Design of a Throttled Surge Tank for Refurbishment by Increase of Installed Capacity at a High-Head Power Plant

Abstract

The Swiss confederation aims to phase out nuclear power production with its Energy Strategy 2050 program by increasing the renewable energy contribution to its overall energy generation. Hydroelectricity, which is the most important form of renewable energy in Switzerland, supplying almost 60% of the electricity in 2015, should increase its production capacity to achieve this goal. The case study presented in this paper focuses on the replacement of the third turbine in the Gondo high-head power plant with a turbine with a higher discharge capacity. The results of one-dimensional (1D) numerical simulations shown that throttling the surge tank is an efficient measure to adapt the existing hydraulic system for the increased discharge. Physical-scale modeling was performed to validate the design of the grid throttle placed at the bottom of the lower chamber of the existing surge tank. The grid throttle geometry and its head losses are compared with two existing similar throttles in Switzerland. Finally, prototype tests of the temporal evolution of water levels in the surge tank using the throttle coefficients obtained experimentally showed good agreement. Hybrid modeling using a combination of 1D numerical models, threedimensional (3D) physical models, and prototype tests are highly recommended for checking the transient performance of the waterway after a refurbishment of turbines with increased design discharge. Furthermore, placing a throttle at the bottom of an existing surge tank is often an effective and economical solution in the case of small increases in installed capacity.

Experimental Hydraulic Investigation of Angled Fish Protection Systems—Comparison of Circular Bars and Cables

“…A clear definition of the reference velocity v re f was needed [16,17]. For the quantification of head loss at trash racks, the undisturbed cross upstream the structure was used (mean approach velocity) [18].…”

Hydraulic Optimization of Double Chamber Surge Tank Using NSGA-II

“…Therefore, the effects of the lower chamber on upsurge and the upper chamber on downsurge are not seen in the sensitivity analysis. The common variable for upsurge and downsurge is D O , and the positive value of sensitivity in Table 3 indicates the lower value of D O is favorable for all the objectives functions, which was also concluded by many researchers [5,6,11]. Damping of surge waves is due to the frictional loss in the headrace tunnel and the surge tank during mass oscillation.…”

“…Kim et al [4] applied genetic algorithm (GA) and optimized the location and the connector of the surge tank considering safety and cost of the water supply system. Adam et al [5] carried out a 1-D numerical simulation and performed a physical scale modeling test and found that placing a throttle at the bottom of a surge tank is an effective and economical solution to adapt a hydraulic transient. Steyrer [6] compared different types of surge tanks and concluded that the economic surge tank can be achieved with an effective throttling device in connection with surge tanks.…”

Design criteria for a type of asymmetric orifice in a surge tank using CFD

“…An independent laboratory experiment is advisable based on the importance of such a throttle for the hydraulic system. Those validation experiments and comparisons with measurements at the finished HPP help to further enhance the confidence in the numerical method (Adam et al, 2018a;Gabl et al, 2014a,b). As mentioned by Adam (2017), future research efforts should include a deeper investigation of the transient behavior of such structures.…”

“…Stability criteria define the minimum area of the shaft (Thoma, 1910;Ye et al, 1992) and the storage capacity can be enhanced with additional chambers. Large mass oscillations between the surge tank and the upper reservoir can be further damped with the addition of a throttle (Adam et al, 2018a;Li & Brekke, 1989;Vereide et al, 2017). Such a structure can be added in the connection between the surge tank and head race tunnel or at a change of the cross section (Adam et al, 2016a;Richter et al, 2015).…”