Engineering

Abstract: A solid oxide electrolyser coupled to photovoltaic (PV) power must be operated through production, hot standby and night states rather than at a single design point. This work presents a Modelica dynamic model of the complete balance of plant (BoP) of the 25 kW PROMETEO pilot electrolyser, in which ten control loops and a supervisory state machine are driven by the available PV power through a capacity-factor logic with hysteresis. The stack model is validated against 5 kW polarisation data with a relative error below 3%. The constant-voltage, temperature-tracking strategy of the PROMETEO test campaign is simulated over a clear-sky day and an intermittent-cloud day. With a stack thermal capacity of 25 kJ/K and a direct stack heater, the stack is thermally neutral at 1.32 V/cell: the electrochemical heat balances the insulation losses, the sweep-air loop rests at the blower minimum and the current is tracked through the inlet temperatures alone, giving 14.1 kg of hydrogen at 44 kWh/kg over two days. A voltage sensitivity shows that output and specific consumption are flat within the feasible window, which is narrow: below 1.30 V/cell the stack exceeds its 780 °C limit, above 1.34 V/cell the current becomes steam-limited and the stack overheats, so that a current or steam protection is required. The strategy is robust to an eightfold change of the stack thermal capacity. The sweep-air loop must be disabled outside production and coordinated with the temperature references, otherwise blower and heaters saturate and the stack cools.

Abstract: In previous research, scholars aimed to develop an algorithm that maximizes power output considering these nonlinear characteristics of solar energy, where delays in the circuit reduce accuracy in signal regulation. Therefore, a fuzzy rule-based control algorithm is implemented using the same previous algorithm concept. The previous concept was based on feedforward incremental conductance (FFINC). It has many limitations, thus, the same concept is used here in the fuzzy logic to overcome the previous limitations. And hence proposed algorithm is a novel adaptive control algorithm. Additionally, the proposed algorithm effectively manages the overshoot and undershoot of solar power under varying sunlight conditions. A set of solar air water generator (SAWG) exhibits nonlinear characteristics, including a 12 V, 3 A DC furnace mounted on a sink for even heat distribution. A brushless high speed low power fan is placed next to furnace to capture moisture-laden air and separate it into pure water. These whole parameters integrated and given its name solar air water generator. It is applicable in various area like army, medical and for hydrogen fuel cells in electric vehicles (EVs). Moreover, the study includes a comparative between feedforward-based MPPT and Fuzzy rule based MPPT.

Abstract: Gas well productivity prediction serves as a critical bridge connecting petroleum geology, engineering, and economic evaluation, playing an indispensable role throughout the entire natural gas development process. In response to the challenges posed by the low porosity, low permeability, and strong heterogeneity of tight gas reservoirs, this paper systematically reviews relevant domestic and international research achievements and summarizes five mainstream prediction techniques: analytical methods, numerical simulation, physical simulation, analogical empirical methods, and gas-water two-phase analysis. These methods are comparatively analyzed in terms of their principles, accuracy, applicability conditions, advantages, and limitations. The study indicates that existing approaches still face bottlenecks such as difficulties in multi-scale coupling, inadequate characterization of dynamic parameters, and insufficient integration between mechanistic understanding and data-driven methodologies. Although various methods can be adapted to different stages of the full gas reservoir development cycle, each individual technique has inherent limitations. Drawing on the latest advances in flow mechanisms and intelligent algorithms, future efforts should focus on promoting hybrid modeling that integrates physical mechanisms with artificial intelligence, incorporating multi-field coupling and digital twin technologies to build a full-cycle intelligent productivity prediction system, thereby providing solid technical support for the efficient development of tight gas reservoirs.

Abstract: The rapid development of renewable energy sources is steadily increasing the share of photovoltaics, wind power and hydropower in national electricity systems. The aim of this study was to analyse energy curtailment, defined as the difference between the energy that could be produced (estimated with mathematical models) and the energy actually injected into the grid, for photovoltaic (PV), wind (WE) and hydro (HE) installations in 2020–2025. The results show that total positive energy curtailment was approximately 3,146.3 GWh, of which 96.0% was attributable to large installations above 500 kW. The unused potential was most concentrated in large wind sources. This volume of energy could supply about 1,239,320 electric vehicles for one year, assuming an annual demand of 2,550 kWh per vehicle.

