Abstract

Decentralized energy systems and empowerment of local actors are critical for achieving climate neutrality. This work introduces EC²ellular grid, a hierarchical, multi-layered architecture in which individual Energy Community (EC) cells coordinate as building blocks of larger positive energy regions (PERs). Each cell combines local autonomy, real-time peer-to-peer (P2P) negotiation, and edge-based control to optimize local generation, consumption, and flexibility. We validate this approach via a real-world small office/home office (SOHO) pilot, showing clear improvements in renewable self-consumption and active grid support. The study demonstrates that the EC²ellular architecture improves renewable energy utilization and grid resilience while fostering community participation. The results suggest that EC²ellular grids offer a scalable blueprint for future smart grid, aligning distributed energy resources with decarbonization goals.

Abstract

This study investigates water–gas displacement in carbonate reservoirs via in situ X-ray micro-CT. Miniature cores were scanned at staged conditions: connate water, 0.5 PV, 1 PV, and 50 PV. The images were processed to track the pore-scale evolution of gas–water distributions. Results show that during initial charging, gas preferentially occupies large pores with lower entry pressures, bypassing bound water in small throats. In the early flooding stage (0–0.5 PV), the wetting phase forms and thickens water films along pore walls, only compressing gas slightly and yielding limited mobilization. With continued injection (0.5–1 PV), gas is progressively removed from small to medium throats, while macropore gas remains largely unchanged. After substantial injection (1–50 PV), the water phase percolates and invades macropores, causing a marked drop in gas saturation and higher pore-scale displacement efficiency; however, intensified water blocking restricts gas flow, leading to diminishing incremental gains. During post-flooding stage, residual gas persists in blob-, cluster-, and dot-like morphologies across scales. The in-situ CT evidence clarifies interfacial evolution and trapping mechanisms relevant to mid-to-late development of edge-/bottom-water carbonate gas reservoirs. Corresponding mobilization strategies, such as optimizing drawdown, increasing displacement pressure, and reservoir depressurization, provide a theoretical and technological basis for improving gas recovery.

Abstract

A comparative study using three-dimensional in-situ combustion experiments shows that chemical catalytic ignition (GO-1120-Fe) greatly improves combustion efficiency compared to electric ignition. Chemical ignition increases the oxygen diffusion coefficient by 35%, reaching 4.6×10⁻8m²/s, and boosts thermal conduction power by 29%. The combustion chamber expands in an irregular serrated elliptical shape at a rate of 35.2 cm³/min, which is 43% faster than with electric ignition. Additionally, the coke zone grows 2.6 times faster under chemical ignition (7.14 cm³/min) than with electric ignition, permeability (1822-1962 10-3μm²).This research confirms that chemical ignition effectively optimizes mass and heat transfer, improving the coke zone structure and providing valuable theoretical support for the application of in-situ combustion technology.

Abstract

In recent years, efficient energy storage technologies have become a key factor restricting energy transition and development. Compressed air energy storage (CAES), due to its high reliability, low cost, and minor environmental impact, has gradually emerged as a promising technology for large-scale, long-duration energy storage. To overcome site limitations and utilize geothermal energy, an integrated system combining compressed air energy storage, geothermal utilization, and an organic Rankine cycle (ORC) was proposed. The power output and heat transfer processes of the integrated system under long-term operation were simulated. Seasonal variations in compressor power consumption, power generation, and round-trip efficiency were calculated, and the enhancement effect of the ORC on system round-trip efficiency was confirmed. Furthermore, the influence mechanisms of mass flow rate and compression pressure on system performance were investigated. The results revealed that both production temperature and power generation exhibited seasonal periodic variations with gradual annual declines, while coupling with the ORC improved the round-trip efficiency of the integrated system. With increasing mass flow rate and compression pressure, the round-trip efficiency was reduced. This study provides theoretical support for the design and optimization of CAES systems utilizing hot dry rock resources and demonstrates significant application potential and research value.

