As critical facilities in pharmaceutical, electronics, and other precision manufacturing industries, cleanrooms are increasingly confronted with the issue of high energy consumption. Energy consumption during non-production periods can be significantly reduced through the adoption of a standby mode with a low air change rate (ACH); however, dynamic differential pressure instability is often triggered during the bidirectional switching between production mode and standby mode, resulting in the reversal of the differential pressure gradient in the production zones with high cleanliness demand. To address this, we propose a nonlinear stepwise coordinated control strategy for bidirectional switching. Natural cubic spline interpolation is innovatively employed to generate nonlinear switching step sizes, thereby accurately matching the asymmetric dynamics of supply airflow rate adjustment. Experiments show differential pressure fluctuation amplitudes during loading/unloading are reduced to 46.8 %/25.5 % (17.4 %/8.3 % improvements over linear strategies), with 49.08 % energy savings, 50 % shorter switching time, and critical zone differential pressure gradient deviation controlled within +/- 2.21 Pa. By establishing a nonlinear coordinated regulation mechanism of fan frequency and damper opening, the study further investigates the effects of infiltration air volume on differential pressure under multi-zone airflow coupling. This work provides a dynamic-stable and energy-efficient control solution for cleanroom HVAC systems during mode transitions.

Microalgal CO₂ fixation is a promising strategy for industrial carbon capture, yet its application remains limited by inefficient light utilization. Although the flashing light effect has been explored as a light-management strategy for improving photon utilization in microalgal cultivation, its effectiveness depends on spectral composition, flashing frequency, duty cycle, and cultivation conditions. In this study, light quality, including red (R), blue (B), white (W), and mixed red-blue (RB) light, and PWM flashing parameters, including frequency (10–1000 Hz) and duty cycle (30

Multilayer selective emitters suffer from thermal degradation at high temperatures even in vacuum, limiting their application in thermophotovoltaic (TPV) systems. Although the thermal degradation is commonly attributed to oxidation and grain growth, the important role of stress evolution in driving these processes and resultant performance failure remains poorly understood. A single-layer molybdenum thin-film emitter was employed as a simplified model system and annealed from 800 to 1400 K at 3.5 & times; 10(-4) Pa. Measurements of stress, structural morphologies and spectral emittances of the emitters before and after annealing were conducted to investigate how stress evolution drives oxygen diffusion and hole formation, as well as their effects on the emittances. Furthermore, a physically motivated interpretation model consistent with the observations was established. It is indicated that residual stress changes from compressive to tensile with increasing temperature. Concurrently, a substantial decline in spectral efficiency from 31.63% at 1200 K to 22.94% at 1400 K is exhibited, indicating significant thermal degradation. This degradation is highly correlated with stress evolution, which is regarded as the primary driving force for hole formation, surface diffusion and abnormal grain growth. Consequently, the thin-film structure is compromised by these stress-induced processes, and oxygen diffusion is accelerated. Based on these findings, the emittance can be interpreted by the proposed model, which additionally accounts for resistivity variations caused by grain growth. Ultimately, stress evolution is considered to play an important role in the degradation of the single-layer emitter's spectral control abilities. A novel theoretical basis is thus provided for designing high-stability TPV emitters.

A novel arrayed tangential-circular jet swirling plate photobioreactor (ATCJSP) was developed to promote microalgal growth and carbon fixation by enhancing the flashing light effect, improving mass transfer and mixing, and reducing bubble diameter. In this system, the microalgae solution was injected through four symmetrically arranged nozzle sets with four nozzles in each set to create vortices parallel to the light path. These vortex arrays collectively drove an efficient spiral flow, which accelerated the light-dark cycle of the microalgae cells and strengthened gas-liquid mass transfer. Under optimal structural parameters (relative tangential circle diameter = 0.3, 4 nozzle sets, inlet velocity = 1.59 m s-1), the ATCJSP significantly outperformed the conventional airlift flat-plate photobioreactor (AFPP). Specifically, it increased the light-dark cycle frequency by 46.5 times, reduced bubble diameter by 64.7%, enhanced the mass transfer coefficient by 7.17 times, and shortened the mixing time by 65.43%. Furthermore, the flow dead zones were reduced by 78.12%. These improvements resulted in a 63% increase in biomass dry weight and a 75% increase in the average CO2 fixation rate. Consequently, this novel vortex-driven design provides a highly efficient, scalable, and robust strategy for industrial microalgal cultivation and biological carbon mitigation.

