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Triboelectric nanogenerator (TENG) systems have been demonstrated to generate power with high density. However, the electrical output power obtained from wave energy harvesting using TENG systems is typically limited to several milliwatts. To address this limitation and support various ocean buoy systems, an efficient method to scale-up TENG systems is required. In this paper, we present a self-powered ocean buoy (SPOB) incorporating a disk-type, soft-contact, mechanical frequency regulator TENG (DSMFR-TENG). The mechanical frequency regulator (MFR) enables the conversion of low-frequency wave energy to high-speed mechanical rotation, facilitating high power generation with the disk-type TENG. The SPOB was tested in a wave tank, reaching a peak power output of 470 mW and an average power output of 130 mW after the MFR released the rotational energy. To further enhance the functionality of the buoy, the DSMFR-TENG and a microcontroller, temperature sensor, and acoustic transmitter were integrated with the SPOB. The acoustic transmitter successfully transmitted signals 7, 23, and 30 times over a one-minute period at wave frequencies of 0.33 Hz, 0.5 Hz, and 1 Hz, respectively, thereby demonstrating the power supply capability of the TENG system for ocean buoys. [Display omitted] • A disk-type, soft-contact, mechanical frequency regulator TENG is designed to power ocean buoys. • A mechanical frequency regulator is designed to generate high-speed mechanical rotation using low frequency wave. • The TENG reached a peak and average power output of 470 and 130 mW after the MFR released the rotational energy. • The acoustic transmitter successfully sent signals 7 times over a one-minute period at a wave frequency of 0.33 Hz. [ABSTRACT FROM AUTHOR]

• The first physical & biological evaluation of hydro turbines in Lower Mekong River. • Testing was conducted on an older 17.5-MW turbine and a newer 40-MW turbine. • The newer turbine had fewer occurrences of severe acceleration events. • The newer turbine had better pressure environment for fish during runner passage. • This study can be used to guide the design of new hydropower in the region. The Mekong River is one of the most biodiverse rivers on Earth. Many communities located near the river rely on fisheries for sustenance and economics. Along the Mekong River mainstem there are plans for 11 new hydropower projects, with potentially several hundred smaller projects along tributaries. To understand the hydraulic conditions at existing dams in the region, Sensor Fish were deployed at Nam Ngum Dam in Laos. The data collected by Sensor Fish can be used to predict fish injury/mortality if there is a dose-response relationship for the species of interest. The Sensor Fish were released through two units—Unit 1, an older 17.5-MW Francis turbine, and Unit 4, a newer 40-MW Francis turbine. Comparisons were made between the Sensor Fish measurements at Nam Ngum to those from four hydroelectric dams in the U.S. Between the newer and older turbine units tested at Nam Ngum, the newer Unit 4 had a higher median nadir pressure of 126 kPaA compared to 99 kPaA. With respect to both pressure and acceleration, the older Unit 1 had more severe hydraulic conditions. By understanding the physical conditions within existing hydropower projects, and the potential ecological impact those conditions could have on the local fauna, better informed decisions can be made regarding project operations. The results from this study can also be used to guide the engineering design of new hydropower turbines that will improve ecological conditions. [ABSTRACT FROM AUTHOR]

Abstract Siphon turbines are an attractive type of small-scale hydropower turbines because they can be retrofitted into existing structures where there is already a drop in water elevation. A siphon turbine conveys water from an upper reservoir to a lower reservoir through the use of a siphon structure that goes over the top of the dam. A small, neutrally buoyant autonomous sensor package known as a Sensor Fish was deployed through a siphon turbine at the Head of the U Hydroelectric Project in Idaho, USA. Comparisons were made between the siphon turbine in this study and other low-head turbines that have been studied using Sensor Fish. The Sensor Fish measurements indicate that this siphon turbine can generate nadir (i.e., minimum) pressures during runner passage of 22.4 kPaA, which is much lower than those of other low-head turbine types that have been studied using Sensor Fish and could be potentially harmful to fish species susceptible to barotrauma injury. Severe acceleration events occurred in the wicket gate and runner regions at rates of 12% and 47% respectively. These numbers are comparable or lower than other low-head turbines that have been studied with Sensor Fish. Due to the low nadir pressures measured, stakeholders should determine the presence of any fish species-of-concern in the area that are susceptible to barotrauma, and if so, methods to avoid or reduce fish entrainment such as screening technologies or diversions should be investigated. Highlights • Sensor Fish used to characterize hydraulic conditions through a siphon turbine. • Nadir pressures measured during runner passage were very low (22.4 KPaA). • Over 50% of releases experienced at least one occurrence of high acceleration. • Data can be used to guide cleaner power production from low-head hydropower. [ABSTRACT FROM AUTHOR]

