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This paper is a commentary on 'Decarbonizing the Chilean Electric Power System: A Prospective Analysis of Alternative Carbon Emissions Policies' -an article published by Babonneau et al. in the Energies Journal. On the one hand, our aim is to point out and discuss some issues detected in the article regarding the literature review, modelling methods and cost assumptions, and, on the other hand, to provide suggestions about the use of state-of-the-art methods in the field, transparent and updated cost assumptions, key technologies to consider, and the importance of designing 100% renewable multi-energy systems. Furthermore, we end by highlighting suggestions that are key to modelling 100% renewable energy systems in the scientific context to contribute to expanding the knowledge in the field. [ABSTRACT FROM AUTHOR]

Electrical energy storage (EES) is a promising flexibility source for prospective low-carbon energy systems. In the last couple of years, many studies for EES capacity planning have been produced. However, these resulted in a very broad range of power and energy capacity requirements for storage, making it difficult for policymakers to identify clear storage planning recommendations. Therefore, we studied 17 recent storage expansion studies pertinent to the U.S., Europe, and Germany. We then systemized the storage requirement per variable renewable energy (VRE) share and generation technology. Our synthesis reveals that with increasing VRE shares, the EES power capacity increases linearly; and the energy capacity, exponentially. Further, by analyzing the outliers, the EES energy requirements can be at least halved. It becomes clear that grids dominated by photovoltaic energy call for more EES, while large shares of wind rely more on transmission capacity. Taking into account the energy mix clarifies—to a large degree—the apparent conflict of the storage requirements between the existing studies. Finally, there might exist a negative bias towards storage because transmission costs are frequently optimistic (by neglecting execution delays and social opposition) and storage can cope with uncertainties, but these issues are rarely acknowledged in the planning process. [ABSTRACT FROM AUTHOR]

• To date the most complete model for planning South America's power sector. • South America's transition relies on solar, wind, and gas as bridging technology. • Lithium batteries and pumped hydro are the main storage technologies. • Modeling 30 nodes is a good trade-off between complexity and quality of results. • Hydrogen exports aid the integration of renewable generation. Europe and North America have numerous studies on 100% renewable power systems. South America, however, lacks research on zero-carbon energy systems, especially understanding South America as an interconnected region, despite its great renewable energy sources, increasing population, and economic productivity. This work extends the cost-optimization energy planning model LEELO and applies it to South America. This results in the to-date most complete model for planning South America's power sector, with a high temporal (8760 time steps per year) and spatial (over 40 nodes) resolution, and 30 technologies involved. Besides the base case, we study how varying spatial resolution for South America impacted investment results (43, 30, 16, 1 node). Finally, we also evaluate green hydrogen export scenarios, from 0% to 20% on top of the electricity demand. Our study reveals that South America's energy transition will rely, in decreasing order, on solar photovoltaic, wind, gas as bridging technology, and also on some concentrated solar power. Storage technologies equal to about 10% of the total installed power capacity would be required, aided by the existing hydropower fleet. Not only is the transition to renewables technically possible, but it is also the most cost-efficient solution: electricity costs are expected to reach 32 €/MWh from the year 2035 onwards without the need for further fossil fuels. Varying the spatial resolution, the most-resolved model (43 nodes) reveals 11% and 6% more costs than the one-node and one-node-per-country (16) models, respectively, with large differences in investment recommendations, especially in concentrated solar and wind power. The difference between 43 and 30 nodes is negligible in terms of total costs, energy storage, and technology mix, indicating that 30 nodes are an adequate resolution for this region. We then use the 30-node model to analyze hydrogen export scenarios. The electricity costs drop, as hydrogen is not only a load but also a flexibility provider. Most green hydrogen is produced in Chile, Argentina, and northeast Brazil. For future work, we propose to do an integrated energy plan, including transport and heat, for the region, as well as modeling local hydrogen demands. This work aims to inform policymakers of sustainable transitions, and the energy community. [ABSTRACT FROM AUTHOR]

