Steam Generation Efficiency Research Articles

Enhancing efficiency of interfacial solar steam generation with biomimetic hierarchical porous graphene activated by NaOH

Interfacial solar steam generation (ISSG) provides a low-cost and green route to produce clean drinking water, meeting the urgent demand in remote and off-grid regions. To fabricate high-efficiency ISSG devices, researchers have harnessed graphene as an effective photothermal material of ISSG devices. However, the intricate fabrication and pristine hydrophobicity of graphene still limits the efficiency of ISSG devices. In this work, we present an approach to enhance the efficiency of ISSG using biomimetic hierarchically porous laser-induced graphene (LIG), activated by NaOH. The method involves one-step laser processing of polyimide films accompanied by NaOH activation, creating porous graphene structures with enhanced water wicking and evaporation rates. The optimal sample, activated by 5 M NaOH solution, exhibited superior evaporation performance at 2.41 kg/(m2·h) under one-sun irradiation. This advancement offers a promising avenue for cost-effective and efficient ISSG devices.

Steam generator efficiency optimization under uncertainty through multi-fidelity modeling

The steam generator is an essential equipment in power plants, and understanding its behavior with the aid of mathematical models allows for improved decision-making aiming toward better efficiency. Well-calibrated models can help identify new operating conditions that lead to efficiency enhancement. Unfortunately, due to the complexity of steam generators, computationally efficient models based solely on energy-mass balance usually present limiting simplifications. Alternatively, computational fluid dynamics can solve reacting flow phenomena but require a great amount of computational time. Purely data-driven models often extrapolate poorly as they do not necessarily contain the physical equations that drive the system’s behavior. In this scenario, the multi-fidelity approach is an attractive solution because it combines physics-grounded representation with a low computational footprint and allows for mapping the efficiency of the steam generator considering uncertainty propagation. This paper presents a multi-fidelity model that simulates the efficiency of a steam generator from the PECÉM power plant. The model is assembled by the sum of two Gaussian processes, trained using one high-fidelity and one low-fidelity dataset. The high-fidelity dataset is formed by the observed operation of the actual power plant at varying operating conditions. These same operating parameters are the input for the energy-mass balance model built using the EBSILON software to generate the low-fidelity dataset. The observed efficiency of the PECÉM power plant ranged from 82.89% to 84.37%, with a mean value of 83.58%. The resulting multi-fidelity model presents a root mean square error of 0.19%, which is six times lower than the error obtained by the energy-mass balance model. This model is then used for global sensitivity analysis and robust optimization. A Pareto front mapping expected efficiency and its confidence level is built by exploring not yet experimented operational points. Finally, data clustering allowed the identification of efficiencies around 86%, which adds 1.63% to the power plant’s maximum level.

Highly efficient 3D-screen printed interfacial solar water desalination system

Interfacial solar steam generation (ISSG) using floating devices is one of the most efficient and simple methods of purifying saline water. In this work, multi-layered solar steam generation systems are fabricated using 3D-screen printing. The printed devices with a uniform layer-by-layer structure contain light-harvesting, thermal insulation, thermal conduction, and water-transfer layers. The graphite (Gr) photothermal layer as an absorber layer is screen printed on the felt substrate with three different 3D patterns, which is isolated by transparent hydrophobic silica aerogel (SA) as a light scattering agent to provide efficient photon capturing and heat localization. Furthermore, to transfer the generated heat to the water proficiently, a copper (Cu) layer is coated on the downside of the absorber layer. The devices with the best performances are introduced by evaluating the effect of the fabricated layers thickness and different configurations. The multi-layered device containing a photothermal layer with SP1-3rd pattern and different thicknesses of SA 32 μm (under Cu), Cu 16 μm, Gr 32 μm, and SA 32 μm (on top of the Gr) shows a steam generation efficiency of 97 %, and water evaporation flux of 1.43 kg.m−2.h−1, which are 86 % higher than the performance of the reference system.