Previous studies reported that the electrical output of triboelectric nanogenerator (TENG) materials is higher at low temperatures (below −20 °C) than at room temperature, indicating that a TENG device may be suitable in low-temperature environments such as the Arctic Ocean. However, research on TENG systems for extreme weather conditions (temperatures as low as) −40 °C is lacking. This paper presents the design of Arctic-TENG, which efficiently generates electricity to power a satellite communication system in Arctic Ocean conditions. Arctic-TENG was designed for low-temperature operations and performs better at cold temperatures than at room temperature. Using an out-of-water wave simulator at 0.2 Hz, the peak power density of Arctic-TENG reached 21.4 W/m3. Realistic energy requirements were obtained by implementing a satellite communication system, and the available energy from Arctic-TENG was measured and evaluated considering the available wave energy in the Arctic Ocean. The total energy generated per year from Arctic-TENG is 8.59 kJ. One Arctic-TENG can transmit 540 bytes of data per day over a year, which demonstrates the power supply capability of Arctic-TENG for long-term operation of a satellite communication system. [Display omitted] • Arctic-TENG was designed to efficiently generates electricity to power a satellite communication system in Arctic Ocean. • Arctic-TENG successfully showed stable operation at − 40 °C. • The peak power density of Arctic-TENG reached 21.4 W/m3 using a wave simulator at 0.2 Hz. • Experimental results demonstrated the power supply capability of Arctic-TENG for satellite communication system. [ABSTRACT FROM AUTHOR]

Hydropower plays an important role as the global energy system moves towards a less carbon-intensive and sustainable future as promoted under the Sustainable Development Goals (SDGs). This article provides a systematic review of the impacts from policy, climate change and Water-Energy-Food (W-E-F) nexus on hydropower development at global scale. Asia, Africa and Latin America are hotspots promoting hydropower development with capacity expansion, while Europe and North America focus on performance improvement and environment impacts mitigation. Climate change is projected to improve gross hydropower potential (GHP) at high latitude of North Hemisphere and tropical Africa and decrease that in the US, South Africa and south and central Europe. Analysis from W-E-F nexus highlights the importance of integrated approaches as well as cross-sectoral coordination so as to improve resources use efficiency and achieve sustainable hydropower development. These three factors together shape the future of hydropower and need to be considered for planning and operation purpose. [ABSTRACT FROM AUTHOR]

Microbatteries play a critical role in determining the lifetime of downsized sensors, wearable devices, medical applications, and animal acoustic telemetry transmitters among others. More often, structural batteries are required from the perspective of aesthetics and space utilization, which is however rarely explored. Herein, we discuss the fundamental issues associated with the rational design of practically usable high energy microbatteries. The tubular shape of the cell further allows the flexible integration of microelectronics. A functioning acoustic micro-transmitter continuously powered by this tubular battery has been successfully demonstrated. Multiple design features adopted to accommodate large mechanical stress during the rolling process are discussed providing new insights in designing the structural microbatteries for emerging technologies. [ABSTRACT FROM AUTHOR]

In recent years, distributed renewable energy-generation technologies, such as wind and solar, have developed rapidly. Nevertheless, the utilization of ultra-low-head (ULH) water energy (i.e., situations where the hydraulic head is less than 3 m or the water flow is more than 0.5 m/s with zero head) has received little attention. We believe that, through technological innovations and cost reductions, ULH hydropower has the potential to become an attractive, renewable, and sustainable resource. This paper investigates potential sites for ULH energy resources, the selection of relevant turbines and generators, simplification of civil works, and project costs. This review introduces the current achievements on ULH hydroelectric technology to stimulate discussions and participation of stakeholders to develop related technologies for further expanding its utilization as an important form of renewable energy. [ABSTRACT FROM AUTHOR]

Fish can be injured or killed during turbine passage. This paper reports the first in-situ evaluation of hydraulic conditions that fish experienced during passage through Francis turbines using an autonomous sensor device at Arrowrock, Cougar, and Detroit Dams. Among different turbine passage regions, most of the severe events occurred in the stay vane/wicket gate and the runner regions. In the stay vane/wicket gate region, almost all severe events were collisions. In the runner region, both severe collisions and severe shear events occurred. At Cougar Dam, at least 50% fewer releases experienced severe collisions in the runner region operating at peak efficiency than at the minimum and maximum opening, indicating the wicket gate opening could affect hydraulic conditions in the runner region. A higher percentage of releases experienced severe events in the runner region when passing through the Francis turbines than through an advanced hydropower Kaplan turbine (AHT) at Wanapum Dam. The nadir pressures of the three Francis turbines were more than 50% lower than those of the AHT. The three Francis turbines had much higher magnitudes and rates of pressure change than the AHT. This study provides critical information on hydraulic conditions and fish passage information of Francis turbines, which can help guide future laboratory studies of fish passing through Francis turbine, design fish-friendly turbines, and optimize the operation of existing turbines for better fish passage conditions. [ABSTRACT FROM AUTHOR]

