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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]

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]

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]

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]

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]

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]