Design and performance evaluation of a fully submerged bulb kaplan turbine for low-head applications

Abstract The worldwide transition to renewable energy, especially hydropower, is essential for reducing reliance on fossil fuels, ensuring energy stability, and mitigating environmental damage. Low-head hydropower (LHP) offers a promising alternative to large-scale hydropower plants, addressing significant challenges including high capital costs of conventional hydropower installation, ecological impacts like habitat disruption and sedimentation, and inadequate infrastructure. This work presents a fully submerged Bulb Kaplan turbine designed for low-head applications, with experimental validation. Operating with a net head of 0.353 meters and discharge rates up to 3 cubic feet per minute, it is ideally suited for small-scale hydropower projects, particularly in areas like Gilgit-Baltistan, Pakistan, where low-flow channels and seasonal water fluctuations are common. The turbine is housed in a hermetically sealed, bulb-shaped enclosure that protects the generator, reducing energy losses and mechanical degradation. It also features a convergent divergent duct that maximizes the water flow’s velocity head, hence improving efficiency and minimizing the need for complex dam infrastructure, unlike traditional Kaplan turbines. Moreover, extensive testing in a controlled open-channel setup confirmed the turbine’s efficacy across a diverse range of discharge rates (0–3 ft 3 min −1 ). The turbine exhibited a nonlinear increase in power output, peaking at 4.9 watts with an efficiency of 50.8% and a nearly linear rise in rotational speed, reaching 248 rpm at maximum flow. These findings, which are closely consistent with theoretical predictions, highlight the turbine’s suitability for low-head, small-scale applications. With a 4.9-watt power output, this turbine shows its capability for decentralized energy generation, while its modular design allows scalability for larger low-head systems or incorporation into existing infrastructure. This research highlights the turbine’s potential as a cost-effective and efficient energy solution for resource-limited areas by demonstrating improved performance and lower installation costs compared to existing LHP technologies, hence contributing to the advancement of renewable energy technology.