Robust and multifunctional MXene/rGO composite aerogels toward highly efficient solar-driven interfacial evaporation and wastewater treatment

Given the ever-growing global water resource crisis, exploiting multifunctional materials featuring with high interfacial solar steam generation efficiency and good purification capability to achieving seawater desalination and wastewater treatment simultaneously are highly desired, yet it still remains a huge challenge to date. Herein, robust and multifunctional MXene/rGO (MRGA) and polydopamine & chitosan @ MRGA (CS&PDA@MRGA, CPM) three-dimensional composite aerogels with distinct interconnected cellular architecture were developed via a facile ice template-assisted chemical reduction self-assembly technology and subsequent sequential deposition modification. Due to the favorable graphene oxide-assisted assembly behavior, the resultant aerogels displayed a desirable mechanical robustness along with an excellent lightweight property. Benefiting from the strong electrostatic interaction deriving from aerogel surface moieties and dye molecules, MRGA-12 exhibited a prominent adsorption capability towards various dyes and achieved a superb adsorption capacity of up to 396.05 mg/g for malachite green (MG). Moreover, by virtue of the synergistic effect between the intentionally regulated low reduction degree of rGO and the integration of PDA and CS, CPM-12 achieved a dramatically reduced evaporation enthalpy of water from 2256 to 1617.18 J/g. Accordingly, this distinct feature resulted in an extraordinary solar-driven interfacial evaporation performance with a remarkable evaporation rate of 1.86 kg/m2/h and a high evaporation efficiency of 83.28 % under 1 sun illumination. Therefore, together with the terrific oil/water separation capability, these novel MXene-based aerogels hold a great potential for high-performance solar-driven interfacial evaporation and wastewater treatment.

Integrated application of synergetic approach for enhancing intelligent steam generator control systems

This article focuses on the integrated application of the synergetic approach to enhance the quality of intelligent steam generator control systems.By combining various techniques such as model-based control, adaptive control, and artificial intelligence, an efficient and flexible control system can be developed. Model-based control utilizes mathematical models of steam generators to formulate control algorithms and predict system behavior. Adaptive control enables the system to adapt to changing conditions by adjusting control parameters based on real-time measurements. Artificial intelligence techniques, including neural networks and genetic algorithms, facilitate learning, optimization, and data-driven decision-making processes. The objectives of this research are to investigate the benefits of the synergetic approach in steam generator control, including improved steam generation efficiency, optimized energy consumption, enhanced system stability and reliability, and adaptability to varying operating conditions and disturbances. The findings and conclusions of this study are expected to provide valuable insights for engineers, researchers, and professionals involved in the design and implementation of intelligent steam generator control systems. By integrating the synergetic approach, substantial enhancements in control quality can be achieved, leading to optimal operation and maximum efficiency of power plants.

Spongy polyelectolyte hydrogel for efficient Solar-Driven interfacial evaporation with high salt resistance and compression resistance

The hydrogel-based evaporator for interface evaporation provides a method for sustainable freshwater production. However, salt accumulation on the surface of the steam generator affects light absorption and reduces steam generation efficiency. Achieving a high-performance, salt-resistant steam generator remains challenging. Here, sponge-like polyelectrolyte composite hydrogel-based solar steam generator (MPS) is reported. The steam generator is designed with an interpenetrating network topology and is made by in-situ polymerizing sodium polyacrylate (P(SA)) in a sponge-like polyvinyl alcohol (PVA) hydrogel framework, using molybdenum disulfide (MoS2) as a photothermal conversion material. Through the foaming process, MPS achieves self-floating and good water transportation performance, which enhances the thermal localization effect on the hydrogel surface and improves energy utilization efficiency (92.95 %), enabling efficient evaporation (3.22 kg m−2h−1). Meanwhile, due to the coupling of P(SA), MPS exhibits excellent salt resistance, maintaining a long-term evaporation rate of 2.8 kg m−2h−1 in high concentration saltwater (20 wt%). The porous structure and interconnected polymer chains enhance the mechanical performance of MPS, making it highly compressible and convenient for collecting freshwater marine and wilderness environments. The preparation strategy of MPS provides a feasible method to simultaneously improve the performance and durability of the interface steam generator in practical applications.

Waste Tea-Derived Theabrownins for Solar-Driven Steam Generation.

