arXiv subjects

Emile Emery

Publications and source records attributed to Emile Emery.

3 recordsLinked to original sources

arXiv2026

Energy-Optimal Allocation of Storage in Transmission Grid Networks

The deployment of renewable energy technologies supposes the connection to the power grid of many new, distributed, and variable electricity production facilities. Among the investments deeply needed for a successful shift to clean energy, electricity storage systems are key to provide power reliably, continuously and economically. Here, we are concerned with the energy that must be invested and embodied in storage devices and in production oversizing to cope with natural variations of renewable electricity production, and compensate for any gap between production and consumption. We developed a model to analyze the variation of energy expenses with the location in the grid, capacity of storage and production oversizing. We apply it to a time scale of fluctuations of a few hours that can be taken care of by Li-ion batteries to calculate the optimal storage capacity and production oversizing yielding a maximum value of the ESOI ratio [Energy Stored On energy Invested] at a given satisfaction rate of customer demand. We evaluate these values for a rescaled present-time French power mix and two idealized zero-emission mixes (100% PV and 100% wind). In parallel, using a recently developed model of French transmission grid, a centrality-based analysis shows that locating storage at nodes of maximal installed power minimizes additional Joule losses. These results generalize existing grid-level energy return frameworks to incorporate storage sizing, placement, and transmission losses into a unified assessment of future power grid configurations.

physics.soc-ph↗

arXiv2026

Connecting Electrical Grid Length and Material Stock to Population Density: Comparison of a French-Calibrated Scaling with 35 Electrified Countries

The expansion of global electricity distribution systems necessitates the deployment of massive infrastructure. Assessing its implications from a spatial and material perspective requires an understanding of the core drivers of a distribution grid configuration. Our model samples substation locations using a non-linear relationship with population density and constructs a proxy network applying the Kruskal algorithm. This streamlined approach generates a proxy grid layout at the local scale and provides reasonable aggregate estimates of the total network length at the national scale. Using highly granular population data, this local model reveals a connection between population spread and distribution grid, which appears to persist at larger scales. Potentially driven by the emergent properties of population scaling laws, the aggregated network characteristics appear to be well described by multivariate power laws on aggregated population and area. Benchmarked against reported aggregate data for 35 countries, these results provide new multi-scale tools for characterizing electrical infrastructure and reveal key determinants of distribution grid extent. Combining network length estimates with material intensity data, we derive country-scale inventories of copper invested in medium-voltage lines, bounded by aerial and underground cabling assumptions. The same scaling law directly yields a macro-level proxy for copper mass as a function of population and area, extending the framework toward prospective assessments of material demand in electricity grid expansion.

physics.soc-ph↗

arXiv2025

Time-varying ecological interactions characterise equilibrium and stability

Ecological communities are composed of species interactions that respond to environmental fluctuations. Despite increasing evidence of temporal variation in these interactions, most theoretical frameworks remain rooted in static assumptions. Here, we develop and apply a time-varying network model to five long-term ecological datasets spanning diverse taxa and environments. Using a generalized Lotka-Volterra framework with environmental covariates, we quantify temporal rewiring of interspecific interactions, asymmetry patterns, and structural stability. Our results reveal contrasting dynamics across ecosystems: in datasets with rich temporal resolution, interaction networks exhibit marked rewiring and shifts in cooperation-competition ratios that correlate with environmental stress, consistent, though not always linearly, with the stress-gradient hypothesis. Conversely, in datasets with coarser temporal sampling, networks retain constant interaction sign structure and remain in cooperation-dominated regimes. These findings highlight the importance of temporal resolution and environmental context in shaping ecological coexistence.

q-bio.PE↗