Optimization of low-carbon multi-energy systems with seasonal geothermal energy storage: The Anergy Grid of ETH Zurich

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Synchronous deposition of volcanic ash and sulfate aerosols over Greenland in 1783 from the Laki eruption (Iceland)

Sulfate aerosols from the 1783–1784 A.D. Laki eruption are widely used as a reference horizon for constraining Greenland ice core time scales, yet the timing of the arrival of the sulfate remains under discussion. Two ice cores from western Greenland, analyzed with high temporal resolution, confirm that sulfate aerosols arrived over Greenland late in 1783, concomitant with the tephra, elevated concentrations of Cd, Bi, and Tl, all indicators of volcanic emissions, and with a short‐lived Rare Earth Elements anomaly. Thereafter sulfate deposition declined rapidly. Very modest concentrations of sulfate in 1784 snowfall, evident in six Greenland cores, suggest a relatively short (less than 1 year) atmospheric residence time and an injection height limited to the lower stratosphere. An improved estimate of the associated stratospheric sulfate burden is calculated and provides an important input for models assessing climatic impacts of this volcanic eruption

Net-zero emissions chemical industry in a world of limited resources

The chemical industry is responsible for about 5% of global CO2 emissions and is key to achieving net-zero targets. Decarbonizing this industry, nevertheless, faces particular challenges given the widespread use of carbon-rich raw materials, the need for high-temperature heat, and the complex global value chains. Multiple technology routes are now available for producing chemicals with net-zero CO2 emissions based on biomass, recycling, and carbon capture, utilization, and storage. However, the extent to which these routes are viable with respect to local availability of energy and natural resources remains unclear. In this review, we compare net-zero routes by quantifying their energy, land, and water requirements and the corresponding induced resource scarcity at the country level and further discuss the technical and environmental viability of a net-zero chemical industry. We find that a net-zero chemical industry will require location-specific integrated solutions that combine net-zero routes with circular approaches and demand-side measures and might result in a reshaping of the global chemicals trade.</p

Direct Instanton Effects in Current-Current Correlators

We compute the effect of small-size instantons on the coefficient function of the chiral condensate in the operator product expansion of current-current correlators. Furthermore, we also compute the instanton corrections associated with four-quark and six-quark operators in the factorization approximation. We discuss the phenomenological implications of our result.Comment: 24 pages, Late

Optimal design of multi-energy systems with seasonal storage

Optimal design and operation of multi-energy systems involving seasonal energy storage are often hindered by the complexity of the optimization problem. Indeed, the description of seasonal cycles requires a year-long time horizon, while the system operation calls for hourly resolution; this turns into a large number of decision variables, including binary variables, when large systems are analyzed. This work presents novel mixed integer linear program methodologies that allow considering a year time horizon with hour resolution while significantly reducing the complexity of the optimization problem. First, the validity of the proposed techniques is tested by considering a simple system that can be solved in a reasonable computational time without resorting to design days. Findings show that the results of the proposed approaches are in good agreement with the full-scale optimization, thus allowing to correctly size the energy storage and to operate the system with a long-term policy, while significantly simplifying the optimization problem. Furthermore, the developed methodology is adopted to design a multi-energy system based on a neighborhood in Zurich, Switzerland, which is optimized in terms of total annual costs and carbon dioxide emissions. Finally the system behavior is revealed by performing a sensitivity analysis on different features of the energy system and by looking at the topology of the energy hub along the Pareto sets

Environmental impacts of carbon capture, transport, and storage supply chains: Status and the way forward

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Effects of emissions caps on the costs and feasibility of low-carbon hydrogen in the European ammonia industry

The European ammonia industry emits 36 million tons of carbon dioxide annually, primarily from steam methane reforming (SMR) hydrogen production. These emissions can be mitigated by producing hydrogen via water electrolysis using dedicated renewables with grid backup. This study investigates the impact of decarbonization targets for hydrogen synthesis on the economic viability and technical feasibility of retrofitting existing European ammonia plants for on-site, semi-islanded electrolytic hydrogen production. Results show that electrolytic hydrogen cuts emissions, on average, by 85% (36%-100% based on grid price and carbon intensity), even without enforcing emission limits. However, an optimal lifespan average well-to-gate emission cap of 1 kg carbon dioxide equivalent (CO2e)/kg H2 leads to a 95% reduction (92%-100%) while maintaining cost-competitiveness with SMR in renewable-rich regions (mean levelized cost of hydrogen (LCOH) of 4.1 euro/kg H2). Conversely, a 100% emissions reduction target dramatically increases costs (mean LCOH: 6.3 euro/kg H2) and land area for renewables installations, likely hindering the transition to electrolytic hydrogen in regions with poor renewables and limited land. Increasing plant flexibility effectively reduces costs, particularly in off-grid plants (mean reduction: 32%). This work guides policymakers in defining cost-effective decarbonization targets and identifying region-based strategies to support an electrolytic hydrogen-fed ammonia industry