Abstract

Understanding the adsorption/desorption kinetics of adsorbate-adsorbent is critical for optimising the adsorption-based cooling systems, where heat and mass transfer strongly affect specific cooling power (SCP). In an adsorption chiller, adsorption and desorption occur at constant pressure and are driven by temperature swing of the adsorbent. In this study, the kinetics of the water/MIL-101(Cr) pair are experimentally investigated under such conditions using the Large Temperature Jump (LTJ) method.MIL-101(Cr) powder loosely packed in an aluminium pan. Adsorbent layer height is varied (1.3, 2.6, and 3.9 mm) while maintaining a fixed mass of 0.3 ± 0.001 g. Measurements are performed at water vapourpressures of 1.2 kPa and 5.6 kPa, corresponding to evaporator and condenser temperatures of 283 K and 308 K, respectively. The pan base temperature is changed from 320 K to 298 K (adsorption) and 324 K to 338 K (desorption). Instantaneous uptake data are fitted using the Linear Driving Force (LDF) equation, which provides good agreement across all tested heights. The characteristic time(τ) increase with adsorbent bed height, indicating greater mass transfer resistance in thicker layers. The highest SCP (5.1kW/kg) is achieved for the thinnest bed (1.3 mm), while SCP decreases nearly linearly with increasing bed thickness. Under conservative operation (80% cycle utilization), the SCP remains substantial at 3.2kW/kg for the thinnest bed.This study further demonstrates that assigning shorter duration to desorption than adsorption enhances SCP. This strategy aligns with the faster desorption kinetics and enables more frequent cycling without compromising net water uptake.These findings underline the potential of MIL-101(Cr) as a high-performance adsorbent and provide useful design guidance for optimizing MOF-based adsorption chillers. However, practical implementation must account for the trade-offbetween enhanced kinetics and increased system thermal mass in thin-layer configurations, reinforcing the need forintegrated system-level optimization.

Abstract

Buildings account for around 40% of the world’s primary energy consumption. The growing energy demand from the building sector highlights the critical need for sustainable heating, ventilation, and air conditioning (HVAC) systems that can maintain occupant thermal comfort at a lower energy cost. This study focuses on utilizing a PCM-based thermal energy storage (TES) system for developing a sustainable HVAC solution. For this, the thermal performance of the shell-and-multitube TES system was evaluated experimentally during HVAC operation. The TES achieved mean temperatures of 117-124°C and 55-67°C at the end of subsequent charging and discharging cycles, respectively. With the application of the TES system and proper water flow rate regulation, the heating capacity of the HVAC system can be varied between 4.12 kW and 2.76 kW, based on load requirement. The thermal comfort analysis of the TES coupled fan coil unit (TES-FCU) system showed that higher FCU water flow rates improve heat transfer and help in achieving indoor temperatures of up to 23.42°C, with 40.86% relative humidity. Out of the 5 operating cases tested, case 1 (PMV: -0.09, PPD: 5%) and case 2 (PMV: -0.39, PPD: 8%) complied with ASHRAE 55 thermal comfort standards for Delhi’s winter climate. The results demonstrated the importance of the TES system, FCU speed, and water flow rate for achieving thermal comfort and sustainable heating solutions for cold regions.

Abstract

The energy- and cost-efficient operation of industrial energy supply systems is challenging for conventional rule-based control strategies. Operational control algorithms, such as deep reinforcement learning or model predictive control, can improve the operation strategy, but are often benchmarked against simulation without the transfer to the real world. This work presents a Python framework for the development, benchmarking and simulation-to-real transfer of optimized control strategies. The framework application is demonstrated on the heating network of the ETA Research Factory, a representative industrial use case. The implementation is based on the eta_utility library to provide standardized environments and connectivity. The simulation model is based on the ThermalSystemsControlLibrary, which is a Modelica library and models the physical components, automation data model and conventional control strategy. Parameter identification is used to fine-tune selected simulation model parameters and minimize the simulation-to-real gap. Validation experiments are performed with the conventional control strategy for both the real system and the simulation model. During a 24-hour period, the simulation model shows a relative error of -13.3 % for electrical energy consumption and -11.6 % for gas consumption compared to the real system. This framework enables future research to develop and evaluate control strategies in a real-world industrial energy supply system, and it can be used for comprehensive experiments. In future work, various optimization algorithms should be implemented, benchmarked, and compared.

