Extending the range of electric vehicles.
The objective of the research project was to evaluate the
effectiveness of auxiliary energy storage systems, used in addition to
a battery, for extending the range of an electric vehicle. Initially,
the work focused around the use of a high speed flywheel to complement
the electric vehicle battery. The work was then extended to cover
auxiliary energy storage in general.
Practical work was carried out using a Bedford/Chloride CF Van, which
was equipped with various sensors by Bristol Polytechnic. Using
measurements carried out on milk rounds in the local area, a driving
cycle was derived, and used to characterise the CF van. This was in
turn used to create a pro-forma for a typical battery current demand
profile experienced during the driving cycle.
Laboratory testing was carried out by repeatedly putting the battery
through this basic current cycle. Further cycles were then derived
from the basic cycle. These were designed to show the effect of
various amounts of auxiliary storage on battery current demand, and
hence overall energy output. These were used with the battery in the
same way as the basic cycle, allowing a comparison of the battery with
and without energy storage.
At the same time as the laboratory work was being done, a computer
simulation of the Bedford CF was written. Having validated the model
against both laboratory results and road test data, it was used to
extend the results derived in the laboratory more generally. This was
done by running simulated driving cycles for different battery
conditions, by varying the performance of the simulated vehicle
transmission, and by using different driving cycles. Flywheel
auxiliary storage was also simulated, and its efficiency varied.
Results from the project establish criteria by which auxiliary
storage systems may be judged, by comparing them with the battery
alone, and also for comparing regenerative and non-regenerative
battery current cycles. This framework is then used to create general
criteria which auxiliary energy storage systems must meet if they are
to be effective. Possible avenues for future work are also put