Evaluating fish behavior and migration in response to environmental changes is a fundamental component of fisheries research and recovery of freshwater ecosystems. While spatial distribution and behavior of fishes has been well studied around hydropower facilities, little research has been conducted at a mid-reach location between two dams. The Juvenile Salmon Acoustic Telemetry System (JSATS) cabled receiver system was developed and employed as a reference sensor network for detecting and tracking juvenile salmon in the Columbia River Basin. To supplement acquisition of detection and three-dimensional (3-D) tracking data to estimate survival and fish behavior in the forebays of Little Goose and Lower Monumental dams on the Snake River in eastern Washington State, a mid-reach location was needed to investigate the spatial distribution of migrating juvenile salmon in open-water conditions between the two dams. Lyons Ferry Bridge on State Route 261 at the confluence of the Snake and Palouse Rivers was chosen as the mid-reach location. A JSATS-cabled receiver system configuration was successfully designed and deployed from the bridge's pier structure. Theoretical analysis confirmed the functionality and precision of the deployment design. Validation tests demonstrated sub-meter accuracy of 3-D tracking up to a horizontal distance of 50 m upstream and downstream from the Lyons Ferry Bridge piers. Detection and tracking probabilities of the LFB cabled array were estimated to be 99.98% from field application. This research provided a detailed description of acoustic telemetry system deployment and 3-D tracking as guidance for better understanding of fish migration behavior as they pass through dams and continue downstream through the river between dams. [ABSTRACT FROM AUTHOR]

Cylindrical triboelectric nanogenerators (C-TENGs) have been designed for low frequency wave energy harvesting. However, the random, and low amplitude and frequency of the ocean waves represent a major challenge for the operation and performance of most C-TENGs. A C-TENG must be able to operate and be triggered by any wave conditions, even in the middle of the ocean, with uniform, low amplitude, and low frequency water waves. Here, a frequency-multiplied cylindrical TENG (FMC-TENG) that uses magnets to store potential energy and instantly release it to produce high frequency kinetic energy, was designed to increase the operating frequency of the TENG using low frequency, uniform water waves and increase the power generated. A semi-analytical modeling of the FMC-TENG was performed to theoretically verify its effectiveness. Then, the electrical characteristics of the FMC-TENG were evaluated by comparison with a conventional C-TENG in a wave motion simulator. The FMC-TENG was optimized in a 12 m long water tank, and its peak power density reached 6.67 W/m3 under a wave frequency of 0.33 Hz. Finally, an array of FMC-TENGs successfully powered an acoustic transmitter, demonstrating the ability to power an ocean observation system. [Display omitted] • An innovative FMC-TENG was designed to increase the operating frequency of the TENG using low frequency ocean waves. • Two-magnets mechanism was used to store potential energy and release it to produce high frequency kinetic energy. • Peak power density reached 6.67 W/m3 under a wave frequency of 0.33 Hz in a 12 m long water tank. • An array of FMC-TENGs successfully powered an acoustic transmitter. [ABSTRACT FROM AUTHOR]

Insufficient service life and the resulting need for battery replacements have been a great challenge for implantable electronic devices. This is particularly true for animal tracking applications, because recapturing animals is often unlikely once they are released to the wild. To tackle this problem, we developed a biomechanical energy harvester that uses a Macro Fiber Composite™ (MFC) piezoelectric beam to harvest the mechanical energy from animals' body bending movements as the power source for implantable and wearable devices. Prototypes of an underwater acoustic transmitter using this technology were subdermally implanted into juvenile white sturgeon and their energy harvesting performance was evaluated through the devices' transmissions. The fish successfully recovered from the implantation surgery and freely swam inside a tank. The transmitter prototypes in the fish continually transmitted signals for a period up to 5 weeks. A benchtop test setup was also created to emulate the fish's body bending, estimate the device's energy harvesting performance in the live fish, and perform accelerated fatigue testing of the energy harvester by applying test parameters learned from a video study of the fish's body movement and behavior characteristics. The gradual depolarization of the piezoelectric ceramic material in the MFC under cyclic mechanical loading was the main limiting factor for the life span of the energy harvester. Pathways for improvement are proposed to achieve long-term efficacy of powering implantable and wearable electronic devices. [Display omitted] • Developed an implantable, lightweight, biomechanical energy harvester that successfully powered an integrated microelectronic device. • The host animal fully recovered from the implantation surgery and freely moved about without any inhibitions for an extended period. • The durability and failure modes of a piezoelectric energy harvester in an aquatic animal host under quasi-realistic conditions were investigated. • The host animal's physiology and behavior were investigated and quantified to guide the design of the prototype. [ABSTRACT FROM AUTHOR]

