Abstract

In response to the frequent faults and low efficiency caused by response delay and power imbalance in dual-unit intercooled reheat gas turbine/solid oxide fuel cell (IRGT/SOFC) hybrid systems under multiple operating scenarios, this study proposes a multi-input multi-output (MIMO) long short-term memory (LSTM) neural network for dynamic identification and prediction. By integrating physics-based modeling with data-driven training, the proposed framework captures the transient behaviors of a marine parallel IRGT-SOFC system across varying fuel scenarios. Sensitivity analyses on sampling rate, hidden layer configuration, and learning rate demonstrate that a single-layer LSTM with 50 neurons and 0.01 s sampling interval provides the optimal balance between prediction accuracy and computational cost. The trained model achieved R² values exceeding 0.998 across all key outputs, with MAPE consistently below 0.79% except T_FCavg, effectively predicting power output, SOFC temperature, and overall system efficiency. The proposed model effectively captures the transient response patterns of dual-unit systems under varying fuel input, laying a high-precision modeling foundation for predictive power control of next-generation marine propulsion systems in complex operational scenarios.

Abstract

Geothermal development in abandoned reservoirs with CO₂ recirculation aligns with energy-transition goals, yet more efficient system designs are needed. This study reconfigures multi-stage fractured horizontal well patterns into a fractured closed-loop geothermal system (FCLG), in which injection-production fractures interconnect to create multiple rows of high-conductivity channels for heat extraction. We build numerical models to compare a conventional closed-loop system (CLG), a conventional multi-stage fractured horizontal well system (MSFHW), and the proposed FCLG, and we obtain dynamic fracture conductivity from core displacement experiments under geothermal conditions. The multiphysics simulations reveal three characteristic production stages for FCLG: an initial plateau, a decline, and a secondary plateau. Sensitivity analysis indicates injection temperature governs heat-extraction efficiency most strongly, followed by injection flow rate and temperature difference; lower injection temperatures, lower flow rates, and larger temperature differences improve performance. Relative to MSFHW, FCLG delivers ~1.7× higher heat-extraction efficiency, ~3× longer stable production, a maximum produced-fluid temperature increase of 12.5-19.9 K, and a maximum net thermal-power gain of 8.9-9.4 MW. Even a single-fracture FCLG (SFCLG) outperforms CLG, achieving 2.27× higher efficiency, a 5.5-16.4 K rise in peak produced temperature, and a 2.25-3.6 MW increase in maximum net heat power. These results demonstrate that the FCLG concept and accompanying models can substantially enhance geothermal recovery from abandoned reservoirs, offering a robust framework for high-efficiency energy applications.

Abstract

Data centers, as rapidly growing contributors to
global electricity demand, play a critical role in deep
decarbonization. Meanwhile, regions rich in renewable
energy, exemplified by Qinghai province, China, face high
curtailment rates, with wind and solar curtailment
exceeding 7.3% and 8.9% respectively in 2022. This paper
proposes a strategic solution: integrating data centers
into industrial parks rich in renewable energy to form a
localized green energy consumption ecosystem. This
approach will not only increase the utilization rate of
renewable energy, but also open up new ways for
attracting high-quality industrial investment to
underdeveloped regions with abundant renewable
energy, like Qinghai. The core difficulty lies in designing
mechanisms to incentivize data center investments,
while capturing the nonlinear feedback between policy
choices and market adoption. To investigate the strategic
interactions among key stakeholders, including the
government, state grid corporation, and data center
investors, this study develops a three-dimensional
evolutionary game model that includes carbon penalties,
renewable energy subsidies, and consumer incentives.
This study sets up a case of building data centers in
Qinghai province for calculation and analysis. The results
show that subsidies for investors significantly accelerate
the adoption of renewable energy by state grid
corporation, while modest upfront support for data
center investment can effectively stimulate enterprise
participation and accelerate green uptake on the
demand side. This study offers policy framework and
institutional design path for regions with high power
curtailment rates, such as Qinghai province, emphasizing
the important role of these regions in China’s national
energy transformation and highlighting their potential to
attract green digital infrastructure investment.

Abstract

This study proposes a modeling framework and power system selection process for the deployment of high-payload drones in timber extraction operations, with the objective of promoting sustainable forestry practices. The introduction of such drones is expected to improve labor efficiency and operational productivity by reducing hazardous and physically demanding tasks, and lowering the labor and cost requirements associated with forest road development. To support optimal power system selection, evaluation criteria were established from the perspectives of economic efficiency, operational feasibility, and environmental impact. Simulations were conducted for four candidate power systems, battery-powered systems (BPS), BPS with off-grid charging, series hybrid systems (SHS), and tethered power supply systems (TPS), across payload capacities of 100 kg, 200 kg, and 300 kg. The results indicate a general trend of increasing overall performance scores with larger payloads. While both the BPS and TPS exhibited favorable performance, the operational advantages of the BPS were found to be limited in remote forest environments due to challenges in securing high-voltage grid access and operational interruptions associated with battery replacement. In contrast, the TPS demonstrated superior scalability and operational stability at higher payloads in all weighting scenarios, benefiting from a higher payload-to-airframe ratio and a continuous power supply. These findings suggest that the TPS offers strong potential for large-scale deployment, particularly in the transport of heavy thinning and clear-cut timber.