Abstract: Accurate short-term forecasting of photovoltaic (PV) generation, long a concern for grid operators, is increasingly relevant to prosumers as well: the households and small businesses that both produce and consume electricity and must plan storage, self-consumption, and grid export. This paper studies solar forecasting under the constraint that users rarely possess years of historical generation data that data-hungry deep models assume. We release an open-source toolkit that integrates 7 forecasting models, spanning gradient-boosted trees, recurrent and convolutional sequence models, and attention- and basis-expansion architectures. We evaluate the toolkit’s performance on a newly released dataset of two grid-connected 50 kWp PV systems in southwestern Romania, using a strict rolling-origin walk-forward protocol. Across all experiments, XGBoost and LightGBM lead: on the primary site, they achieve 10.4% normalized RMSE against 12.9% for the best deep model, and they already beat a naive persistence baseline after a single month of training data. A dedicated small-window study shows that the boosting advantage is concentrated in the cold-start regime and narrows steadily as history accumulates, from a factor of 2.1 at one month to 1.08 at twelve, with no model saturating inside the available record. A cross-site replication on a second, independent installation reproduces the full model ranking almost exactly (Spearman ρ=0.964), strong evidence that the finding is not a single-dataset artifact. The resulting forecaster is deliberately lightweight and cost-efficient: a few hundred shallow trees over a seven-feature lag/rolling core that trains in under a second per month on a commodity CPU. We publicly release the toolkit and the anonymized two-site dataset to support reproducible prosumer-scale PV forecasting research.

Abstract: Nuclear cogeneration is increasingly proposed to support decarbonisation, partly via hydrogen (H2) production through electrolysis, thermolysis, or a combination of these, but wide-scale adoption is limited by process inefficiencies, high costs, and concerns around nuclear wastes. Recent work demonstrated that gamma radiation, sourced from 137Cs, splits water into H2 at high yields with a TiO2 photocatalyst, extrapolating that world spent nuclear fuel (SNF) stockpiles could generate ~60% of world hydrogen demand, worth ~90 billion USD/y. This is achievable using present technology and would valorise SNF, commonly viewed as a waste, and decouple H2 production from reactor operations, but would limit operations to open fuel cycles, replacing the cooling ponds therein. By combining advanced separations in SNF recycle, partitioning the high-heat radionuclides (137Cs, 134Cs, and 90Sr) responsible for most SNF radiation, and forming these into dedicated sources for hydrogen production, a closed fuel cycle option is afforded. This would lower remaining SNF recycle raffinates to intermediate level waste and free the actinides for further energy generation, turning nuclear wastes from liabilities into resources. In this publication, we discuss the scientific, technological, and regulatory development needed to realise this concept in full. As this H2 production approach is distinct from others on the “colour spectrum”, we propose to call radiolytically-produced H2 “platinum hydrogen”.

Abstract: Rapid urban growth in Latin America challenges municipal solid waste (MSW) man-agement. This study models energy recovery from landfill gas (LFG) and associated carbon credit generation in the Cuernavaca metropolitan area, Mexico. Based on pop-ulation projections (1.47% annual growth) and per capita generation (0.8832 kg capi-ta/day), a landfill with a 10-year lifespan would receive 3.93×106 Mg of MSW, produc-ing 2.65×105 Mg of CH4 over a 21-year horizon, estimated using the US EPA Landfill Gas Emissions Model. Accounting explicitly for gas-collection efficiency (75%), cover oxidation, and excluding biogenic CO₂, enclosed flaring reduces greenhouse gas emis-sions by 66.7%, while modular electricity generation in gas engines (12 MW, staged) achieves 71.8% and delivers 1.12×10⁶ MWh of renewable electricity. Techno-economic analysis indicates financial viability (net present value USD 15.7 million; internal rate of return 20.2%; levelized cost of energy USD 0.065 kWh⁻¹; discounted payback 10 years). Carbon credits contribute 28% of revenue under full baseline crediting (USD 32.4 million) but fall to USD 2.3 million if regulatory flaring defines the baseline, mak-ing additionality the decisive question for credit revenue, but not for project viability. Fuel cells maximize mitigation but are financially unviable; gas engines offer the best overall compromise.

