Variable-Speed Propeller Turbine for Small Hydropower Applications

Abstract

Standard technical solutions are not cost-effective for many small hydropower sites. This study aims to demonstrate the workflow for the tailor-made variable-speed axial propeller turbine and provide proof of this concept. The turbine is designed to meet the site’s specific space limitations and operating range needs. The runner shape is adjusted to the variable-speed operation and defined hydraulic profile using a parametric geometry model and CFD-based optimization. The variable-speed propeller turbine shows excellent flow control while keeping the mechanical design simple. The tailor-made approach minimizes construction costs using existing structures and is highly suitable for mini-hydropower applications. The prototype—an atypical turbine designed for highly restricted space and installed on-site—serves as proof of the concept. The findings on the design of axial variable-speed turbines are presented.

A Comparative Analysis of Distributor and Rotor Single Regulation Strategies for Low Head Mini Hydraulic Turbines

“…A fixed rotor blade stagger angle implies β 2 = β 2design and β 1blade = β 1design . The residual absolute tangential velocity component at the rotor exit, c θ2 , can be evaluated from Equation (7) with w θ2 = k x φ u tanβ 2 :…”

“…In this context, the tubular axial turbine (TAT) assumes a fundamental role, particularly in mini and micro hydropower applications [5,6]. However, the economic sustainability requires simplified mechanical and manufacturing solutions, although preserving, as much as possible, reliability and conversion efficiency [7]. Moreover, the deployment of sophisticated regulating mechanisms may be economically impractical.…”

Optimization of Elbow Draft Tubes for Variable Speed Propeller Turbine

“…Since it was a design stage, the calculations could not be verified experimentally. However, previous work regarding the same concept of variable speed turbines (Bílková et al [3]) compared the CFD and measured data of manufactured turbines. Since the measurement was done in situ without complying with the values specified in the standard IEC 62006, the precise error values are unknown.…”

“…For this reason, a fixed-blade propeller turbine with variable revolutions was developed for low heads (approx. up to 10 m) regulated by guide vane control and the variable speed of a runner [3,4]. Variable speed propeller turbine is mechanically simpler than the Kaplan turbine and, at the same time, allows for good discharge regulation.…”