Dynamic Modelling and Simulation of Electrochemical Energy Systems for Electric Vehicles

Abstract

The current energy scenery is dominated by fossil fuels, especially oil. This dependency is turning critical due to the reducing reserves, uncertain oil resources, and political and economical ramifications of a concentration of fossil fuel reserves in a limited number of regions. The transportation sector is especially affected by this situation and needs to develop new energy vectors and systems to reduce the oil dependency whilst attending to environmental issues. Therefore, vehicle manufacturers are turning to hybrid and electric vehicles. Hybrid vehicles combine an internal combustion engine (ICE) with energy storage systems, which allows reducing the installed power of the ICE, and consequently the fuel consumption and pollutant emissions. With this power train, the user is capable of driving in a pure electric mode, through the energy storage system (normally batteries), or in a hybrid mode with both ICE and storage for more challenging driving cycles. Electric vehicles are especially interesting due to the exclusion of the ICE, which reduces to zero the emissions, and presents a higher efficiency of the power train and environmentally friendly operation. However, even if these reasons are activating its interest, there are several drawbacks which should be solved before reaching a mass production scale. Some of these issues include the development of energy technologies able to guarantee an adequate vehicle range, attractive power ratings and safe, simple and fast recharge. Nowadays there is no electric energy storage technology which can exhibit both high energy and power densities, necessary to meet range and accelerating requirements. Therefore, there is an intensive research to develop new materials for electrochemical energy devices and to hybridize electrochemical energy systems to reach the necessary power and energy specifications. The most popular technologies are Ni-Mh and Li-based batteries, which present higher energy densities than classic Pb-acid batteries. However, these technologies cannot achieve the range obtained with fossil fuels. Therefore, other energy systems, such as fuel cells or flow batteries are being studied as part of a hybrid electric vehicle power train. Finally, this energy system research should be done taking into account the particular situation of transportation, where the weight, volume and cost of the systems included are relevant for a successful and massive use of the electric vehicle. To carry out this research in the final application stage of electrochemical systems, it is necessary to be able to test, model and simulate this system in real operating conditions.