Abstract: Hydrogen compression is a critical interface between production, storage and end use in decentralized green hydrogen infrastructure, where fluctuating electrolyzer output and intermittent demand require operation over variable pressure and flow conditions. This review provides a cross-technology and application-oriented assessment of conventional mechanical, liquid-piston, electrochemical, metal-hydride and hybrid compression systems using common criteria including pressure ratio, specific energy consumption, thermal behavior, hydrogen purity, dynamic flexibility, reliability, scalability and technology readiness. The comparison shows that mechanical compressors remain the reference choice when high pressure, high throughput and commercial maturity dominate. Liquid-piston systems may offer advantages where thermal management and near-isothermal operation are priorities, but their performance depends on working-fluid properties, interface stability, chamber scaling and hydraulic efficiency. Electrochemical compressors are attractive for compact, high-purity and moderate-flow applications, although membrane durability, hydrogen crossover and water management remain key barriers. Metal-hydride systems are most relevant where low-grade or waste heat is available, while hybrid systems can distribute complementary compression functions between stages. Overall, no single technology is optimal; selection should consider the complete operating envelope and integration with electrolyzer operation, buffer storage and downstream demand. Future development requires standardized reporting, long-term cyclic validation, and realistic lifetime and cost data.

Abstract: This paper evaluates the technical and economic feasibility of retrofitting the Tendaho Dam in Ethiopia for hydropower generation while preserving its primary function of irrigation water delivery. The study responds to the widespread underutilization of large irrigation dams that possess substantial untapped energy potential. An integrated analytical framework combining hydrological assessment, hydraulic modeling, and techno-economic evaluation is applied to three retrofit configurations: a Dedicated Waterway Strategy, a Bifurcation Strategy integrated with the existing irrigation tunnel, and a low-head Channel Utilization Strategy at the downstream regulator. Flow-duration analysis indicates that dependable Q30 discharge conditions can sustain installed capacities exceeding 16 MW for the principal retrofit options, yielding annual electricity generation above 111,000 MWh. Economic performance is evaluated using RETScreen and discounted cash-flow analysis, demonstrating levelized costs of energy between 0.013 and 0.017 USD/kWh, substantially below international benchmark values. Comparative assessment shows that the Bifurcation Strategy offers the most favorable balance between capital efficiency, operational flexibility, and hydraulic compatibility with irrigation requirements. The findings confirm that hydropower retrofitting at Tendaho Dam represents a technically and economically competitive pathway for expanding renewable electricity supply while safeguarding agricultural water allocation in regulated river basins.

Abstract: Life cycle assessment of photovoltaic systems still rests on aggregated, time-invariant inventories. In Colombia, where registered solar projects grew 128.6% between 2018–2022 and 2022–2025, environmental follow-up is self-reported, semi-annual and unmeasured by the authority. We report IMPACT Energy.CO, an infrastructure running in that authority’s production environment, which normalises heterogeneous sensor telemetry onto a versioned canonical vocabulary, hash-chains every derived indicator, and drives openLCA headlessly. A matrix of 144 candidate indicators was screened to 32 and scored independently by external experts and by communities in Magdalena and Cesar. On fifteen shared social indicators the two rankings show no detectable association (Spearman’s ρ = −0.07), yet their disagreement is ordered by stakeholder category: communities move an indicator up in priority the further its category lies from the firm’s internal sphere, and down the closer it lies (Kendall’s τ_b = 0.63, p = 0.004, utility-scale track). Experts rank labour conduct highest; communities rank their own channels of recourse highest. Of seventeen environmental indicators exactly two—energy and carbon payback time—cannot be obtained as impact-assessment results, because both are defined on measured generation; experts ranked them second and third. Harmonising IEA PVPS figures to Colombian irradiance lowers the mono-Si global warming potential by 32%, and carbon payback time varies three-fold across grid emission factors published for the same year. Static inventories cannot deliver the indicators their own users rank highest.

Abstract: The Florida citrus industry has collapsed by >90% in two decades, driven primarily by Huanglongbing disease transmitted by the Asian citrus psyllid (ACP). While physical barriers such as citrus under protective screens systems effectively exclude ACP, their high capital costs ($ 43,560/acre) yield payback periods >29 years, making them economically unviable for most growers. This study investigates vertical agrivoltaic shield walls as a self-funding biosecurity solution that combines ACP exclusion with sustainable electricity generation. A case study is presented evaluating a representative small-family farm-sized (35 acres) citrus grove. Structural designs compliant with Building Code and ASCE 7-22 were developed, and two deployment scenarios were simulated in Vero Beach, Florida: perimeter-only fencing (622.6 kW-DC, Case 1) and perimeter plus interior wind shields (954.8 kW-DC, Case 2). Techno-economic analysis under FPL tariffs shows 25-year bill savings of $ 1.27M (Case 1) and $ 1.97M (Case 2) under net metering, invariant across sub-cases. Under the owner-developed deployment, both cases achieve positive ROI on energy economics alone (Case 1: 20.34%, Case 2: 29.51%), while wholesale export under COG-1 is uniformly uneconomic. GIS-based statewide scaling indicates that fence-mounted PV on Florida citrus groves alone could provide 11.9 GW of capacity generating 15.4 TWh annually. This would produce 6% of Florida's electricity consumption or raised to 25.5% if extended to the rest of the state’s farmlands producing 65.03 TWh without sacrificing any growing area. The economic results are promising as they indicate agrivoltaic shield walls can simultaneously combat HLB, diversify farm revenue, and accelerate sustainable and renewable energy generation.