Abstract: Juvenile fall Chinook salmon (Oncorhynchus tshawythscha) and an autonomous sensor device (Sensor Fish) were exposed to turbulent shear flows to determine how hydraulic conditions affected fish injury response. Studies were designed to establish correlation metrics between Sensor Fish device measurements and live fish injuries by conducting concurrent releases in a range of turbulent shear flows. Comparisons were made for two exposure scenarios. In the fast-fish-to-slow-water scenario, test fish were carried by the fast-moving water of a submerged turbulent jet into the standing water of a flume. In the slow-fish-to-fast-water scenario, test fish were introduced into a turbulent jet from standing water through an introduction tube placed just outside the edge of the jet. Motion-tracking analysis was performed on high-speed, high-resolution digital videos of all the releases at water jet velocities ranging from 3 to 22.9 ms−1. Velocities of the Sensor Fish were very similar to those of live fish, but maximum accelerations of live fish were larger than those of Sensor Fish for all the nozzle velocities of both scenarios. A 10% probability of major injury threshold was found to occur at Sensor Fish accelerations of 513 and 260ms−2 for the fast-fish-to-slow-water and slow-fish-to-fast-water scenarios, respectively. The findings provide a linkage between laboratory experiments of fish injury, field survival studies, and numerical modeling. [Copyright &y& Elsevier]

Climbing on a vertical ship hull underwater while using surface cleaning tools remains a great challenge for climbing robots. In this study, we design a negative-pressure adsorptive underwater climbing robot using the Bernoulli negative-pressure generation mechanism. Computational fluid dynamics modelling is performed with a sliding mesh to explore the optimal adhesion performance. The factors that influence the adsorptive force are investigated, such as the contra-rotating propellers (CRPs) speed and gap distance between the bottom plate of the robot and the adsorbate, and their cause and effect are established by taking into consideration the fluid pressures and velocities for the Bernoulli negative-pressure effect on the bottom plate of the robot. Based on the optimal parameters determined from the numerical simulations, a prototype adsorptive climbing robot is fabricated and tested in a water pool. Comparisons with the experimental results show that the numerical model predicts the adsorptive force with an accuracy of 94.1%. The proposed method and the findings reported in this paper are valuable in guiding the design of negative-pressure adsorptive parameters for climbing robots, and will significantly improve the robot's capability to precisely adjust the adsorptive force by driving the CRP motor accordingly. • Designed an underwater robot by Bernoulli's theorem to generate adsorptive force. • Robot adapts to various adsorbates, with contactless, large and controllable force. • Factors that affect the optimal adsorptive force were studied. • The sliding mesh method was performed to reveal the formation process of the force. • A numerical model to estimate the force was validated with the experimental data. [ABSTRACT FROM AUTHOR]

Abstract: Bio-indexing of hydro turbines is an important means to optimize passage conditions for fish by identifying operations for existing and new design turbines that minimize the probability of injury. Cost-effective implementation of bio-indexing requires the use of tools such as numerical and physical turbine models to generate hypotheses for turbine operations that can be tested at prototype scales using live fish. Numerical deterministic and stochastic blade-strike models were developed for a 1:25-scale physical turbine model built by the U.S. Army Corps of Engineers for the original design turbine at McNary Dam and for prototype-scale original design and replacement minimum gap runner (MGR) turbines at Bonneville Dam’s first powerhouse. Blade-strike probabilities predicted by both models were comparable with those observed in both prototype-scale live fish survival studies and a physical turbine model using neutrally buoyant beads. Predictions from the stochastic model were closer to experimental data than predictions from the deterministic model because the stochastic model considered the aspects of fish approaching to the leading edges of turbine runner blades. Therefore, the stochastic model should be the preferred method for the prediction of blade strike and injury probability for juvenile salmon and steelhead using numerical blade-strike models for evaluating the biological performance of Kaplan hydro turbines. [Copyright &y& Elsevier]

Abstract: A micro-acoustic Doppler velocimeter (ADV) was used to measure three-dimensional mean velocity and turbulence characteristics in a full-scale culvert with spiral corrugations. The culvert was set up in a test bed constructed to examine juvenile salmon passage success in various culvert types. The test culvert was 12.2m long and 1.83m in diameter and set at a 1.14% slope. The corrugations were 2.54cm deep by 7.62cm peak to peak with a 5° right-handed pitch. Cross-sectional grids of ADV measurements were taken at discharges of 0.028, 0.043, 0.071, 0.099, 0.113, 0.227, and 0.453m3/s at nine locations. In the uniform flow region, the centerline velocity profiles were consistent with fully rough turbulent flows and the friction factor was independent of Reynolds number and was very close to theoretical results. Secondary flow induced by the spiral corrugations caused asymmetries in the velocity and turbulence distributions creating a reduced velocity zone (RVZ) on the right side of the culvert as seen looking upstream, which small fish could utilize to aid their upstream passage. Velocity and axial components of turbulence in the RVZ were found to be much less than in mid-channel or on the left of the culvert, and the difference became greater at increased flow rates. In addition, cross-stream and vertical velocity components within the RVZ were small relative to the downstream axial component, while lateral and vertical turbulence intensities were comparable to the axial component. Observations from a concurrent fish passage study showed that more juvenile fish migrate through the right side of the culvert within the RVZ. [Copyright &y& Elsevier]

