Biomass is plant or animal material that stores both chemical and solar energies, and that is widely used for heat production and various industrial processes. Biomass contains a large amount of the element hydrogen, so it is an excellent source for hydrogen production. Therefore, biomass is a sustainable source for electricity or hydrogen production. Although biomass power plants and reforming plants have been commercialized, it remains a difficult challenge to develop more effective and economic technologies to further improve the conversion efficiency and reduce the environmental impacts in the conversion process. The use of biomass-based flow fuel cell technology to directly convert biomass to electricity and the use of electrolysis technology to convert biomass into hydrogen at a low temperature are two new research areas that have recently attracted interest. This paper first briefly introduces traditional technologies related to the conversion of biomass to electricity and hydrogen, and then reviews the new developments in flow biomass fuel cells (FBFCs) and biomass electrolysis for hydrogen production (BEHP) in detail. Further challenges in these areas are discussed.
Power to hydrogen (P2H) provides a promising solution to the geographic mismatch between sources of renewable energy and the market, due to its technological maturity, flexibility, and the availability of technical and economic data from a range of active demonstration projects. In this review, we aim to provide an overview of the status of P2H, analyze its technical barriers and solutions, and propose potential opportunities for future research and industrial demonstrations. We specifically focus on the transport of hydrogen via natural gas pipeline networks and end-user purification. Strong evidence shows that an addition of about 10% hydrogen into natural gas pipelines has negligible effects on the pipelines and utilization appliances, and may therefore extend the asset value of the pipelines after natural gas is depleted. To obtain pure hydrogen from hydrogen-enriched natural gas (HENG) mixtures, end-user separation is inevitable, and can be achieved through membranes, adsorption, and other promising separation technologies. However, novel materials with high selectivity and capacity will be the key to the development of industrial processes, and an integrated membrane-adsorption process may be considered in order to produce high-purity hydrogen from HENG. It is also worth investigating the feasibility of electrochemical separation (hydrogen pumping) at a large scale and its energy analysis. Cryogenics may only be feasible when liquefied natural gas (LNG) is one of the major products. A range of other technological and operational barriers and opportunities, such as water availability, byproduct (oxygen) utilization, and environmental impacts, are also discussed. This review will advance readers' understanding of P2H and foster the development of the hydrogen economy.
Aqueous solutions of tertiary amines are promising absorbents for CO2 capture, as they are typically characterized by a high absorption capacity, low heat of reaction, and low corrosivity. However, tertiary amines also exhibit very low kinetics of CO2 absorption, which has made them unattractive options for large-scale utilization. Here, a series of novel nanoporous carbonaceous promoters (NCPs) with different properties were synthesized, characterized, and used as rate promoters for CO2 absorption in aqueous N,N-diethylethanolamine (DEEA) solutions. To prepare a DEEA–NCP nanofluid, NCPs were dispersed into aqueous 3 mol∙L-1 DEEA solution using ultrasonication. The results revealed that among microporous (GC) and mesoporous (GS) carbonaceous structures functionalized with ethylenediamine (EDA) and polyethyleneimine (PEI) molecules, the GC–EDA promoter exhibited the best performance. A comparison between DEEA–GC–EDA nanofluid and typical aqueous DEEA solutions highlighted that the GC-EDA promoter enhances the rate of CO2 absorption at 40 °C by 38.6% (36.8–50.7 kPa∙min-1) and improves the equilibrium CO2 absorption capacity (15 kPa; 40 °C) by 13.2% (0.69–0.78 mol of CO2 per mole of DEEA). Moreover, the recyclability of DEEA–GC–EDA nanofluid was determined and a promotion mechanism is suggested. The outcomes demonstrate that NCP–GC–EDA in tertiary amines is a promising strategy to enhance the rate of CO2 absorption and facilitate their large-scale deployment.
In this report, we show that hyperspectral high-resolution photoluminescence mapping is a powerful tool for the selection and optimiz1ation of the laser ablation processes used for the patterning interconnections of subcells on Cu(Inx,Ga1-x)Se2 (CIGS) modules. In this way, we show that in-depth monitoring of material degradation in the vicinity of the ablation region and the identification of the underlying mechanisms can be accomplished. Specifically, by analyzing the standard P1 patterning line ablated before the CIGS deposition, we reveal an anomalous emission-quenching effect that follows the edge of the molybdenum groove underneath. We further rationalize the origins of this effect by comparing the topography of the P1 edge through a scanning electron microscope (SEM) cross-section, where a reduction of the photoemission cannot be explained by a thickness variation. We also investigate the laser-induced damage on P1 patterning lines performed after the deposition of CIGS. We then document, for the first time, the existence of a short-range damaged area, which is independent of the application of an optical aperture on the laser path. Our findings pave the way for a better understanding of P1-induced power losses and introduce new insights into the improvement of current strategies for industry-relevant module interconnection schemes.