Abstract: In this study, impact compression tests were conducted on sandstone, shale, and conglomerate using a split Hopkinson pressure bar (SHPB) apparatus to investigate their mechanical responses and constitutive relationships under dynamic loading. Stress–strain curves at different strain rates were obtained, and the strain-rate enhancement effect, failure mode, and fragmentation fractal characteristics of each rock type were systematically analyzed. Based on continuum damage mechanics and statistical strength theory, a dynamic statistical damage constitutive model for rocks was developed, and the model parameters were identified and validated using experimental data. The results indicate that the proposed model effectively simulates the dynamic mechanical behavior of rocks under impact loading, with theoretical curves showing good agreement with experimental results. The dynamic compressive strength of rocks exhibits significant strain-rate sensitivity, and the fragment size distribution follows a distinct fractal law. This study provides theoretical support and experimental evidence for dynamic hazard warning and protective design in deep rock mass engineering.

Abstract: Displaced persons in resource-constrained contexts experience a lack of access to energy, with consequences for health, safety, livelihoods and wellbeing. Existing research and implementation in displacement contexts continue to exhibit three recurring limitations: insufficient attention to lived needs and context, technology-centred intervention logics, and linear approaches to change. This article uses a structured critical and interpretive synthesis of academic and grey literature to examine these limitations and derive a synthesis-grounded integrative approach for transformations towards equitable and sustainable energy services. We frame improved energy access not as technology delivery but as a non-linear, locally grounded transformation process. Considerations of needs and context are addressed by whose knowledge and experiences inform priorities, how decisions are made and how competing interests and trade-offs assessed. The resulting approach combines four domains for shaping energy-services arrangements namely context, needs, capacities and sustainability with three cross-cutting dimensions namely inclusion, participation and normative orientation. It provides guidance and instructions for inquiry, research and implementation by identifying dimensions that need to be explored, questions they raise and methodological entry points through which locally grounded transformation can be actioned and shaped. The approach is intended to help researchers, humanitarian organisations, public authorities and energy providers structure problem definition, option development, implementation and learning. The underlying logic of the approach is applicable beyond displacement, to other resource-constrained contexts, however, its empirical validity and transferability should be tested across diverse contexts, including acute emergency, protracted, urban, rural and non-displacement contexts.

Abstract: The increasing penetration of photovoltaic (PV) generation, battery energy storage systems (BESS), and electric vehicles (EVs) creates a need for coordinated energy-management strategies that operate across the household and community scales. This paper presents a reproducible benchmark for tariff-aware, peak-constrained battery dispatch in a residential energy community. The study uses an open dataset representing 250 households with 15-minute PV, demand, BESS, EV, tariff, and grid-limit information [1]. A linear program aggregates the community profiles and optimizes battery charging, discharging, state of charge, grid import, and grid export. The model enforces power balance, charge and discharge limits, battery efficiency, initial and terminal state-of-charge equality, a small throughput penalty, and an import cap equal to the unmanaged baseline peak. On the representative day supplied with the dataset, the optimized dispatch reduces modeled operating cost from EUR 724.15 to EUR 537.22, corresponding to a 25.81% reduction. Grid import decreases from 4364.71 kWh to 3622.13 kWh, direct PV utilization increases from 1770.58 kWh to 2390.86 kWh, and the maximum grid import remains fixed at 453.85 kW. The result demonstrates the value of coordinated storage for increasing PV self-consumption without increasing the feeder peak. The work is deliberately positioned as a transparent benchmark rather than a final claim of annual performance. Future extensions should include household-level battery constraints, flexible EV charging, multi-day validation, stochastic forecasts, and carbon-intensity signals.

