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Challenges in Implementation of Small Hydro Schemes on Hilly Streams
Published in C.V.J. Varma, A.R.G. Rao, Renewable Energy Small Hydro, 2020
The flash floods that occur in the hilly streams of small catchment areas not only cause extensive erosion in the stream bed but also convey large amount of coarse as well as fine sediments into the power intake. There are several instances where the diversion weir designed with some pondage behind the weir to be used to produce peak power, got filled up with sediments and hardly any pondage was available and the plant had to be operated as a run-of-the river scheme. It becomes obligatory to provide suitable silt excluders for flushing out the coarse sediments before the flow enters into the power intake. If the boulders are rolling during the floods, some boulder catches located upstream may be necessary. In addition, it will be necessary to provide a desilting basin for excluding hard particle size larger than 0.2mm to prevent erosion of the turbine blades. There are several case histories in our country, where the silt erosion has been experienced in the turbines requiring large scale repairs to the runners resulting in closing down the units and less than satisfactory performance of the plant.
Techno-economic analysis of In-stream technology: A review
Published in International Journal of Green Energy, 2023
Upendra Bajpai, Sunil Kumar Singal
Generally speaking, most nations have access to plentiful water resources and ideal circumstances for the development of SHPs, allowing them to produce clean power without harming the environment. For developing nations, RoR hydropower is particularly appealing (Berga 2016; Kuriqi and Jurasz 2022). The government of many countries started supporting it by providing subsidies, especially to RoR, and the technology proliferated on a global scale (Alban et al. 2019b). The technology is typically seen as environmentally friendly and sustainable. However, these hydropower projects can change the natural flow pattern and harm the fluvial ecology at various tropic levels (Alban et al. 2021). The primary environmental impacts of the three types of small run-off river hydropower systems- dam-toe, pondage, and diversion weir were discussed, and the dam-toe hydropower scheme was observed to be more eco-friendly compared to the pondage and diversion weir hydropower scheme (Alban et al. 2020). To minimize the environmental effect and safeguard the hydropower industry’s profit, the environment flow (e-flow) for the ROR scheme needed to be properly determined. Less e-flow did not always worsen habitat conditions, while greater e-flow did not always result in maximum habitat availability. The dynamic approach e-flow method produced consistent results and was better because it suggested 10–35% more hydropower with minimal impact on hydrological parameters (Alban et al. 2019a). To maximize power output and minimize detrimental effects on the riverine ecosystem, Suwal et al. (2020) created an optimization model for the cascade reservoir. The need for a large generation capacity in ROR systems could also be lessened by an energy storage device. Consequently, decreasing the quantity of water diverted and lowering the ecological effects. Several examples of energy storage systems (ESS) include sodium-sulfur batteries, compressed air energy storage, and pumped hydroenergy storage systems (Malka et al. 2022). In pumped hydroenergy systems, pump as turbine (PAT), which is a reversely operated pump, is employed. The turbine suffers from the problem of tip leakage vortex, tip leakage flow, and cavitation resulting in energy loss and reduced hydraulic efficiency (Kan et al. 2022). PAT cavitation is decreased via geometric design modification, and flow dynamics interference approaches, for example, by improving blade tip geometry, volute casing design, providing splitter blades, gap drainage blades, and J-grooves (Kan et al. 2022). Water, as a renewable energy source, possesses energy in two forms. The former is represented by the potential head, and the latter is represented by kinetic energy. In SHP schemes, this kinetic energy is available in the form of flowing water velocity in various environments such as rivers, canals, tidal, and marine water ways.