Daytime radiative cooling relies on a high reflectivity in the solar spectrum and a high emissivity in the atmospheric window spectrum. However, the reflected solar radiation, as a high-quality energy, is wasted. Based on the incident solar radiation primarily concentrated at a specific angle and the emitter's hemispherical heat exchange with space, it is possible to collect it. There has been no work to date that collects the substantial energy reflected by the emitter yet. Here, an idea of enhancing solar power generation during the daytime while ensuring day-and-night radiative cooling was proposed in this work. It is indicated that the emitter with only five layers can achieve a weighted average reflectivity of 95.22 % in the solar spectrum and a weighted average emissivity of 94.74 % in the atmospheric window spectrum. Outdoor experiments show that the average temperature reduction from 10:30 AM to 3:30 PM is 2.3 degrees C, which can further decrease to 8.4 degrees C from 3:30 PM to 8:00 PM. Under direct sunlight, the maximum output power density of the solar cell is 125.5 W/m2, which can be enhanced to 163.5 W/m2 by aligning the orientation of the solar cell with the emitter using a simple angle controller, representing a remarkable enhancement of 30.3 %. Finally, through simulations on a 5.4 x 4.4 x 3.4 m3 communication base station, it is determined that without convective losses, the chamber temperature reduction is 11.7 K, and the generated power can be as high as 169.4 W/m2 from the portion reflected by the emitter and 177.9 W/m2 from the portion directly from the sun. The results highlight the great potential for the commercial application of combining radiative cooling with a photovoltaic system.

The growing mismatch between freshwater availability and energy demand presents a critical sustainability challenge. Solar-driven interfacial evaporation (SDIE) coupled with evaporation-induced hydrovoltaic generation (EIHG) holds promise for zero-carbon water-electricity co-production, but existing systems suffer from limitations in evaporation-power generation synergy, environmental adaptability, and output stability. Here, we present a hybrid hydrogel MOF-303/PVA-PPy gel (MPPG) embedding MOF-303 (zeta potential=-25 mV, specific surface area=783.34 m2 g-1) within a PVA-PPy hydrogel network to integrate SDIE and EIHG to produce water and electricity concurrently. The mechanism relies on synergistic effects between the photothermal-induced pressure gradients and the nanoconfined directional ion transport. MPPG nanochannel fluid transport modeling and experiments reveal environmental influences (ion concentration, wind, humidity, temperature) on electricity output. Under 1-sun irradiation in deionized water, MPPG achieves 3.02 kg m-2 h-1 evaporation and 0.552 V output, representing 11-fold and 4-fold increases in voltage and current density compared to bare PVA-PPy hydrogel. In artificial seawater, voltage further increases to 1.12 V, and collected freshwater meeting WHO drinking water standards. The system maintains 91 % performance over 72 h (<0.14 %/h degradation), and is scalable via series/parallel integration. This work provides an efficient, stable, and zero-carbon solution to simultaneously address freshwater scarcity and distributed energy supply challenges.