Solar-driven seawater desalination has been considered an effective and sustainable solution to mitigate the global freshwater crisis. However, the substantial cost associated with photothermal materials for evaporator fabrication still hinders large-scale manufacturing for practical applications. Herein, we successfully obtained high yields of theabrownins (TB), which were oxidation polymerization products of polyphenols from waste and inferior tea leaves using a liquid-state fermentation strategy. Subsequently, a series of photothermal complexes were prepared based on the metal-phenolic networks assembled from TB and metal ions (Fe(III), Cu(II), Ni(II), and Zn(II)). Also, the screened TB@Fe(III) complexes were directly coated on a hydrophilic poly(vinylidene fluoride) (PVDF) membrane to construct the solar evaporation device (TB@Fe(III)@PVDF), which not only demonstrated superior light absorption property and notable hydrophilicity but also achieved a high water evaporation rate of 1.59 kg m-2 h-1 and a steam generation efficiency of 90% under 1 sun irradiation. More importantly, its long-term stability and exceptionally low production cost enabled an important step toward the possibility of large-scale practical applications. We believe that this study holds the potential to pave the way for the development of sustainable and cost-effective photothermal materials, offering new avenues for utilization of agriculture resource waste and solar-driven water remediation.

Crystal Plane Engineering to Boost Water Cluster Evaporation for Enhanced Solar Steam Generation.

Polymer based low evaporation enthalpy materials have become a universal selection for improving the efficiency of solar steam generation. Although water cluster and intermediate water mechanisms have been proposed to explain the low evaporation enthalpy, the production process and microstructure of activated water are still unclear. Here, crystal plane engineering is used to investigate the intermediate water state and the water cluster activation mechanism. The unique open-closed coordination structure on the optimized crystal surface promotes the generation of firm water clusters by optimizing the intermediate water state. Under the similar solar energy absorption of all materials, crystal plane engineering increased the solar steam generation rate of the evaporator by 31.2% and increased the energy efficiency to 94.8%. Exploring the micro-evaporation process and activated water structure is expected to stimulate the development of the next generation low evaporation enthalpy materials.

Optimizing Thermal Performance in Parabolic Trough Solar Power Systems: An Experimental Design and Analysis

The efficiency of a Parabolic Trough (PT) Solar Power Plant heavily relies on its thermal performance. Modern technology has allowed for the creation of more efficient methods of producing steam and of collecting solar energy for thermal power generation. Ministry of New & Renewable Energy (MNRE) built and tested an 11.1 m2 parabolic trough concentrator (PTC). A system that generates steam indirectly by using concentrating solar power (CSP) is examined. The study examined absorbers' thermal properties, thermal efficiency of combined thermal exchangers, concentration ratio, heat efficiency, and steam generation to determine their influence on energy efficiency. The experimental findings display that 557.85 watts of energy are absorbed by the PTC receiver. The PT solar plant system has a thermal energy efficiency of 25 to 29 % and a concentration factor of about 200 on average. The parabolic trough concentrator generates a maximum of 9.1 kg.h-1 of steam.

All-in-one self-floating porous foams as robust heat-blocking layers for efficient photothermal conversion and solar desalination

Solar-driven interfacial evaporation is a highly efficient and ecofriendly technology for producing freshwater. Herein, self-floating plasmon Ag/black TiO2/carbon porous layered foams (Ag-BTCFs) were demonstrated as efficient solar-thermal convectors using freeze-drying cast-molding and high-temperature surface hydrogenation strategies. This all-in-one three-dimensional (3D) cross-linked self-floating porous layered foam material with full-spectrum absorption can fully harvest sunlight (∼95.45%) and effectively block heat transfer to its sublayer. The synergy of sufficient utilization of absorbed ultraviolet radiation by black TiO2 (b-TiO2), visible light absorption by Ag nanoparticles (Ag NPs) via localized surface plasmon resonance, and near-infrared absorption by layered-amorphous carbon can achieve full-solar-spectrum absorption to concentrate thermal energy. In addition to their synergistic effect, they are conducive to the relaxation of hot electrons when utilizing photogenerated holes to degrade pollutants in domestic wastewater. The steam generation efficiency of Ag-BTCFs is up to 1.79 kg m−2h−1 due to their solar energy conversion efficiency of 81.74% under 1 sun irradiation, which is five times higher than the evaporation rate of pure water. Notably, the material’s efficient ion removal rate of 99.80% for solar desalination indicates its high potential for various applications. This strategy provides new insights for fabricating recyclable heat-blocking layer systems against thermal loss to enhance solar steam generation.

