic converters inefficient.

Figure 3 kWhr/km vs average km/day

The fuel cost of running an EV has been worked out using the standard residential unit cost of €0.17 per unit.  The average distance covered by the fleet was 15km/day; that would cost €0.24/day or €1.68/week. The fuel to run  a small ICE would cost  would cost €1.05/day or €7.30/week at current fuel prices (€1.39/ltr). These are realistic values which consider normal daily usage as well as self-discharge of batteries.

The project proved that with the right team of professional this can be implemented and maintained over a good period of time. Without any doubt high quality and robust design of every part of the drive system has to be ensured in order for the electric car to compete with the quality and reliability of modern ICE cars. Customer feedback also has shown that they expect the design and comfort of electric cars should be of the same quality and standard of the equivalent ICE engines.

Government support is crucial at the initial stage; in fact the three main incentives that were introduced by the Maltese Government have contributed to the success of this pilot project. There is now increased interest in ensuring an increase in the number of electric cars on the road especially in Europe. This is mainly due to the targets set out by the European Union with respect to particle emissions.