Solar-driven interfacial evaporation (SDIE) has become an innovative and sustainable technology for seawater desalination to produce fresh water, and its integration with other energy conversion technologies (photoelectric, piezoelectric, etc.) for power generation, wastewater treatment, etc. has attracted increasing attention. In this work, a light absorber based on nickel foam-loaded CNTs doped with TiO2 and Ag is fabricated, which can utilize solar energy at different wavelengths, by simultaneous photothermal and photoelectric conversion; Meanwhile, a BT-P(VDF-TrFE) piezoelectric film is formed via P(VDF-TrFE) doped with BaTiO3 (BT); these two layers, together with the thermal insulating water transport layer and the electrode, form the solar/wave driven interfacial evaporation unit (SWDIEU), which produces fresh water and electricity. Besides, a hinge-like structure is designed to connect and extend the SWDIEU to solve the problem of piezoelectric layer deformation limited by other structures. The piezoelectric voltage of the 2-unit system is increased by 45 times and the power density of 489 times compared to the single-unit system, making the integrated system easily scalable. The system achieves an evaporation rate of 1.46 kg m-2h- 1 and an electric power output of 1.01 W/m- 2 under 1 sun and 1 Hz waves, and is capable of organic wastewater treatment.

With the growing of demand for the low temperature pharmaceutical cold chain, the Stirling cooler has been attractive for years. However, the heat transfer inside the refrigerator could be ineffective by natural convection due to the small area of the plug-in Stirling cold finger. In this paper, the double two-phase thermosyphon loops (DTPTLs) used for low temperature Stirling refrigerator is developed. The characterization of heat transfer and pressure drop in the DTPTLs is investigated by theoretical calculation for various working refrigerants. Then the basic structure of the DTPTLs is modified and improved for dragging and moving convenience. Moreover, the comparison of the temperature distribution inside the refrigerator container between the DTPTLs and the plug-in cold finger methods is demonstrated by numerical simulation. The simulation result indicates that a well temperature distribution inside the container can be obtained by using DTPTLs. In the end, an experimental test is conducted at room temperature. It's shown that the no-load cooling temperature could reach-80 degrees C in a few minutes. Over steady-state operation, the maximum temperature difference all inside the container is less than 5 degrees C, which proved the positive heat transfer effect of the DTPTLs on the cooling performance of the low temperature Stirling refrigerator system.

The paper and pulp industry is one of the critical sectors with respect to regulations of carbon emissions. In this study, real-time data from a specialty papermaking enterprise were collected to analyze the life-cycle carbon footprint of fine-grained grammage paper products, and pathways for economic carbon mitigation in papermaking enterprises were proposed. The results showed that the carbon footprint of the products ranged from 0.95 to 1.83 tCO2e/t paper. Low-grammage products have a high life-cycle carbon footprint and manufacturing emissions owing to their high raw materials and energy consumption. Conversely, high-grammage products have a low lifecycle carbon footprint but high manufacturing emissions owing to their low energy consumption and high raw material consumption. Various scenarios have shown that purchasing green electricity and implementing rooftop photovoltaics are the most cost-effective measures for enterprises to substantially reduce their carbon footprint. In addition, using information technology and intelligence to optimize and control papermaking systems can provide a more efficient and economical approach for mitigating carbon emissions without relying on external changes in energy structures. This study offers valuable insights for papermaking enterprises to reduce their carbon footprint and adhere to China's carbon emission regulations.

Structured spectrally selective emitters show good spectral performance in thermophotovoltaic (TPV) systems, but most of them cannot maintain good spectral emittance at high temperatures as expected. A Mo-doped HfO2 monolayer structure was proposed to improve the thermal stability of the structured emitters. A simulation model based on the transfer matrix method and effective medium theory was used to design the doped monolayer emitters. Thermal annealing and characterization measurements were conducted to investigate the proposed emitter after 1273 K-1473 K thermal annealing, and a TPV system model was built to evaluate their spectral performance after thermal annealing. The results revealed that 20% Mo doping can improve the spectral performance of a 90 nm HfO2 monolayer structure, making the spectral efficiency up to 60.93% at 1273 K. Due to the combined action of the Mo oxidation, grain growth and phase transition of HfO2 during thermal annealing, the formation of holes and Mo oxides were observed. Consequently, the spectral emittance of the doped emitters changed. Nevertheless, no obvious decline in the system efficiency (approximately 1%) of the TPV system with the doped emitter after 1273K thermal annealing for 12 h was observed. The proposed Mo-doped HfO2 monolayer emitter shows good spectral performance compared with the undoped one. The investigation of the thermal degradation of the proposed emitters can lay a foundation for promoting their applications of TPV systems.