• Sensor Fish used to characterize biological performance of a modified Francis. • Nadir pressures measured during runner passage were between 56.6 and 74.7 kPaA. • 50–64% of releases experienced an acceleration event in the guide vane region. • Results comparable to other Francis turbines studied using Sensor Fish. There are two strategies to lower overall project costs to an extent that will make many potential sustainable hydropower sites economically viable: (1) design standardized/modular components; (2) use advanced tools to reduce environmental evaluation costs. In this study an autonomous sensor device (Sensor Fish) was used to study a Francis turbine retrofitted with a modular guide vane. The median nadir pressures measured were 74.7, 66.6, and 56.6 kPaA for 90-, 190-, and 380-kW operating conditions respectively. These nadir pressures were compared to other Francis turbines studied using Sensor Fish and were found to be within the same range. The proportion of Sensor Fish releases with severe acceleration events (acceleration ≥ 95G) was also investigated. The proportion ranged from 73 to 80% (runner region), 50 to 64% (guide vane region), and 9 to 28% (draft tube region), which was within the range of the other turbines used for comparison. The Sensor Fish testing that was conducted at Hurley Dam demonstrates that the modular guide vane that was retrofitted to the existing Francis turbine is potentially a suitable replacement that can provide biological performance similar to the guide vane used with other existing Francis turbines, but with the benefit of reduced fabrication costs. [ABSTRACT FROM AUTHOR]

To investigate the removal characteristics of ammonium-nitrogen (NH 4 +-N), nitrite-nitrogen (NO 2 −-N), nitrate-nitrogen (NO 3 −-N), and total nitrogen from groundwater by a degradable composite active medium, kinetics, thermodynamics, and equilibrium adsorption, experiments were performed using scoria and degrading bacteria immobilized on scoria. Removal of NH 4 +-N, NO 2 −-N, and NO 3 −-N was conducted in adsorption experiments using different times, initial concentrations, pH values, and groundwater chemical compositions (Ca2+, Mg2+, HCO 3 −, CO 3 2−, Fe2+, Mn2+, and SO 4 2−). The results showed that the removal of nitrogen by the composite active medium was obviously better than that of scoria alone. The removal rates of NH 4 +-N (C 0 = 5 mg/L), NO 2 −-N (C 0 = 5 mg/L), and NO 3 −-N (C 0 = 100 mg/L) by the composite active medium within 1 h were 96.05%, 82.40%, and 83.16%, respectively. The adsorption kinetics were well fitted to a pseudo-second order model, whereas the equilibrium adsorption agreed with the Freundlich model. With changes in the pH, variation in the removal could be attributed to the combined effect of hydrolysis and competitive ion adsorption, and the optimum pH was 7. Different concentration conditions, hardness, alkalinity, anions, and cations showed different promoting and inhibiting effects on the removal of nitrogen. A careful examination of ionic concentrations in adsorption batch experiments suggested that the sorption behavior of nitrogen onto the immobilized medium was mainly controlled by ion exchange. The degrading bacteria on the scoria surface were eluted and analyzed by metagenomic sequencing. There were significant differences in the number of operational taxons, relative abundances, and community diversity among degrading bacteria after adsorption of the three forms of nitrogen. The relative abundance of degrading bacteria was highest after NO 3 −-N removal, and the diversity was highest after NO 2 −-N removal. Pseudomonas and Serratia were the dominant genera that could efficiently remove NH 4 +-N and NO 2 −-N. Image 1 • A composite active medium was prepared for nitrogen-contaminated groundwater remediation. • Groundwater chemical components showed different promoting and inhibiting effects on nitrogen removal. • Pseudomonas , the frequently isolated only represented the 3rd most relative abundant. • The most abundant bacteria, Serratia , were observed by sequencing after adsorption. [ABSTRACT FROM AUTHOR]

Structural simplification and efficient hydraulic performance are key to effectively utilizing ultra-low head water power resources and reducing hydroelectric unit costs. In this study, a computational fluid dynamics (CFD) method was used to predict hydraulic performance of an axial turbine at the Gaoliangjian power station. CFD results agreed well with field test data. Using the same numerical method, a new siphon turbine was then designed based on the original distributor and turbine runner equipment. This study investigated the effect of different siphon outlet passage geometry parameters, runner blade shapes, and distributors on the hydraulic performance of the siphon turbine. The maximum hydraulic efficiency increased to 87.9% under a head of 2.87 m. Finally, the hydraulic performance of the turbine was compared for four different distributor designs after adding an intake sump at the turbine entrance. The bell-shaped distributor with four guide vanes resulted in the highest power output at the lowest head. Therefore, the siphon turbine is a good option for energy conversion in ultra-low water head settings. • An Ultra-Low Head Siphon Hydro Turbine was developed. • The hydraulic performance of the tail pipe was optimized by orthogonal experiment. • The best blade design can both improve the efficiency of the impeller and reduce hydraulic losses in the outlet passage. • The 4-guide vane of the bell-shaped distributor possesses the best inflow condition for the runner. [ABSTRACT FROM AUTHOR]