Abstract: The natural gas distributed energy system can achieve the purpose of energy saving and emission reduction with the stepped supply of the combined cooling heating and power, but as a new type of clean energy supply mode, the reasonable benefit in the process of its promotion needs to be estimated. In this paper, the comprehensive evaluation for the applicability of the natural gas distributed energy system was carried out from features such as economic and environment, the applicability evaluation indicator system was built and the semantic classification of the evaluation levels was determined. Then, the weight of each indicator was calculated by the analytic hierarchy process and the applicability level was determined by the set pair analysis theory. Finally, a hotel in Xi’an, Shaanxi province, was taken as an example to evaluate and the results were compared with traditional energy supply methods. The following research results were obtained. First, the comprehensive evaluation result is high availability, and the economy and environment are the key influence factors for the applicability of the natural gas distributed energy system. Second, compared with the traditional energy supply method, the efficiency of energy conservation and emission reduction is remarkable, and the advantages of clean energy and stepped supply method are reflected. Third, the distributed energy system has obvious economical effect, especially in low price areas of natural gas. It is concluded that the research results provide a more scientific decision-making method and the reference for the promotion and application of the natural gas distributed energy system.

Abstract: Winter surface condensation on the walls and false ceiling of paper production halls degrades the building fabric, promotes mould growth and disturbs the process environment, yet the choice between the available remedies — envelope insulation, ventilation intensification and mechanical dehumidification — is rarely supported by a common quantitative basis. This paper reports a measurement-calibrated assessment of the three solution families for a tissue mill in Petrești, Romania, housing two tissue machines in a 34 800 m³ hall enclosed by an uninsulated 200 mm reinforced-concrete wall (U = 3.89 W m⁻² K⁻¹). Two measurement campaigns established an exhaust airflow of 85 500 m³ h⁻¹ (2.46 h⁻¹) and a process-driven humidity-ratio increment across the hall of Δx = 8.0 g kg⁻¹ with one machine running and 12.2 g kg⁻¹ with both, corresponding to a moisture uptake of 18.4 and 27.2 t d⁻¹ respectively — 3.7 to 3.9 times the value declared in the process water balance, which indicates substantial hood spillage. A one-dimensional surface-temperature model coupled to a psychrometric zone model was driven by an 8 760-hour typical meteorological year, yielding 5 053 cold-season hours (outdoor temperature below 12 °C). On the existing wall the internal surface resistance carries 50.6 % of the total thermal resistance, so the surface temperature closely tracks the outdoor temperature and condensation occurs in 91–100 % of cold-season hours for any indoor temperature between 20 and 35 °C; eliminating it by heating alone would require 45–52 °C indoors. Adding 50 mm of external EPS and holding the hall at 27 °C removes condensation in all 5 053 hours, saves 826 MWh per season and pays back in 1.6–2.6 years, whereas ventilation intensification (2.3× the present airflow) and hybrid coil-plus-desiccant dehumidification achieve the same technical result at ten-year costs of 3.6–4.1 M€. Once the wall is insulated the dehumidification duty falls to zero and the required airflow drops below the installed capacity: insulation does not compete with the alternatives, it makes them unnecessary.

Abstract: The artificial intelligence integrated aerodynamic flow control mechanisms is an important direction for improving the performance of Vertical Axis Wind Turbines (VAWTs). Despite their advantage as urban energy systems, VAWTs have the disadvantage of comparatively lower efficiency to Horizontal Axis Wind Turbines (HAWTs). The reasons are dynamic stalls, flow separation, and negative torque generation on returning blades. This review systematically examines the current state of research across three interconnected domains: VAWT performance challenges, deflector-based aerodynamic enhancement, and artificial intelligence applications in wind energy systems. The analysis reveals that while deflector-assisted designs can improve power coefficients by 15% to 60% depending on configuration, most existing solutions employ fixed-angle deflectors that cannot adapt to fluctuating wind conditions. Simultaneously, AI techniques, particularly reinforcement learning, have demonstrated strong potential for real-time optimization but remain largely confined to HAWT applications or offline design optimization. A critical research gap exists at the intersection of these domains, with limited studies combining AI-driven adaptive control with deflector mechanisms for VAWTs. This article reviewed recent research works with preferred reporting items for systematic reviews and meta-analyses (PRISMA), identified the research gap of adaptive deflector control, and proposed a framework of creating smart, self-improving vertical axis wind turbine (S-VAWT) systems.