The potential for utilizing flue gas as a carbon source in microalgal cultivation holds great promise. Incorporating flue gas as a carbon source into microalgae culture processes can accelerate the growth rate of microalgae, consequently enhancing the overall economic viability of the integrated process. There are two key sources of flue gas to consider: flue gas from coal-fired power plants, characterized by a CO2 concentration of 12–15 w/w%, and flue gas from coal chemical processes, boasting a CO2 concentration of 90–99 w/w%. Additionally, the choice between an open or sealed microalgae culture system can also influence economic efficiency. Thus, there are four distinct microalgal cultivation routes to assess: in-situ open systems, off-situ open systems, in-situ sealed systems, and off-situ sealed systems. The incorporation of flue gas as a carbon source in microalgae cultivation demonstrates significant potential for reducing both environmental impact and costs, rendering it a highly promising and sustainable approach for economically efficient microalgae cultivation. In this review, the in-situ open route is recommended for the situation with high flue gas CO2 concentration and the target products of low-margin commodities, while the off-situ sealed route is suitable for the situation with low flue gas CO2 concentration and the target products of high value-added products.

Selective emitter and filter are different spectral modules in a solar thermophotovoltaic (STPV) system, whereas the guidelines of their applications for various operation conditions are lacking, especially when the thermalization of the photovoltaic cell is considered. To conduct a comprehensive analysis, an energy transfer model of the STPV system was established based on spectral modules under both ideal and actual conditions, and in particular the cooling consumption was considered. It is observed that when an emitter (E system) or emitter combined with a filter (E + F system) is used, the system efficiency slowly increases with increasing concentration ratio (CR). When a filter (F system) is utilized, an initial increase followed by a subsequent decrease in the system efficiency is shown. The InGaAs cell is suitable for the E + F system, the GaSb cell is preferred for the E system, and the Si cell is better suited for the F system. The cooling consumption occupies up to 1100 W, which can cause the system efficiency to be below 0, indicating that the generated power cannot drive the cooling device. In particular, ideal spectral regulation is not superior to the actual spectral regulation when PV cell thermalization is considered. A foundation for optimization of spectral modules and application of STPV systems can be established by this work.

A microalgae carbon based magnetic solid acid catalyst (MCMSA) was prepared using microalgal residue after lipids extraction as carbon source through magnetization, carbonization and sulfonation. The effects of three preparation conditions of pore-forming agent type, carbonization temperature, and sulfonation agent type on the MCMSA were studied. The specific surface area, functional group, acidity and magnetism of MCMSA were studied to determine the optimized catalyst. The MCMSA prepared under the condition that the pore-forming agent is NaCl (1:1 m/m), the carbonization temperature is 800 degrees C, and the sulfonation agent is H2SO4 (1:10 m/v, 150 degrees C) has a high specific surface area (124.70 m2/g), high acidity (3.64 mmol/g) and high magnetism (1.042 emu/g), and shows good thermal stability at transesterification temperature of 90 degrees C with low loss of acid groups. MCMSA showed high conversion efficiency (98.51 %) in the microwave-assisted catalytic transesterification at 90 degrees C with MCMSA dosage of 5 wt% and methanol to wet microalgae ratio of 6.25:1 (v/m). It could maintain catalytic activity in five consecutive cycles without further treatment, and the average conversion efficiency was approximately 85.5 %. The results showed that the MCMSA could replace the traditional homogeneous acid catalyst for the preparation of microalgae biodiesel.

