SUBAT: An assessment of sustainable battery technology
Introduction
In urban traffic, due to their beneficial effect on environment, electric vehicles are an important factor for improvement of traffic and more particularly for a healthier living environment [1]. This is the case independently of the electricity production mix and is even more beneficial when using renewable energy sources [2]. When analysing electric vehicles, the battery is often considered to be the main environmental concern, be it pertinent or not. Anyhow, the environmental impact of the battery should be assessed. To this effect, the SUBAT project [3] has been performed in the context of the European Sixth Framework Programme. The main aim of SUBAT is to assess different types of traction batteries from a technological, ecological and economical point of view.
Because the main environmental impact can lie in different life stages for different products, an overall approach is a must when wanting to obtain an appropriate assessment. The most adapted approach to compare the overall environmental burden of the different battery technologies is the life cycle analysis.
The first step of the analysis was to study the available technologies for battery and hybrid electric vehicle appliances.
Afterwards, a model for the different battery types has been developed and introduced in the Simapro® software tool. This model allows an individual comparison of the different phases of the life cycle of traction batteries. This makes it possible to identify the heaviest burden on the environment for each life phase of each battery.
The final step is the compilation of these results to obtain an overall environmental score for each battery type. The attribution of these scores is only possible after normalisation and weighting of the intermediate results. The overall scores of the different batteries have been calculated, and the different battery technologies can be ranked according to their environmental performances. The main difficulty encountered while performing this study was the gathering of appropriate, comparable and accurate data.
Finally, to demonstrate the robustness of the results, a sensitivity analysis has been performed.
Section snippets
Lead–acid
Lead–acid represents the oldest and best known electrochemical couple. For vehicle use, it strongly dominates the market of SLI batteries, and is also the most widely used battery for industrial electric vehicles such as fork lift trucks and the like. The main advantage of the lead–acid battery is its low cost compared to other battery types.
For electric road vehicles however, lead–acid presents a considerable drawback due to its low specific energy of typically 30 Wh kg−1. Advanced battery
Generalities
Life cycle assessment (LCA) allows the practitioner to study the environmental aspects and the potential impacts of a product throughout its life from raw material acquisition through production, use and disposal. The so-called “cradle-to-grave” approach makes LCA unique and useful.
LCA is one of the most efficient tools to compare the complete environmental burden of different products. This can be explained by the fact that different products may have burdens in different parts of their life
Environmental impact assessment
When considering the life cycle of the batteries, it appeared that the energy losses in the battery and the energy losses due to the additional mass of the battery have a very significant impact on the environment (Table 3 and Fig. 3). However, this impact is strongly dependent on the way electricity is produced. In the present calculations the European electricity production mix has been used, but the impact would be strongly decreased if renewable energy sources were used more intensively.
Conclusions
A key conclusion is that the impacts of the assembly and production phases can be compensated to a large extent when the collection and recycling of the batteries is efficient and performed on a large scale.
When excluding the energy losses during the use phase (due to the battery efficiencies and the additional masses of the batteries), the following environmental ranking is obtained (decreasing environmental impact): lead–acid, nickel–cadmium, lithium-ion, nickel-metal hydride, sodium–nickel
Acknowledgment
The research underlying this paper has been made possible in the framework of a research project supported by the European Sixth Framework Programme.
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