Sammendrag
The energy transition requires secure, affordable, and sustainable solutions to mitigate climate change and other ecological damages. However, energy supply involves complex and diverse resource-intensive sectors in the value chains, requiring a holistic solution. An energy system model developed in GAMS, including a wide range of energy production, transmission, and storage technologies of electricity and fuels, is integrated with life cycle assessment (LCA) to meet the energy demand at minimal total economic-environmental cost of future energy systems with profiles of wind/solar resource in Germany. Twelve categories of monetized life cycle impact (LCI) assessed using Simapro with European Environmental Footprint (EF 3.0) methods, connected with LCI monetary valuation coefficients (MVCs). Results show that completing the full LCA instead of the conventional practice of only considering direct CO2 emissions has a significant impact, increasing total system costs by around 50% and causing large changes to the optimal energy mix. Imposing the full LCA leads to nuclear power and natural gas (NGCC and decarbonized fuel production) increasing their shares while solid fuels (coal/biomass blend with CCS) and renewables (wind and solar) declining, where the inclusion of ecotoxicity and land-use impacts are the main drivers of these trends. Those results are generated under the assumptions of applying geometric mean of MVCs derived from literature data, which are subject to high uncertainty. An uncertainty quantification study reveals that, among the twelve impact categories considered, climate change, land use, ecotoxicity, and resource depletion MVCs dominate the outcome of the energy system optimization. The climate change MVC presents the largest effect on the optimal technology distribution but only a limited effect on the system cost. A higher CO2 price strongly benefits nuclear and biomass with CCS at the expense of natural gas. The land use MVC has the highest effect on the system cost, reducing the shares of biomass and renewables while benefitting natural gas with higher values. Ecotoxicity has the second highest effect on the system cost as it is primarily related to mining/extraction processes that feature in the value chains of all technologies. Solid fuel is suppressed due to coal mining while natural gas gains from higher Ecotoxicity. A higher fossil resource depletion MVC reduces the share of natural gas while benefiting more abundant nuclear and solid fuels. Based on these results, consideration of full LCA is very important for energy system optimization. However, the optimal energy system changes greatly depending on the levels selected for the highly uncertain MVCs. Thus, there is a strong need for future research efforts to reduce the uncertainty bounds of these MVCs to facilitate effective energy system design. These efforts should focus on the most influential impact categories of land use, ecotoxicity and resource depletion.