Renewable energy systems are now accepted to be mandatory for climate change mitigation. These systems require a higher material supply than conventional ones. Particularly, they require more copper. The production of this metal, however, is intensive in energy consumption and emissions. Therefore, renewable energy systems must be used to improve the environmental performance of copper production. We cover the current state of research and develop recommendations for the design of renewable energy systems for copper production. To complement our analysis, we also consider studies from other industries and regional energy systems. We provide six recommendations for future modeling: (a) current energy demand models for copper production are overly simplistic and need to be enhanced for planning with high levels of renewable technologies; (b) multi-vector systems (electricity, heat, and fuels) need to be explicitly modeled to capture the readily available flexibility of the system; (c) copper production is done in arid regions, where water supply is energy-intensive, then, water management should be integrated in the overall design of the energy system; (d) there is operational flexibility in existing copper plants, which needs to be better understood and assessed; (e) the design of future copper mines should adapt to the dynamics of available renewable energy sources; and (f) life cycle impacts of the components of the system need to be explicitly minimized in the optimization models. Researchers and decision-makers from the copper and energy sector will benefit from this comprehensive review and these recommendations. We hope it will accelerate the deployment of renewables, particularly in the copper industry. • Copper is required to build energy systems of the future. • Smart integration of renewables can lower the cost of cleaner copper production. • We provide six recommendations to model these systems. • Further efforts are required in the modeling of energy demand and flexibility. • Following these recommendations will enable cleaner and cheaper designs. [ABSTRACT FROM AUTHOR]

Sustainable energy transitions (SET) are complex processes spanning over decades and subject to deep uncertainty from a variety of sources, such as climate change, technology development, and social and institutional contexts. Although this is a recognized issue in SET, previous studies and reviews in this field lack a comprehensive identification of the deep uncertainty sources and the capacities of methods to cope with them. Based on the review of nearly 100 selected references that involve 19 case studies, this review systematically identifies and characterizes these sources of deep uncertainty for the first time. In doing so, it considers the techno-economic, political, and socio-technical dimensions of SET and analyses Decision Making under Deep Uncertainty (DMDU) methods to cope with the specific characteristics of SET. The analysis of the applicability of DMDU methodologies to SET reveals that no predominant methodology covers all aspects of deep uncertainty sources and that the DMDU paradigm could benefit from a multi-method perspective specifically designed for SET. Thus, through some final recommendations, this review aims to provide guidance in the process of deep uncertainty characterization in SET studies and to constitute a basis to support decision-makers in selecting the adequate DMDU method or on generating new dedicated approaches for conducting SET studies under deep uncertainty considering the specific local contexts. [Display omitted] • Characterization of deep uncertainty sources in Sustainable Energy Transitions. • Basis for selection of adequate methods for Decision Making under Deep Uncertainty. • Sustainable Energy Transitions require a specific deep uncertainty treatment method. • A multi-method approach could benefit model-based Sustainable Energy Transitions. [ABSTRACT FROM AUTHOR]

The cost-optimal pathway for moving from the current fossil-fuel based energy system to 100% renewables is still an open question. This work presents the first study that analyses the transition towards a 100% renewable energy system under different spatial resolutions (1-node, 6-nodes electrically isolated and interconnected) and various coupling configurations for the power, heat, transport and desalination sectors. With the LUT Energy System Transition Model for the case of Chile, 12 scenarios were investigated in an hourly resolution and considering more than one hundred energy-related technologies. The results show that: (1) 1-node systems deliver too simplistic results for key metrics; (2) power sector simulations can lead to a strongly distorted resources allocation compared to scenarios that include other sectors; (3) a multi-node model better reflects transmission bottlenecks and local resources, and; (4) the lowest-cost solution is reached when power transmission lines are considered. Thus, it is concluded that a cost-optimal, balanced, and realistic solution to reach a fully defossilised energy system is transitioning towards a multi-node, interconnected, and fully sector-coupled energy system. This can be called, in short, the 'Power-to-X economy', which in the case of Chile would more accurately be a 'Solar-to-X economy', given the high solar share found in the simulations. • 12 scenarios analysed with different spatial resolution and sector coupling setups. • Various coupling setups for the power, heat, transport and desalination sectors. • Electricity is the main energy carrier followed by e-hydrogen mainly for e-fuels. • A multi-node, interconnected and sector-coupled system is the most optimal solution. • First explanation of the 'Solar-to-X economy' concept. [ABSTRACT FROM AUTHOR]