As an alternative to conventional encapsulation concepts for a double glass photovoltaic (PV) module, we introduce an innovative ionomer-based multi-layer encapsulant, by which the application of additional edge sealing to prevent moisture penetration is not required. The spontaneous moisture absorption and desorption of this encapsulant and its raw materials, poly (ethylene-co-acrylic acid) and an ionomer, are analyzed under different climatic conditions in this work. The relative air humidity is thermodynamically the driving force for these inverse processes and determines the corresponding equilibrium moisture content (EMC). Higher air humidity results in a larger EMC. The homogenization of the absorbed water molecules is a diffusion-controlled process, in which temperature plays a dominant role. Nevertheless, the diffusion coefficient at a higher temperature is still relatively low. Hence, under normal climatic conditions for the application of PV modules, we believe that the investigated ionomer-based encapsulant can ″breathe″ the humidity: During the day, when there is higher relative humidity, it ″inhales″ (absorbs) moisture and restrains it within the outer edge of the module; then at night, when there is a lower relative humidity, it ″exhales″ (desorbs) the moisture. In this way, the encapsulant protects the cell from moisture ingress.
Coal is the dominant energy source in China, and coal-fired power accounts for about half of coal consumption. However, air pollutant emissions from coal-fired power plants cause severe ecological and environmental problems. This paper focuses on near-zero emission technologies and applications for clean coal-fired power. The long-term operation states of near-zero emission units were evaluated, and synergistic and special mercury (Hg) control technologies were researched. The results show that the principle technical route of near-zero emission, which was applied to 101 of China's coal-fired units, has good adaptability to coal properties. The emission concentrations of particulate matter (PM), SO2, and NOx were below the emission limits of gas-fired power plants and the compliance rates of the hourly average emission concentrations reaching near-zero emission in long-term operation exceeded 99%. With the application of near-zero emission technologies, the generating costs increased by about 0.01 CNY∙(kW∙h)–1. However, the total emissions of air pollutants decreased by about 90%, resulting in effective improvement of the ambient air quality. Furthermore, while the Hg emission concentrations of the near-zero emission units ranged from 0.51 to 2.89 μg∙m–3, after the modified fly ash (MFA) special Hg removal system was applied, Hg emission concentration reached as low as 0.29 μg∙m–3. The operating cost of this system was only 10%–15% of the cost of mainstream Hg removal technology using activated carbon injection. Based on experimental studies carried out in a 50 000 m3∙h–1 coal-fired flue gas pollutant control pilot platform, the interaction relationships of multi-pollutant removal were obtained and solutions were developed for emissions reaching different limits. A combined demonstration application for clean coal-fired power, with the new ″1123” eco-friendly emission limits of 1, 10, 20 mg∙m–3, and 3 μg∙m–3, respectively, for PM, SO2, NOx, and Hg from near-zero emission coal-fired power were put forward and realized, providing engineering and technical support for the national enhanced pollution emission standards.
China's past economic growth has substantially relied on fossil fuels, causing serious air pollution issues. Decoupling economic growth and pollution has become the focus in developing ecological civilization in China. We have analyzed the three-decade progress of air pollution controls in China, highlighting a strategic transformation from emission control toward air quality management. Emission control of sulfur dioxide (SO2) resolved the deteriorating acid rain issue in China in 2007. Since 2013, control actions on multiple precursors and sectors have targeted the reduction of the concentration of fine particulate matter (PM2.5), marking a transition to an air-quality-oriented strategy. Increasing ozone (O3) pollution further requires O3 and PM2.5 integrated control strategies with an emphasis on their complex photochemical interactions. Fundamental improvement of air quality in China, as a key indicator for the success of ecological civilization construction, demands the deep de-carbonization of China's energy system as well as more synergistic pathways to address air pollution and global climate change simultaneously.