Plasmon-Mediated Solar Steam Generation over Au@Cu7S4 Yolk@Shell Nanocrystals

In recent years, solar steam generation has attracted extensive attention because it can address the shortage of water resources. Traditional techniques enabling solar steam generation are based on heating water under concentrated solar irradiation, suffering from low solar to heat conversion efficiency. By exploiting the heat localization effect from photothermal materials, the efficiency of solar steam generation can be significantly improved. Similarly, electromagnetic field confinement induced by plasmonic materials has also proven efficient for promoting solar steam generation. In this study, Au@Cu7S4 yolk@shell nanocrystals were prepared and employed as plasmonic mediums for superior solar steam generation. Here, Au was a typical plasmonic metal showing a plasmon resonance peak around 550 nm. Cu7S4, on the other hand, represented a self-doped plasmonic semiconductor capable of absorbing photons beyond 1000 nm. The combination of Au and Cu7S4 in Au@Cu7S4 nanocrystals allowed a broadband light absorption across the visible and near infrared regions. The superior solar steam generation over Au@Cu7S4 was attributed to the broadband light absorption and the enhanced solar to heat conversion efficiency rendered by the combined plasmonic effects of Au and Cu7S4.

D-A-Type Molecules with Free Rotors for Highly Efficient Interfacial Solar-Driven Steam Generation and Thermoelectric Performance.

Three "π"-shaped D-A-type thiodiazoloquinoxaline derivatives with different electronic structures and rotations have been prepared. Their particular structures allow these molecules to possess a broad absorption range and sufficient intramolecular motions, dissipating energy through a thermal deactivation pathway. Among the three materials, TPA-TQN showed the best steam generation efficiency (84.52%) and water-electricity cogeneration efficiency (63.95%). This study suggests that D-A structures with different electronic configurations, free rotors, and hydrophilicities make great contributions to the overall solar energy conversion performances.

Aspects of Thermal Protection of Machine-Building and Power Equipment: Application of Oxidation-Resistant Combined Nickel-Based Coatings

Introduction. In the areas of power engineering where the thermal energy of superheated steam is used, an important aspect of providing the reliability and safety of equipment is the heat resistance of the materials employed. In the manufacture of induction superheaters, the optimal material for the steam pipe (coil) is copper. However, its ultimate resistance to oxidation does not exceed 400 °C, which significantly limits the efficiency of steam generators. Therefore, the objective of the work was to study the kinetics of oxidation of the combined galvanic coating of the Mo-Ni-Cr system applied to copper tubular samples and intended for thermal protection of steam generator coils.Materials and Methods. A combined electroplating of the Mo-Ni-Cr system with a total thickness of 12–35 μm was formed on the experimental copper tubular samples. A Mo sublayer with a thickness of about 1.5 μm on the surface of the copper tube was formed to prevent the diffusion of Cu into the Ni coating. A 1.5 μm thick chromium layer on the coating surface acted as an indicator of the oxidation process. A comparative analysis of the oxidation processes of the copper surface and the combined coating of the Mo-Ni-Cr system on a copper substrate was carried out using the methods of optical and electron microscopy, energy dispersive analysis, and precision determination of the growth parameters of oxide films.Results. The intervals of thermal stability of the copper substrate and nickel coating were experimentally determined. The obtained experimental dependences characterized the parabolic law of copper oxidation with the formation of a single-phase diffusion zone of CuO at temperatures above 350 °C, and nickel at temperatures above 750 °C, when the transition of NiO monoxide into oxide Ni2O3 began. The growth of oxide films according to quadratic laws provided a rapid increase in the thickness of the films, the accumulation of stresses in them, cracking, and chipping.Discussion and Conclusion. It is shown that the Mo-Ni-Cr electroplating is resistant to heating during long-term operation up to temperatures of 750–800 °C. The functional roles of Mo and Cr in the coating architecture were described. The work focused on the applied aspect of using the coating under study to increase the thermal stability of the steam pipelines of industrial induction superheaters with low and medium power.