Highlights • Quantified climate and water management impacts on juvenile Salmon. • Climate change does not necessarily reduce smolt survival rate. • Future fate of juvenile salmon varies between locations and climate scenarios. Abstract Water temperature has manifold effects on the biology of Pacific salmon. Thermal optima enable Pacific salmon to maximize growth while temperatures above thermal optima can induce stress and lead to mortality. This study investigated the impacts of climatic changes and water management practices on Chinook and Steelhead smolts in the Columbia River Basin using an integrated earth system model and a multiple regression model that incorporated nonlinear survival responses to water temperature. Results revealed that the effects would vary significantly with the species, location, and climate change scenario. Mean survival rates may increase by more than 10% in Upper Columbia River, while reduce by 1˜13% and 2˜35% for Chinook and Steelhead smolts respectively, in the Lower Columbia River by 2080s. This study highlights the importance of integrating the nonlinear response of survival rate to river temperature and water management effects in climate change vulnerability analysis for salmonid stocks. [ABSTRACT FROM AUTHOR]

Enabling the future of interconnected devices through miniature sensors and functional materials. [Display omitted] The advent of the Internet of Things and smart applications such as smart cities, smart health care, and smart electronics will require the use of a vast array of sensors. Sensors are a key part of the revolution in interconnected devices. The growing need for sensing, monitoring, and collecting data at scales from small to large will help, for example, prevent future pandemics, elucidate climate change, optimize industrial processes, and train machine learning models. Recent progress in materials science, micro/nano technologies, and integrated circuits has made it possible to reduce the size and cost of sensors while integrating them into more complex machines, ranging from wearable/implantable devices to onboard laboratories for planetary exploration rovers. However, the small dimensions of miniature sensors present some challenges, including power supply, active sensing materials, and material flexibility. In this article, we review microbatteries to power miniature sensors. We discuss materials and architectures for microbatteries and their fabrication methods. We also discuss energy harvesting materials for self-powered miniature sensors. We review in detail advanced materials for active sensing, including organic, inorganic, and composite materials with emphasis on wearable/implantable sensors targeted at humans and animals. In addition, flexible electronics as well as substrates and encapsulation materials and their integration are reviewed. Finally, future perspectives and challenges of these functional materials for next-generation miniature sensors are highlighted. [ABSTRACT FROM AUTHOR]

Uncrewed underwater vehicles (UUVs) significantly benefit from phase change material (PCM)-based ocean thermal energy harvesting for long mission duration. However, this technology relies on different parameters that are critical to its efficiency. Sea trials indicated that a design using this technology has lower performance than its initial specifications. This underperformance results from different factors—mainly, the UUV's trajectory, travel time, temperature fluctuations, and biofouling on the heat exchanger due to long-term underwater operations. Therefore, there exists a need to continuously monitor the ambient energy harvesting system and predict system performance for mission planning. Two major parameters that influence the energy harvesting system include the pressure inside the hydraulic accumulator and the electrical load. This work focuses on the hydraulic-to-electric energy conversion system. A combination of numerical simulation and experimental tests is used to develop a predictive model using artificial neural network (ANN) in MATLAB. 1000 data samples from a numerical model are used to train the ANN. Compared to experimental results, the ANN model predicts the designed benchtop system's total efficiency with a maximum efficiency of 51 % and an overall relative error of less than 15 %. This work will enable energy-efficient mission planning for UUVs using PCM-based ocean thermal energy harvesting. • Modeling of a benchtop hydraulic-to-electric energy conversion system. • The ANN predictive model uses the system pressure and electrical load parameters. • The maximum energy conversion efficiency is 51 %. • The system's total efficiency is predicted with <15 % relative error. • The prediction time (<1s) is suitable for UUVs where onboard energy is limited. [ABSTRACT FROM AUTHOR]