Abstract

Recycled concrete aggregates and recycled bricks, collectively known as construction and demolition wastes, are renewable resources. Considering the poor performance of recycled aggregate, geosynthetics are generally used to improve its roadability, and the geosynthetics with different strengths have an impact on the interface of the reinforced soil. The monotonic direct shear test on the interface of geosynthetics and reclaimed aggregate are studied based on large-scale direct shear instrument, and consider the influence of normal stress on the interface shear stiffness and damping ratio. Tests showed that: The peak shear stress at the recycled material / geosynthetic interface increases with the increase of the normal stress. The dilatancy of the unreinforced test is stable in the late shearing period, while the dilatancy of the reinforced test is increasing. The peak strength and residual strength of the interface are obviously improved with the increase of the strength of the glass fiber reinforced material, but the integrity of the soil is reduced to a certain extent, which affects the cohesion.

Abstract

Since 2001, China’s photovoltaic (PV) industry has evolved from a latecomer to the global leader. Grounded in innovation ecosystem theory, this paper examines the development of China’s PV industry through four stages characterized by technology, market, finance, and policy dynamics: Pre-commercialization R&D accumulation stage (prior to 1995), Initial commercialization stage driven by rapid international market expansion (1996-2008), Technology and industrial chain integration stage accelerated by domestic market growth (2009-2017), Intense competition and phase out stage under widely technological diffusion and overcapacity (post-2018). This study reveals that policy tools should strategically coordinate technological, market, and financial elements to guide innovation ecosystem participants, thereby facilitating the evolution of the whole innovation ecosystem in different development stages. This coordinated governance mechanism proves critical for achieving leapfrog development in emerging industries.

Abstract

Data-driven fault inference in building HVAC systems faces a critical challenge due to the absence of labeled operational data in the target working condition. To address this, transfer learning-based methods are proposed to leverage inference knowledge from labeled datasets acquired in distinct operational contexts, defined as the source domain. However, these methods typically assume that fault categories between source and target domains are the same. This assumption is invalid in real applications where the target domain often contains fewer fault types than the source. Such scenarios may introduce negative transfer caused by irrelevant source domain categories. To solve this problem, a novel dual-weight partial domain adaptation (DW-PDA) method is proposed, which implements selective knowledge transfer by the class-wise adversarial learning for category-aware feature alignment, and a dual-weight mechanism for dynamic sample selection. Experimental results on both HVAC air-side and water-side datasets demonstrate the effectiveness of the DW-PDA in partial domain adaptation scenarios. Compared to the global domain adaptation methods, the average accuracy improvement of the DW-PDA is 30.87% and 25.26% in AHU and chiller tasks, respectively.

Abstract

Compressed air energy storage is considered one of the most promising large scale energy storage technologies due to its advantages of large scale, high efficiency and long service life. Isobaric system, compared to isochoric system, can effectively improve the energy density of the system. Therefore, this paper proposes an isobaric system with water compensation. The thermodynamic model of the system is established, and it is used to analyze the effects of molten salt low temperature, compressor polytropic efficiency, turbine polytropic efficiency, gas storage pressure and depth on the system performance. The analysis results show that within a certain range, increasing the molten salt low temperature, compressor polytropic efficiency, and turbine polytropic efficiency can effectively improve the round-trip efficiency of the system. Moreover, the deeper the underground depth, the higher the round-trip efficiency and energy density of the system. The increase in gas storage pressure can enable the system to achieve a higher energy density.

Abstract

Shared Socioeconomic Pathways (SSPs), which provide national-level scenarios for population and gross domestic product (GDP), are useful for analyzing future energy demand. However, their spatial resolution is too coarse to apply them for urban energy management, which typically requires data at the building or district level. Unfortunately, it is unclear how to downscale GDPs whose spatially detailed historical data are unavailable. To address this issue, this study develops a method for downscaling GDP scenarios from the national level to the building level while ensuring consistency with SSPs. We leverage micro-scale auxiliary variables and apply the power law, which captures the rank-size relationships underlying gross products, to accurately project the GDPs for each SSP. The proposed method is applied to project the building-level GDP under the SSPs for Yokohama, Japan. Furthermore, we assess the model’s applicability to other regions.

Abstract

In high-density cities, anthropogenic heat (AH) emissions are an important factor affecting the urban heat island effect. Especially in summer, the heat stress on the outdoor thermal environment caused by AH emissions cannot be ignored. Due to the oversimplification of AH emissions in previous studies, the spatial differences in the role of different types of AH emissions in the urban thermal environment are not well understood. Therefore, this study proposes an interpretable machine learning framework to model and predict AH emissions and their thermal impacts in dense urban areas, with a focus on quantifying the differential responses of land surface temperature (LST) to sector-specific AH emissions (e.g., buildings, industry, transportation). The results demonstrate that the ExtraTreesRegressor model achieves optimal performance, with a coefficient of determination (R²) of 0.8. The Shap analysis reveals that, among the seven types of selected urban factors, NDVI, Building-related AH, and Industry-related AH are the key driving factors of LST across Shenzhen, China. Sensitivity experiments demonstrate that any reduction in the AHE intensity results in a corresponding decrease in the spatially averaged LST. Under an 80% reduction in AHE, the mean LST in Shenzhen decreased by 0.57 °C (buildings), 0.46 °C (industry), and 0.23 °C (transportation). Furthermore, the cooling response to AH reduction varied spatially across Shenzhen. A reduction in building or industry-related AH emissions induced significant cooling areas in inland districts, including Guangming, Longhua, Pingshan, and parts of Futian. In contrast, coastal districts such as Nanshan and Futian exhibited more pronounced cooling effects when transportation-related AH emissions were reduced. This study elucidates the mechanistic response of urban thermal environments to spatially heterogeneous and source-specific AH emissions,providing novel insights and a theoretical foundation for developing targeted urban heat mitigation strategies.