A high-efficient and salt-rejecting 2D film for photothermal evaporation

The solar-driven desalination is seen as a sustainable way to combat water scarcity. However, the solar steam generation efficiency has long been restricted by the high vaporization enthalpy of water and low energy density of natural sunlight. We introduced graphene oxide (GO) cross-linked with polyethyleneimine (PEI) as the photothermal material, with the enriched ammonic functional groups in modified GO membrane (GPM) activating water molecules to evaporate with much lower energy consumption. The vaporization enthalpy at the air-film interface is reduced up to 42% in GPM film by tuning the thermodynamic states of water. Consequently, GPM film enables a high evaporation rate of 2.48kg m-2 h-1 with 95.7% energy conversion efficiency under 1 sun. With the aid of positive charges introduced by hydrolysis of PEI, the GPM exhibits excellent salt resistance and delivers an evaporation rate around 1.8kg m-2 h-1 when treating 20 wt% NaCl solution.

Interface engineering of Co3O4 nanoparticle for high-efficiency interfacial solar steam generation

Solar steam generation has been proven to be an innovative and sustainable technology to mitigate the issue of clean water shortage. But, to-date, optimizing a suitable candidate material system to improve the evaporation efficiency is an urgent need, especially the interface engineering tailored heat transfer of materials has not yet made a breakthrough. Herein, we successfully designed a Co3O4 nanoparticle that can promote the optimization of the heat transfer performance using interface engineering. The optimized Co3O4 nanoparticles creates a close contact with the cotton sheet, creating an efficient channel for heat transfer and achieving high photothermal steam generation efficiency. The interfacial solar steam generation has been found to achieve a high evaporation rate of 2.72 kg/m2·h, which is higher than that of traditional bulk phase heating. Our findings not only showcase the efficacy of interface engineering in the design of solar steam generation, but also present a cost-effective and straightforward methodology that can be applied for water purification purposes.

Dual-Layer Starch-based Biological Hydrogel Durable Evaporator for Efficient Solar Steam Generation

Solar-powered desalination is an effective means to address the global freshwater shortage and combat water pollution. However, the light absorption capacity, thermal insulation performance, and water transmission efficiency of most current solar evaporators cannot be effectively combined, resulting in a relatively low utilization rate of solar energy. In this study, a double-layer solar evaporator was reported by using starch as the biological hydrogel matrix and carbon nanotubes as an efficient light-absorbing material, which greatly improved the solar energy utilization rate of the evaporator and the steam generation efficiency was as high as 2.21 kgm−2h−1 under 1.0 sun.

Biorenewable Polymer-Based Light-Absorbing Porous Hydrogel for Efficient Solar Steam Desalination.

An efficient interfacial heating system composed of a light-absorbing material and a hydrophilic porous support is developed through eco-friendly and energy-effective fabrication processes. Lignin nanoparticles (NPs) and cellulose nanofibers (CNFs) are harnessed as biorenewable light absorbers and hydrophilic supports, respectively. Lignin NPs are prepared using a solvent exchange process of the fractionated lignin with organic solvents to improve its π-π stacking and light-absorbing property for efficient photothermal conversion. Then, the lignin NPs are mixed with CNFs and lyophilized to obtain a light-absorbing porous hydrogel (LAPH), and the resulting LAPHs are covalently cross-linked and hybridized with Au NPs through a seed-mediated growth to further enhance their mechanical stability, hydrophilicity, and photothermal conversion properties. The resulting LAPHs exhibit an outstanding and prolonged performance as a solar steam generator such as high salt and pH tolerance, evaporation rate (3.17 kg m-2 h-1), and solar steam generation efficiency (83.4%) under 1 sun irradiation.