Abstract

Mediterranean cities face major challenges at the crossroads of energy poverty, air pollution, and climate change, where winter wood burning and summer overheating increase health risks and social inequalities. This study develops a rooftop nexus framework that links energy, water, food, biodiversity, and health benefits to assess building-scale measures like photovoltaics (PVs), green roofs, and hybrid options across Local Climate Zones (LCZs). Using Ioannina, Greece, as a case study, LCZ mapping was performed and combined with morphological scaling to estimate rooftop availability for interventions. Scenario analysis at this stage considered PV deployment and measured health impacts from PM2.5 reduction by replacing wood combustion with ongoing advances in green roof benefits. Results indicate that LCZ-specific rooftop interventions can generate enough electricity to replace residential wood burning, leading to significant decreases in PM2.5 exposure and related premature deaths. Importantly, connecting LCZ types with socio-economic vulnerability shows that targeted rooftop interventions, combined with energy-sharing schemes, can meet both climate mitigation and equity goals. This research emphasizes the potential of LCZ-informed rooftop strategies as an adaptable framework for health-centered, climate-resilient changes in Mediterranean cities.

Abstract

In carbon capture, utilization, and storage (CCUS) systems, the wellbore cement sheath serves as a critical barrier to ensure the safety and effectiveness of the entire system. Its integrity is directly related to the long-term storage performance of carbon dioxide. During cementing, expansion and shrinkage resulting from cement hydration are primary causes of stress concentration, micro-fracture development, and interfacial bond failure. However, conventional cementing monitoring methods are limited to capturing the cement sheath condition at discrete measurement points or specific time instances, which falls short of the requirements for long-distance and real-time continuous monitoring. As a distributed optical fiber sensing technology, optical frequency domain reflectometry (OFDR) offers high precision, high sensitivity, and high spatial resolution, enabling accurate strain monitoring of target objects. This study employs optical frequency domain reflection technology to conduct calibration tests on both bare and tight-sheathed optical fibers, as well as strain monitoring tests at the first interface during the cement hydration process. The differences in monitoring performance between bare and tight-sheathed fibers are investigated, and the strain evolution at various locations of the first interface throughout cement hydration is elucidated. The results demonstrate that OFDR-based optical fiber monitoring technology can accurately track interfacial strain variations and cement expansion-shrinkage behavior during the cement hydration process in CCUS well cementing. The research results can provide reference and guidance for optical fiber monitoring of cement hydration and integrity evaluation of cement sheath in CCUS injection wells.

Abstract

Small modular reactors (SMRs) are gaining traction in providing clean nuclear energy due to cost-effectiveness, less complexity, and safer than conventional nuclear power plants (NPPs). However, installing SMRs in permafrost regions presents challenges due to ground thawing caused by reactor heat. This paper proposes an innovative artificial ground freezing (AGF) method using hybrid thermosyphons that utilize cold environmental air in winter and excess heat from SMR in summer. In this way, the ground can be continuously cooled throughout the year without the need for additional electrical energy. A three-dimensional numerical model of the ELENA SMR in Iqaluit, Canada, is developed, incorporating thermosyphons around the reactor structure. The results indicate significant improvement in ground freezing conditions, with up to 58% reduction of thawing radius. Further design refinements and parameters optimizations are expected to enhance the AGF effectiveness. This concept will be useful in reducing greenhouse emissions and providing a viable solution for SMR deployment in permafrost regions.