This paper presents the conceptual design, preliminary experimental validation, and performance evaluation of a novel bio-inspired bi-stable piezoelectric energy harvester for self-powered animal telemetry tags. The overall conceptual design, which includes a bio-inspired attachment and a bi-stable piezoelectric energy harvester, is introduced firstly with a specific application example of marine fish tracking. The self-powered telemetry tag can be externally deployed on fish (dorsal fin) to monitor fish habitats, population, and underwater environment. Inspired by the Venus flytrap's rapid shape transition, a bi-stable piezoelectric energy harvester is developed to scavenge energy from fish maneuvering and the surrounding fluid flow for a sustainable power supply. The bistability of the harvester is characterized by the measured force-displacement curve and double potential wells. A bluff body is integrated to the free end of the bistable piezoelectric energy harvester to enhance the structure-fluid interaction for the large-amplitude snap-through vibrations and higher voltage output. Controlled laboratory experiments are conducted in a water tank on the bio-inspired bi-stable piezoelectric energy harvester using a servo motor system to simulate fish swing motion at various conditions to evaluate the power generation performance. The preliminary underwater experimental results demonstrated that the proposed bio-inspired bi-stable piezoelectric energy harvester could effectively convert fish swing motions into electricity. The device collected 17.25 mJ of energy over 130 s under a peak-to-peak swing angle of 30o at 1.5 Hz in the capacitor charging experiments. [Display omitted] • A conceptual design of a self-powered animal telemetry tag was introduced. • A bio-inspired bistable piezoelectric energy harvester was developed, characterized, and tested. • Underwater energy harvesting from swing motions was demonstrated and studied. • More energy was attained from the large-amplitude snap-through oscillation at a low swing frequency. [ABSTRACT FROM AUTHOR]

Many riverine fish species disperse downstream as eggs, juveniles, or adults, which can expose them to injury and death at hydraulic structures. Low-head weirs are one example of a structure that can kill fish, and this impact has been shown to be substantially higher for undershot weirs when compared to overshot weirs. In this study, autonomous sensor devices were released at an overshot and undershot weir under similar discharges to assess what stressors maybe contributing to differences in the survival rates of fish. Although the undershot weir was more likely to expose fish to rapid decompression, the intensity of decompression was mild and it is more likely that higher levels of fluid shear at the undershot are more damaging to early life stage and small-bodied fish. Both weirs showed potential for strike, but this could be managed through improvements in design. [ABSTRACT FROM AUTHOR]

Abstract Stream sites are abundantly available for small, ultra low head, hydropower applications with minimal environmental and ecological impacts compared to large-scale hydropower projects. However, little attention has been paid to these resources because of the relatively high weight and deployment costs of small turbines compared to the amount of power generated, which results from the use of stainless steel (SS) as the turbine material. Therefore, this study investigated the potential of replacing the machined SS blades in a small propeller-type turbine with light-weight composite blades injection molded from a fiber reinforced polymer. Using computational fluid dynamics models and finite element analysis, a carbon fiber-reinforced thermoplastic was selected from three candidate composite materials for its lower density and smaller blade tip displacement. Injection molded blades using this material were then manufactured and tested in a lab-scale turbine performance test loop to compare with the SS blades of the same design. With the same flow rates, the composite turbine blades generated more power but required a slightly higher head (∼0.08 m) than the SS blades. Both the composite and SS blades displayed similar peak turbine efficiencies, demonstrating the viability of the composite material in replacing SS from the perspective of power-generation performance. Highlights • Performance of a composite turbine blade was compared to that of a stainless steel blade. • A composite material was selected from candidate materials using finite element analysis. • The composite blades generated more power but required a slightly higher head. • The composite and stainless steel blades showed similar peak turbine efficiency. [ABSTRACT FROM AUTHOR]

