Spherical nematics with a threefold valence

We present a theoretical study of the energetics of thin nematic shells with two charge one-half defects and one charge-one defect. We determine the optimal arrangement: the defects are located on a great circle at the vertices of an isosceles triangle with angles of 66 degrees at the charge one-half defects and a distinct angle of 48 degrees, consistent with experimental findings. We also analyse thermal fluctuations around this ground state and estimate the energy as a function of thickness. We find that the energy of the three-defect shell is close to the energy of other known configurations having two charge-one and four charge one-half defects. This finding, together with the large energy barriers separating one configuration from the others, explains their observation in experiments as well as their long-time stability.Comment: 8 pages, 7 figure

Prospective LCA of alkaline and PEM electrolyser systems

This prospective life cycle assessment (LCA) compares the environmental impacts of alkaline electrolyser (AE) and proton exchange membrane (PEM) electrolyser systems for green hydrogen production with a special focus on the stack components. The study evaluates both baseline and near-future advanced designs, considering cradle-to-gate life cycle from material production to operation. The electricity source followed by the stacks are identified as major contributors to environmental impacts. No clear winner emerges between AE and PEM in relation to environmental impacts. The advanced designs show a reduced impact in most categories compared to baseline designs which can mainly be attributed to the increased current density. Advanced green hydrogen production technologies outperform grey and blue hydrogen production technologies in all impact categories, except for minerals and metals resource use due to rare earth metals in the stacks. Next to increasing current density, decreasing minimal load requirements. improving sustainable mining practices (including waste treatment) and low carbon intensity steel production routes can enhance the environmental performance of electrolyser systems, aiding the transition to sustainable hydrogen production

Present and future cost of alkaline and PEM electrolyser stacks

We use complementary bottom-up and top-down approaches to assess the current cost of AE and PEM stacks and how the costs are expected to come down by 2030. The total AE and PEM stack cost reduce from a range of 242–388 €/kW and 384–1071 €/kW in 2020 to 52–79 €/kW and 63–234 €/kW in 2030 respectively. The main drivers of these cost reductions are an increased current density and a reduction and/or replacement of expensive materials with cheaper alternatives. To a lesser extent, manufacturing and labor costs reduction is expected due to mass manufacturing at a GW scale. The total cost decrease is less prominent for AE than PEM due to AE's maturity. The uncertainty range for PEM stacks is due to the low TRL associated with the advanced design PEM stack.</p

Present and future cost of alkaline and PEM electrolyser stacks

We use complementary bottom-up and top-down approaches to assess the current cost of AE and PEM stacks and how the costs are expected to come down by 2030. The total AE and PEM stack cost reduce from a range of 242–388 €/kW and 384–1071 €/kW in 2020 to 52–79 €/kW and 63–234 €/kW in 2030 respectively. The main drivers of these cost reductions are an increased current density and a reduction and/or replacement of expensive materials with cheaper alternatives. To a lesser extent, manufacturing and labor costs reduction is expected due to mass manufacturing at a GW scale. The total cost decrease is less prominent for AE than PEM due to AE's maturity. The uncertainty range for PEM stacks is due to the low TRL associated with the advanced design PEM stack.</p

Stakeholder perspectives on the scale-up of green hydrogen and electrolyzers

Green hydrogen is a promising alternative to fossil fuels. However, current production capacities for electrolyzers and green hydrogen are not in line with national political goals and projected demand. Considering these issues, we conducted semi-structured interviews to determine the narratives of different stakeholders during this transformation as well as challenges and opportunities for the green hydrogen value chain. We interviewed eight experts with different roles along the green hydrogen value chain, ranging from producers and consumers of green hydrogen to electrolyzer manufacturers and consultants as well as experts from the political sphere. Most experts see the government as necessary for scale-up, by setting national capacity targets, policy support and providing subsidies. However, the experts also accuse the governments of delaying development through overregulation and long implementation times for regulations. The main challenges that were identified are the current lack of renewable electricity and demand for green hydrogen. Demand for green hydrogen is influenced by supply costs, which partly depend on prices for electrolyzers. However, one key takeaway of the interviews is the skeptical assessments by the experts on the currently discussed estimates for price reduction potential of electrolyzers. While demand, supply, and prices are all factors that influence each other, they result in feedback loops in investment decisions for the energy and manufacturing industries. A second key takeaway is, that according to the experts, current investment decisions in new production capacities are not solely dependent on short-term financial gains, but also based on expected first mover advantages. These include experience and market share which are seen as factors for opportunities for future financial gains. Summarized, the results present several challenges and opportunities for green hydrogen and electrolyzers, and how to address them effectively. These insights contribute to a deeper understanding of the dynamics of the emerging green hydrogen value chain

Detailed modelling of basic industry and material flows in a national energy system optimization model

National energy system models are often ill-equipped to examine the interconnections between material and energy systems, and the tradeoffs between energy or material use of limited resources are left unaddressed. An adapted energy system model (IESA-Opt) combined with a revised dataset, including 22 new material flows, 33 new processes, and revisions to existing processes, broadens the range of solutions. We show that including additional detail in the major energy-intensive material production sectors has a significant impact on the results of a net-zero emissions scenario for the Netherlands. The result is different optimal technology investment pathways compared to the previous scenario, and total system costs that are 0.8 % lower over the time horizon. The results highlight the value of explicitly including detail on energy-intensive material and industry in analyzing interactions between sectors – particularly waste, chemicals and fuel production – and points to improvements in energy system modelling for industry

Implications of a Paris-proof Scenario for Future Supply of Weather-dependent Variable Renewable Energy in Europe

To meet the European Union's 2050 climate neutrality target, future electricity generation is expected to largely rely on variable renewable energy (VRE). VRE supply, being dependant on weather, is susceptible to changing climate conditions. Based on spatiotemporally explicit climate data under a Paris-proof climate scenario and a comprehensive energy conversion model, this study assesses the projected changes of European VRE supply from the perspective of average production, production variability, spatiotemporal complementarity, and risk of concurrent renewable energy droughts. For the period 2045–2055, we find a minor reduction in average wind and solar production for most of Europe compared to the period 1990–2010. At the country level, the impact of climate change on average VRE production is rather limited in magnitude (within ±3% for wind and ±2% for solar). The projected mid-term changes in other aspects of VRE supply are also relatively small. This suggests climate-related impacts on European VRE supply are less of a concern if the Paris-proof emission reduction pathway is strictly followed. Based on spectral analysis, we identify strong seasonal wind-solar complementarities (with an anticorrelation between -0.6 and -0.9) at the cross-regional level. This reduces the demand for seasonal storage but requires coordinated cross-border efforts to develop a pan-European transmission infrastructure. The risk of concurrent renewable energy droughts between a country and the rest of Europe remains non-negligible, even under the copperplate assumption. Central Western European countries and Poland are most vulnerable to such risk, suggesting the need for the planning of adequate flexibility resources