• Energy Research

The growth of European wind and solar power capacity is associated with increasing electricity curtailment to manage excess generation and ensure safe network operations. Instead, this surplus electricity could be used to produce hydrogen, thereby reducing the need for fossil-fueled hydrogen production in ammonia and refining industries. Based on historical data, we estimate the potential for surplus electricity from wind and solar power for 27 countries across Europe. Following an optimization-based approach, we determine the cost-optimal design and operation of a system producing hydrogen from surplus electricity, including the option of battery and hydrogen storage. Two potential applications are analyzed: (1) a fuel-saving scenario, where electrolytic hydrogen substitutes fossil-fuel-derived hydrogen, whenever surplus electricity is available, and (2) a fuel-replacing scenario, where hydrogen from surplus electricity fully replaces a subset of fossil-fueled hydrogen production facilities. Our findings suggest that hydrogen from surplus electricity could substitute 30% (1.9 MtH2/y) of fossil hydrogen, reducing ammonia and refinery emissions by 18% (20 MtCO2/y). However, fully replacing fossil-fueled hydrogen production facilities increases hydrogen production costs substantially as it requires costly battery and/or hydrogen storage capacity to balance hydrogen production and supply. Nonetheless, about 19% (1.2 MtH2/y) of the fossil-fueled hydrogen production could be replaced cost-effectively. Environmental Science & Technology, 59 (7) ISSN:0013-936X ISSN:1520-5851

AbstractThe 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 H2leads 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.

In a world where corporate sustainability commitments are increasing, and governments are starting to phase out of renewable energy subsidy schemes, renewable power purchase agreements (PPAs) can act as a substitute to the governmental support. The combination of renewable energy projects placed in multiple locations (multi-location) and based on different technologies (multi-technology) has the potential to offset the volatility of single renewable energy projects and the risk associated with them. This paper presents a stochastic optimization framework to maximize the expected financial performance of multi-location and multi-technology PPAs while minimizing the financial risk associated with them, which is defined as the likelihood of having low financial performance, from the corporate off-taker perspective. This is achieved through the assessment and optimization of multi-location and multi-technology PPA portfolios. Conditional value at risk is applied to reduce the risk of low financial performance while preserving high expected financial gains. The developed framework enables the identification of the optimal trade-offs between expected financial performance and financial risk, and of the corresponding optimal configurations of PPA portfolios. The benefits of multi-technology and multi-location on portfolio risk reduction are demonstrated via the application to two PPAs portfolios, namely, one compounding projects with different technologies located in the same country, and one compounding different technologies across different countries. Results show that higher expected financial gains are obtained by investing in the single, most-convenient PPA project, whereas combining projects reduces the overall financial risk and allows to meet the off-taker energy demand profile with higher expected financial performance. Energy Economics, 109 ISSN:0140-9883 ISSN:1873-6181

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. One Earth, 6 (6) ISSN:2590-3322

Hydrogen is considered one of the key pillars of an effective decarbonization strategy of the energy sector; however, the potential of hydrogen as an electricity storage medium is debated. This paper investigates the role of hydrogen as an electricity storage medium in an electricity system with large hydropower resources, focusing on the Swiss electricity sector. Several techno-economic and climate scenarios are considered. Findings suggest that hydrogen storage plays no major role under most conditions, because of the large hydropower resources. More specifically, no hydrogen storage is installed in Switzerland if today's values of net-transfer capacities and low load-shedding costs are assumed. This applies even to hydrogen-favorable climate scenarios (dry years with low precipitation and dam inflows) and economic assumptions (high learning rates for hydrogen technologies). In contrast, hydrogen storage is installed when net-transfer capacities between countries are reduced below 30% of current values and load-shedding costs are above 1,000 EUR/MWh. When installed, hydrogen is deployed in a few large-scale installations near the national borders. Energy Conversion and Management, 302 ISSN:0196-8904 ISSN:1879-2227

Multi-energy systems can improve the performance of traditional energy systems, where energy carriers and sectors are decoupled, in terms of economic, environmental, and social sustainability, measured as the total cost of energy, emissions per energy demand, and self-sufficiency, respectively. This study assesses the impact that policy mechanisms can have in enabling these sustainability benefits. A mixed-integer linear problem is implemented, which optimizes the design and operation of multi-energy systems to minimize the total annual cost of supplying energy to residential end-users. Four policy types are tested for a Swiss case study, namely a feed-in tariff, an investment support mechanism, a carbon tax, and a regulation-based carbon cap. To assess how the policy impact varies between different end-users, we distinguish between passive consumers, that cannot access subsidies, and prosumers, who can. In our case study, subsidies, such as a feed-in tariff and an investment support mechanism, decrease the cost of energy for prosumers by up to 10%, but increase the cost for consumers by up to 33%, which points to the need of including energy equity considerations when designing policies. The carbon cap and the carbon tax impact all end-users equally, and tend to perform better in terms of reducing emissions. Emission reductions of up to 60% and 39% are observed for the carbon cap and carbon tax, respectively. The feed-in tariff and carbon cap perform best in fostering self-sufficiency and achieve balanced energy autonomy for high policy levels, revealing a trade-off between the different sustainability dimensions. Applied Energy, 344 ISSN:0306-2619 ISSN:1872-9118

Net-zero chemical production can be achieved through electrification, biomass-based processes, and carbon capture, utilization, and storage. However, these net-zero pathways require more resources than business-as-usual processes. One possibility to produce net-zero chemicals at a lower resource consumption is the combination of net-zero pathways based on locally available resources. This study determines the optimal combinations of net-zero pathways for producing chemicals with net-zero emissions that minimize the use of renewable energy, land, and water while complying with local waste biomass and CO2 storage availability. Waste biomass is defined as residue biomass that does not compete for land and water with other sectors. The analysis is performed worldwide at the country level and considers the production of ammonia, methanol, and plastics, which, when combined, account for similar to 5% of the global CO2 emissions. Findings show that, when considering net-zero pathways individually, waste biomass is preferably used for producing ammonia and methanol, whereas carbon capture and storage is preferably deployed for plastics production. At the same time, a mixed strategy using carbon capture, utilization, and storage, and waste biomass, allows one to achieve a net-zero chemical industry with a nearly 60% reduction in energy consumption and 90% reduction in land and water consumption, with respect to single-pathway strategies. Finally, we find that adopting a net-zero portfolio that minimizes water allows water consumption to be reduced by more than 90% and land consumption to be reduced by more than 70% at the cost of an energy increase of only 5%, when compared to the minimum-energy portfolio. Industrial & Engineering Chemistry Research, 63 (31) ISSN:1520-5045 ISSN:0888-5885