In this paper, a thermophotovoltaic (TPV) emitter that combines a one-dimensional photonic crystal with two-dimensional periodic nanoarray cavities was proposed. The Finite-Difference Time-Domain (FDTD) method was adopted to analyze the spectral emittance and its sensitivity to the emission angle for the proposed emitter. The results show that the main emission mechanisms of the emitter are Cavity Resonances (CRs), Fabry-Perot (FP) resonances, and Magnetic polaritons (MPs). In the convertible band of a TPV cell, CRs and FP resonances are coupled together to broaden the emitting bandwidth of the emitter. The cut-off wavelength of structural spectral emittance increases with depth and radius but decreases with a period. In addition, the spectral emittance is non-sensitive to the emission angle of less than 50°, highlighting the wide-angle stability of the composite structure. The proposed emitter has wide-angle adaptability and achieves a fine-tunning of bandgap wavelength while maintaining a good spectral selectivity. This work provides new insight into the design of the TPV emitter.

The solar interfacial evaporation system can generate steam efficiently by localizing solar thermal energy to heat air-water interface, which has great application potential in seawater desalination, sewage treatment, and other fields. At present, the solar absorption layer and substrate of the interfacial evaporation system are mainly made of carbon materials, sponges, foams, and other porous media materials. However, the transient interfacial evaporation heat and mass transfer model and the influence of the physical parameters of porous media on evaporation performance have rarely been investigated. Based on heat and mass transfer theory of porous media, a transient theoretical model of porous media interfacial evaporation system is established in this paper. Moreover, the effects of physical parameters such as the porosity and thermal conductivity of porous media on evaporation performance are analyzed, and the accuracy of the model is verified through outdoor experiments. Based on the model calculation, as the porosity of the substrate increases, the evaporation rate and efficiency of the evaporator first increase and then decrease. The lower the thermal conductivity of the substrate and the higher the porosity and thermal conductivity of the solar absorption layer are, the better the evaporation performance is, but the growth rate gradually decreases. Therefore, the relationship between the improvement of evaporation performance and the increased cost caused by the improvement of material properties needs to be considered. The model and related theoretical analysis results can provide a theoretical basis for system structure optimization, material selection and other aspects of future research on double-layer porous media interfacial evaporation system.

A nanowire-based hyperbolic metamaterial emitter is widely used in a near-field thermophotovoltaic system. However, it is generally hypothesized that the emitter is stable enough to be less subject to the thermal degradation. To make an improvement, the thermal degradation of a W-Al2O3 metamaterial emitter was investigated. On this basis, an improved energy transfer model of the near-field thermophotovoltaic system with the thermal degradation was constructed, and the effects of the heating time, emitter temperature and partial pressure of the oxygen on the emitter and system performances were analyzed. The results show that the thermal degradation in the emitter is mainly caused by the oxidation of the metal W. The produced WO3 is volatile at a high temperature, leading to the reduction of the W nanowire diameter. The diameter reduction rate decreases from 6.67 nm·h−1 to 0.04 nm·h−1 by changing the emitter temperature and partial pressure of the oxygen. It is noted that the increasing temperature has the dual effects on the spectral efficiency. On one hand, it can make the oxygen atoms diffuse more easily, resulting in the increase in the oxidation rate and leading to the decrease in the spectral efficiency. On the other hand, the increasing temperature is beneficial for the spectral efficiency of the emitter according to the Wien's displacement law. Compared to the system without the oxidation, there exhibits a reduction rate of the spectral efficiency up to 13.47 % for the system involving the oxidation, meaning that the system efficiency without the oxidation is seriously overestimated. Therefore, to promote the development of the near-field TPV system applications, the prevention of the thermal degradation is a key point.

Materials based on biochar have good application prospects in the field of solar interfacial evaporation. However, due to their amorphous structure, most biochar materials often require additional chemical treatment for interfacial evaporation, which is inconsistent with the original intention for low cost and easy fabrication. Here, a solar absorption layer made of loofah sponge biochar prepared by direct compression and carbonization and a substrate with water conveyance and heat insulation effects were combined into a squashed loofah sponge biochar interfacial evaporator (SLSBIE). The SLSBIE achieved an evaporation rate of 1.565 kg m(-2) h(-1) and an evaporation efficiency of 80.66% under 1 sun (1000 W m(+2)). The good performance of the SLSBIE is mainly due to the porosity (554.1 m(2) g(+1)), light absorptivity (89.21%), and hydrophilicity (rich in C-O and C=O) of the structure of loofah sponge biochar, as well as the optimization. The heat loss and energy balance of LSBIE were analyzed in detail. The measured concentrations of Na+, Mg+, K+, Ca2+ and total dissolved solids of condensate water met the standards of the World Health Organization for drinking water, which indicated that SLSBIE had good practicability.

