Designing sustainable and renewable energy systems. Designing renewable energy systems means desining systems that can deal with and even thrive on the variability of solar and wind power. In a fully sector-coupled energy system where heat and transport are partially or fully electrified and synthetic fuels replace fossil ones, different strategies to balance renewable generation are available and come with their advantages and disadvantages: from continent-spanning electricity grids, to large-scale hydrogen storage, to demand response through heat electrification. All of this requires models that depict the necessary spatial and temporal resolution. Climate change is not the only urgent global problem. The design of truly sustainable energy systems also requires examining trade-offs between the energy transition and other issues, such as land use, material requirements, ecosystem impacts, and ramifications for society. As part of efforts in this area, we develop deeper integration of our models with those from other fields, such as industrial ecology.