Clearing the cloudy crystal balls: Hybrid modelling for energy and climate change mitigation scenarios – A case study for Portugal

Dissertação para obtenção do Grau de Doutor em Ambiente

Energy and greenhouse gas (GHG) emissions scenarios, generated by energy-economy-environment (E3) models, have been used to explore alternative futures and support energy and climate mitigation policy decisions. The uncertainty carried in these scenarios comes from inherent uncertainty of future conditions, reflected in the models input assumptions, and from the models intrinsic features (e.g. technology bottom-up vs. economic top-down models). The present research aims to improve future scenarios generation for energy and climate policy analysis by advancing on E3 modelling, using the Portuguese energy system as the case study. Main objectives include: (i) the assessment on how uncertainty impacts climate-energy policy decisions, (ii) the integration of storylines with energy modelling, providing a coherent context to modelling assumptions; (iii) the development of an hybrid modelling platform, combining the strengths of bottom-up and top-down models. Socio-economic driver was identified as a major assumption contributing to overall uncertainty on GHG emissions scenarios. Therefore, the socioeconomic storylines, built by stakeholders from different knowledge fields, were translated directly into energy modelling assumptions, which proved to increase the robustness of scenario development and its comprehensiveness. Separate use of the bottom-up TIMES_PT and top-down GEM-E3_PT revealed different mitigation options, which have a significant impact on policy design (i.e., low-carbon technologies vs. end-use energy efficiency). In consequence, the hybrid-modelling platform (HYBTEP) was built through the soft-link between TIMES_PT and GEM-E3_PT, combining cost minimizing detailed energy technology choices with sector disaggregated macroeconomic responses, respectively. The research also provides an empirical understanding of how to enable a low carbon transition for Portugal. According to TIMES_PT, it is technological feasible to reduce, in the long term (2050), the country’s energy-related GHG emissions up to 80% below 1990 emissions, being renewable power generation technologies a key for decarbonisation. However, HYBTEP outcomes suggest that, with a carbon tax in line to what is projected at EU-wide level, the country do not accomplish such mitigation target, reducing just 47% its GHG emissions, associated with loss of gross domestic product (GDP) of around 2% (according to revenue-recycling scheme assumed). On the opposite, a subsidy to renewable energy revealed long-term positive impacts at both environmental and economic level (i.e., emissions reduction by 31% and GDP gains above 2.8%). These results highlights the relevance of addressing the impacts to economy while considering the most cost-effective technologies over the development of low carbon scenarios, which is accomplish by HYBTEP modelling platform.

Portuguese Foundation for Science and Technology - scholarship SFRH/BD/27549/2006 and the research project HybCO2 (PTDC/AAC-CLI/105164/2008)