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Technology Mix Optimization for Zero-Emission Fleets Adopting a Multi-Criteria Decision Analysis within a Life Cycle Assessment Framework

Creative Commons 'BY' version 4.0 license

Aiming to reduce criteria air pollutant and greenhouse gas emissions, several initiatives have been announced throughout the world to incorporate zero emission buses into public transit agencies within the next 15 years. One example is the California Air Resources Board “Innovative Clean Transit Regulation” with the goal to transform the statewide transit bus fleet by 2040 with zero emission buses. In response, transit authorities face decisions between multiple bus technologies, each with different strengths and weaknesses as well as infrastructure requirements. Furthermore, because the performance of new bus technologies depends on the operating conditions of each transit agency, the results from demonstration projects are not typically applicable to another district.

This dissertation addresses the use of Life Cycle Assessment (LCA) to compare different zero-emission bus (ZEB) technologies for transit districts in the State of California. For LCAs conducted to date, the focus has been on one-on-one bus technology comparisons rather than a combination of bus technologies integrated into bus fleets (mixed fleet). This dissertation extends the traditional LCA approach by using Multi-Objective Linear Programming (MOLP) to identify the optimal ZEB technology mix.

The novelty of this extended LCA is the use of a consistent framework across multiple powertrain types with the same operating conditions. The fleet optimization incorporates essential aspects of a fleet operation such as operational constraints, route length, required infrastructure, and cost. Additionally, a Multi-Criteria Decision Analysis (MCDA) is incorporated to evaluate parameter weighting in the optimization problem, thereby creating an optimization solution that considers real constraints and priorities from stakeholders, users, and regulatory agencies.

The combination of these capabilities (LCA, MOLP, and MCDA) provides a comprehensive tool, including a variety of energy supply chains, which can inform transit agencies in the design of an electric bus fleet comprised by a mix of available and emerging ZEB technologies.

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