Highlights • Water supplement can induce the rheotaxis but may not increase the collection rate. • Warm white light is the best choice to attract mosquitofish. • Suitable combination of multiple factors can improve the effectiveness of FCTS. • Our study provides a theoretical basis for the design of bubble curtain in FCTS. Abstract Fish-collection and transportation systems (FCTS) have been introduced and applied as innovative approaches to facilitate fish passage in China for several years. The efficacy of FCTSs depends directly on the efficiency of the fish-guidance measures employed. In this study, the effects of three parameters—water flow, artificial lighting, and bubble curtains—on the attraction of mosquitofish (Gambusia affinis) was investigated using a fish barge model in a large pond. The experiment was conducted in two steps. First, a univariate experiment was performed, and then, a multivariate experiment using an orthogonal design was performed. Four different colors of light were tested: 1) yellow light (570 nm), 2) blue light (460 nm), 3) warm white light (3000 K), and 4) a weak light control group, whose illuminance belongs to the interval 0.001 lx to 0.3 lx. Supplementing water flow within the barge decreased the number of attracted fish (i.e., the number of the targeted fish species that appeared within 1.5 m of the barge model's entrance) but increased the fish-collection ratio of the fish-collecting platform (i.e., the ratio of the number of attracted fish to the number of collected fish). Warm white light was shown to be significantly effective in attracting fish, while no obvious effect was observed in terms of the fish-collection ratio. The bubble curtain exhibited excellent fish-attraction efficacies, but also had no significant effect on the attraction and collection efficacy of the fish-collecting platform. During the day, the optimal combination for fish attraction was to have no water flow with a bubble curtain, while the optimal combination for fish collection was to have no water flow and no bubble curtain. During the night, the optimal combination for fish attraction was to have no water flow, no bubble curtain, and a warm white light, while the optimal combination for fish collection was to have water flow, no bubble curtain, and a weak light. This study tested the combined efficacies of various fish-guidance measures on a fish-collecting platform, thus providing experimental support for optimizing various fish-attraction measures and the application of these measures in FCTS projects. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess the effects of an acoustic micro transmitter (tag) on survival and swimming ability of juvenile American eels ( Anguilla rostrata ). The transmitter was designed for implantation through a < 3 mm opening into the body cavity of anguilliform fishes without the need for sutures. Potential transmitter effects on swimming performance were examined by comparing critical swimming speeds ( U crit , an index of prolonged swimming performance) for six size groups ( n = 120, 113–175 mm) of tagged and non-tagged eels. There was no significant difference in U crits between tagged and non-tagged eels. Median U crits for tagged eels ranged from 50.2 cm/s for the smallest group tested (113–119 mm) to 63.9 cm/s for eels 141–150 mm in length. Non-tagged group median U crits ranged from 47.2 cm/s for the smallest group to 66.9 cm/s for the 141–150 mm group. An additional 26 eels (115–208 mm) were tagged and held for 38 days (without undergoing swimming performance tests) to assess survival and tag loss. No mortality occurred during the holding period and a tag loss of 3.8% ( n = 1) was observed within the first 20 days post-tagging, which is the current projected battery life of the tag at a 5 s ping rate interval. Tag loss increased to 50% overall ( n = 13) for eels held up to 38 days. Our results indicate that micro acoustic tags can be successfully implanted in juvenile American eels with no apparent effects on swimming ability or survival, and would be a viable option for examining eel movement patterns in river systems and near hydroelectric facilities. [ABSTRACT FROM AUTHOR]

Abstract: Barotrauma-injuries sustained following rapid decompression occur in many different fisheries applications. Previous attempts to quantify barotrauma in fish have been limited by the functionality of hypo/hyperbaric systems. Further, field studies often are confounded by covariates. The mobile aquatic barotrauma laboratory (MABL) was designed to address these limitations. Specifically, this testing facility allows the user to evaluate similar complex pressure scenarios to which migrating juvenile salmonids are exposed following turbine or spillway passage. In this paper, we describe the MABL and present a case study in which negative and neutrally buoyant juvenile Chinook salmon were exposed to simulated hydro-turbine passage (STP). The severity of the decompression profile and the fish''s ability to gain neutral buoyancy were used as predictor variables. We determined that following STP, fish that achieved neutral buoyancy during a 16-h acclimation period had a greater risk of mortality and injury (gill emboli, swim bladder rupture, and internal hemorrhaging) than negatively buoyant conspecifics. This research solidifies the need to allow fish to become neutrally buoyant when assessing barotrauma and mortality in field and laboratory applications. Future research examining injury and mortality of turbine-passed fish needs to consider the fish''s buoyancy to more appropriately evaluate these endpoints. [Copyright &y& Elsevier]

• The behavior of Ptychobarbus kaznakovi was studied in visible light of 15−120 lx. • Fish locomotion strategy was used to quantify light-induced behaviors. • Stress response and innate preference promote the fish swim in red and green light. • Red and green lights are ideal in fish expulsion and attraction. • An optimized light environment can facilitate fish protection effort. Light environment significantly impacts the effectiveness of fish population restoration in developed watersheds, subserving fish passage reconstruction in hydraulic complex and habitat rehabilitation. To develop an interior connection between light-related fish response from the laboratory and field fish conservation practice, we employed a new indexing system, consisting of phototaxis rate, relative swimming speed (RSS), and optic evasion coefficient (OEC), to quantify the light-induced behaviors in Ptychobarbus kaznakovi , a representative rare cyprinid in Tibet, China, at four experimental illuminance levels (15 lx, 30 lx, 60 lx, 120 lx) and four wavelengths (red, yellow, green, blue). The fish showed negative phototaxis at all given illuminances and wavelengths. Under red light, the OEC increased significantly from 0.642 at 15 lx to 0.782 at 30 lx (P = 0.029), while the RSS decreased significantly from 3.752 to 2.383 (P < 0.001). Behaviorally, the fish shifted from sprint to wandering around, indicating the alteration of dominant physiological activity from behavioral stress response to negative phototaxis. Under the green treatment, P. kaznakovi swam around quickly and presented slight negative phototaxis, and OEC values were uniform among all illuminances, probably because of the similarity of green light to the ambient color of the habitat. Accordingly, ecologists and fisheries practitioners can utilize red light to exclude fish from dangerous waters and green light to guide them to ideal habitats, laying the necessary groundwork for the light-driven fish recovery effort. Furthermore, the appropriate light configuration can yield economic benefits through the tradeoff among fish protection, power generation, and investment costs. [ABSTRACT FROM AUTHOR]