Defect-enriched red phosphorus nanosheets as efficient and stable photothermal absorber material for interfacial solar desalination

The development of efficient photothermal materials has gained increasing attention for solar thermal-energy conversion. A good photothermal material has a strong light-absorption property, low thermal conductivity, high wettability, and high solar-to-thermal conversion efficiency. In this study, we prepared uniform, sub-micron, and defect-rich red phosphorus (RP) nanosheets via a simple ball-milling method to demonstrate their efficient and durable solar steam generation properties. Three RPs of different sizes were prepared by controlling the milling time (0 h: RP0, 30 h: RP30, and 60 h: RP60). Notably, RP60 exhibited the smallest particle (lateral) size, nanosheet morphology, and defect-rich surface. Furthermore, RP60 exhibited the distinctive properties of a small band gap (1.44 eV), low thermal conductivity (0.07 W/m·K), and low heat capacity (0.66 J/g·K) with exceptional wettability. With simulated sunlight illumination (100 mW/cm2, 1 sun), the RP60 photothermal absorber demonstrated a high water evaporation rate of 1.34 kg/m2·h with a stable solar steam generation efficiency of 74.1 % for over 10 h. A one-dimensional water path and porous polyurethane support facilitated the water supply, large contact area, heat localization, and steam escape. By employing plasmonic resonance-heating silver nanoparticles on the RP60, we achieved a significantly improved solar steam generation efficiency of over 96.0 % and a water evaporation rate of 1.75 kg/m2·h. This study highlights the critical role of morphology, particle size, and defects control in improving the photothermal properties for efficient and durable interfacial seawater desalination.

Surpassing 2D Photoabsorbers with Palm Fiber Upcycling as Highly Hydrophilic and Low-Cost Photothermal Materials for Improved Water Transport Interfacial Solar Steam Generation

Solar steam generation (SSG) has been proposed in the recent years as one of the countermeasures for solving the increasing risk of water scarcity on a global scale. SSG outshines conventional water treatment technologies with solar energy being its primary driving energy as well as its relatively simple system design. Nevertheless, challenges have been addressed for SSG, particularly the low efficiency of steam generation and dubious economic feasibility. In this study, a solar evaporator consisting of low-temperature carbonized oil palm fibers with integration of polydopamine is used to construct a biomass-based solar evaporator. Owing to the synergistic effect of the wide solar absorption spectrum of the carbonized fiber and highly hydrophilic characteristics of polydopamine, a water evaporation rate of 1.637 kg m–2 h–1 is achieved under 1 sun irradiation. To demonstrate the ability of the as-designed system for water treatment applications, actual lake water and seawater are employed as water reservoirs, and the water purification effect is assessed in terms of total dissolved solids and salinity. This biomass-derived evaporator offers a design rationale for cost-effective steam generation via biomass waste upcycling of the oil palm industry, which is advantageous for the scalable setup of the system in water-scarce, impoverished area.

Surface hydrophobicity-hydrophilicity switching induced interface heat and water transfer enhancement for high-efficiency solar steam generation

Beyond photothermal conversion, the surface wettability of light-absorbing materials should be also determinative to the efficiency of solar-driven interfacial steam generation (SISG). Herein, by modifying hydrophobic Cu nanoparticles (NPs) with a hydrophilic carbon (C) shell, hydrophilic Cu@C core–shell NPs were successfully fabricated and used for constructing evaporation films for SISG. In comparison to the film constructed with Cu NPs, the evaporation films constructed with Cu@C core–shell NPs exhibit much increased SISG efficiency, reaching 94.6% as high. Except for the localized surface plasmon resonance (LSPR) effect of Cu NPs ensuring the excellent photothermal conversion, it is experimentally and theoretically revealed that the surface wettability switching from hydrophobicity to hydrophilicity, as induced by C coating, is beneficial to heat transfer at the solid/liquid interface and water transport at the evaporative surface, thus improving the thermal-evaporation conversion performance for efficient SISG. However, the further thickened C shells would weaken the LSPR effect and hinder the interface heat and water transfer, leading to the decreased photothermal and thermal-evaporation conversion efficiencies, and thus the lowered SISG performances. This demonstration gives an alternative and promising access to the rational design of photothermal materials featured with switchable surface wettability ensuring interface heat and water transfer enhancement for efficient SISG.