Transition to sustainable transport systems : Perspectives on alternative fuels, collaborative development of coherent scenarios and policy analysis for the case of the Danish energy system

Abstract

As the urgency of tackling climate change becomes apparent, the transition to lowcarbon energy systems requires unparalleled and concerted efforts. The continuous growth in global mobility demand, coupled with a long-lived dependence on fossil energy resources, poses a significant challenge in ensuring the future sustainability of the transport sector. This calls for actions advancing technological developments, establishing regulatory frameworks and promoting social changes to reduce the impact of mobility demand on energy use and environment. At the same time, uncertainty around the evolution of this interdependent socio-technical system implies that its future configuration cannot be forecasted, but rather shaped, by initiating and supporting scenario discussions among stakeholders and policy-makers. This process in turn can clarify suitable interventions, implementation barriers, potential synergies, expected acceptability and effectiveness of policy instruments. This Ph.D. thesis builds on the research field of energy systems analysis to explore the formulation of robust energy and transport planning. This study investigates the case of the Danish energy and transport system, bringing advancements to two main components: (i) integrated energy and transport modelling, and (ii) collaborative scenario development and policy analysis. A critical review of the structure of existing models covering the energy and transport sectors lays the basis for this research. Advantages, potentials and challenges of each model type are identified, as well as the parameterization of key features within the transport sector, with focus on behaviour representation. Harnessing the strength of energy system modelling in uncovering, assessing and comparing integrated system configurations, this thesis further develops the optimization energy system model TIMES-DK, by performing a technology characterisation of fuel production technologies and by extending the representation of fuel supply chains. In particular, for residual biomass, environmental considerations are introduced and a comprehensive resource assessment is performed through soft-linkage with a spatially and temporally detailed power and heat model. The performed socio-economic optimization on residual biomass reveals the attractiveness of the gasification route with subsequent Fischer–Tropsch synthesis for the production of biofuels to supply the heavy segments of the transport sector. The possibility of recovering the excess heat from the plants in the district heating grid and returning bioashes for restoring soil nutrients and carbon in the agriculture fields contributes to the feasibility of this technology option. The second component of this Ph.D. thesis enriches the development of coherent and policy-relevant energy and transport scenarios, by embedding quantitative energy and transport modelling within an iterative and participatory process. First, the use of driving forces in bridging qualitative and quantitative tools for scenario creation and analysis is explored, hereby identifying the drivers with potential high impact and uncertainty on the future system, followed by the translation into model attributes and their quantification. Second, recognising the need for a shared understanding and interpretation of future scenarios, a Scenario Interface tool is developed to support the communication and connect the academic and technical perspective with the energy and transport policy arena. Third, the tool is applied to assess the impact and effectiveness of combined technology and regulatory measures for the energy and transport sectors in complying with emission reduction targets. The advanced participatory approach brings the advantage of simultaneously combining a set of consistent assumptions on the future energy and transport system, and quantitatively assessing the impact of those changes on model results. The positive implications for policy-making include a more transparent and democratic discussion around system transitions, along with favouring mutual learning and awareness, both from the perspective of advancing model development and the recognition of critical aspects of the energy system. From a modelling viewpoint, stakeholders’ inputs contribute to the validation of assumptions and in determining the feasible spectrum of policy change. The policy analysis highlights the higher impact of market signals in the form of taxes and subsidies in complying with energy and climate targets. Restrictions on fossil fuels also prove effective in reducing carbon emissions in inland transport, when considering introduction and retirement profiles of vehicles. Moreover, the integrated multi-sectoral model can inform on synergy and competition dynamics among policy instruments for the coherent design of policy packages.