The technology of flue gas CO2 fixation by microalgae is highly attractive in the era of CO2 neutrality. However, CO2 emission along the whole process has yet to be sufficiently evaluated. Here, a life-cycle assessment was performed to evaluate the energy conversion characteristics and environmental impacts of flue gas CO2 fixation from coal-fired power plant (Case 1) and coal chemical plant (Case 2) by microalgae. The results show that total energy consumption and CO2 gas emissions for Case 1 are 27.5–38.0 MJ/kg microalgae power (MP) and 5.7–7.7 kg CO2 equiv/kg MP, respectively, which are lower than that for Case 2 (122.5–181.3 MJ/kg MP and 32.7–48.6 kg CO2 equiv/kg MP). The CO2 gas aeration rate and microalgae growth rate are the two most sensitive parameters for the energy conversion and net CO2 emission. Therefore, increasing the CO2 aeration efficiency and microalgae growth rate are key to advance the technology of flue gas CO2 fixation by microalgae which will contribute to carbon naturality.

In this study, HfO2-based multilayer spectrally selective emitters embedded with VO2 nanoparticles were designed and their spectral performance was analyzed. To verify the thermal stability of the designed emitters, in situ X-ray diffraction (XRD) was performed on the VO2 nanoparticles and the HfO2 film. The figure of merit (FOM), spectral selectivity efficiency (eta(s)), and spectral cutoff efficiency (eta(c)) were first adopted as the evaluation criteria, and an in-depth analysis of their relationship was conducted. Meanwhile, an ideal thermophotovoltaic (TPV) system was built to evaluate the spectral performance of the emitters that met the evaluation criteria requirements. Furthermore, the mechanism of the spectral selectivity of the proposed emitter was investigated. The in situ XRD results show that both the VO2 nanoparticles and HfO2 film can maintain thermal stability below 1300 K. The FOM is focused on the output energy of the emitter in the convertible waveband, while eta(s) and eta(c) are aimed at evaluating the energy conversion efficiency of the emitter. The emitters with maximum FOM, eta(s), and eta(c) show good performance in the TPV system. A trilayer emitter with a 100 nm embedded layer sandwiched by 10 nm HfO2 films can provide the TPV system with the highest conversion efficiency (13.4%) through the design process. The total thicknesses of the structures with good spectral performance are concentrated in the range of 90-165 nm. The structures can have good spectral performance in terms of their spectral emittance in the convertible waveband, which can be enhanced due to the influence of scattering of the nanoparticles. This study can provide guidelines for the development of a spectrally selective emitter with high thermal stability.

It is a great challenge for traditional passive camouflage materials to respond to spectral changes with environmental transitions. Hence, a spectrally tunable light source (STLS) sample composed of multitype light-emitting diodes for matching different background spectra was proposed. The common background spectra were measured. These spectra can provide the guidance and verification of the STLS sample in terms of spectral matching. The STLS sample was designed by a spectral fitting method with an equal interval of the peak wavelength, and an optimization method was proposed to match the different background spectra quickly and accurately. The theoretical results show that at least 30 light sources with different peak wavelengths are required to match all the collected spectra from the typical backgrounds. The correlation index between the measured STLS spectrum and the background spectrum of the gravel clay can increase from 0.5045 to 0.9518 after the optimization, indicating an accurate match. Except for the extremely low energy spectra, the correlation indexes can be maintained above 0.9275 for the collected spectra versus the different environments and time, exhibiting the verification of matching the different background spectra. Thus, we confirm the feasibility of the proposed STLS sample, which can provide a preliminary exploration for the application and development of dynamic spectral matching. (c) 2022 Society of Photo-Optical Instrumentation Engineers (SPIE)