Emerging and Innovative Materials for Hydropower Engineering Applications: Turbines, Bearings, Sealing, Dams and Waterways, and Ocean Power

Summary For a remote area or an isolated island, where the grid has not extended, a standalone hybrid energy system can provide cheap and adequate power for local users. However, with the development of society, the load demand will increase and the original system cannot completely meet the load demand. This situation occurs in Xiaojin, Sichuan, China. The existing photovoltaic-pumped hydro storage (PV-PHS) hybrid system in this area as the original system cannot completely meet the load requirements at present. The term ?repowering? aims to maximize the reliability of power supply and the utilization of the PV-PHS hybrid energy system that differs from traditional planning optimization to build all components. The repowering strategy is to integrate wind turbines (WTs) and battery into the original system. For the repowering system, a power management strategy is proposed to determine the operating modes of the PHS and battery. Three objectives, which are minimizing percentage of the demand not supplied, levelized cost of energy, and curtailment rate of renewable energy, are considered in the optimization model. Simulation is conducted by single-objective, biobjective, and triobjective particle swarm optimization (PSO) techniques. For the single-objective optimization, the comparison of PSO and genetic algorithm (GA) is made. For the double-objective optimization, multiobjective PSO (MOPSO) is compared with weighted sum approach (WSA), and fuzzy satisfying method is utilized to find the win-win solution. The results reveal that the repowering strategy can help to achieve maximum reliability of power supply after load demand increases significantly, and the battery plays an important role in such a hybrid system.

Implementation of repowering optimization for an existing photovoltaic‐pumped hydro storage hybrid system: A case study in Sichuan, China

Using physical model and numerical simulation techniques, some technical problems were studied systemati- cally, including layout of power station, measures of sediment and floating debris discharging, types of intake, embed- ded types of spiral ease, layout of underground powerhouse tunnel group and block reinforcement. It was optimal in technique and economy with the arrangement of powerhouse at the dam-toe of both banks ＋ underground powerhouse in the right bank, as well as the intake with a single and small orifice. The sediment and debris problems could be solved with disperse sediment ejection and floating debris discharging holes. With the adoption of techniques for spiral cases such as heat and pressure preservation, cushion layer and combined embedding, the stable operation of generating units can be guaranteed. The arrangement of tailrace tunnel with sloping ceiling was better than that of tailrace surge tank. The technical requirements related to the embedding type of spiral case were proposed. The reinforcement of huge unfavorable blocks was discussed and the new idea for block reinforcement using anti-sliding piles and normal compressive stress of structural plane was put forward.

The design of Three Gorges Hydropower Station

Low-cycle fatigue issue of steel spiral cases in pumped-storage power plants under China's and US's design philosophies: A comparative numerical case study

A spiral case refers to a water passage in a substructure of a hydropower house. The substructure is thus also known as a spiral case structure (SCS). For medium and high head hydroelectric power plants (HPPs), inner walls of spiral cases are steel-lined. For a steel-lined SCS, the embedment condition of the steel liner (steel spiral case) in the concrete is the dominant factor to determine the composite system's structural performance. Hence the issue of embedment of steel spiral cases has been a controversial and much disputed subject concerning the design and construction of HPPs. The purpose of the current work was to share China's experience on methods of embedment of steel spiral cases in concrete. The work has highlighted China's design philosophy of P-type and M-type SCSs. It is a joint-IWP-resisting philosophy for balancing the structural strength against integrity of SCSs. The work has also underlined an innovative solution (NM-hybrid-type SCSs) for excessively uneven lifts of generator pedestal structures confronting N-type SCSs. We believe that the experience can broaden the world's current knowledge of the design and construction of HPPs.

He-Gao Wu

Papers

Embedment of steel spiral cases in concrete: China's experience