Abstract: Real-time and accurate inversion of drilling-fluid hydraulic parameters while drilling, together with the coordinated optimization of drilling parameters, is critical for safe and efficient drilling in deep and complex formations. Conventional methods are limited by single-source observations, insufficient prior constraints, weak surrogate-model generalization, and isolated parameter optimization. To address these issues, this paper proposes a three-layer intelligent decision-making framework. The first layer is a dual-prior-constrained temporal inversion module that fuses a pre-drill mechanistic baseline prior with an offset-well statistical prior and estimates plastic viscosity, yield point, annular cuttings concentration, and equivalent eccentricity from standpipe-pressure and rotary-torque observations through a four-term loss function. The second layer is a Fourier neural operator (FNO) surrogate trained on data generated by an in-house two-phase hydraulics solver. The third layer is a hydraulic–mechanical coupled multi-objective optimization framework that coordinates weight on bit, rotary speed, and flow rate using online Bayesian optimization and probabilistic safety constraints. Numerical experiments show that the dual-prior constraints reduce the inversion root-mean-square error by 42.7%, that the FNO surrogate is three orders of magnitude faster than numerical simulation while maintaining an accuracy above 98.3%, and that three-parameter optimization improves overall drilling efficiency by 28.5%. The framework provides an accurate, efficient, and robust solution for real-time intelligent drilling decision-making.

Abstract: The cement industry’s shift toward carbon neutrality is expanding the use of alternative fuels such as waste synthetic resin (WSR). Because WSR particles are approximately 500 times larger than pulverized coal, their thermal inertia delays devolatilization and repositions heat release relative to the sintering zone. Using three-dimensional steady-state RANS CFD at approximately 21% thermal substitution, we use the devolatilization-completion distance (x_dev) as a primary diagnostic proxy for sintering-zone heat-release confinement. The particle-size effect was decomposed into a single-diameter axis (SD: 5–25 mm)andanoversize-tail axis (Rosin–Rammler distributions, PSD: upper limits 20–35 mm). Across these cases, D₉₀, the 90th-percentile diameter of the fed distribution, acts as a first-order coarse-tail scale for organizing x_dev, while the upper-tail shape and the population of the largest particles provide secondary corrections. Under the present modeled conditions, xdev generally falls within the sintering zone or near its rear boundary (within the 0.5 m post-processing resolution) when D₉₀ is near or below approximately 20 mm, placing this value as a boundary-sensitive coarse-tail scale rather than a sharp confinement threshold; the centerline CO-rich region can persist downstream, further reducing the rear margin at the 20 mm level, with the SD single-diameter baseline at d = 15 mm (SD3) providing the safer mechanistic reference condition. The double-peak flame structure observed in monodisperse (SD) cases reflects the single-diameter idealization: for the studied d_m = 15 mm PSD conditions it is smoothed into a single broad peak, with SD3 showing an approximately 86 °C higher peak than PSD1. These results indicate that managing coarse-tail metrics such as D₉₀, rather than relying only on nominal upper-limit or arithmetic-mean diameters, is more directly connected to sintering-zone heat-release localization.

Abstract: This paper develops a reproducible spectral-thermodynamic model for ideal single-junction photovoltaic conversion under the ASTM G173 AM1.5G terrestrial spectrum and the ASTM E490 air-mass-zero (AM0) extraterrestrial spectrum. The formulation converts tabulated spectral irradiance to photon flux, evaluates step-function absorption, and enforces radiative detailed balance through the cell blackbody emission current. A bounded voltage-retention factor, 0 < Vf ≤ 1, is introduced as a phenomenological sensitivity parameter for aggregate voltage losses without permitting energy creation. Spectral Shannon entropy is retained only as a grid-controlled distribution descriptor; it is not subtracted directly from an energy flux. At 300 K and with one-sided radiative emission, the calculated AM1.5G maximum is 33.71% near a 1.34-eV bandgap, while the E490 AM0 model window yields 30.60% near 1.26 eV and a larger absolute power density. For AM1.5G, reducing Vf from 1.00 to 0.85 lowers the optimum efficiency from 33.71% to 28.18%. A silicon temperature study using a Varshni bandgap relation predicts decreasing open-circuit voltage and radiative-limit efficiency from −100 °C to 100 °C. The resulting model unifies terrestrial, space, voltage-loss, spectral-distribution, and temperature analyses while clearly separating theoretical limits from realizable device performance.