Sustainable processes for purifying water, capturing carbon, producing biofuels, operating fuel cells, and performing energy-efficient industrial separations will require next-generation membranes. Solvent-less fabrication for membranes not only eliminates potential environmental issues with organic solvents, but also solves the swelling problems that occur with delicate polymer substrates. Furthermore, the activation procedures often required for synthesizing microporous materials such as metal–organic frameworks (MOFs) can be reduced when solvent-less vapor-phase approaches are employed. This perspective covers several vacuum deposition processes, including initiated chemical vapor deposition (iCVD), initiated plasma-enhanced chemical vapor deposition (iPECVD), solvent-less vapor deposition followed by in situ polymerization (SLIP), atomic layer deposition (ALD), and molecular layer deposition (MLD). These solvent-less vapor-phase methods are powerful in creating ultrathin selective layers for thin-film composite membranes and advantageous in conformally coating nanoscale pores for the precise modification of pore size and internal functionalities. The resulting membranes have shown promising performance for gas separation, nanofiltration, desalination, and water/oil separation. Further development of novel membrane materials and the scaling up of high-throughput reactors for solvent-less vapor-phase processes are necessary in order to make a real impact on the chemical industry in the future.
Burgeoning growth of tall buildings in urban areas around the world is placing new demands on their performance under winds. This involves selection of the building form that minimizes wind loads and structural topologies that efficiently transfer loads. Current practice is to search for optimal shapes, but this limits buildings with static or fixed form. Aerodynamic shape tailoring that consists of modifying the external form of the building has shown great promise in reducing wind loads and associated structural motions as reflected in the design of Taipei 101 and Burj Khalifa. In these buildings, corner modifications of the cross-section and tapering along the height are introduced. An appealing alternative is to design a building that can adapt its form to the changing complex wind environment in urban areas with clusters of tall buildings, i.e., by implementing a dynamic facade. To leap beyond the static shape optimization, autonomous dynamic morphing of the building shape is advanced in this study, which is implemented through a cyber–physical system that fuses together sensing, computing, actuating and engineering informatics. This approach will permit a building to intelligently morph its profile to minimize the source of dynamic wind load excitation, and holds the promise of revolutionizing tall buildings from conventional static to dynamic facades by taking advantage of the burgeoning advances in computational design.
Water-triggered materials are receiving increasing attentions due to their diverse capabilities such as easy operation, soft actuation, low cost, environmental friendliness, and many more other advantages. However, most of such materials generally have a long reaction time and require strict preservation conditions, which limit their adaptability in practice. In this study, a novel water-triggered material based on Al-NaOH-composited eutectic gallium–indium alloys (eGaIn) was proposed and demonstrated, which is rather fast-responsive and deformable. Once water is applied, the material thus fabricated would achieve a temperature rise of 40 °C in just several seconds along with gas production, indicating its big potential to be used as a thermal and pneumatic actuator. Further, the new material's reusability and degradation ability were also tested. Following that, a double-layer-structure smart bandage was designed, whose bulk was filled with Al-NaOH-composited eGaIn while BiInSn served as outer supporting material. According to the experiments, a sheet structure with a thickness of 2 mm would support a weight of 1.8 kg after it was subjected to a cooling process, which is much better than the weight-bearing capability of fiberglass. In addition, a prototype of a water-triggered sphere robot was also fabricated using Al-NaOH-eGaIn, which realized rolling and bouncing behaviors under specific external stimulation. These findings indicate the potential value of the present material in developing future wearable devices, soft actuators, and soft robotics.
This study presents a connected vehicles (CVs)-based traffic signal optimization framework for a coordinated arterial corridor. The signal optimization and coordination problem are first formulated in a centralized scheme as a mixed-integer nonlinear program (MINLP). The optimal phase durations and offsets are solved together by minimizing fuel consumption and travel time considering an individual vehicle's trajectories. Due to the complexity of the model, we decompose the problem into two levels: an intersection level to optimize phase durations using dynamic programming (DP), and a corridor level to optimize the offsets of all intersections. In order to solve the two-level model, a prediction-based solution technique is developed. The proposed models are tested using traffic simulation under various scenarios. Compared with the traditional actuated signal timing and coordination plan, the signal timing plans generated by solving the MINLP and the two-level model can reasonably improve the signal control performance. When considering varies vehicle types under high demand levels, the proposed two-level model reduced the total system cost by 3.8% comparing to baseline actuated plan. MINLP reduced the system cost by 5.9%. It also suggested that coordination scheme was beneficial to corridors with relatively high demand levels. For intersections with major and minor street, coordination conducted for major street had little impacts on the vehicles at the minor street.