Conventional Approaches to Overcoming the Range Problem of BEVs
Attempts to overcome the range limitations of BEVs have mainly focussed on designing a vehicle-based
solution such as the plug-in hybrid car. The batteries in conventional electric hybrid vehicles are very small and
necessitate expensive Nickel Metal Hydride (NiMH) technology to provide the durability requirements
necessary for continuous short term cycling of the battery. However, if the batteries were larger and fully
charged they could be used to store sufficient energy from the electric mains supply to travel a reasonable
distance, this is the concept of a plug in hybrid. Unfortunately, since the small NiMH batteries are already very
expensive, enlarging them appears to be a commercially unattractive option. For example, a plug-in hybrid Prius
fleet with only a 30-mile all-electric range requires an additional battery pack costing $10,000-11,000.
One solution is to use Lead acid batteries in conjunction with NiMH batteries to make the economics far more
attractive. If the longer trips using the IC engine were powered from renewable liquid biofuels, the plug in
hybrid concept could provide a complete low carbon transport vehicle. However, this would still be an
expensive and complex solution, and a substantial proportion of the total distance travelled (of the order of 40%
according to figure 16
would still be driven using the IC engine. This would necessitate more renewable
biofuel resources than is likely to be available for a complete low carbon solution.
Another approach is to simply use the BEV for short journeys and swap to another longer distance transport
mode on the occasions longer distances are required such as a conventional car or a train. This could be a local
or out of town car pool. This would have the advantage of allowing high and low mileage drivers to share a
range of vehicles and so reduce the number of overall cars required for their transport requirements along with
overall costs and life cycle emissions. However, a potential limitation of swapping to IC engined cars for long
journeys is that there will be high demand during the holiday/vacation season, whilst many will be left idle
outside these periods. It would also necessitate users to readjust vehicle settings when swapping drivers, and
moving baggage when swapping vehicles.
In the following section we focus on a different approach that could extend the BEV range to virtually any
distance and instead of compromising convenience it has several important advantages over present practices.
This brings us to the main concept for BEVs, the Electric Car Transporter or ELECAT.
Transport Concept 3: Electric Car Transporter ELECAT
Consolidating vehicles by means of an Electric Car Transporter (ELECAT)
It is proposed that a car transporter with an on-board charging system could best solve the distance limitations of
BEVs over longer journeys by extending their range by a combination of ferrying and recharging. This
simultaneously bridges the range gap, releases the motorist from the tedious task of highway driving, and
increases road space. This concept is called the ELEctric CAr Transporter or ELECAT.
This system approach exploits the higher efficiency and low CO2 emissions of BEVs for urban driving and the
high efficiency of the Diesel/biodiesel IC engined vehicle during highway driving via the ELECAT. Although
the chief purpose of the ELECAT would be to extend the range of BEVs, they would initially transport both
conventional IC engined vehicles and BEVs due to the economies of scale and the greater efficiency of road
space this offers.
ELECATs would travel along the major road networks and stop at transfer stations at strategically situated
points to load and unload cars. The road version of the ELECAT is essentially a modified car transporter
powered by an IC engine which also drives an on-board electric generator to charge the BEVs it is carrying see
However, it is also possible to power the ELECAT directly from an electric grid and guideway as
part of a heavy vehicle fleet which is described in section 6.
Since only 3% of journeys and 25% of the total distance travelled by motorists exceed 80km in length in the
ELECATs would only be required for a small proportion of total trips.
43 In "real world" testing using normal drivers, some Prius PHEV conversions may not achieve much better fuel economy than HEVs. For
example, a plug-in Prius fleet, each with a 30 mile all-electric range, averaged only 51 mpg in a 17,000 mile test in Seattle, and similar
results with the same kind of conversion battery models at Google.org. Moreover, the additional battery pack costs $10,000-11,000.
44 In the UK only 2% of journeys exceed 50 (80km) miles in length constituting approximately 77% of total distance travelled