Concentrating photovoltaic thermal (CPV/T) systems are emerging as an efficient way to utilize solar energy because they provide both clean electricity and thermal energy simultaneously. Moreover, recent advances in high-temperature, high-efficiency photovoltaic cells have made higher-concentration-ratio systems feasible, allowing for smaller receiver areas, fewer controls and drives, and therefore lower costs. However, at high concentration ratios, it becomes essential to implement design modifications and configurations that ensure optimal performance and facilitate the easy integration of photovoltaic cells. In this study, an innovative octagonal receiver is proposed, and a comprehensive numerical model is developed, verified, and validated against experimental data to investigate its optical, thermal, and thermodynamic performance. The optical model was developed in a Monte Carlo ray-tracing tool, while the thermal and thermodynamic model was built in a finite-volume computational fluid dynamics tool. Results show that receiver's deviation from the focal line of less than 10 mm and collector slope errors of less than 2 mrad have a minimal impact on the intercept factor and receiver average heat flux. In addition, the operating inlet temperature affects the thermal transport properties of the heat transfer fluid and, in turn, electrical and thermal efficiency. With a 350 K inlet temperature and a volumetric flow rate of 17.4 m3/hr, the octagonal receiver shows a thermal efficiency of 45.2% and an electrical efficiency of 35.6%. The electrical efficiency begins to decline at flow rates beyond 69.6 m3/hr because the pumping power consumption outweighs the benefits gained from enhanced heat transfer, while thermal efficiency remains nearly constant for flow rates beyond 17.4 m3/hr across all the inlet temperatures considered. The thermal exergy efficiency increases with increasing inlet temperatures, while electrical exergy efficiency decreases.
Thermal adaptation of regenerative cooling structures is critical for scramjet combustors subjected to highly non-uniform heat loads. This study develops a Bayesian-driven framework for adapting a multi-channel regenerative cooling panel to a combustor-side heat load that is non-uniform in both the streamwise and lateral directions. The thermal boundary, represented by the adiabatic wall temperature and gas-side heat-transfer coefficient, is extracted from three-dimensional reacting-flow simulations. A fast model couples a one-dimensional plug-flow-reactor (PFR) coolant solver with two-dimensional solid heat conduction, and station-wise sequential Bayesian optimization redistributes the lateral channel positions by minimizing the area-weighted cross-sectional solid-temperature non-uniformity. The discrete solution is reconstructed as smooth three-dimensional channels and assessed by conjugate heat-transfer and thermo-mechanical simulations. Relative to the uniform baseline, the reconstructed layout reduces the coolant outlet-temperature standard deviation from 16.66 to 2.61 K and the maximum solid temperature from 972 to 943 K; its channel pressure drops remain within 6.27–6.49 kPa, and the maximum equivalent stress decreases modestly from 345 to 336 MPa. The results show that the framework improves thermal matching by redistributing the available cooling capacity toward local high-heat-load regions.
As the intermittent and fluctuating characteristics of renewable energy sources such as solar power become increasingly prominent, the pumped thermal energy storage (PTES) system emerges as a key peak-shaving technology and a potential solution. This study proposes a coupled system of the PTES system and the supercritical CO2 Brayton cycle for a concentrated solar power (CSP) system with a preheating thermal storage and a bypass heating discharging cycle. Based on typical daily operating conditions, a quasi-steady-state thermodynamic model of the system is developed. The results indicate that there are optimal values for the high-temperature compressor inlet temperature, the low-temperature compressor pressure ratio, and the compressor inlet pressure that maximize system performance. The compressor isentropic efficiency, the compressor inlet pressure, and the expander isentropic efficiency significantly affect system performance. The heat exchanger pressure drop exerts a greater impact than energy conversion efficiency, whereas direct normal irradiance has a greater impact on the system than ambient temperature. Under the summer operating condition, the maximum power ratios of the CSP input and PTES output are 58.96% and 29.86%, respectively. Under the winter operating condition, they are 60.20% and 28.87%, respectively. The maximum round-trip efficiency and energy density under the summer operating condition are 60.62% and 26.78 kWh/m3, respectively, which are 0.32% and 4.18 kWh/m3 higher than those under the winter operating condition. Under both operating conditions, the round-trip efficiency and energy density are highly sensitive to the isentropic efficiency and inlet pressure of the low-temperature compressor, and the isentropic efficiency of the high-temperature expander.
The escalating heat fluxes in 1kW+ AI accelerators, power-dense electric vehicle (EV) electronics, and deep-space missions are driving significant advances in passive thermal management. While Loop Heat Pipes (LHPs) offer superior long-distance heat transport, their transition from niche aerospace applications to high-volume industrial sectors remains constrained by complex transient instabilities and a lack of standardized reliability benchmarks. Distinct from prior LHP reviews that primarily compile experimental results, this review synthesizes the literature into transferable design principles, a consistent framework for cross-study performance comparison, and a feasibility-based roadmap for next-generation manufacturing. This review provides a critical synthesis of the 'Porosity-Permeability Nexus,' evaluating how multi-morphology composite wicks and additive manufacturing (AM) are reshaping the mechanical-thermal trade-off. We outline the evolution of numerical frameworks, from traditional zero-dimensional approximations to multi-physics CFD and, prospectively, AI-driven predictive modeling for digital twin integration, an area where LHP-specific implementations remain largely undeveloped. Moving beyond descriptive literature, this work identifies the primary failure modes of traditional mechanical seals and proposes a strategic technical roadmap toward 'zero-leakage' monolithic architectures, while noting that quantitative hermeticity validation specific to this architecture remains an open research need. By recasting thermal resistance as a directly comparable performance gradient and identifying gaps in standardized benchmarking, this review aims to support the transition from experimental LHP prototypes toward industrial deployment.
A new COG-fueled integrated multi-generation system is proposed and evaluated for simultaneous production of electricity, hydrogen, heating and cooling. The system consists of an organic Rankine, a modified Kalina, an electrolyzer, and liquefied-natural-gas cold-energy usage, while a cascaded heat recovery is employed to enhance resource utilization. 4E (exergy, energy, environmental, economic) assessments and a life cycle assessment (LCA) of environmental impacts are carried out to comprehensively test the system. Moreover, a hybrid Light Gradient Boosting Machine–Crow Search Algorithm framework is developed for the identification of optimal operating conditions under various multi-objective optimization situations. Under the baseline scenario, the setup yields an energetic efficiency of 62.51%, an exergetic efficiency of 37.44% and a net power generation of 16,007 kW, H2 output of 8.06 kg/h, energy levelized cost (LCOE) of 0.0952 $/kWh, and CO2 emission intensity of 0.216 kg/kWh. The economic evaluation results in a payback period of 5.538 years and a net present value of 50.969 M$. The LCA leads to a total global-warming of 0.64 kgCO₂-eq/kWh. The multi-objective optimization results in an even better system performance with an exergetic stability factor of 0.252, an LCOE of 0.073 $/kWh and an exergetic efficiency of 42.49%. By presenting the outcomes, the potential of the suggested integrated setup and hybrid optimization approach to enhance the thermo-economic-environmental performance of COG-fueled multi-generation systems was demonstrated.
